阅读说明：本技术 照明装置、包括该照明装置的摄像系统、包括该摄像系统的内窥镜系统及显微镜系统 (Illumination device, imaging system including the illumination device, endoscope system including the imaging system, and microscope system ) 是由 山本英二 大道寺麦穗 佐佐木靖夫 于 2017-05-19 设计创作，主要内容包括：照明装置(102)具有：照明脉冲生成器(110),其生成相干光的照明脉冲；散斑调制器(200),其对由所述相干光产生的散斑进行调制；以及同步控制器(240),其使所述照明脉冲生成器的脉冲生成定时与所述散斑调制器的驱动定时同步地进行控制。(The lighting device (102) comprises: an illumination pulse generator (110) that generates an illumination pulse of coherent light; a speckle modulator (200) that modulates speckle produced by the coherent light; and a synchronization controller (240) that controls the pulse generation timing of the illumination pulse generator in synchronization with the drive timing of the speckle modulator.)

1. An illumination device having:

an illumination pulse generator that generates an illumination pulse of coherent light;

a speckle modulator that modulates speckles generated by the coherent light; and

a synchronous controller that controls a pulse generation timing of the illumination pulse generator in synchronization with a driving timing of the speckle modulator.

2. The lighting device of claim 1,

the synchronization controller controls so that the speckle modulator is operated at least during pulse light emission of each of the illumination pulses.

3. The lighting device of claim 2,

the speckle modulator periodically varies a driving intensity of the speckle modulator.

4. The lighting device of claim 3,

when the pulse emission period is 1/2 shorter than a speckle modulation period, the synchronization controller controls the illumination pulse generator and the speckle modulator so that the pulse emission period includes a time at which a rate of change in the drive intensity of the speckle modulator becomes substantially maximum.

5. The lighting device of claim 4,

the synchronization controller controls the illumination pulse generator and the speckle modulator so that a center of the pulse emission period becomes a time when a rate of change in drive intensity of the speckle modulator becomes substantially maximum.

6. The lighting device of claim 3,

when the pulse emission period is 1/2 shorter than a speckle modulation period, the synchronization controller controls the illumination pulse generator and the speckle modulator so that neither of a maximum value and a minimum value of the drive intensity of the speckle modulator is included in the pulse emission period.

7. The lighting device of claim 6,

the synchronization controller controls the illumination pulse generator and the speckle modulator in such a manner that the pulse emission period includes a time at which the drive intensity of the speckle modulator takes a value at the center of a substantial maximum value and a substantial minimum value.

8. The lighting device of claim 7,

the synchronization controller controls the illumination pulse generator and the speckle modulator so that the center of the pulse emission period becomes a value at which the driving intensity of the speckle modulator substantially has the center of the maximum value and the minimum value.

9. The lighting device of claim 3,

when the pulse emission period is equal to or longer than 1/2 times of a speckle modulation cycle, the synchronization controller controls the illumination pulse generator and the speckle modulator such that the pulse emission period includes a time at which the drive intensity of the speckle modulator is at a maximum value and a time at which the drive intensity of the speckle modulator is at a minimum value.

10. The lighting device of claim 1,

the speckle modulator includes a1 st speckle modulator and a2 nd speckle modulator, and the synchronization controller controls a pulse generation timing of the illumination pulse generator in synchronization with a driving timing of the 1 st speckle modulator and/or the 2 nd speckle modulator.

11. The lighting device of claim 2,

when a variation width of the drive intensity of the speckle modulator, in which reduction of speckle is saturated with respect to variation of the drive intensity of the speckle modulator, is set to a drive intensity threshold width, the drive intensity amplitude of the speckle modulator is set to a drive intensity threshold width or more.

12. The lighting device of claim 11,

the amplitude of the drive intensity of the speckle modulator is set so that the amplitude of change in the drive intensity of the speckle modulator in the pulse emission period is equal to or greater than a threshold amplitude of the drive intensity.

13. The lighting device according to claim 1 or 2,

the speckle modulator has a phase modulator that changes the phase of the coherent light with a change in time.

14. The lighting device of claim 13,

the phase modulator includes a light guide member changing device that applies mechanical change to a light guide member included in a light guide optical system that guides the coherent light.

15. The lighting device of claim 13,

the phase modulator has an asperity plate having an asperity larger than 1/10 of the wavelength of the coherent light.

16. The lighting device of claim 13,

the phase modulator is a refractive index modulator that changes a refractive index of a light guide optical system that guides the coherent light with time.

17. The lighting device of claim 16,

the refractive index modulator includes at least one of an electro-optical element and an acousto-optical element.

18. The lighting device of claim 14,

the light guide optical system includes an optical fiber, and when a core diameter of the optical fiber is Φ c, a drive intensity amplitude of the speckle modulator is 5 Φ c or more when the drive intensity amplitude is a displacement of vibration of the optical fiber generated by the light guide member varying device.

19. The lighting device of claim 14,

the light guide optical system includes an optical fiber, and the driving intensity amplitude of the speckle modulator is 10 ° or more as an angle for twisting the optical fiber.

20. The lighting device of claim 16,

when the length of the refractive index modulator in the light guiding direction is Lm, the change in the refractive index is Δ n/n, and the center wavelength of the spectrum of the illumination pulse is λ c, the amplitude of the driving intensity of the speckle modulator is Δ n/n ≧ λ c/Lm as the change in the refractive index of the refractive index modulator.

21. A camera system, wherein,

the imaging system includes:

a lighting device as claimed in any one of claims 2 to 12; and

and an imager that performs imaging during a predetermined exposure period.

22. The camera system of claim 21,

the synchronization controller controls the pulse generation timing of the illumination pulse generator, the driving timing of the speckle modulator, and the imaging timing of the imager in synchronization with each other.

23. The camera system of claim 21,

the synchronization controller controls the pulse generation timing of the illumination pulse generator, the driving timing of the speckle modulator, and the imaging timing of the imager in synchronization with each other, and controls the illumination pulse generator to generate the illumination pulse during the exposure of the imager.

24. The camera system of claim 21,

the synchronization controller controls the pulse generation timing of the illumination pulse generator, the driving timing of the speckle modulator, and the imaging timing of the imager in synchronization,

setting the driving intensity amplitude of the speckle modulator as I_mod，0And setting a drive intensity threshold amplitude, which is an amplitude of change in drive intensity of the speckle modulator that saturates with a decrease in speckle with respect to a change in drive intensity of the speckle modulator, to Δ I_mod，thAnd setting the pulse emission period of the illumination pulse generated by the illumination pulse generator to t_pw，illAnd setting a modulation period when the speckle modulator is periodically driven to t_modAnd is set to M₀＝I_mod，0/ΔI_mod，thWhen the synchronous controller is in M₀≧ 1 driving the speckle modulator and the illumination pulse generator, and t_mod≤2M₀t_pw，illDriving the speckle modulator and the illumination pulse generator.

25. The camera system of claim 21,

the synchronization controller controls the pulse generation timing of the illumination pulse generator, the driving timing of the speckle modulator, and the imaging timing of the imager in synchronization,

setting the driving intensity amplitude of the speckle modulator as I_mod，0And setting a drive intensity threshold amplitude, which is an amplitude of change in drive intensity of the speckle modulator that saturates with a decrease in speckle with respect to a change in drive intensity of the speckle modulator, to Δ I_mod，thAnd setting the pulse emission period of the illumination pulse generated by the illumination pulse generator to t_pw，illAnd setting a modulation period when the speckle modulator is periodically driven to t_modAnd is set to M₀＝I_mod，0/ΔI_mod，thWhen the synchronous controller is in M₀≧ 1 driving the speckle modulator and the illumination pulse generator, and t_pw，ill＜t_mod≤M₀t_pw，illFor the speckle modulator and the illuminationThe pulse generator is driven.

26. An endoscope system comprising the imaging system according to any one of claims 21 to 25,

the imaging system further includes:

an image processing circuit that performs image processing on an image captured by the imager; and

and an image display unit that displays an image subjected to image processing by the image processing circuit.

27. A microscope system comprising the imaging system according to any one of claims 21 to 25,

the imaging system further includes:

an image processing circuit that performs image processing on an image captured by the imager; and

and an image display unit that displays an image subjected to image processing by the image processing circuit.

28. A camera system, wherein,

the imaging system includes:

an illumination light generator that generates coherent light;

a speckle modulator that modulates speckles generated by the coherent light; and

an imager that performs imaging during a predetermined exposure period,

the imaging system has a synchronization controller that controls imaging timing of the imager in synchronization with driving timing of the speckle modulator.

29. The camera system of claim 28,

the synchronization controller controls so that the speckle modulator is operated at least during the exposure.

30. The camera system of claim 28 or 29, wherein,

the speckle modulator periodically varies a driving intensity of the speckle modulator.

Technical Field

The present invention relates to an illumination device using coherent light.

Background

In an imaging system using coherent light represented by a laser light source for illumination, the following is known: when the observation target has a scattering structure such as a slight unevenness, a fine speckle pattern (speckle) is generated on the imaging surface of the imager, and appears as noise (this is referred to as speckle noise) in the acquired image, which hinders visibility. This phenomenon occurs not only in an electronic imaging system but also in the retina of a living body corresponding to an imaging surface, and therefore, the same problem occurs in an illumination device that uses coherent light for illumination, for example, a laser projector or the like. It is known that the cause of the speckle is interference of light scattered from irregularities or the like of an observation target, and a fine bright-dark pattern is formed on an imaging surface and a retina.

Various speckle reduction methods for reducing the speckle are known, and representative methods are listed below. In the following description, although "coherent light" is often described as "laser light" as a representative example thereof, the description may be replaced with ordinary "coherent light". In addition, the general "coherent light" also includes "partially coherent light".

(1) [ method for reducing speckle noise by reducing effective coherence of light source itself ]

(1-a) when an LD (laser diode) is driven by a current, the effective spectral width is widened by, for example, superimposing high frequencies as a drive waveform to promote multimode spectrum.

(1-b) the LD is equipped with a pulse function to disturb the phase and wavelength of light.

(1-c) broadening the effective spectral width by changing the spectrum of the wavelength-variable laser at a high speed.

(1-d) combining a plurality of lasers independent of each other to reduce effective coherence.

(2) [ method of changing a light and dark pattern formed by speckles with time and reducing effective speckle noise by using the time superposition effect of the light and dark pattern ]

(2-a) vibrating the observation object to change the speckle pattern.

(2-b) causing a change in the phase of light in the optical path from the light source to the observation object, causing a change in the speckle pattern.

As an example of (2-b), the following method is proposed: in a structure in which laser light is guided and irradiated by an optical fiber, the shape and stress of the optical fiber are changed to change the light guide pattern over time, thereby causing a phase change of the irradiated laser light to change the speckle pattern.

For example, japanese patent application laid-open No. 2003-156698 discloses a laser light source device having such a configuration. In this laser light source device, laser light emitted from a laser light source enters an incident end of an optical fiber and is emitted from an emission end as laser illumination light. An oscillation device for applying oscillation to the optical fiber is provided in the intermediate portion of the optical fiber. When the optical fiber is vibrated by the vibration device, a phase change of light due to mode conversion of laser light or the like occurs in the optical fiber. The change in the characteristics of the laser beam (here, the change in the phase of the light) shifts or changes the fringe pattern due to the speckle generated when the observation target is irradiated from the optical fiber. Since the stripe pattern caused by the speckles moves or changes at such a speed that the human eye cannot perceive, the human body receives a pattern in which the stripe patterns caused by the speckles are superimposed and averaged, and thus speckle noise is reduced.

In the method (1-a), the laser light that can be used is limited to LDs, and the spectral broadening method differs depending on individual differences of LDs, and a stable and sufficient effect in reducing speckle is not always obtained in many cases. The methods (1-b) and (1-c) require a laser beam having a specific function, and the method (1-d) requires a plurality of laser beams, and therefore, the cost of the imaging system must be increased to achieve a sufficient reduction effect.

On the other hand, the method (2-a) is limited to the case where the observation target may be slightly vibrated as in the case of a screen of a projector or the like, and thus is difficult to be applied to the observation target such as a microscope or an endoscope. The method (2-b) does not require vibration of the observation target, and therefore, although it does not restrict the observation target, it requires mechanical changes in the shape and stress of the optical fiber, and therefore, the restriction on the optical modulation speed is large. Therefore, in this method, for example, in an electronic imaging system, it is predicted that the speckle pattern superimposition effect cannot be sufficiently exhibited when the frame rate of imaging is fast or the imaging time is short.

Disclosure of Invention

The invention aims to provide an illumination device capable of stably and effectively reducing speckle noise.

The lighting device of the present invention comprises: an illumination pulse generator that generates an illumination pulse of coherent light; a speckle modulator that modulates speckles generated by the coherent light; and a synchronization controller that synchronizes and controls a pulse generation timing of the illumination pulse generator and a driving timing of the speckle modulator.

Drawings

Fig. 1A shows a speckle modulator constituted by a vibration device that vibrates an optical fiber.

Fig. 1B shows a case where the phase and the mode of the laser light in the optical fiber change with time by vibrating the optical fiber, and the speckle pattern changes with time.

FIG. 1C is the result of an experiment actually carried out by the present inventors and shows that the effective speckle contrast is measured with respect to the vibration amplitude X of the optical fiber_mod，0The result obtained by the above-described variation.

FIG. 2A is a graph showing wavelength at vibration amplitude λ_modThe spectrum of the laser light changing with time.

FIG. 2B shows the vibration amplitude λ at the wavelength of the laser light shown in FIG. 2A_modThe corresponding one-dimensional light intensity distribution of the speckle pattern.

FIG. 2C shows the amplitude of change Δ λ of the vibration amplitude of the effective speckle contrast with respect to the wavelength of the laser light_mod，0A change in (c).

FIG. 3A1 shows the drive waveform of the speckle modulator, the illumination waveform of the illumination pulse generator optimally synchronized with the drive waveform, and the effective modulation amplitude factor M that is an indicator of the speckle reduction effect_effAnd speckle reduction effect, particularly showing that the pulse width of the illumination waveform is shorter than half of the modulation period of the speckle modulator and M₀Case < 1.

FIG. 3A2 shows the drive waveform of the speckle modulator, the illumination waveform of the illumination pulse generator optimally synchronized with the drive waveform, and the effective modulation amplitude factor M that is an indicator of the speckle reduction effect_effAnd speckle reduction effect, particularly showing that the pulse width of the illumination waveform is equal to half the period of the modulation period of the speckle modulator and M₀Case < 1.

FIG. 3B1 shows the drive waveform of the speckle modulator, the illumination waveform of the illumination pulse generator optimally synchronized with the drive waveform, and the effective modulation amplitude factor M that is an indicator of the speckle reduction effect_effAnd speckle reduction effect, particularly showing that the pulse width of the illumination waveform is shorter than half of the modulation period of the speckle modulator and M₀The case is 1.

FIG. 3B2 shows the drive waveform of the speckle modulator, the illumination waveform of the illumination pulse generator optimally synchronized with the drive waveform, and the effective modulation amplitude factor M that is an indicator of the speckle reduction effect_effAnd speckle reduction effect, particularly showing that the pulse width of the illumination waveform is equal to half the period of the modulation period of the speckle modulator and M₀The case is 1.

FIG. 3C1 shows the drive waveform of the speckle modulator, the illumination waveform of the illumination pulse generator optimally synchronized with the drive waveform, and the effective modulation amplitude factor M that is an indicator of the speckle reduction effect_effAnd speckle reduction effect, particularly showing that the pulse width of the illumination waveform is shorter than half of the modulation period of the speckle modulator and M₀2 > 1.

FIG. 3C2 shows the drive waveform of the speckle modulator, the illumination waveform of the illumination pulse generator optimally synchronized with the drive waveform, and the effective modulation amplitude factor M that is an indicator of the speckle reduction effect_effAnd speckle reduction effect, particularly showing that the pulse width of the illumination waveform is equal to half the period of the modulation period of the speckle modulator and M₀2 > 1.

Fig. 4a1 shows the effective modulation amplitude factor M that is an index of the speckle reduction effect, the illumination waveform of the illumination pulse generator, and the drive waveform of the speckle modulator with respect to the elapsed time_effAnd speckle reduction effect, showing modulation amplitude factor M of speckle modulator₀1 and t_mod/2M₀＞t_pw，illThe case (1).

Fig. 4a2 shows the effective modulation amplitude factor M that is an index of the speckle reduction effect, the illumination waveform of the illumination pulse generator, and the drive waveform of the speckle modulator with respect to the elapsed time_effAnd speckle reduction effect, showing modulation amplitude factor M of speckle modulator₀2 > 1 and t_mod/2M₀＞t_pw，illThe case (1).

FIG. 4B1 shows the effective modulation amplitude factor M that is an index of the speckle reduction effect, the illumination waveform of the illumination pulse generator, and the drive waveform of the speckle modulator with respect to the elapsed time_effAnd speckle reduction effect, showing modulation amplitude factor M of speckle modulator₀1 and t_mod/2M₀＝t_pw，illThe case (1).

FIG. 4B2 shows the effective modulation amplitude factor M that is an index of the speckle reduction effect, the illumination waveform of the illumination pulse generator, and the drive waveform of the speckle modulator with respect to the elapsed time_effAnd speckle reduction effect, showing modulation amplitude factor M of speckle modulator₀2 > 1 and t_mod/2M₀＝t_pw，illThe case (1).

FIG. 4C1 shows the drive waveform of the speckle modulator and the illumination waveform of the illumination pulse generator with respect to the elapsed time, which is the speckle reduction effectEffective modulation amplitude factor M of index_effAnd speckle reduction effect, showing modulation amplitude factor M of speckle modulator₀1 and t_mod/M₀＝t_pw，illThe case (1).

FIG. 4C2 shows the effective modulation amplitude factor M that is an index of the speckle reduction effect, the illumination waveform of the illumination pulse generator, and the drive waveform of the speckle modulator with respect to the elapsed time_effAnd speckle reduction effect, showing modulation amplitude factor M of speckle modulator₀2 > 1 and t_mod/M₀＝t_pw，illThe case (1).

Fig. 5 schematically shows the overall configuration of an endoscope system including the image pickup system of embodiment 1.

Fig. 6A schematically shows a configuration of a light guide characteristic modulator that changes the optical characteristics of laser light guided by the 1 st optical fiber by vibrating the 1 st optical fiber.

Fig. 6B schematically shows the structure of a light guide characteristic modulator that changes the optical characteristics of the laser light guided by the 1 st optical fiber by rotating the 1 st optical fiber.

Fig. 6C schematically shows the structure of a light guide characteristic modulator that changes the optical characteristics of laser light by changing the refractive index of the optical path between the collimator lens and the 2 nd fiber coupling lens.

Fig. 6D schematically shows the structure of a light guide characteristic modulator that changes the optical characteristics of laser light by changing the optical path length of the optical path between the collimator lens and the 2 nd fiber coupling lens.

Fig. 7 schematically shows the overall configuration of an endoscope system including the image pickup system of embodiment 2.

FIG. 8A shows an illumination waveform of an illumination pulse generator in a single pulse type pulse width modulation system, a driving waveform of a speckle modulator, and an effective modulation amplitude factor M which is an index of a speckle reduction effect_eff。

FIG. 8B shows the illumination waveform of the illumination pulse generator, the driving waveform of the speckle modulator, and the driving waveform of the speckle reduction effect in the multi-pulse division type pulse width modulation systemEffective modulation amplitude factor M_eff。

Fig. 9A schematically shows a speckle modulator constructed by combining the same two modulators.

Fig. 9B schematically shows a speckle modulator constructed by combining two modulators having different drive mechanisms but the same optical principle.

Fig. 9C schematically shows a speckle modulator configured by combining two modulators different in optical principle.

Fig. 10 schematically shows the overall configuration of the lighting device according to embodiment 4.

Fig. 11 schematically shows the overall configuration of a microscope system including the imaging system of embodiment 5.

Detailed Description

[ preparations for discussing effects of principal means ]

First, before discussing the structure or requirement for reducing speckle noise in detail, a general reduction mechanism of a speckle reduction effect by an illumination device or an imaging system using modulators of optical characteristics of various laser beams will be described with reference to fig. 1A, 1B, 1C, 2A, 2B, and 2C. In this specification, modulators of various optical characteristics such as: in order to reduce speckle, the intensity and intensity of an observed speckle pattern, the intensity distribution, or the position of the speckle pattern is changed by changing optical characteristics in an optical path from a light source to an observation object including optical characteristics of light emitted from the light source itself.

The magnitude of driving of the speckle modulator for causing modulation of various optical characteristics to obtain the speckle reduction is defined as "the driving intensity of the speckle modulator", and is denoted as I_mod. Here, specific examples of the "driving intensity of the speckle modulator" include a driving intensity of a wavelength modulation circuit of the laser light for causing expansion and contraction of an effective spectral width of the laser light or a shift of a wavelength of the laser light, a driving intensity of a phase modulator disposed in a middle of an optical path for guiding the laser light from the light source to the observation object for causing a change in a phase of the laser light, and a driving intensity of the laser light when the laser light is usedIn the case where the optical fiber is used as an optical path for guiding light from a light source to an observation object, the driving strength of a vibration device for changing the mechanical bending of the optical fiber to change the phase of the light, the driving strength of a stress applying device for changing the stress applied to the optical fiber, the driving strength of a rotating device for twisting the optical fiber, and the like are given.

Fig. 1A to 1C illustrate a speckle reduction mechanism caused by the presence of an optical fiber in the optical path of laser light reaching an observation object from a laser light source, mechanically vibrating the optical fiber.

Fig. 1A shows a speckle modulator constituted by a vibration device that vibrates an optical fiber. A vibration motor MT is provided to a fixing member, not shown, via a damper DP for absorbing vibration. A weight having an asymmetric center of gravity with respect to the rotation shaft is attached to the rotation shaft of the vibration motor MT. The contact member TP is fixed to the vibration motor MT. The abutment member TP is connected to the optical fiber FB. When the rotation shaft of the vibration motor MT rotates, the vibration motor MT vibrates. The vibration is transmitted to the optical fiber FB via the contact member TP. As a result, the optical fiber FB vibrates.

By vibrating the optical fiber FB in this way, the phase and the mode of the laser beam in the optical fiber FB are changed with time, and the speckle pattern can be changed with time (fig. 1B). In the image formed on the imaging surface, a speckle pattern that changes with time is observed in an overlapping manner over the time of one imaging frame, and therefore, the speckle pattern is averaged, and effective speckle noise on the imaging surface can be reduced. As shown in fig. 1B, when the change (or amount of movement) of the speckle pattern in the imaging time is sufficiently large and the state is considered to be a state in which the overlapping of the speckle patterns in the imaging time is sufficiently averaged, it is considered that the speckle reduction effect due to the overlapping of the speckle patterns in accordance with the time average is saturated even if the vibration amplitude is further increased.

FIG. 1C shows the results of experiments actually performed by the inventors, in particular, the measurement of the effective speckle contrast with respect to the vibration amplitude X of the optical fiber_mod，0The result obtained by the above-described variation. In accordance with the contents predicted in association with fig. 1B, the vibration amplitude is Δ X around a certain threshold value_mod，thThe maximum amplitude is obtained, and the speckle reduction effect hardly changes even if the amplitude is further increased, and a saturated result is obtained. In addition, in this experiment, the speckle contrast when imaging was performed over a long imaging time so that the speckle patterns were sufficiently overlapped in the imaging time was evaluated.

FIG. 2A shows wavelength at vibration amplitude λ_modThe spectrum of the laser light changing with time. FIG. 2B shows the vibration amplitude λ at the wavelength of the laser light shown in FIG. 2A_modThe corresponding one-dimensional light intensity distribution of the speckle pattern. FIG. 2C shows the amplitude of change Δ λ of the vibration amplitude of the effective speckle contrast with respect to the wavelength of the laser light_mod，0A change in (c). As shown in fig. 2B and 2C, the vibration amplitude λ when the wavelength of the laser light is increased_modIn the meantime, the light intensity distribution due to the speckle phenomenon becomes small (i.e., the speckle contrast becomes small). This is because modulating the wavelength of the laser light as a speckle modulator makes the width of the wavelength of the light integrated during the imaging time appear to be widened, which corresponds to effectively reducing the coherence of the laser light. The threshold value Δ λ corresponding to the wavelength change width for saturating the speckle reduction effect is determined according to the resolution of the imaging optical system and the imager_mod，thHowever, as in the case of fig. 1A to 1C, even if a further wavelength change is performed within the imaging time, the speckle reduction effect hardly changes.

In this specification, the effect of various speckle modulators for reducing speckle is discussed more generally, and the drive strength of the speckle modulator is I independently of the speckle modulator for reducing speckle noise_modSetting the driving intensity amplitude as I_mod，0In addition, the time period when the speckle modulator is periodically driven is set as a speckle modulation period t_mod. The width of the drive intensity corresponding to the condition that the reduction in speckle contrast is almost maximized and the speckle reduction effect is saturated at a further drive intensity is set as the drive intensity threshold amplitude Δ I of the speckle modulator_mod，thThe amplitude of change in the drive intensity of the speckle modulator corresponding to the exposure period of the imager within one imaging frame time is set asΔI_mod. (pulse light emission period t of light source is not limited within imaging frame time_pw，illInstead, the exposure period (or light accumulation period) t of the imager is limited_pw，expThus, the light amount adjustment by PWM can be performed, and in this case, the exposure period t can be set to be shorter_pw，expThe variation width of the inner drive strength is Δ I_mod) Furthermore, the drive intensity threshold amplitude Δ I of the speckle modulator will be utilized_mod，thAmplitude of driving intensity of speckle modulator_mod，0The normalized value is defined as the modulation amplitude factor M₀Will utilize Δ I_mod，thAmplitude of change Δ I of driving strength of speckle modulator_modThe normalized value is defined as the effective modulation amplitude factor M_eff。

In general, the exposure time t for the imager in one imaging frame is determined according to the above discussion_ONOr the pulse light emitting period t of the light source_pw，illWhen the speckle modulator is driven at a sufficiently fast cycle or the imaging timing of the imager, the driving timing of the speckle modulator, and the irradiation timing of the laser are optimally synchronized, the variation width Δ I of the driving intensity of the speckle modulator is increased_modAt a time of Δ I_modIs converted into Delta I_mod，thPreviously, the speckle reduction effect became monotonically higher, at Δ I_modIs converted into Delta I_mod，thIs saturated in the vicinity of (a). In addition, when the amplitude of change Δ I of the driving strength of the speckle modulator is increased_modEqual and increasing the effective modulation amplitude factor M_effThe speckle reduction effect is also M_effBecome monotonous all together, and when a single speckle reduction mechanism is operated, M is the number_effThe speckle reduction effect is considered to be almost saturated at > 1.

Furthermore, the drive strength threshold amplitude Δ I_mod，thThe displacement in vibration of a light guide member varying device, which will be described later, for applying mechanical variation to an optical fiber serving as a light guide member is 0.1mm, and therefore, the driving intensity amplitude I of the speckle modulator_mod，0The displacement of the optical fiber vibration caused by the light guide member varying device is preferably 0.1mm or more. This is the experimental core diameter Φ c of the optical fiber which is 0.02mm or so by 5 times, and therefore the amplitude I of the drive intensity of the speckle modulator_mod，0The displacement of the optical fiber due to vibration of the light guide member varying device is preferably 5 Φ c or more.

In addition, the drive strength threshold amplitude Δ I_mod，thThe amplitude I of the driving intensity of the speckle modulator is 10 ° when the angle of the twisted optical fiber is described later_mod，0The angle of the twisted optical fiber is preferably 10 ° or more.

When a refractive index change of a refractive index modulator (electro-optical element, acousto-optical element) described later is used as the speckle modulator, a change corresponding to 1 wavelength (2 pi as a phase) when passing through the refractive index modulator is considered to correspond to the drive intensity threshold width Δ I_mod，th. That is, when the optical wavelength is λ, the length on the optical axis of the refractive index modulation unit is Lm, the refractive index is n, and the amount of change in the refractive index is Δ n, it is desirable to perform modulation with Lm · Δ n/n/λ c ≧ 1. Therefore, when the length of the refractive index modulator in the light guiding direction is Lm, the change in the refractive index is Δ n/n, and the center wavelength of the spectrum of the illumination pulse is λ c, the driving intensity amplitude I of the speckle modulator is_mod，0When the refractive index of the refractive index modulator is changed, the desired value is Δ n/n ≧ λ c/Lm. As a typical example, when Lm is 5mm and λ c is 0.5 μm, the amount of change in refractive index is about 0.01%.

[ definition of terms to be discussed for summarizing the effect of the speckle modulator ]

〈I_mod: driving strength of speckle modulator-

Specifically, the present invention refers to the drive intensity of a wavelength modulation circuit for laser light for expanding the effective spectral width of the laser light or shifting the wavelength of the laser light, the drive intensity of an optical phase modulator disposed in the middle of the optical path for guiding the light from the light source to the observation target, the mechanical bending intensity for changing the phase of the light on the optical path when an optical fiber is used as the optical path for guiding the light from the light source to the observation target, the stress intensity, the bending intensity, and the like.

〈I_mod，0: of speckle modulatorsAmplitude of driving intensity >

When the speckle modulator is periodically driven, when the maximum value of the driving intensity of the speckle modulator is set to I_mod，maxSetting the minimum value as I_mod，minWhen it becomes I_mod，0＝I_mod，max-I_mod，min。

〈t_mod: speckle modulation period >

Is the time period when the speckle modulator is periodically driven.

〈ΔI_mod: amplitude of variation of driving strength of speckle modulator >

In an imaging system, the range of change in the drive intensity of a speckle modulator during the exposure period of an imager (or during the light accumulation period of the imager) in one imaging frame is set. In an illumination apparatus without an imager, the amplitude of change in the drive intensity of the speckle modulator in a time (33 msec in the case where a living body is a human) which is considered as a response time of the living body to an image change is set.

〈ΔI_mod，th: threshold amplitude of drive intensity for speckle modulator-

Is the magnitude of change in the drive strength for saturating the speckle reduction effect when the drive strength of the speckle modulator is increased.

〈M₀: modulation amplitude factor >

M₀＝I_mod，0/ΔI_mod，th

〈M_eff: effective modulation amplitude factor-

M_eff＝ΔI_mod/ΔI_mod，th

M_effSince the speckle reduction effect has a positive correlation with the speckle reduction effect, the speckle reduction effect can be used as an index of the speckle reduction effect. In addition, when a single speckle reduction mechanism is operated, M is_effThe speckle reduction effect is almost saturated when the value is more than or equal to 1.

Fig. 3a1 and 3a2, 3B1 and 3B2, 3C1 and 3C2 illustrate "driving amplitude of speckle modulator" and "driving amplitude of speckle modulator" with respect to the aforementioned timing of image pickup, illumination, modulation“M_effAnd speckle reduction effect ″, FIGS. 3A1 and 3A2 show M₀< 1 case, FIG. 3B1 and FIG. 3B2 show M₀Fig. 3C1 and 3C2 show M for the case of 1₀2 > 1. In fig. 3a1 and 3a2, 3B1 and 3B2, and 3C1 and 3C2, the upper layer shows a drive waveform of the speckle modulator with respect to elapsed time, the middle layer shows an illumination waveform of the illumination pulse generator optimally synchronized with the drive waveform at a time axis, and the lower layer shows M, which is an index of the speckle reduction effect, with respect to the center timing of the illumination pulse generator_effAnd speckle reduction effects. Here, M_effThe integral value of the irradiation waveform corresponding to the center timing of the irradiation timing. Fig. 3a1, 3B1, and 3C1 show pulse widths (i.e., pulse light emission periods) t of irradiation waveforms_pw，illShorter than half the modulation period of the speckle modulator (t)_mod/2＞t_pw，ill) Fig. 3a2, 3B2, and 3C2 show pulse widths (i.e., pulse light emission periods) t of irradiation waveforms_pw，illThe case equal to half the modulation period of the speckle modulator (t)_mod/2＝t_pw，ill). In fig. 3a1 and 3a2, 3B1 and 3B2, and 3C1 and 3C2, the value of the speckle reduction effect is proportional to the reciprocal of the speckle contrast, and is shown by normalizing the speckle contrast at which the speckle reduction effect of the speckle modulator is maximized. Therefore, the numerical value of the speckle reduction effect is rendered to be 1 under the condition that the reduction effect of the speckle modulator is saturated and maximized.

From the above description, it is desirable that the timing of exposure by the imager is synchronized with the irradiation timing, and the exposure period needs to include at least a part of the irradiation period, and desirably includes all of the irradiation period. (synchronization may not be necessary, e.g., if at t_pw，expIf the relationship of having a plurality of irradiation pulses is established, the speckle reduction effect is obtained even if the periods are asynchronous. )

On the contrary, when PWM is applied during exposure of the imager, the light emission period t of the light source is set by fig. 3a1 and 3a2, 3B1 and 3B2, 3C1 and 3C2_pw，illReplacement by exposure period t of imager_pw，expThis can provide the same speckle reduction effect. In this case, t is of course required vice versa_pw，illIncluding t_pw，expA part or all of.

The same can be said for fig. 4a1 and 4a2, fig. 4B1 and 4B2, and fig. 4C1 and 4C2, which will be described later.

The contents known from fig. 3a1 and 3a2, 3B1 and 3B2, 3C1 and 3C2 are summarized and collated as follows.

When increasing M₀、M_effWhen the driving amplitude or the driving width of the speckle modulator is increased, the speckle reduction effect is monotonously increased.

When the amplitude of change Δ I of the drive strength of the speckle modulator is measured in terms of time axis_modThe increased mode maximizes speckle reduction when synchronizing the speckle modulator with the illumination pulse generator.

If the pass is set to M_effThe speckle reduction effect can be maximized by optimizing the timing of the imaging, illumination, and modulation to 1 or more. In addition, when M is formed_effUnder the condition of more than or equal to 1, the speckle reduction effect is saturated, the timing dependence of image pickup, illumination and modulation is small, and the stable speckle reduction effect is obtained.

Therefore, M is increased to optimize the driving timing of the speckle modulator, the timing of illumination, and the timing of image capturing_effAnd a synchronous controller is provided to fully exert the speckle reduction effect. Here, the timing of illumination refers to the timing of the pulse light emission period generated by the illumination pulse generator, and the timing of image capturing refers to the light reception timing of the imager within one image capturing frame.

As a method of performing the synchronization control for optimizing the timing of image capturing, the timing of illumination, and the timing of driving the speckle modulator described above, various synchronization methods such as the following method can be applied: 1) a method of synchronizing the timing of illumination and the timing of driving the speckle modulator at a predetermined timing with the timing of imaging as a main time; 2) a method of synchronizing the timing of image capturing and the timing of driving the speckle modulator at a predetermined timing with the timing of illumination as a main timing; 3) a method of synchronizing the timing of image pickup and the timing of driving the speckle modulator at a predetermined timing with the timing of driving the speckle modulator as a main time; 4) a method of synchronizing the timing of image pickup, the timing of illumination, and the timing of driving the speckle modulator with the system clock of the illumination device and the imaging system as the master time.

In addition, regarding the cycle (frame rate) 1/f of image pickup_rA generation period t of the illumination pulse_pDriving period t of speckle modulator_modThese periods need not be the same as long as they can achieve the synchronization described above.

Fig. 4a1 and 4a2, 4B1 and 4B2, 4C1 and 4C2 will illustrate the timing of the aforementioned image capture, illumination, modulation amplitude factor M of the speckle modulator₀As parameters, "modulation speed and M of speckle Modulator" are explained_effAnd speckle reduction effect ", fig. 4a1 and 4a2 show that the modulation speed of the speckle modulator is relatively slow and t_mod/2M₀＞t_pw，ill4B1 and 4B2 show that the modulation speed of the speckle modulator is exactly and t_mod/2M₀＝t_pw，illFig. 4C1 and 4C2 show that the modulation speed of the speckle modulator is relatively fast and t_mod/M₀＝t_pw，illThe case (1). In fig. 4a1 and 4a2, 4B1 and 4B2, 4C1 and 4C2, the upper layer shows the drive waveform of the speckle modulator with respect to the elapsed time, the middle layer shows the illumination waveform of the illumination pulse generator with respect to the time axis, and the lower layer shows the modulation amplitude factor M effective as an index of the speckle reduction effect with respect to the illumination timing of the illumination pulse generator_effAnd speckle reduction effects. Here, fig. 4a1, 4B1, and 4C1 show the modulation amplitude factor M of the speckle modulator₀Fig. 4a2, 4B2, and 4C2 show the modulation amplitude factor M of the speckle modulator at 1₀2 > 1. Further, in fig. 4a1 and 4a2, 4B1 and 4B2, 4C1 and 4C2, the value of the speckle reduction effect is proportional to the reciprocal of the speckle contrast, and the speckle reduction effect by the speckle modulator is utilizedThe speckle contrast that becomes the maximum is normalized to show the speckle reduction effect. Therefore, the numerical value of the speckle reduction effect is rendered to be 1 under the condition that the reduction effect of the speckle modulator is saturated and maximized.

The contents known from fig. 4a1 and 4a2, 4B1 and 4B2, 4C1 and 4C2 are summarized and organized as follows.

Even at t_mod＞2M₀t_pw，illAlso in the case of (2), when the speckle modulator is synchronized with the illumination pulse generator, the speckle reduction effect is most effectively exerted. However, at M_effIf < 1, the speckle reduction effect cannot be reduced to a degree at which it is saturated.

By addition of M₀Drive the speckle modulator by more than or equal to 1 even if t is not the same_mod＜2t_pw，illThe speckle modulator is driven in such a high-speed manner, even at a speed M slower than that of the speckle modulator₀Conditions for doubling (t)_mod≤2M₀t_pw，ill) By synchronizing the speckle modulator and the illumination pulse generator, the effect of the maximum level of speckle reduction effect saturation can also be exhibited.

In M₀1 or more of the speckle modulator is driven and t_mod≤M₀t_pw，illIn the case of (2), the speckle reduction effect can be stably brought close to the maximum value without depending on the timing of the synchronization control.

Irrespective of the modulation amplitude factor M₀In the conventional method for considering the concept of (1), if t is not satisfied, it is considered that_mod＜t_pw，illThe speckle reduction effect cannot be maximized and does not vary in time, but even if the modulation speed of the speckle modulator is slowed down by M₀Doubling (or shortening the pulse light emission period by M)₀Multiple), the speckle reduction effect can be stable and maximized.

As described above, the driving period t of the speckle modulator_modTiming the light emitting period t in the lighting device due to the pulse_pw，illAnd its timing greatly affects the speckle reduction effect. Also, the driving period t of the speckle modulator_modTiming in an imaging system with an imager due to an exposure period t_pw，expAnd its timing greatly affects the speckle reduction effect.

Therefore, in the following embodiments, even if the pulse light emission period is entirely replaced with the pulse light emission period or the exposure period t of the imager_pw，expOr any of their overlapping portions, is also true.

[ embodiment 1]

Fig. 5 schematically shows the overall configuration of an endoscope system including the image pickup system of embodiment 1.

The endoscope system 300 includes an endoscope body 310 and an endoscope controller 320. The endoscope scope portion 310 and the endoscope controller portion 320 are coupled by a scope portion connector 312 and a controller portion connector 322.

The imaging system 100 of the present embodiment includes: an illumination device 102 that illuminates an observation target 190; and an imaging device 104 that images the observation target 190 illuminated by the illumination device 102.

In fig. 5, the scope portion connector 312 and the controller portion connector 322 that connect the endoscope scope portion 310 and the endoscope controller portion 320 are depicted as being integrated with each other, but the endoscope scope portion 310 side and the endoscope controller portion 320 side of the illumination device 102 and the endoscope scope portion 310 side and the endoscope controller portion 320 side of the imaging device 104 may be connected by separate connectors.

The illumination device 102 includes: an illumination light generator 110 that generates illumination light of coherent light; a light guide optical system 120 that guides the coherent light emitted from the illumination light generator 110; and a light distribution optical system 140 that adjusts the light distribution of the coherent light guided by the light guide optical system 120 and emits the adjusted light.

The illumination light generator 110 includes a laser light source 112 that emits laser light as coherent light, and a driver 114 that drives the laser light source 112. The illumination light generator 110 emits light in a predetermined pulse emission period t for generating coherent light_pw，illThe illumination pulse generator of (3). In the following description, unless otherwise specifiedThe illumination light generator 110 is constituted by an illumination pulse generator.

The light guide optical system 120 includes the 1 st optical fiber 124 and the 2 nd optical fiber 130 as light guide members for guiding coherent light. The light guide member is not limited to an optical fiber, and instead, for example, a flexible waveguide may be applied. The light guide optical system 120 further includes: a1 st fiber coupling lens 122 for coupling the coherent light emitted from the laser light source 112 to the optical fiber 124; a collimator lens 126 for collimating the light beam emitted from the 1 st optical fiber 124; and a2 nd fiber coupling lens 128 for coupling the light beam collimated by the collimating lens 126 with a2 nd fiber 130. The 1 st fiber coupling lens 122, the collimator lens 126, and the 2 nd fiber coupling lens 128 are schematically illustrated as 1 lens in fig. 5, but may actually be constituted by 1 lens or a plurality of lenses.

The imaging device 104 includes: with a predetermined exposure period t_pw，expAn imager 150 for taking a picture; an image processing circuit 160 that performs necessary image processing on image information acquired by the imager 150; and a display 170 for displaying the image processed by the image processing circuit 160.

The laser light emitted from the laser light source 112 is condensed by the 1 st fiber coupling lens 122, enters the 1 st optical fiber 124, and is guided by the 1 st optical fiber 124. The laser beam emitted from the 1 st optical fiber 124 is converted into a parallel beam by the collimator lens 126, propagates through the space, is condensed by the 2 nd fiber coupling lens 128, enters the 2 nd optical fiber 130, and is guided by the 2 nd optical fiber 130. The laser light guided by the light guide optical system 120 is emitted with its light distribution adjusted by the light distribution optical system 140. The light L1 emitted from the light distribution optical system 140 is irradiated to the observation target 190.

The light L1 irradiated to the observation object 190 is reflected, diffracted, scattered, or the like by the observation object 190. A part L2 of the light reflected, diffracted, scattered, or the like by the observation target 190 enters the imager 150. The imager 150 acquires image information of the observation object 190 based on the light L2 received from the observation object 190. The image information acquired by the imager 150 is subjected to image processing by the image processing circuit 160 and then displayed on the display 170.

In an imaging system using coherent light, when an observation target has a scattering structure such as a slight unevenness, speckle is generated on an imaging surface of an imager, and appears as speckle noise in an acquired image. This phenomenon is not limited to an electronic imaging system, but also occurs on the retina of a living body corresponding to an imaging surface, and therefore, the same problem occurs in an illumination device using coherent light. The speckle is caused by interference of light scattered from irregularities or the like of an observation target, and a fine bright and dark pattern is formed on an imaging surface and a retina.

In order to reduce the speckle noise, the illumination device 102 includes a speckle modulator 200 that modulates speckle caused by coherent light.

The speckle modulator 200 may be configured by, for example, a light guide characteristic modulator that changes the optical characteristics of coherent light guided by the light guide optical system 120. Alternatively, the speckle modulator 200 may be a wavelength modulator that changes the optical characteristics of coherent light.

The light guide characteristic modulator may be constituted by, for example, a phase modulator that changes the phase of coherent light guided by the light guide optical system 120 with time. The phase modulator may be constituted by, for example, a light guide member varying device that applies mechanical variation to a light guide member included in the light guide optical system 120 that guides coherent light. The mechanical variation applied to the light-guiding member may be, for example, vibration, rotation or torsion. Alternatively, the phase modulator may be constituted by a refractive index modulator that changes the refractive index of a part of the light guide optical system 120 for guiding coherent light with time. The refractive index modulator may for example have an electro-optical element or an acousto-optical element. The phase modulator may further have, for example, a concavo-convex plate having concavities and convexities larger than 1/10 which is the wavelength of the coherent light. Alternatively, the phase modulator may be constituted by a wavelength modulator that changes the wavelength of the coherent light emitted from the illumination light generator 110 with time.

In the present embodiment, the speckle modulator 200 includes: a1 st light guiding characteristic modulator 210 disposed in a middle portion between both ends of the 1 st optical fiber 124; and a2 nd light guiding characteristic modulator 220 disposed on the optical path of the collimated light beam between the collimator lens 126 and the 2 nd fiber coupling lens 128. The speckle modulator 200 further includes a wavelength modulator 230 that changes the wavelength of the laser light emitted from the laser light source 112 with time.

The wavelength modulator 230 is composed of the laser light source 112 having a variable wavelength and a wavelength modulation circuit 232, and the wavelength modulation circuit 232 controls the laser light source 112 so that the wavelength of the laser light emitted from the laser light source 112 changes with time. The structures of the 1 st light guiding characteristic modulator 210 and the 2 nd light guiding characteristic modulator 220 will be described later with reference to fig. 6A to 6D.

The speckle modulator 200 does not have to include all of the 1 st light guiding characteristic modulator 210, the 2 nd light guiding characteristic modulator 220, and the wavelength modulator 230, and may include at least one of them.

The illumination device 102 further includes a synchronization controller 240, and the synchronization controller 240 controls the illumination light generator 110 and the speckle modulator 200 in synchronization with the pulse generation timing of the illumination light generator 110 and the driving timing of the speckle modulator 200. For example, the synchronization controller 240 controls the pulse generation timing of the illumination light generator 110 in synchronization with the driving timing of the 1 st light guiding characteristic modulator 210 and/or the 2 nd light guiding characteristic modulator 220. Further, the synchronization controller 240 can also control the illumination light generator 110, the speckle modulator 200, and the imager 150 in synchronization with the pulse generation timing of the illumination light generator 110, the driving timing of the speckle modulator 200, and the imaging timing of the imager 150.

A synchronization controller 240 is provided so as to make even the amplitude I of the driving intensity of the speckle modulator 200_mod，0And a pulse light emission period t of the illumination light generator 110_pw，illThere are restrictions on optimizing the driving timing of the speckle modulator 200, the timing of illumination, and the timing of image capture, and increasing M_effThe speckle reduction effect is fully exerted.

Here, the timing of illumination refers to the timing in time of the pulse light emission period generated by the illumination light generator 110, and the timing of image capturing refers to the light reception timing of the imager 150 within one image capturing frame.

As a method of performing the synchronization control for optimizing the timing of image capturing, the timing of illumination, and the timing of driving the speckle modulator described above, various synchronization methods such as the following method can be applied: 1) a method of synchronizing the timing of illumination and the timing of driving the speckle modulator at a predetermined timing with the timing of imaging as a main time; 2) a method of synchronizing the timing of image capturing and the timing of driving the speckle modulator at a predetermined timing with the timing of illumination as a main timing; 3) a method of synchronizing the timing of image pickup and the timing of driving the speckle modulator at a predetermined timing with the timing of driving the speckle modulator as a main time; 4) a method of synchronizing the timing of image pickup, the timing of illumination, and the timing of driving the speckle modulator with the system clock of the illumination device and the imaging system as the master time.

In addition, regarding the cycle (frame rate) 1/f of image pickup_rA generation period t of the illumination pulse_pDriving period t of speckle modulator_modThe same is not necessarily required as long as the synchronization described above can be achieved. For example, n is a natural number and is 1/f_r＝2n·t_p＝2n·t_modAnd t_p＝2n·t_modEven if the mutual period is an integral multiple, the relationship can be applied. (the case where a plurality of illumination pulses are generated in 1 frame is explained in embodiment 2.) furthermore, here, an imaging system is considered in which a plurality of illumination pulses are distributed at t_onHowever, in an illumination device (a photographic device for visual observation) having no imager, a desired effect is obtained by multi-pulse division. In this case, the effective pulse light emission period t_pw，effCan be defined as the start of the next illumination pulse from the widest pulse interval to the end of the last illumination pulse. In other words, the effective pulse light emission period t_pw，effIt can be said that the period from the lighting time of the first illumination pulse to the extinguishing time of the last illumination pulse in one illumination pulse group.

Fig. 6A, 6B, 6C, and 6D show examples of the structure of a light guide characteristic modulator functioning as a speckle modulator. Among them, fig. 6A and 6B show a configuration example of the 1 st light guiding characteristic modulator 210 disposed at an intermediate position of the optical fiber, and fig. 6C and 6D show a configuration example of the 2 nd light guiding characteristic modulator 220 disposed on the optical path between the collimator lens 126 and the 2 nd fiber coupling lens 128.

Fig. 6A schematically shows the structure of the light guide characteristic modulator 210A that changes the optical characteristics of the laser light guided by the 1 st optical fiber 124 by vibrating the 1 st optical fiber 124.

The light guide characteristic modulator 210A includes: a light guide member changing device 2110 for applying mechanical change to the 1 st optical fiber 124 for guiding the laser beam; and an actuator 2130 for driving the light guide member varying device 2110. Here, the light guide member varying device 2110 is an optical fiber vibrating device that applies vibration to the 1 st optical fiber 124. The light guide member varying device 2110 includes a vibration motor 2112. The vibration motor 2112 is provided on a vibration absorber 2118 that absorbs vibrations. The damper 2118 is provided to a fixing member not shown. A weight 2116 is attached to a rotation shaft 2114 of the vibration motor 2112, and the weight 2116 has an asymmetric center of gravity with respect to the rotation shaft 2114. An abutment member 2120 is fixed to the vibration motor 2112. The abutment member 2120 is in contact with the 1 st optical fiber 124.

When the vibration motor 2112 receives a current from the driver 2130 via the electric wiring 2140, the rotation shaft 2114 rotates. A weight 2116 having an asymmetric center of gravity is attached to the rotation shaft 2114, and therefore, when the rotation shaft 2114 rotates, the vibration motor 2112 vibrates. The vibration is transmitted to the optical fiber 124 via the contact member 2120. As a result, the 1 st optical fiber 124 is vibrated. Accordingly, since the bending of the 1 st optical fiber 124 changes periodically, the phase and the mode of the laser light guided by the 1 st optical fiber 124 change with time.

In the light guiding characteristic modulator 210A, it is preferable that the driving intensity amplitude I of the light guiding characteristic modulator 210A is set to Φ c when the core diameter of the 1 st optical fiber 124 is set_mod，0The displacement of the 1 st optical fiber 124 caused by the light guide member varying device 2110 is 5 Φ c or more.

In addition, the drive intensity amplitude I of the light guide characteristic modulator 210A_mod，0Can be changed as followsLarge: the vibration amplitude X is increased by increasing the centrifugal force by increasing the rotation speed of the vibration motor 2112, and utilizing this principle_mod，0And the like. Alternatively, when the weight 2116 is attached to the periphery of the rotation shaft 2114 of the vibration motor 2112 via an elastic member, the weight 2116 is configured such that the asymmetry of the center of gravity of the weight 2116 with respect to the rotation shaft 2114 increases along with the increase in the rotation speed of the vibration motor 2112. Therefore, when the rotation speed of the vibration motor 2112 is increased, the vibration amplitude becomes further larger.

Fig. 6B schematically shows the structure of the light guide characteristic modulator 210B that changes the optical characteristics of the laser light guided by the 1 st optical fiber 124 by rotating the 1 st optical fiber 124.

The light guide characteristic modulator 210B includes: a light guide member changing device 2150 for mechanically changing the 1 st optical fiber 124 for guiding the laser beam; and an actuator 2170 for driving the light guide member changing device 2150. Here, the light guide member changing device 2150 is an optical fiber rotating device that applies reciprocating rotation to the 1 st optical fiber 124. The light guide member changing device 2150 includes a rotation motor 2152. The rotary motor 2152 is provided on a fixed member not shown. A gear 2156 is attached to a rotating shaft 2154 of the rotary motor 2152. The gear 2156 meshes with a gear 2158 fixed to the 1 st optical fiber 124.

When the rotary motor 2152 receives a current from the driver 2170 via the electric wiring 2180, the rotary shaft 2154 periodically rotates clockwise and counterclockwise in a predetermined angular range. This reciprocating rotational motion is transmitted to a gear 2158 fixed to the 1 st optical fiber 124 via a gear 2156. As a result, the 1 st optical fiber 124 is rotated back and forth. Accordingly, the 1 st optical fiber 124 is periodically twisted around the axis, and thus the phase and mode of the laser light guided by the 1 st optical fiber 124 change with time.

In the light guiding characteristic modulator 210B, it is preferable that the driving intensity amplitude I of the light guiding characteristic modulator 210B is_mod，0The angle of the twisted 1 st optical fiber 124 is 10 ° or more.

Drive intensity amplitude I of light guide characteristic modulator 210B_mod，0Can be increased by: by enlarging the rotary motor 2152 to increase the torsional amplitude theta_mod，0And the like.

Fig. 6C schematically shows the structure of the light guide characteristic modulator 220A that changes the optical characteristics of the laser light by changing the refractive index of the optical path between the collimator lens 126 and the 2 nd fiber coupling lens 128.

The light guiding characteristic modulator 220A includes: a refractive index modulator 2210 disposed on an optical path between the collimator lens 126 and the 2 nd fiber coupling lens 128; and a driver 2220 that drives the refractive index modulator 2210. The refractive index modulator 2210 is an optical element that changes the refractive index of the optical path of the laser light passing through the refractive index modulator 2210 with time. The refractive index modulator 2210 may be constituted of, for example, an electro-optical element. Or the refractive index modulator 2210 may be constituted by an acousto-optic element, for example. The refractive index modulator 2210 includes an optical medium 2212 transmitting laser light and a driving electrode 2214 provided to the optical medium 2212.

The refractive index modulator 2210 periodically changes the refractive index of the optical medium 2212 with a change over time when an alternating voltage is applied from the driver 2220 to the driving electrode 2214 via the electric wiring 2230. Thereby, the phase of the laser light passing through the optical medium 2212 changes with time.

In the light guiding characteristic modulator 220A, it is preferable that the driving intensity amplitude I of the light guiding characteristic modulator 220A is set to Lm, the change in refractive index is set to Δ n/n, and the center wavelength of the spectrum of the illumination pulse is set to λ c, where the length of the refractive index modulator 2210 in the light guiding direction is set to Lm_mod，0When the refractive index of the refractive index modulator 2210 is changed, Δ n/n is not less than λ c/Lm.

Drive intensity amplitude I of light guide characteristic modulator 220A_mod，0Can be controlled according to the magnitude of the applied voltage applied to the refractive index modulator 2210.

Fig. 6D schematically shows the configuration of the light guide characteristic modulator 220B that changes the optical characteristics of the laser light by changing the optical path length of the optical path between the collimator lens 126 and the 2 nd fiber coupling lens 128.

The light guiding characteristic modulator 220B includes: a refractive index modulator 2240 arranged on an optical path between the collimator lens 126 and the 2 nd fiber coupling lens 128; and a driver 2260 driving the refractive index modulator 2240. Refractive index modulator 2240 has phase difference disk 2250 arranged on the optical path. The phase difference disc 2250 has an uneven pattern 2252, and the uneven pattern 2252 has unevenness larger than 1/10, which is the wavelength of laser light. The phase difference disc 2250 is supported to be rotatable about an axis deviated from the optical path. A gear 2254 is formed on the outer periphery of the phase difference disc 2250. Refractive index modulator 2240 further has rotation motor 2242 that rotates phase difference disk 2250. The rotary motor 2242 is provided on a fixed member not shown. A gear 2246 is attached to a rotation shaft 2244 of the rotation motor 2242. Gear 2246 meshes with gear 2254 of phase difference disc 2250.

When the rotation motor 2242 receives supply of electric current from the driver 2260 via the electric wiring 2270, the rotation shaft 2244 rotates. This rotational motion is transmitted to gear 2254 formed in phase difference disc 2250 via gear 2246. As a result, the phase difference disc 2250 is rotated, and the uneven pattern 2252 moves across the optical path. Accordingly, the optical path length of the laser beam passing through the phase difference disc 2250 changes periodically, and thus the phase of the laser beam changes with time.

The drive intensity amplitude I of the light guide characteristic modulator 220B can be increased by increasing the applied voltage to the rotation motor 2242 to increase the rotation speed_mod，0。

In the imaging system 100 shown in fig. 5, when any one of the light guiding characteristic modulators 210A, 210B, 220A, and 220B shown in fig. 6A to 6D is mounted as the speckle modulator 200, the speckle modulator 200 has the following operation and effect as described with reference to fig. 1A to 1C, fig. 2A to 2C, and fig. 3a1 to 3C 2.

When the amplitude of change Δ I of the driving strength of the speckle modulator 200 is increased_modAt a time of Δ I_modIs converted into Delta I_mod，thThe speckle reduction effect becomes high before, at Δ I_modIs converted into Delta I_mod，thIs saturated in the vicinity of (a).

When Δ will be utilized_Imod，thVarying the drive strength of the speckle modulator 200Amplitude Δ I_modThe normalized value is set as the effective modulation amplitude factor M_effIf (by increasing the amplitude of change Δ I of the driving strength of the speckle modulator 200)_mod) Increasing the effective modulation amplitude factor M_effThe speckle reduction effect is also equal to M_effIs raised together at M_effThe speckle reduction effect is considered almost saturated > 1.

In addition, the first and second substrates are,

when increasing M₀、M_effWhen the driving amplitude and the driving amplitude of the speckle modulator 200 are increased, the speckle reduction effect is improved.

Therefore, when the amplitude Δ I of the change in the driving strength of the speckle modulator 200 is used_modWhen the speckle modulator 200 is synchronized with the illumination light generator 110 in the enlarged manner, the speckle reduction effect becomes maximum.

If the pass is set to M_effThe speckle reduction effect can be maximized by optimizing the timing of the imaging, illumination, and modulation to 1 or more. In addition, when M is formed_effUnder the condition of more than or equal to 1, the speckle reduction effect is saturated, the timing dependence of image pickup, illumination and modulation is small, and the stable speckle reduction effect is obtained.

As described with reference to fig. 4a1 to 4C2, the driving period t of the speckle modulator_modPulse light emission period t_pw，illModulating the amplitude factor M₀The speckle reduction effect is as follows.

Even at t_mod＞2M₀t_pw，illEven when the speckle modulator 200 is synchronized with the illumination light generator 110, the speckle reduction effect can be most effectively exhibited. However, at M_effIf < 1, the speckle reduction effect cannot be reduced to a degree at which it is saturated.

By addition of M₀The speckle modulator 200 is driven at 1 or more even if t is not t_mod＜2t_pw，illThe speckle modulator 200 is driven at such a high speed, even M slower₀Conditions for doubling (t)_mod≤2M₀t_pw，ill) By making the speckle modulator 200 optically coupled with the illumination lightThe synchronization of the image forming devices 110 also enables the maximum level of saturation of the speckle reduction effect to be exhibited.

In M₀1 or more of the speckle modulator 200 and t_mod≤M₀t_pw，illIn the case of (2), the speckle reduction effect can be stably brought close to the maximum value without depending on the timing of the synchronization control.

As described above, the imaging system 100 according to the present embodiment can vary the pulse light emission period t of the illumination light generator 110_pw，illThe light quantity adjustment based on PWM can be performed according to t of the imager 150_pw，expThe light amount adjustment based on PWM is performed.

During the pulse light emission period t according to the illumination light generator 110_pw，illWhen the light amount adjustment is performed by PWM, the imaging system 100 of the present embodiment operates as follows.

The synchronous controller 240 controls so that the pulse light emission period t of at least each illumination pulse_pw，illCausing the speckle modulator 200 to act.

Speckle modulator 200 causes the driving strength I of speckle modulator 200_modPeriodically changing. Drive intensity amplitude I of speckle Modulator 200_mod，0Is preferably set to the drive strength threshold amplitude Δ I_mod，thThe above. For example, the drive intensity amplitude I of the speckle modulator 200_mod，0Is set so that the pulse light-emitting period t_pw，illAmplitude of change Δ I of driving strength of internal speckle modulator 200_modBecomes the driving strength threshold amplitude Delta I_mod，thThe above values.

In order to improve the speckle reduction effect, the synchronization controller 240 performs control such that at least the pulse generation timing of the illumination light generator 110 is synchronized with the drive timing of the speckle modulator 200, as follows.

The synchronization controller 240 performs control such that the exposure period t of the imager 150_pw，expCausing the illumination light generator 110 to generate illumination pulses.

During the pulse light-emitting period t_pw，illIs less than the speckle modulation period t_mod1/2, the synchronous controller 240 emits light in pulses for a period t_pw，illDrive intensity I comprising speckle Modulator 200_modThe illumination light generator 110 and the speckle modulator 200 are controlled so as to substantially maximize the change rate of (b). For example, the synchronous controller 240 emits light with a pulse for a period t_pw，illBecomes the driving strength I of the speckle modulator 200_modThe illumination light generator 110 and the speckle modulator 200 are controlled so as to substantially maximize the change rate of (b). (Condition A) or during a pulse light emission period t_pw，illIs less than the speckle modulation period t_mod1/2, the synchronization controller 240 controls the speckle modulator 200 to drive at the driving strength I_modNeither of the maximum value nor the minimum value of (d) is included in the pulse emission period t_pw，illThe illumination light generator 110 and the speckle modulator 200. For example, the synchronous controller 240 emits light with a pulse for a period t_pw，illDrive intensity I comprising speckle Modulator 200_modThe illumination light generator 110 and the speckle modulator 200 are controlled so as to take a value at the time of the center of the substantially maximum value and the minimum value. Especially, the synchronous controller 240 emits light with a pulse for a period t_pw，illBecomes the driving strength I of the speckle modulator 200_modThe illumination light generator 110 and the speckle modulator 200 are controlled so as to take a value at the time of the center of the substantially maximum value and the minimum value. (Condition B)

In addition, in the pulse light emitting period t_pw，illModulating the period t for the speckle_modWhen the period is equal to or longer than 1/2, the synchronous controller 240 emits light in pulses for a period t_pw，illDrive intensity I comprising speckle Modulator 200_modThe illumination light generator 110 and the speckle modulator 200 are controlled so that the timing of the maximum value and the timing of the minimum value are taken. (Condition C)

There may also be one or more illumination pulses with different time delays synchronized to the speckle modulator 200. Less than t during the pulse light emission_mod1/2 (1), either (condition a) or (condition B) may be satisfied. For example, in the initial illumination pulseIn the case where the 2 nd illumination pulse arrives right after the half-cycle of the pulse, if the initial illumination pulse includes the driving intensity I of the speckle modulator 200_modWhen the (absolute value of the) slope of (b) becomes maximum, the 2 nd illumination pulse also includes the driving intensity I of the speckle modulator 200_modWhen (the absolute value of) the slope of (B) becomes maximum (see fig. 3B 1). During the pulse light emission period is t_modWhen the value is equal to or greater than 1/2, the condition (C) may be satisfied.

The synchronization controller 240 controls the pulse generation timing of the illumination light generator 110, the driving timing of the speckle modulator 200, and the imaging timing of the imager 150 in synchronization with each other. Synchronization controller 240 is clocked by M₀The speckle modulator 200 and the illumination light generator 110 are driven by ≧ 1. In addition, the synchronization controller 240 is synchronized with t_mod≤2M₀t_pw，illThe speckle modulator 200 and the illumination light generator 110 are driven. Or synchronize controller 240 with t_pw，ill＜t_mod≤M₀t_pw，illThe speckle modulator 200 and the illumination light generator 110 are driven.

The above is the pulse light emission period t according to the illumination light generator 110_pw，illThe operation in the case of performing the light amount adjustment by PWM will be described, but instead, t is the time t of the imager 150_pw，expWhen the light amount adjustment is performed by PWM, the imaging system 100 according to the present embodiment operates as follows. In this case, the illumination light generator 110 does not necessarily have to emit light for a predetermined pulse light emission period t during which coherent light is generated_pw，illThe illumination pulse generator of (3).

The synchronous controller 240 controls so that at least during the exposure period t_pw，expCausing the speckle modulator 200 to act.

Speckle Modulator 200 causes the drive Strength I of the speckle Modulator_modPeriodically changing. Drive intensity amplitude I of speckle Modulator 200_mod，0Is set to the driving strength threshold amplitude Delta I_mod，thThe above. For example, the drive intensity amplitude I of the speckle modulator 200_mod，0Is set so that the exposure period t_pw，expInternal speckle modulationAmplitude Δ I of variation in drive strength of the brake 200_modBecomes the driving strength threshold amplitude Delta I_mod，thThe above values.

The synchronization controller 240 performs control so as to synchronize at least the imager 150 and the speckle modulator 200 as follows in order to improve the speckle reduction effect.

During the exposure period t_pw，expIs less than the speckle modulation period t_mod1/2, the synchronous controller 240 exposes the light for a period t_pw，expDrive intensity I comprising speckle Modulator 200_modThe imager 150 and the speckle modulator 200 are controlled so that the change rate of (c) becomes substantially the maximum. For example, the controller 240 is synchronized with the exposure period t_pw，expBecomes the driving strength I of the speckle modulator 200_modThe imager 150 and the speckle modulator 200 are controlled so that the change rate of (c) becomes substantially the maximum.

Or during the exposure period t_pw，expIs less than the speckle modulation period t_mod1/2, the synchronization controller 240 controls the speckle modulator 200 to drive at the driving strength I_modNeither of the maximum value nor the minimum value of (d) is included in the exposure period t_pw，expTo control the imager 150 and the speckle modulator 200. For example, the controller 240 is synchronized with the exposure period t_pw，expDrive intensity I comprising speckle Modulator 200_modThe imager 150 and the speckle modulator 200 are controlled in such a way that the time of the value of the center of the substantially maximum value and the minimum value is taken. In particular, the controller 240 is synchronized with the exposure period t_pw，expBecomes the driving strength I of the speckle modulator 200_modThe imager 150 and the speckle modulator 200 are controlled in such a way that the time of the value of the center of the substantially maximum value and the minimum value is taken.

In addition, during the exposure period t_pw，expIs the speckle modulation period t_modThe synchronous controller 240 uses the exposure period t in the case of the period above 1/2_pw，expDrive intensity I comprising speckle Modulator 200_modThe imaging device 150 is controlled by taking the time of the maximum value and the time of the minimum valueThe speckle modulator 200.

In the imaging system 100 according to the present embodiment, the speckle noise can be stably and effectively reduced by the operation of the above configuration. Further, a structure for reducing speckle noise can be added stably and efficiently to an existing illumination device and imaging system without a large cost. In addition, even the driving intensity amplitude I of the speckle modulator 200_mod，0And a pulse light emission period t of the illumination light generator 110_pw，illThere is a restriction in increasing M by optimizing the driving timing of the speckle modulator 200, the timing of illumination, and the timing of image capturing_effThereby, the speckle reduction effect can be sufficiently exhibited. In particular, speckle noise can be reduced stably and effectively even in a short exposure period or a short pulse emission period per imaging frame, which is required when imaging is performed at a high imaging frame rate, when imaging is performed instantaneously in a short time, when dimming is performed by a Pulse Width Modulation (PWM) method, or the like.

In the conventional imaging system, the method of reducing speckle by mechanically changing the optical fiber is predicted to fail to sufficiently exhibit the effect of superimposing speckle patterns when the frame rate of imaging is fast or the imaging time is short. As a typical example, the image pickup frame rate f of the image pickup system is set_r60fps is set, and half of the time corresponding to the reciprocal of the imaging frame rate is set as the exposable period t of each imaging frame of the imager_onExposure period t of each image frame of the imager_pw，expBecomes t_pw，exp≤t_onIt is considered that the shape and stress of the optical fiber need to be mechanically changed at a cycle faster than that of 1/2 × 1/60sec, which is about 8.3 msec. In addition, when exposure is required to be performed in a shorter time than that (when high-speed imaging is required), it is expected that the effect of averaging due to overlapping of speckle patterns is difficult to obtain due to a constraint of a vibration speed of a machine.

In addition, in the case of adjusting the light quantity by Pulse Width Modulation (PWM) which is often used in an illumination device using a laser, the pulse emission period (or irradiation pulse width) of the light sourcet_pw，illThe minimum value of (a) is an exposure period t per imaging frame of the imager_pw，expDivided by the number of divisions of the dimming. For example, assuming a dimming range of 30dB, the minimum pulse emission period (or irradiation pulse width) t_pw，ill(＝t_pw，exp) The frequency of 8.3msec/1000 is about 8.3 μ sec, but it is considered difficult to realize a mechanical vibration cycle corresponding to this.

In addition, if the eye is visually observed, the temporal response time of the eye can be regarded as the exposure period t of each imaging frame of the imager_pw，expIt is necessary to end the speckle superimposition within a time period shorter than about 1/30 seconds (30fps (frames/second)). When PWM-based dimming is considered as a dimming method of lighting, a more strict requirement is imposed on the drive cycle of the mechanical oscillation cycle for the same reason as described above.

In contrast, the imaging system 100 according to the present embodiment increases M by optimizing the driving timing of the speckle modulator 200, the timing of illumination, and the timing of imaging_effSince the speckle reduction effect can be sufficiently exhibited, it is possible to meet such a demand. That is, speckle noise can be stably and effectively reduced even in a short exposure period or a short pulse emission period per imaging frame, which is required when imaging is performed at a high imaging frame rate, when imaging is performed for a short time at a moment, when dimming is performed by a Pulse Width Modulation (PWM) method, or the like.

[2 nd embodiment ]

Fig. 7 schematically shows the overall configuration of an endoscope system including the image pickup system of embodiment 2. In fig. 7, the members denoted by the same reference numerals as those shown in fig. 5 are the same members, and detailed description thereof is omitted. Hereinafter, the description will focus on different parts. That is, portions not mentioned in the following description are the same as those in embodiment 1.

The imaging system 100A of the present embodiment is different from the imaging system 100 of embodiment 1 in an illumination device 102A. In the illumination apparatus 102A, the illumination light generator 110 generates an illumination pulse group train obtained by repeating one illumination pulse group including a plurality of illumination pulses. For example, the number of the plurality of illumination pulses included in one illumination pulse group is 3 or more.

The period from the lighting time of the first illumination pulse to the extinguishing time of the last illumination pulse in one illumination pulse group is set as an effective pulse lighting period. In this case, the effective pulse emission period is, for example, a period 2 times or more the actual pulse emission period of the plurality of illumination pulses included in one illumination pulse group.

In order to control the illumination light generator 110 in this manner, the illumination device 102A includes a Pulse Width Modulation (PWM) type light controller 250. The PWM mode light controller 250 controls the effective pulse emission period t_pw，effThe pulse width of the plurality of illumination pulses in the optical path is adjusted to adjust the effective illumination light amount. The pulse width modulation type light controller 250 controls the pulse light emission period t corresponding to a desired dimming amount_pwDivided into a plurality of pulse light emission periods t_pw，ill，1、···、t_pw，ill，nA multi-pulse-division type pulse width modulation optical controller (n is a natural number of 2 or more). Here, n denotes the number of a plurality of illumination pulses included in one illumination pulse group. In addition, the pulse light emission period t_pw，ill，i(i-1, …, n) represents a light emission period of the i-th illumination pulse included in one illumination pulse group.

In other words, the illumination device 102A is configured by adding the multi-pulse-division type pulse width modulation system light controller 250 to the illumination device 102 of embodiment 1. The pulse width modulation mode light controller 250 controls the driver 114 of the illumination light generator 110 based on a signal input from the synchronization controller 240.

The "multi-pulse-division pulse width modulation method" (fig. 8B) will be described in comparison with the well-known "single-pulse width modulation method" (fig. 8A). Fig. 8A and 8B show the illumination waveform of the illumination pulse generator, the driving waveform of the speckle modulator, and the effective modulation amplitude that is an index of the speckle reduction effect in each pulse width modulation methodFactor M_eff。

As shown in the upper layer of fig. 8A, the "pulse width modulation method of the single pulse type" is as follows: during the exposable period t_onWithin the time interval, the time width (or the writing period) of the illumination pulse is set to a pulse light emission period t corresponding to a desired light quantity_pw，illThe illumination light amount is adjusted.

On the other hand, the "multi-pulse-division type pulse width modulation system" proposed in the present application is a system as follows: as shown in the upper level of FIG. 8B to become t_pw，ill＝Σt_pw，ill，iThe method (2) is divided into a plurality of pulses to adjust the amount of illumination light.

Even if the driving waveforms of the speckle modulators are the same as shown in the middle layer of fig. 8A and the middle layer of fig. 8B, in the "pulse width modulation method of single pulse type" as shown in the lower layer of fig. 8A, the pulse emission period t is set to be equal to the pulse emission period t_pw，illWhen it becomes smaller,. DELTA.I_modBecomes smaller in substantial proportion thereto, and therefore, M_effHowever, as shown in the lower layer of fig. 8B, in the "multi-pulse division type pulse width modulation system", the emission timing of the irradiation pulse is dispersed, and thus even if the pulse emission period t is reduced to reduce the irradiation light amount, the pulse emission period t is reduced_pw，illThe effective pulse emission period can be extended, and as a result, the effective Δ I can be extended_mod(it is set to Δ I)_mod，eff). Therefore, the effective modulation amplitude factor M that becomes an index for reducing speckle can be effectively increased_eff。

In addition, when the exposable period t_onThe time width of the transmission of the plurality of illumination pulses (difference し transition し) in the pulse emission period t is set to be effective_pw，effIn the meantime, the "multi-pulse-division type pulse width modulation light controller" functions as an "effective pulse emission period expander" that effectively expands the pulse emission period. Here, the concept of the "effective pulse emission period expander" is that, as described above, the effective pulse emission period can be expanded by temporally dividing the illumination pulse without being used for light amount adjustment, and therefore, the effective pulse emission period is larger than that of the "multi-pulse division type pulseThe concept of the pulse width modulation type light controller is large.

In the case of using the "effective pulse emission period amplifier" or the "multi-pulse division type pulse width modulation system light controller", it is desirable to increase Δ I for the synchronous controller 240_mod，eff、t_pw，effThe time interval of the illumination pulse and the timing of the illumination pulse are set.

The imaging system 100A of the present embodiment operates as follows.

The synchronization controller 240 controls so that the speckle modulator 200 is operated at least during the active pulse light emission period.

The synchronization controller 240 controls the pulse generation timing of the illumination light generator 110, the driving timing of the speckle modulator 200, and the imaging timing of the imager 150 in synchronization with each other. For example, the synchronization controller 240 performs control such that during the exposure of the imager 150 (t)_pw，exp) Causing the illumination light generator 110 to generate illumination pulses.

Speckle Modulator 200 causes the drive Strength I of the speckle Modulator_modPeriodically changing. Drive intensity amplitude I of speckle Modulator 200_mod，0Preferably set to the drive strength threshold amplitude deltai_mod，thThe above. For example, the drive intensity amplitude I of the speckle modulator 200_mod，0Set to make the effective pulse light-emitting period t_pw，effAmplitude of change Δ I of driving strength of internal speckle modulator 200_modBecomes the driving strength threshold amplitude Delta I_mod，thThe above values.

In addition, the synchronization controller 240 controls at least the illumination light generator 110 and the speckle modulator 200 in synchronization as follows to improve the speckle reduction effect.

During the effective pulse light-emitting period t_pw，effIs less than the speckle modulation period t_mod1/2, the synchronous controller 240 emits light with an effective pulse for a period t_pw，effDrive intensity I comprising a speckle modulator_modThe illumination light generator 110 and the speckle modulator are controlled so as to be at the time when the change rate of (2) becomes maximum200. For example, the synchronization controller 240 includes the driving intensity I of the speckle modulator with any one of a plurality of illumination pulses_modThe illumination light generator 110 and the speckle modulator 200 are controlled so as to be at the time when the change rate of (2) becomes maximum. Or the synchronous controller 240 emits light with an effective pulse for a period t_pw，effBecomes the driving strength I of the speckle modulator_modThe illumination light generator 110 and the speckle modulator 200 are controlled so as to be at the time when the change rate of (2) becomes maximum. (Condition D)

Or during the active pulse light emission period t_pw，effIs less than the speckle modulation period t_mod1/2, the synchronization controller 240 controls the speckle modulator to drive at the speckle modulator driving intensity I_modNeither of the maximum value nor the minimum value of (d) is included in the effective pulse emission period t_pw，effThe illumination light generator 110 and the speckle modulator 200. (Condition E)

Or during the active pulse light emission period t_pw，effIs less than the speckle modulation period t_mod1/2, the synchronous controller 240 emits light with an effective pulse for a period t_pw，effDrive intensity I comprising a speckle modulator_modThe illumination light generator 110 and the speckle modulator 200 are controlled so as to take a value at the time of the center of the substantially maximum value and the minimum value. For example, the synchronous controller 240 may include the driving intensity I of the speckle modulator 200 with any one of the plurality of illumination pulses included in one illumination pulse group_modThe illumination light generator 110 and the speckle modulator 200 are controlled so as to take a value at the time of the center of the substantially maximum value and the minimum value. Or the synchronous controller 240 emits light with an effective pulse for a period t_pw，effBecomes the driving strength I of the speckle modulator 200_modThe illumination light generator 110 and the speckle modulator 200 are controlled so as to take a value at the time of the center of the substantially maximum value and the minimum value. (Condition F)

In addition, in the effective pulse light emitting period t_pw，effIs the speckle modulation period t_modThe synchronous controller 240 has a period of time above 1/2Effective pulse light emission period t_pw，effDrive intensity I comprising a speckle modulator_modThe illumination light generator 110 and the speckle modulator 200 are controlled so that the timing of the maximum value and the timing of the minimum value are taken. (Condition G)

There may also be one or more groups of illumination pulses with different time delays synchronized with the speckle modulator 200. Less than t during the effective pulse light emission_mod1/2 (1), the condition (D), (E) or (F) may be satisfied. For example, in the case where the 2 nd illumination pulse group arrives right after the half period of the initial illumination pulse group, if the initial illumination pulse group includes the driving intensity I of the speckle modulator 200_modAt the time when (the absolute value of) the slope of (becomes maximum), the 2 nd illumination pulse group also includes the driving intensity I of the speckle modulator 200_modThe time when (the absolute value of) the slope of (b) becomes maximum. During the effective pulse light emitting period is t_modWhen the value is equal to or greater than 1/2, the condition (condition G) may be satisfied.

The synchronization controller 240 controls the pulse generation timing of the illumination light generator 110, the driving timing of the speckle modulator 200, and the imaging timing of the imager 150 in synchronization with each other. Synchronization controller 240 is clocked by M₀The speckle modulator 200 and the illumination light generator 110 are driven by ≧ 1. In addition, the synchronization controller 240 is synchronized with t_mod≤2M₀t_pw，effThe speckle modulator 200 and the illumination light generator 110 are driven. Or synchronize controller 240 with t_pw，eff＜t_mod≤M₀t_pw，effThe speckle modulator 200 and the illumination light generator 110 are driven.

[ embodiment 3]

In embodiment 1 (fig. 5) and embodiment 2 (fig. 7), the speckle modulator 200 may be configured by at least one of the 1 st light guiding characteristic modulator 210, the 2 nd light guiding characteristic modulator 220, and the wavelength modulator 230, but may be configured by a combination thereof.

Fig. 9A, 9B, and 9C show examples of a speckle modulator 200 configured by combining two speckle modulators. The effect of speckle reduction by the combination of these is as follows.

Fig. 9A schematically shows a speckle modulator 200 configured by combining two speckle modulators M1 having the same drive mechanism and optical principle. The speckle modulator M1 is configured to apply vibration to the 1 st optical fiber 124. In fig. 9A, each speckle modulator M1 is representatively depicted as a light guiding characteristic modulator 210A shown in fig. 6A.

When two speckle modulators M1 that are the same are combined, the effective modulation amplitude factor for each light guide characteristic modulator 210A is set to M_eff，1、M_eff，2In this case, since the speckle pattern changes equally among the light guide characteristic modulators 210A, the overall speckle reduction effect M is obtained_eff，totalAt M_eff，1+M_eff，2If < 1, M is_eff，total＝M_eff，1+M_eff，2At M_eff，1+M_eff，2In the case of not less than 1, M is_eff，total1. This is an effective configuration in the case where the speckle reduction effect by one speckle modulator M1 is insufficient.

Fig. 9B schematically shows a speckle modulator 200 configured by combining two speckle modulators M1, M2 different in driving mechanism but identical in optical principle. The speckle modulator M1 is as described above. The speckle modulator M2 is configured to apply rotation to the 1 st optical fiber 124. In fig. 9B, the speckle modulator M2 is representatively depicted as the light guiding characteristic modulator 210B shown in fig. 6B.

In this case, since the temporal superposition effect of the speckle-based light and dark patterns is also used, the speckle modulators M1 and M2 of the same kind are optically combined, and basically, the effect of adding the effective modulation amplitude factors is observed as in fig. 9A. However, the speckle-based light and dark pattern patterns generated by the speckle modulators M1 and M2 may change differently. Therefore, due to the effect of overlapping the plurality of bright and dark pattern patterns, the speckle reduction effect is often further enhanced (i.e., M is obtained) than in the case of the configuration example of fig. 9A_eff，total＞1)。

Fig. 9C schematically shows a speckle modulator 200 configured by combining two speckle modulators M1, M3 that differ in optical principle. The speckle modulator M1 is as described above. The speckle modulator M3 is configured to change the wavelength of the laser light with time. In fig. 9C, the speckle modulator M3 is depicted as the wavelength modulator 230 shown in fig. 5.

Two speckle modulators M1, M3, which differ in optical principle, are connected in series. In this case, since the optical principle causing speckle reduction is different, it is different from M_eff，1+M_eff，2Is M independently of the size of_eff，total＝M_eff，1+M_eff，2。

In the configurations of fig. 9A, 9B, and 9C, the operation and effects of the synchronization controller 240 and the like are the same as those of embodiment 1 and embodiment 2.

[4 th embodiment ]

Fig. 10 schematically shows the overall configuration of the lighting device according to embodiment 4. In fig. 10, the members denoted by the same reference numerals as those shown in fig. 5 and 7 are the same members, and detailed description thereof will be omitted.

The illumination device 102B of the present embodiment includes an illumination light generator 110, a light guide optical system 120B that guides laser light emitted from the illumination light generator 110, and an irradiation optical system 140B that irradiates the laser light guided by the light guide optical system 120B.

The light guide optical system 120B includes: a collimator lens 122B for collimating the light beam emitted from the illumination light generator 110; and a coupling lens 124B that couples the light beam collimated by the collimator lens 122B with the illumination optical system 140B. The collimator lens 122B and the coupling lens 124B are schematically depicted as 1-piece lenses in fig. 10, but may actually be constituted by 1-piece lens, or may be constituted by a plurality of pieces of lenses.

The illumination device 102B further includes a speckle modulator 200, a synchronization controller 240, and a pulse width modulation type light controller 250. The speckle modulator 200 includes a light guide characteristic modulator 220 and a wavelength modulator 230. The light guide characteristic modulator 220 is disposed on the optical path of the collimated light beam between the collimator lens 122B and the coupling lens 124B.

The details of the speckle modulator 200, the light guide characteristic modulator 220, the wavelength modulator 230, and the synchronization controller 240 are the same as those described in embodiment 1, and the details of the pulse width modulation optical controller 250 are the same as those described in embodiment 2.

In the illumination device 102B without an imager, the same speckle reduction effect as in embodiments 1 to 3 can be obtained for the observer by considering the variation width of the drive intensity of the speckle modulator 200 in a time (which is about 33msec in the case where the living body is a human) considered as a response time of the living body to the image variation.

[5 th embodiment ]

Fig. 11 schematically shows the overall configuration of a microscope system including the imaging system of embodiment 5. In fig. 11, the members denoted by the same reference numerals as those shown in fig. 5 and 7 are the same members, and detailed description thereof will be omitted.

The imaging system 100C of the present embodiment includes an illumination device 102C that illuminates an observation target 190, and an imaging device 104.

The illumination device 102C includes an illumination light generator 110, a light guide optical system 120C that guides laser light emitted from the illumination light generator 110, and an illumination optical system 300 that irradiates the laser light guided by the light guide optical system 120C.

The light guide optical system 120C includes an optical fiber 126C for guiding the laser light, a collimator lens 122C for collimating the light beam emitted from the illumination light generator 110, and a fiber coupling lens 124C for coupling the light beam collimated by the collimator lens 122C to the optical fiber 126C. The collimator lens 122C and the fiber coupling lens 124C are schematically depicted as 1-piece lenses in fig. 11, but may actually be constituted by 1-piece lens or a plurality of pieces of lenses.

The illumination optical system 300 includes: a collimating optical system 310 that collimates the light beam emitted from the optical fiber 126C; a beam splitter 320 that splits the light beam collimated by the collimating optical system 310 into 2 light beams; a1 st mirror 330A that reflects one of the light fluxes split by the beam splitter 320; a1 st illumination optical system 340A that illuminates the light flux reflected by the 1 st mirror 330A from below toward the observation target 190 placed on the sample stage 350; a2 nd mirror 330B that reflects the other light flux split by the beam splitter 320; and a2 nd illumination optical system 340B that illuminates the light beam reflected by the 2 nd mirror 330B from obliquely above toward the observation object 190.

The illumination device 102C further includes a speckle modulator 200, a synchronization controller 240, and a pulse width modulation type light controller 250. The speckle modulator 200 includes a1 st light guide characteristic modulator 210, a2 nd light guide characteristic modulator 220, and a wavelength modulator 230. The 2 nd light guiding characteristic modulator 220 is disposed on the optical path of the collimated light beam between the collimator lens 122C and the fiber coupling lens 124C. The 1 st light guiding characteristic modulator 210 is disposed in the middle of the optical fiber 126C.

The speckle modulator 200, the 1 st light guiding characteristic modulator 210, the 2 nd light guiding characteristic modulator 220, the wavelength modulator 230, and the synchronization controller 240 are described in detail in the same manner as in embodiment 1, and the pulse width modulation optical controller 250 is described in detail in the same manner as in embodiment 2.

The imaging system 100C further includes an objective optical system 360 disposed so as to face the sample stage 350, a barrel 370 supporting the objective optical system 360, and an eyepiece and an imaging optical system 380 attached to the barrel 370.

The laser light emitted from the light guide optical system 120C is split into 2 beams by the beam splitter 320 via the collimating optical system 310. One light flux is reflected by the 1 st mirror 330A and irradiated from below toward the observation target 190 via the 1 st irradiation optical system 340A. The other light flux is reflected by the 2 nd mirror 330B and is irradiated from obliquely above toward the observation target 190 via the 2 nd irradiation optical system 340B.

The light irradiated to the observation target 190 is reflected, diffracted, scattered, or the like by the observation target 190. A part of the light reflected, diffracted, scattered, or the like by the observation target 190 enters the objective optical system 360. The light incident on the objective optical system 360 is focused on the light receiving surface of the imager 150 via, for example, an eyepiece and the imaging optical system 380, and the imager 150 acquires image information of the observation target 190. The image information acquired by the imager 150 is subjected to image processing by the image processing circuit 160 and then displayed on the display 170. Alternatively, the light incident on the objective optical system 360 is focused on the retina of the observer via the eyepiece and the imaging optical system 380, and the observer observes the image of the observation target 190.

In the microscope system including the imaging system 100C of the present embodiment, the operation and effect relating to speckle reduction are similar to those obtained in embodiments 1 to 4.

[ conclusion ]

Summarizing the above, in the present specification, the illumination apparatus and the image pickup system listed below are disclosed. In other words, the above embodiments can be summarized as follows.

[1] An illumination device having:

an illumination pulse generator that generates an illumination pulse of coherent light;

a speckle modulator that modulates speckles generated by the coherent light; and

a synchronous controller that controls a pulse generation timing of the illumination pulse generator in synchronization with a driving timing of the speckle modulator.

[2] The lighting device according to [1], wherein,

the synchronous controller controls so that the pulse light emission period (t) of at least each of the illumination pulses_pw，ill) Causing the speckle modulator to operate.

[3] The lighting device according to [2], wherein,

the speckle modulator causes a driving strength (I) of the speckle modulator_mod) Periodically changing.

[4] The lighting device according to [3], wherein,

during the pulse light emission period (t)_pw，ill) Is less than the speckle modulation period (t)_mod) 1/2, the synchronous controller controls the pulseDuration of time of light emission (t)_pw，ill) Drive intensity (I) comprising said speckle modulator_mod) The illumination pulse generator and the speckle modulator are controlled so as to substantially maximize the rate of change of the illumination pulse generator.

[5] The lighting device according to [4], wherein,

the synchronous controller emits light in the pulse for a period (t)_pw，ill) Becomes the driving strength (I) of the speckle modulator_mod) The illumination pulse generator and the speckle modulator are controlled so as to substantially maximize the rate of change of the illumination pulse generator.

[6] The lighting device according to [3], wherein,

during the pulse light emission period (t)_pw，ill) Is less than the speckle modulation period (t)_mod) 1/2, the synchronization controller controls the speckle modulator to drive at the speckle modulator intensity (I)_mod) Is not included in the pulse light emission period (t)_pw，ill) To control the illumination pulse generator and the speckle modulator.

[7] The lighting device according to [6], wherein,

the synchronous controller emits light in the pulse for a period (t)_pw，ill) Drive intensity (I) comprising said speckle modulator_mod) The illumination pulse generator and the speckle modulator are controlled in such a way that the time of the value of the center of the substantially maximum value and the minimum value is taken.

[8] The lighting device according to [7], wherein,

the synchronous controller emits light in the pulse for a period (t)_pw，ill) Becomes the driving strength (I) of the speckle modulator_mod) The illumination pulse generator and the speckle modulator are controlled in such a way that the time of the value of the center of the substantially maximum value and the minimum value is taken.

[9] The lighting device according to [3], wherein,

during the pulse light emission period (t)_pw，ill) Is the speckle modulation periodPeriod (t)_mod) The synchronous controller controls the pulse emission period (t) to be equal to or longer than 1/2_pw，ill) Drive intensity (I) comprising said speckle modulator_mod) The illumination pulse generator and the speckle modulator are controlled in such a way that the time of the maximum value and the time of the minimum value are taken.

[10] The lighting device according to [1], wherein,

the speckle modulator includes a1 st speckle modulator and a2 nd speckle modulator, and the synchronization controller controls a pulse generation timing of the illumination pulse generator in synchronization with a driving timing of the 1 st speckle modulator and/or the 2 nd speckle modulator.

[11] The lighting device according to [2], wherein,

setting a magnitude of change in drive intensity of the speckle modulator, which saturates a reduction in speckle with respect to a change in drive intensity of the speckle modulator, as a drive intensity threshold magnitude (Δ I)_mod，th) The amplitude (I) of the driving intensity of the speckle modulator_mod，0) Is set to the driving strength threshold amplitude (Delta I)_mod，th) The above.

[12] The lighting device according to [11], wherein,

drive intensity amplitude (I) of the speckle modulator_mod，0) Is set so that the pulse light-emitting period (t)_pw，ill) Amplitude of variation (Δ I) of driving intensity of the speckle modulator_mod) Becomes the driving strength threshold amplitude (Delta I)_mod，th) The above values.

[13] The lighting device according to [1] or [2], wherein,

the speckle modulator has a phase modulator that changes the phase of the coherent light with a change in time.

[14] The lighting device according to [13], wherein,

the phase modulator includes a light guide member changing device that applies mechanical change to a light guide member included in a light guide optical system that guides the coherent light.

[15] The lighting device according to [13], wherein,

the phase modulator has an asperity plate having an asperity larger than 1/10 of the wavelength of the coherent light.

[16] The lighting device according to [13], wherein,

the phase modulator is a refractive index modulator that changes a refractive index of a light guide optical system that guides the coherent light with time.

[17] The lighting device according to [16], wherein,

the refractive index modulator includes at least one of an electro-optical element and an acousto-optical element.

[18] The lighting device according to [14], wherein,

the light guide optical system includes an optical fiber, and the speckle modulator has a drive intensity amplitude (I) when the core diameter of the optical fiber is Φ c_mod，0) And a displacement of 5 Φ c or more in terms of vibration of the optical fiber generated by the light guide member varying device.

[19] The lighting device according to [14], wherein,

the light guide optical system comprises an optical fiber, and the driving intensity amplitude (I) of the speckle modulator_mod，0) The angle for twisting the optical fiber is 10 DEG or more.

[20] The lighting device according to [16], wherein,

the driving intensity amplitude (I) of the speckle modulator is determined by Lm, Δ n/n, and λ c, where Lm is the length of the refractive index modulator in the light guide direction, Δ n/n is the change in the refractive index, and λ c is the center wavelength of the spectrum of the illumination pulse_mod，0) When the refractive index of the refractive index modulator is changed, the refractive index is more than or equal to Deltan/n and more than or equal to lambda c/Lm.

[21] An image pickup system includes:

[2]～[12]the lighting device according to any one of the above; and during a predetermined exposure period (t)_pw，exp) An imager for taking an image.

[22] The imaging system according to [21], wherein,

the synchronization controller controls the pulse generation timing of the illumination pulse generator, the driving timing of the speckle modulator, and the imaging timing of the imager in synchronization with each other.

[23] The imaging system according to [21], wherein,

the synchronization controller controls the pulse generation timing of the illumination pulse generator, the driving timing of the speckle modulator, and the imaging timing of the imager in synchronization with each other, and controls the exposure period (t) of the imager_pw，exp) Causing the illumination pulse generator to generate the illumination pulse.

[24] The imaging system according to [21], wherein,

the synchronization controller controls the pulse generation timing of the illumination pulse generator, the driving timing of the speckle modulator, and the imaging timing of the imager in synchronization,

drive intensity amplitude (I) for the speckle modulator_mod，0) A drive intensity threshold amplitude (Δ I) which is the amplitude of change in the drive intensity of the speckle modulator at which the reduction in speckle is saturated with respect to the change in the drive intensity of the speckle modulator_mod，th) The pulse emission period (t) of the illumination pulse generated by the illumination pulse generator_pw，ill) And a modulation period (t) when the speckle modulator is periodically driven_mod) Is set to M₀＝I_mod，0/ΔI_mod，thWhen the synchronous controller is in M₀The speckle modulator and the illumination pulse generator are driven at t ≧ 1_mod≤2M₀t_pw，illDriving the speckle modulator and the illumination pulse generator.

[25] The imaging system according to [21], wherein,

the synchronization controller controls the pulse generation timing of the illumination pulse generator, the driving timing of the speckle modulator, and the imaging timing of the imager in synchronization,

drive intensity amplitude (I) for the speckle modulator_mod，0) A drive intensity threshold amplitude (Δ I) which is the amplitude of change in the drive intensity of the speckle modulator at which the reduction in speckle is saturated with respect to the change in the drive intensity of the speckle modulator_mod，th) The pulse emission period (t) of the illumination pulse generated by the illumination pulse generator_pw，ill) And a modulation period (t) when the speckle modulator is periodically driven_mod) Is set to M₀＝I_mod，0/ΔI_mod，thWhen the synchronous controller is in M₀The speckle modulator and the illumination pulse generator are driven at t ≧ 1_pw，ill＜t_mod≤M₀t_pw，illDriving is performed.

[26] The imaging system according to [21], wherein,

the speckle modulator has a phase modulator that changes a phase of the coherent light with a change in time.

[27] The imaging system according to [26], wherein,

the phase modulator includes a light guide member changing device that applies mechanical change to a light guide member included in a light guide optical system that guides the coherent light.

[28] The imaging system according to [26], wherein,

the phase modulator has an asperity plate having an asperity larger than 1/10 of the wavelength of the coherent light.

[29] The imaging system according to [26], wherein,

the phase modulator is a refractive index modulator that changes a refractive index of a light guide optical system that guides the coherent light with time.

[30] The imaging system according to [29], wherein,

the refractive index modulator includes at least one of an electro-optical element and an acousto-optical element.

[31] The imaging system according to [27], wherein,

the light guide optical system includes an optical fiber, and the speckle modulator has a drive intensity amplitude (I) when the core diameter of the optical fiber is Φ c_mod，0) And a displacement of 5 Φ c or more in terms of vibration of the optical fiber generated by the light guide member varying device.

[32] The imaging system according to [27], wherein,

the light guide optical system comprises an optical fiber, and the driving intensity amplitude (I) of the speckle modulator_mod，0) The angle for twisting the optical fiber is 10 DEG or more.

[33] The imaging system according to [29], wherein,

the driving intensity amplitude (I) of the speckle modulator is determined by Lm, Δ n/n, and λ c, where Lm is the length of the refractive index modulator in the light guide direction, Δ n/n is the change in the refractive index, and λ c is the center wavelength of the spectrum of the illumination pulse_mod，0) When the refractive index of the refractive index modulator is changed, the refractive index is more than or equal to Deltan/n and more than or equal to lambda c/Lm.

[34] An endoscope system comprising the imaging system according to any one of [21] to [33], wherein the imaging system further comprises: an image processing circuit that performs image processing on an image captured by the imager; and an image display unit that displays an image subjected to image processing by the image processing circuit.

[35] A microscope system comprising the imaging system according to any one of [21] to [33], wherein the imaging system further comprises: an image processing circuit that performs image processing on an image captured by the imager; and an image display unit that displays an image subjected to image processing by the image processing circuit.

[36] An image pickup system includes:

an illumination light generator that generates coherent light;

a speckle modulator that modulates speckles generated by the coherent light;

imager at a specified exposureLight period (t)_pw，exp) The image is taken by the camera to obtain a picture,

the imaging system has a synchronization controller that controls imaging timing of the imager in synchronization with driving timing of the speckle modulator.

[37] The imaging system according to [36], wherein,

the synchronous controller controls so that at least during the exposure period (t)_pw，exp) Causing the speckle modulator to operate.

[38] The imaging system according to [36] or [37], wherein,

the speckle modulator causes a driving strength (I) of the speckle modulator_mod) Periodically changing.

[39] The imaging system according to [38], wherein,

during the exposure (t)_pw，exp) Less than the speckle modulation period (t)_mod) 1/2, the synchronous controller controls the exposure period (t)_pw，exp) Drive intensity (I) comprising said speckle modulator_mod) The imager and the speckle modulator are controlled in such a manner that the change rate of the speckle modulator becomes substantially maximum.

[40] The imaging system according to [39], wherein,

the synchronous controller is controlled by the exposure period (t)_pw，exp) Becomes the driving strength (I) of the speckle modulator_mod) The imager and the speckle modulator are controlled in such a manner that the change rate of the speckle modulator becomes substantially maximum.

[41] The imaging system according to [38], wherein,

during the exposure (t)_pw，exp) Is less than the speckle modulation period (t)_mod) 1/2, the synchronization controller controls the speckle modulator to drive at the speckle modulator intensity (I)_mod) Is not included in the exposure period (t)_pw，exp) To control the imager and the speckle modulator.

[42] The imaging system according to [41], wherein,

the synchronous controller is controlled by the exposure period (t)_pw，exp) Drive intensity (I) comprising said speckle modulator_mod) The imager and the speckle modulator are controlled in a manner that takes the time instant of the value of the center of the substantially maximum value and the minimum value.

[43] The imaging system according to [42], wherein,

the synchronous controller is controlled by the exposure period (t)_pw，exp) Becomes the driving strength (I) of the speckle modulator_mod) The imager and the speckle modulator are controlled in a manner that takes the time instant of the value of the center of the substantially maximum value and the minimum value.

[44] The imaging system according to [38], wherein,

during the exposure (t)_pw，exp) Is the speckle modulation period (t)_mod) The synchronous controller controls the exposure period (t) to be equal to or longer than 1/2_pw，exp) Drive intensity (I) comprising said speckle modulator_mod) The imager and the speckle modulator are controlled by taking the time of the maximum value and the time of the minimum value.

[45] The imaging system according to [36], wherein,

the speckle modulator includes a1 st speckle modulator and a2 nd speckle modulator, and the synchronization controller controls exposure timing of the imager in synchronization with driving timing of the 1 st speckle modulator and/or the 2 nd speckle modulator.

[46] The imaging system according to [36] or [37], wherein,

setting a magnitude of change in drive intensity of the speckle modulator, which saturates a reduction in speckle with respect to a change in drive intensity of the speckle modulator, as a drive intensity threshold magnitude (Δ I)_mod，th) The amplitude (I) of the driving intensity of the speckle modulator_mod，0) Is set to the driving strength threshold amplitude (Delta I)_mod，th) The above.

[47] The imaging system according to [46], wherein,

drive intensity amplitude (I) of the speckle modulator_mod，0) Is set so that the exposure period (t)_pw，exp) Amplitude of variation (Δ I) of driving intensity of the speckle modulator_mod) Becomes the driving strength threshold amplitude (Delta I)_mod，th) The above values.

[48] The imaging system according to [36], wherein,

the speckle modulator has a phase modulator that changes a phase of the coherent light with a change in time.

[49] The imaging system according to [48], wherein,

the phase modulator includes a light guide member changing device that applies mechanical change to a light guide member included in a light guide optical system that guides the coherent light.

[50] The imaging system according to [48], wherein,

the phase modulator has an asperity plate having an asperity larger than 1/10 of the wavelength of the coherent light.

[51] The imaging system according to [48], wherein,

the phase modulator is a refractive index modulator that changes a refractive index of a light guide optical system that guides the coherent light with time.

[52] The imaging system according to [51], wherein,

the refractive index modulator includes at least one of an electro-optical element and an acousto-optical element.

[53] The imaging system according to [49], wherein,

the light guide optical system includes an optical fiber, and the speckle modulator has a drive intensity amplitude (I) when the core diameter of the optical fiber is Φ c_mod，0) And a displacement of 5 Φ c or more in terms of vibration of the optical fiber generated by the light guide member varying device.

[54] The imaging system according to [49], wherein,

the light guide optical system comprises an optical fiber, and the driving intensity amplitude (I) of the speckle modulator_mod，0) The angle for twisting the optical fiber is 10 DEG or more.

[55] The imaging system according to [51], wherein,

the driving intensity amplitude (I) of the speckle modulator is determined by Lm, Δ n/n, and λ c, where Lm is the length of the refractive index modulator in the light guide direction, Δ n/n is the change in the refractive index, and λ c is the center wavelength of the spectrum of the illumination pulse_mod，0) When the refractive index of the refractive index modulator is changed, the refractive index is more than or equal to Deltan/n and more than or equal to lambda c/Lm.

[56] An endoscope system comprising the imaging system according to any one of [36] to [55], the imaging system further comprising: an image processing circuit that performs image processing on an image captured by the imager; and an image display unit that displays an image subjected to image processing by the image processing circuit.

[57] A microscope system including the imaging system according to any one of [36] to [55], the imaging system further comprising: an image processing circuit that performs image processing on an image captured by the imager; and an image display unit that displays an image subjected to image processing by the image processing circuit.