阅读说明：本技术 一种激光照明组件及确定激光照明系统参数的方法 (Laser lighting assembly and method for determining parameters of laser lighting system ) 是由 孙海岳 程广伟 周增军 马宇飞 于 2020-12-21 设计创作，主要内容包括：本发明实施例提供了一种激光照明组件及确定激光照明系统参数的方法,所述激光照明组件包括激光器、驱动电路及变焦透镜,其中：驱动电路与激光器电连接,驱动电路将驱动电流传输至激光器,其中,驱动电流包括直流分量和交流分量；所述激光器与光纤连接,所述激光器发射激光信号,所述激光信号通过所述光纤出射至所述变焦透镜,并通过所述变焦透镜射出为激光照明摄像机中的摄像机组件的监控区域进行补光。通过对激光器的注入电流中加入交流分量扰动,实现对激光器的输出波长的快速调制,实现激光干涉散斑位置的改变,从而通过时间积分可以使得散斑效应明显减弱。同时由于无需加入机械振动部件,激光照明摄像机的稳定性高,画面拍摄效果好。(The embodiment of the invention provides a laser lighting assembly and a method for determining parameters of a laser lighting system, wherein the laser lighting assembly comprises a laser, a driving circuit and a zoom lens, wherein: the driving circuit is electrically connected with the laser and transmits driving current to the laser, wherein the driving current comprises a direct current component and an alternating current component; the laser device is connected with the optical fiber, emits laser signals, and emits the laser signals to the zoom lens through the optical fiber and performs light supplement on a monitoring area of a camera assembly in the laser lighting camera through the emission of the zoom lens. The alternating current component disturbance is added into the injection current of the laser, so that the output wavelength of the laser is rapidly modulated, the laser interference speckle position is changed, and the speckle effect can be obviously weakened through time integration. Meanwhile, since a mechanical vibration part is not required to be added, the laser illumination camera is high in stability and good in picture shooting effect.)

1. A laser lighting assembly, comprising a laser, a driving circuit, and a zoom lens, wherein:

the drive circuit is electrically connected with the laser and transmits a drive current to the laser, wherein the drive current comprises a direct current component and an alternating current component;

the laser device is connected with the optical fiber, emits laser signals, and emits the laser signals to the zoom lens through the optical fiber and performs light supplement on a monitoring area of a camera assembly in the laser lighting camera through the emission of the zoom lens.

2. The laser illumination assembly of claim 1, wherein the driving current comprises an alternating current component that is a high frequency sinusoidal signal, and the driving circuit comprises a high frequency signal generator, a direct current signal generator, and an adder;

the high-frequency signal generator and the direct-current signal generator are respectively electrically connected with the adder, the adder is electrically connected with the laser, and the high-frequency sinusoidal signal generated by the high-frequency signal generator and the direct-current signal generated by the direct-current signal generator are transmitted to the laser after being superposed by the adder.

3. The laser lighting assembly of claim 1 or 2, further comprising a beam splitting lens disposed between the optical fiber and the zoom lens;

a projection is arranged on the light-emitting surface of the beam splitting lens; the laser signal is emitted to the beam splitting lens through the optical fiber and enters the zoom lens through the light emitting surface of the beam splitting lens and the convex light emitting surface.

4. The laser lighting assembly of claim 3, wherein the protrusion is plural;

the thicknesses of the plurality of protrusions are increased progressively along the incident direction of the laser signal, the thickness difference between two adjacent protrusions is not smaller than a preset thickness, and the thickness difference between the smallest one of the thicknesses of the plurality of protrusions and the light emitting surface of the beam splitting lens is not smaller than the preset thickness.

5. The laser lighting assembly of claim 4, wherein the predetermined thickness d is determined using the formula:

wherein Δ λ is an output spectral width of the laser, λ is an output wavelength of the laser, and n is a refractive index of the beam splitting lens.

6. A method for determining parameters of a laser lighting system, the laser lighting system comprising a camera assembly and a laser lighting assembly, the laser lighting assembly comprising a laser, an optical fiber and a zoom lens for supplementing a monitored area of the camera assembly with light, a drive current for the laser comprising a dc component and an ac component, the method comprising:

when the laser has a specified dc component and the camera assembly has a specified exposure time:

acquiring the maximum modulation frequency of the laser;

determining a maximum amplitude value of an alternating current component comprised by a drive current of the laser in response to a current value of the direct current component, the exposure time and a maximum modulation frequency of the laser.

7. The method of claim 6, wherein the step of determining a maximum amplitude value of an alternating current component comprised by a drive current of the laser in response to the current value of the direct current component, the exposure time and a maximum modulation frequency of the laser comprises:

determining a maximum amplitude value i of an alternating current component included in a driving current of the laser based on the following formula in response to a current value of the direct current component, the exposure time, and a maximum modulation frequency of the laser_s：

i_s＝πτTf_Mi₀

Wherein i₀Tau is the maximum value of the percentage of fluctuation of the output energy of the laser which can ensure the picture stability of the monitoring area, T is the exposure time, f is the current value of the direct current component_MIs the maximum modulation frequency of the alternating current component.

8. The method according to claim 6 or 7, wherein the laser illumination assembly further comprises a beam splitting lens disposed between the optical fiber and the zoom lens, the beam splitting lens has at least one protrusion on a light emitting surface thereof, the at least one protrusion has an increasing thickness along an incident direction of the laser signal, a thickness difference between two adjacent protrusions is not less than a preset thickness, and a thickness difference between a smallest one of the thicknesses of the plurality of protrusions and the light emitting surface of the beam splitting lens is not less than the preset thickness;

the method further comprises the following steps:

determining the preset thickness in response to an output spectral width of the laser and an output wavelength of the laser.

9. The method of claim 8, wherein said step of determining said predetermined thickness in response to an output spectral width of said laser and an output wavelength of said laser comprises:

determining the preset thickness d in response to the output spectral width of the laser and the output wavelength of the laser based on the following formula:

wherein Δ λ is an output spectral width of the laser, λ is an output wavelength of the laser, and n is a refractive index of the beam splitting lens.

10. A laser illumination camera, characterized in that it comprises a camera assembly, and a laser illumination assembly according to any one of claims 1 to 5;

the laser lighting assembly is used for supplementing light for the monitoring area of the camera assembly.

Technical Field

The invention relates to the technical field of laser illumination, in particular to a laser illumination assembly and a method for determining parameters of a laser illumination system.

Background

Compared with a common light source, the laser has the advantages that the output laser signal has better directivity and the spectral width of the output spectrum is narrower. When two beams of light with the same wavelength, polarization direction and propagation direction are overlapped in space, the light intensity in the overlapped area will generate uneven distribution due to interference. The brightness changes with the space position, and the interference phenomenon occurs, so the laser signal has strong coherence. When a laser is used as an illumination light source of a camera, an interference phenomenon, which is called speckle, causes a significant bright-dark distribution in a picture photographed by the camera.

The way of eliminating laser speckle needs to analyze the interference condition of laser and control the wavelength, polarization direction or phase of laser. The current approach to eliminate speckle is to add a dynamic scattering or mixing device in the illumination light path to modulate the phase of the laser. Specifically, a light mixing rod is added in a light path, laser is injected into the light mixing rod through a coupling lens, the light mixing rod is vibrated by a mechanical vibration component, phases of different positions in the laser are changed, the positions of speckles of the laser are changed, when the change period is far shorter than the exposure time of a camera, a plurality of speckles in unit time are superposed, and the speckle effect can be weakened through time integration.

In the laser lighting camera, if the speckle effect is weakened by adding the mechanical vibration component in the optical path, the stability of the camera is seriously influenced due to the vibration or rotation of the mechanical vibration component, so that the quality of the picture shot by the camera is seriously influenced.

Disclosure of Invention

The embodiment of the invention aims to provide an assembly and a method for determining parameters of a laser lighting system, which are used for ensuring the speckle elimination effect, ensuring the stability of a laser lighting camera and improving the picture shooting quality. The specific technical scheme is as follows:

in a first aspect, an embodiment of the present invention provides a laser illumination assembly, where the laser illumination assembly includes a laser, a driving circuit, and a zoom lens, where:

the drive circuit is electrically connected with the laser and transmits a drive current to the laser, wherein the drive current comprises a direct current component and an alternating current component;

the laser device is connected with the optical fiber, emits laser signals, and emits the laser signals to the zoom lens through the optical fiber and performs light supplement on a monitoring area of a camera assembly in the laser lighting camera through the emission of the zoom lens.

Optionally, the alternating current component included in the driving current is a high-frequency sinusoidal signal, and the driving circuit includes a high-frequency signal generator, a direct-current signal generator, and an adder;

the high-frequency signal generator and the direct-current signal generator are respectively electrically connected with the adder, the adder is electrically connected with the laser, and the high-frequency sinusoidal signal generated by the high-frequency signal generator and the direct-current signal generated by the direct-current signal generator are transmitted to the laser after being superposed by the adder.

Optionally, the laser illumination assembly further includes a beam splitting lens, and the beam splitting lens is disposed between the optical fiber and the zoom lens;

a projection is arranged on the light-emitting surface of the beam splitting lens; the laser signal is transmitted to the beam splitting lens through the optical fiber and enters the zoom lens through the light emitting surface of the beam splitting lens and the convex light emitting surface.

Optionally, the number of the protrusions is multiple;

the thicknesses of the plurality of protrusions are increased progressively along the incident direction of the laser signal, the thickness difference between two adjacent protrusions is not smaller than a preset thickness, and the thickness difference between the smallest one of the thicknesses of the plurality of protrusions and the light emitting surface of the beam splitting lens is not smaller than the preset thickness.

Optionally, the preset thickness d is determined by using the following formula:

wherein Δ λ is an output spectral width of the laser, λ is an output wavelength of the laser, and n is a refractive index of the beam splitting lens.

In a second aspect, an embodiment of the present invention provides a method for determining parameters of a laser illumination system, where the laser illumination system includes a camera assembly and a laser illumination assembly, the laser illumination assembly includes a laser, an optical fiber, and a zoom lens, and is used to fill a monitored area of the camera assembly with light, a driving current of the laser includes a dc component and an ac component, and the method includes:

when the laser has a specified dc component and the camera assembly has a specified exposure time:

acquiring the maximum modulation frequency of the laser;

determining a maximum amplitude value of an alternating current component comprised by a drive current of the laser in response to a current value of the direct current component, the exposure time and a maximum modulation frequency of the laser.

Optionally, the step of determining a maximum amplitude value of an ac component included in the driving current of the laser in response to the current value of the dc component, the exposure time, and the maximum modulation frequency of the laser includes:

determining a maximum amplitude value i of an alternating current component included in a driving current of the laser based on the following formula in response to a current value of the direct current component, the exposure time, and a maximum modulation frequency of the laser_s：

i_s＝πτTf_Mi₀

Wherein i₀Tau is the maximum value of the percentage of fluctuation of the output energy of the laser which can ensure the picture stability of the monitoring area, T is the exposure time, f is the current value of the direct current component_MIs the maximum modulation frequency of the alternating current component.

Optionally, the laser illumination assembly further includes a beam splitting lens disposed between the optical fiber and the zoom lens, the light exit surface of the beam splitting lens has at least one protrusion, the thickness of the at least one protrusion increases progressively along the incident direction of the laser signal, the thickness difference between two adjacent protrusions is not less than a preset thickness, and the thickness difference between the smallest one of the thicknesses of the plurality of protrusions and the light exit surface of the beam splitting lens is not less than the preset thickness;

the method further comprises the following steps:

determining the preset thickness in response to an output spectral width of the laser and an output wavelength of the laser.

Optionally, the step of determining the preset thickness in response to the output spectral width of the laser and the output wavelength of the laser includes:

determining the preset thickness d in response to the output spectral width of the laser and the output wavelength of the laser based on the following formula:

wherein Δ λ is an output spectral width of the laser, λ is an output wavelength of the laser, and n is a refractive index of the beam splitting lens.

In a third aspect, an embodiment of the present invention provides a laser illumination camera, where the laser illumination camera includes a camera assembly, and the laser illumination assembly of any one of the above first aspects;

the laser lighting system is used for supplementing light for the monitoring area of the camera assembly.

The embodiment of the invention has the following beneficial effects:

in the scheme provided by the embodiment of the invention, the laser lighting assembly comprises a laser, a driving circuit and a zoom lens; the drive circuit is electrically connected with the laser and transmits a drive current to the laser, wherein the drive current comprises a direct current component and an alternating current component. The laser device is connected with the optical fiber, emits laser signals to the zoom lens through the optical fiber, and emits the laser signals to supplement light for a monitoring area of a camera assembly in the laser lighting camera through the zoom lens. The alternating current component disturbance is added into the driving current of the laser, so that the output wavelength of the laser is rapidly modulated, the laser interference speckle position is changed, and the speckle effect can be obviously weakened through time integration. Meanwhile, since a mechanical vibration part is not required to be added, the laser illumination camera is high in stability and good in picture shooting effect. Of course, not all of the advantages described above need to be achieved at the same time in the practice of any one product or method of the invention.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other embodiments can be obtained by using the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a laser lighting assembly according to an embodiment of the present invention;

FIG. 2 is a schematic view of another structure of the laser lighting assembly according to the embodiment of FIG. 1;

FIG. 3 is a schematic diagram of a structure of a beam splitting lens according to the embodiment of FIG. 1;

FIG. 4 is a schematic view of another structure of the laser lighting assembly according to the embodiment of FIG. 1;

FIG. 5 is a graph showing the relationship between the output wavelength and the injection current of the laser in the embodiment of FIG. 1;

fig. 6 is a flowchart of a method for determining parameters of a laser illumination system according to an embodiment of the present invention;

fig. 7 is a schematic structural diagram of a laser illumination camera according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order to ensure the speckle elimination effect, ensure the stability of the laser illumination camera and improve the picture shooting quality, the embodiment of the invention provides a laser illumination assembly, a method for determining parameters of a laser illumination system and the laser illumination camera. The laser lighting assembly provided by the embodiment of the invention can be used in a laser lighting camera to illuminate the shot picture of the camera assembly of the laser lighting camera, namely, to supplement light for the monitored area of the camera assembly in the laser lighting camera. A laser lighting assembly according to an embodiment of the present invention will be described first.

As shown in fig. 1, a laser illumination assembly may include a laser 111, a driving circuit 112, and a zoom lens 113, wherein:

the driving circuit 112 is electrically connected to the laser 111, and the driving circuit 112 transmits a driving current to the laser 111;

wherein the drive current includes a direct current component and an alternating current component.

The laser 111 is connected with an optical fiber 114, the laser 111 emits a laser signal, the laser signal is emitted to the zoom lens 113 through the optical fiber 114, and is emitted through the zoom lens 113 to supplement light for a monitoring area of a camera assembly in a laser lighting camera.

Therefore, in the scheme provided by the embodiment of the invention, the laser illumination assembly comprises a laser, a driving circuit and a zoom lens; the drive circuit is electrically connected with the laser and transmits a drive current to the laser, wherein the drive current comprises a direct current component and an alternating current component. The laser device is connected with the optical fiber, emits laser signals to the zoom lens through the optical fiber, and emits the laser signals to supplement light for a monitoring area of a camera assembly in the laser lighting camera through the zoom lens. The alternating current component disturbance is added into the driving current of the laser, so that the output wavelength of the laser is rapidly modulated, the laser interference speckle position is changed, and the speckle effect can be obviously weakened through time integration. Meanwhile, since a mechanical vibration part is not required to be added, the laser illumination camera is high in stability and good in picture shooting effect.

In the laser lighting assembly, the driving circuit may transmit the dc component and the ac component to the laser, the laser is excited to emit a laser signal, the laser signal is emitted to the zoom lens through the optical fiber and is emitted to the object to be photographed through the zoom lens, and when the camera assembly photographs the object to be photographed, the laser signal may fill a light into a monitoring area of the camera assembly.

The camera assembly may include devices such as a lens and an image sensor, which are not specifically limited herein, and any camera assembly in the field of imaging may be used. The zoom lens is used for adjusting the illumination distance of the laser illumination assembly, and can be selected according to actual illumination requirements.

The output wavelength of the laser signal emitted by the laser device is affected by the injected driving current, when the driving current of the laser device changes, the refractive index inside a PN junction (Positive-Negative junction) of the laser device changes, and the band gap also changes, which both change the output wavelength of the laser device, so that the output wavelength of the laser signal emitted by the laser device can be modulated by modulating the driving current. Wherein the band gap is the energy difference between the lowest point of the conduction band and the highest point of the valence band.

The driving circuit can simultaneously transmit the alternating current component and the direct current component with certain amplitude values to the laser, so that high-frequency disturbance is generated to change the driving current of the laser, and the rapid modulation of the wavelength of a laser signal emitted by the laser is realized. That is, the wavelength of the laser signal emitted by the laser varies with the alternating current component.

The positions of speckle generation are different due to different positions of interference enhancement of laser signals with different wavelengths. The speckle produced when the wavelength of the laser signal changes rapidly with time also changes rapidly with time. When the change period of the wavelength of the laser signal is far shorter than the exposure time of the laser illumination camera, a plurality of speckle patterns can be superposed in unit time, and the speckle can be weakened or even eliminated through time integration, so that the brightness of a monitoring picture shot by the laser illumination camera is uniform.

As an implementation manner of the embodiment of the present invention, as shown in fig. 2, the driving current may include an alternating current component which is a sinusoidal signal capable of high frequency, and the driving circuit 112 may include a high frequency signal generator 1121, a direct current signal generator 1122, and an adder 1123;

the high-frequency signal generator 1121 and the direct-current signal generator 1122 are electrically connected to the adder 1123, the adder 1123 is electrically connected to the laser 111, and the high-frequency sinusoidal signal generated by the high-frequency signal generator 1121 and the direct-current signal generated by the direct-current signal generator 1122 are superimposed by the adder 1123 and transmitted to the laser 111.

The adder may add the high frequency sinusoidal signal and the dc signal to transmit the added current signal to the laser. The laser obtains the driving current to emit a laser signal, and simultaneously, the wavelength of the laser signal is changed along with the disturbance of the high-frequency sinusoidal signal due to the input of the high-frequency sinusoidal signal, so that the speckle is weakened or eliminated.

The high-frequency signal generator can be any signal generator capable of generating a high-frequency sinusoidal signal, and the frequency can be a high frequency of 100 khz to 30 mhz. For example, LC (Inductor-Capacitor) tunable oscillators and the like may be specifically a mutual inductance coupled oscillator, an inductance feedback oscillator, a capacitance feedback oscillator and the like.

Therefore, in this embodiment, the high-frequency signal generator and the direct-current signal generator are respectively electrically connected with the adder, the adder is electrically connected with the laser, the high-frequency sinusoidal signal generated by the high-frequency signal generator and the direct-current signal generated by the direct-current signal generator are transmitted to the laser after being superimposed by the adder, and then the laser is driven to emit the laser signal and generate high-frequency sinusoidal disturbance, the wavelength of the laser signal is changed, and therefore speckle reduction or elimination is achieved.

As an implementation manner of the embodiment of the present invention, as shown in fig. 3, the laser illumination assembly 110 may further include a beam splitting lens 115, where the beam splitting lens 115 is disposed between the optical fiber 114 and the zoom lens 113;

a projection 116 is arranged on the light-emitting surface of the beam splitting lens 115; the laser signal is emitted to the beam splitting lens 115 through the optical fiber 114, and enters the zoom lens 113 through the light emitting surface of the beam splitting lens 115 and the light emitting surface of the protrusion 116.

In order to further improve the speckle eliminating effect, the laser illumination assembly may further include a beam splitting lens, and specifically, the beam splitting lens may have a protrusion on a light exit surface thereof. Thus, after being emitted to the beam splitting lens through the optical fiber, the laser signal is emitted through the light emitting surface of the beam splitting lens and the light emitting surface of the bulge respectively, and then enters the zoom lens. The speckles generated by different light emitting surfaces are mutually independent, and under the action of alternating current component disturbance, the independent speckles rapidly move on a shot picture and then mutually offset under the action of time integration, so that a better speckle elimination effect is achieved.

The convex light-emitting surface on the light-emitting surface of the beam splitting lens may be circular and the like, and is not limited in this respect. The area of the convex light emitting surface is not particularly limited in the embodiments of the present invention.

It is thus clear that, in this embodiment, the laser lighting assembly can also include beam splitting lens, beam splitting lens sets up between optic fibre and zoom lens, can have the arch on beam splitting lens's the play plain noodles, like this, laser signal passes through optic fibre and shoots out to beam splitting lens after, can shoot into zoom lens through beam splitting lens's play plain noodles and bellied play plain noodles, thereby form mutually independent speckle, under the effect of alternating current component disturbance, each independent speckle is at the quick travel on the picture of shooing, and then offset each other under the effect of time integral, reach better speckle elimination effect.

As an implementation manner of the embodiment of the present invention, the number of the protrusions may be plural. For example, the number of the cells may be 4, 5, 6, etc., and is not particularly limited herein.

The thicknesses of the plurality of protrusions are increased progressively along the incident direction of the laser signal, the thickness difference between two adjacent protrusions is not smaller than a preset thickness, and the thickness difference between the smallest one of the thicknesses of the plurality of protrusions and the light emitting surface of the beam splitting lens is not smaller than the preset thickness.

Thickness on a plurality of archs edge laser signal's the incident direction increases progressively, like this, can guarantee that every arch and beam splitting lens's play plain noodles all is not at the coplanar, can produce a plurality of mutually independent speckles, like this under the effect of high frequency current signal disturbance, a plurality of independent speckles move fast on taking the picture, and then offset each other under the effect of time integral, and the elimination effect of speckle is better.

In order to ensure that the laser signals emitted from each protrusion and the light-emitting surface of the beam splitting lens are independent from each other, the contrast of interference fringes between the laser signals needs to be reduced, that is, the optical path difference of the transmission path of each laser signal needs to be greater than the coherence length of the laser signal. The optical path difference of the transmission path of each laser signal is determined by the thickness of the protrusions along the incident direction of the laser signal, so that the thickness difference between two adjacent protrusions is not less than the preset thickness, and the thickness difference between the minimum one of the thicknesses of the protrusions and the light-emitting surface of the beam splitting lens is not less than the preset thickness.

That is, the positions of the light-emitting surface of the beam splitting lens and the light-emitting surface of each protrusion may be gradually increased along the incident direction of the laser signal. The predetermined thickness may be determined according to a relationship between a contrast of the interference fringes and a coherence length of the laser signal.

It can be seen that, in this embodiment, the thickness of the plurality of protrusions on the light-emitting surface of the beam-splitting lens in the incident direction of the laser signal may be increased progressively, the thickness difference between two adjacent protrusions is not less than the preset thickness, and the thickness difference between the smallest one of the thicknesses of the plurality of protrusions and the light-emitting surface of the beam-splitting lens is not less than the preset thickness, so that the laser signals emitted from each protrusion and the light-emitting surface of the beam-splitting lens may be ensured to be independent from each other, thereby further improving the speckle reduction effect.

As an implementation manner of the embodiment of the present invention, the preset thickness d may be determined by using the following formula:

wherein Δ λ is an output spectral width of the laser, λ is an output wavelength of the laser, and n is a refractive index of the beam splitting lens.

The laser signals are transmitted into the beam splitting lens through the optical fibers, a part of the laser signals are transmitted out of the light emitting surface of the beam splitting lens, and a part of the laser signals are transmitted out of the convex light emitting surface. Taking a protrusion with a predetermined thickness as an example of the thickness difference between the protrusion and the light emitting surface 1 of the beam splitting lens, the optical path difference between the paths of the laser signal emitted from the light emitting surface 2 and the laser signal emitted from the light emitting surface 1 is (n-1) · d. Wherein n is the refractive index of the beam splitting lens.

In order to ensure that the two laser signals respectively emitted from the light emitting surface 1 and the light emitting surface 2 are independent from each other to weaken the speckle effect, the contrast K of the interference fringes of the two laser signals needs to be reduced. That is, the optical path difference between the paths of the laser signal emitted from the light emitting surface 2 and the laser signal emitted from the light emitting surface 1 needs to be larger than the coherence length of the laser signal. The expression for the total light intensity I output by the beam splitting lens is:

wherein λ is₀Is the center wavelength of the laser signal, I₀The Δ λ is the output spectral width of the laser for the central light intensity of the laser signal, and can be determined according to the frequency and amplitude of the high-frequency sinusoidal signal and the magnitude of the dc signal, which will be described in detail later. The expression from this for the contrast K of the interference fringes is given by:

it can be seen that when the distance between the light emitting surface 1 and the light emitting surface 2 is betweenWhen the contrast K of the interference fringes is equal to 0, the two laser signals emitted from the light emitting surface 1 and the light emitting surface 2 will not generate interference fringes, and the speckles generated by the two laser signals in the shot picture are also independent of each other. Therefore, the predetermined thickness d may be

It can be seen that, in the embodiment, the above-mentioned preset thickness d can adopt a formulaTherefore, the laser signals emitted by the light-emitting surface of the beam splitting lens and the light-emitting surfaces of the protrusions are mutually independent, speckles generated in a shot picture are mutually independent, and therefore the laser signals are disturbed by high-frequency sinusoidal signalsAnd a plurality of independent speckles move rapidly on a shot picture, and then are mutually offset under the action of time integration, so that the speckle eliminating effect is further improved.

As an implementation manner of the embodiment of the present invention, as shown in fig. 4, the laser lighting assembly 110 may further include a heat dissipation device 117;

the heat sink device 117 is used to dissipate heat for the laser 111.

Because the temperature change of the laser can cause the output wavelength of the laser to change, thereby influencing the speckle elimination effect, in order to prevent the temperature of the laser from being influenced by the environment temperature and the heat possibly generated when the laser works, a heat dissipation device can be arranged in the laser lighting assembly and used for dissipating heat for the laser.

In one embodiment, the heat dissipation device may be a constant temperature heat dissipation component, and the laser may be cooled by air cooling or a cooling method such as a TEC (thermal Electric Cooler).

Therefore, in this embodiment, the laser lighting assembly may further include a heat dissipation device for dissipating heat of the laser, so as to prevent the laser temperature from being affected by the ambient temperature and heat possibly generated during the operation of the laser, and thus the speckle reduction effect is affected.

As an implementation manner of the embodiment of the invention, the amplitude value i of the high-frequency sinusoidal signal generated by the high-frequency signal generator is_sComprises the following steps:

i_s＝πτTfi₀

wherein i₀And the current value of the direct current signal generated by the direct current signal generator is tau, the maximum value of the percentage of fluctuation of the output energy of the laser, which can ensure the stability of the shot picture of the camera assembly, is T, the exposure time of the laser lighting camera, namely the exposure time of the camera assembly, and f is the frequency of the high-frequency sinusoidal signal.

As shown in fig. 5, when the driving current of the laser is increased, the output wavelength of the laser is shifted to a long wavelength direction, i.e., a wavelength red shift phenomenon occurs. Similarly, when the driving current of the laser decreases, the output wavelength of the laser shifts to a short wavelength, i.e., a blue shift of the wavelength occurs.

Laser signals emitted by the laser are coupled by the optical fibers and then emitted to the zoom lens or the beam splitting lens, and finally emitted out through the zoom lens to realize illumination on a long-distance shot object. When no high-frequency sinusoidal signal disturbance is added, the laser signals generate the phase difference of interferenceCan be represented by the following formula:

where Δ x is the optical path difference, related to the position of the interference, and λ is the output wavelength of the laser. When in useWhen the light intensity is integral multiple of 2 pi, the light intensity is maximum due to interference, and speckles appear on a shot picture. When high-frequency sinusoidal signals are added for disturbance, the output wavelength of the laser changes along with time, and phase differences at different interference positions also change along with time, so that the brightness of speckles changes rapidly. However, the laser is affected by the amplitude value of the injected high frequency sinusoidal signal and the maximum variation of the output wavelength is limited.

The amplitude values and frequencies of the direct current signal and the high-frequency sinusoidal signal in the driving current can be set according to the brightness stability of the shot picture. Wherein the current value of the DC signal is i₀The current value of the high-frequency sinusoidal signal isi_sIs the amplitude value of the high-frequency sinusoidal signal, f is the frequency of the high-frequency sinusoidal signal, t is time,is high frequency positiveThe initial phase of the string signal.

The output power of the laser changes approximately linearly with the injection current, and the corresponding coefficient is alpha. The output power p (t) of the laser can therefore be approximated by:

the exposure time is set according to the shooting requirement of the laser lighting camera, and the exposure time of the camera is set to be T. In order to ensure the stability of the shot picture of the laser lighting camera, the output energy of the laser needs to be kept stable within the exposure time T of the laser lighting camera, the maximum value of the allowed percentage fluctuation of the output energy of the laser is tau, and the direct current signal and the high-frequency sinusoidal signal in the injection current need to meet the following conditions:

the frequency of the high-frequency sinusoidal signal can reach kilohertz level, and the period is far less than the exposure time T, so that the frequency of the high-frequency sinusoidal signal in the above formulaCan be formed by₀α T instead. Amplitude value i of high-frequency sinusoidal signal can be obtained_sComprises the following steps:

i_s＝πτTfi₀

the larger the amplitude value of the high-frequency sinusoidal signal is, the more obvious the speckle eliminating effect is, but the frequency of the high-frequency sinusoidal signal can affect the service life of the laser, and the maximum modulation frequency that the laser can bear is f_M. Thus the amplitude value i of the high-frequency sinusoidal signal_sMaximum value of i_sMComprises the following steps:

i_sM＝πτTf_Mi₀

the current value i of the direct current signal generated by the direct current signal generator₀Can be based on the practiceThe lighting requirement settings are known, so can be according to i_sM＝πτTf_Mi₀Calculating to obtain the maximum value i of the amplitude value of the high-frequency sinusoidal signal_sMFrequency of f_MAt this time, the speckle removal effect is optimal.

In summary, on the premise of not affecting the stability of the shot picture of the laser illumination camera, when the amplitude value of the high-frequency sinusoidal signal is the maximum, the speckle elimination effect is the best, and at this time, the injection current i (t) can be represented by the following formula:

according to the formula, the exposure time T of the camera and the maximum modulation frequency f of the laser can be determined_MThe proportion of the high-frequency sinusoidal signals in the injection current i (t) and the proportion of the direct current signals are determined, and the high-frequency signal generator and the direct current signal generator are convenient to select and set.

It can be seen that in this embodiment, the maximum modulation frequency f of the laser can be based on the camera exposure time T_MThe proportion of the high-frequency sinusoidal signals in the injection current i (t) is determined, and the optimal speckle elimination effect can be achieved on the premise of ensuring the stability of a shot picture.

In order to further improve the speckle eliminating effect, it is known that the incoherent laser beam splitting device, i.e. the beam splitting lens, can be arranged for high-frequency sinusoidal signal disturbances with different amplitudes as described in the above embodiments. The output wavelength of the laser and the injection current are in nonlinear change and can be fitted through a polynomial, and the corresponding fitting coefficient is [ a ]₀,a₁…a_i]Wherein i is a preset polynomial fitting term number, and the embodiment of the present invention is not specifically limited herein. The wavelength of the laser changes by an amount Δ λ_mCan be expressed as:

it can be seen that after the high-frequency sinusoidal signal is added for disturbance, the output spectral width of the laser is expanded, and the output spectral width can be expressed as:

wherein, Δ λ₀The output spectral width of the laser when no high-frequency sinusoidal signal disturbance is added. The preset thickness of the projection on the light-emitting surface of the beam splitting lens can be determined according to the output spectrum width determined by the formula. I.e. according to the formulaAnd determining the preset thickness d of the bulge on the light-emitting surface of the beam splitting lens.

Corresponding to the laser lighting assembly, the embodiment of the invention also provides a method for determining the parameters of the laser lighting system. A method for determining parameters of a laser illumination system according to embodiments of the present invention is described below.

As shown in fig. 6, a method for determining parameters of a laser illumination system, the laser illumination system comprising a camera assembly and a laser illumination assembly, the laser illumination assembly comprising a laser, an optical fiber and a zoom lens for supplementing a monitored area of the camera assembly with light, a driving current of the laser comprising a dc component and an ac component, the method comprising:

s601, when the laser has a specified direct current component and the camera assembly has a specified exposure time, acquiring the maximum modulation frequency of the laser;

and S602, determining the maximum amplitude value of the alternating current component included in the driving current of the laser in response to the current value of the direct current component, the exposure time and the maximum modulation frequency of the laser.

Therefore, in the scheme provided by the embodiment of the invention, the laser illumination system comprises a camera assembly and a laser illumination assembly, the laser illumination assembly comprises a laser, an optical fiber and a zoom lens and is used for supplementing light to the monitoring area of the camera assembly, and the driving current of the laser comprises a direct current component and an alternating current component. The electronic device may acquire the maximum modulation frequency of the laser when the laser has a specified direct current component and the camera assembly has a specified exposure time, and determine the maximum amplitude value of the alternating current component included in the driving current of the laser in response to the current value of the direct current component, the exposure time, and the maximum modulation frequency of the laser. Therefore, the electronic equipment can determine the maximum amplitude value of the alternating current component included by the driving current of the laser according to the exposure time of the camera component and the maximum modulation frequency of the laser, so that the rapid modulation of the output wavelength of the laser is realized by adding the disturbance of the alternating current component into the injection current of the laser, the change of the laser interference speckle position is realized, and the speckle effect can be obviously weakened through time integration. Meanwhile, since a mechanical vibration part is not required to be added, the laser illumination camera is high in stability and good in picture shooting effect.

The laser illumination assembly included in the laser illumination system provided in the embodiment of the present application may be the laser illumination assembly described in any of the above embodiments, and the specific structure of the laser illumination assembly has been described in the above embodiments, which is not limited herein.

With respect to the laser illumination assembly, as can be seen from the above description of the embodiments, in the case where the laser has a specified dc component and the camera assembly has a specified exposure time, the larger the amplitude value of the ac component, the more significant the speckle removal effect is, but the frequency of the ac component may have an influence on the lifetime of the laser, and the laser has a tolerable maximum modulation frequency, so that the electronic device may acquire the maximum modulation frequency of the laser when it is necessary to determine the maximum amplitude value of the ac component included in the driving current of the laser. Wherein the alternating current component may be the high frequency sinusoidal signal.

Further, in step S602, the electronic device may determine the maximum amplitude value of the alternating current component included in the driving current of the laser in response to the current value of the direct current component, the exposure time, and the maximum modulation frequency of the laser. In one embodiment, the electronic device may call a function for calculating the maximum amplitude value of the alternating current component, thereby determining the maximum amplitude value of the alternating current component.

As an implementation manner of the embodiment of the present invention, the step of determining the maximum amplitude value of the alternating current component included in the driving current of the laser in response to the current value of the direct current component, the exposure time and the maximum modulation frequency of the laser may include:

determining a maximum amplitude value i of an alternating current component included in a driving current of the laser based on the following formula in response to a current value of the direct current component, the exposure time, and a maximum modulation frequency of the laser_s：

i_s＝πτTfi₀

Wherein i₀And tau is the current value of the direct current component, tau is the maximum value of the percentage of fluctuation of the output energy of the laser which can ensure the picture stability of the monitored area, T is the exposure time, and f is the frequency of the alternating current component.

As an implementation manner of the embodiment of the present invention, the laser illumination assembly may further include a beam splitting lens disposed between the optical fiber and the zoom lens, wherein a light emitting surface of the beam splitting lens has at least one protrusion, a thickness of the at least one protrusion increases along an incident direction of a laser signal, a thickness difference between two adjacent protrusions is not less than a preset thickness, and a thickness difference between a smallest one of thicknesses of the plurality of protrusions and the light emitting surface of the beam splitting lens is not less than the preset thickness;

the above method may further comprise:

determining the preset thickness in response to an output spectral width of the laser and an output wavelength of the laser.

According to the above description of the embodiment of the laser lighting assembly, after the disturbance of the ac component is added, the output spectral width of the laser expands, and the output wavelength of the laser changes, because in order to further improve the speckle eliminating effect, a beam splitting lens may be disposed in the laser lighting assembly. The light-emitting surface of the beam splitting lens is provided with at least one bulge.

For the preset thickness corresponding to the at least one protrusion, since the preset thickness affects the position where the laser signal emitted by the protrusion forms interference, thereby affecting the speckle eliminating effect, the electronic device can determine the preset thickness in response to the output spectral width of the laser and the output wavelength of the laser. In one embodiment, the electronic device may invoke a function for calculating the preset thickness to determine a specific value for the preset thickness.

As an implementation manner of the embodiment of the present invention, the step of determining the preset thickness in response to the output spectral width of the laser and the output wavelength of the laser may include:

determining the preset thickness d in response to the output spectral width of the laser and the output wavelength of the laser based on the following formula:

wherein Δ λ is an output spectral width of the laser, λ is an output wavelength of the laser, and n is a refractive index of the beam splitting lens.

Since the determination of the predetermined thickness d has been described in detail in the above-mentioned embodiment of the laser lighting assembly, it is not particularly limited herein. The electronic equipment according to the formulaThe specific value of the preset thickness d can be calculated.

Corresponding to the laser lighting assembly, the embodiment of the invention also provides a laser lighting camera. The following describes a laser illumination camera provided by an embodiment of the present invention.

As shown in fig. 7, a laser illumination camera includes a camera assembly 120, and the laser illumination assembly 110 of any of the above embodiments;

the laser lighting assembly 110 is used for supplementing light to the monitored area of the camera assembly 120.

It can be seen that, in the solution provided by the embodiment of the present invention, the laser illumination camera includes a laser illumination component and a camera component, wherein: the laser lighting assembly comprises a laser, a driving circuit and a zoom lens; the drive circuit is electrically connected with the laser and transmits a drive current to the laser, wherein the drive current comprises a direct current component and an alternating current component. The laser device is connected with the optical fiber, the laser device emits laser signals, the laser signals are emitted to the zoom lens through the optical fiber, and the zoom lens transmits the laser signals to supplement light for a monitoring area of the camera assembly. The alternating current component disturbance is added into the driving current of the laser, so that the output wavelength of the laser is rapidly modulated, the laser interference speckle position is changed, and the speckle effect can be obviously weakened through time integration. Meanwhile, since a mechanical vibration part is not required to be added, the laser illumination camera is high in stability and good in picture shooting effect.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the embodiment of the laser illumination camera, since it is substantially similar to the embodiment of the laser illumination assembly, the description is simple, and the relevant points can be referred to the partial description of the embodiment of the laser illumination assembly.

The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall fall within the protection scope of the present invention.