阅读说明：本技术 一种新型强天光背景下暗弱目标探测装置 (Novel dark and weak target detection device under strong sky light background ) 是由 董磊 王建立 李洪文 王斌 于 2019-12-12 设计创作，主要内容包括：本发明涉及一种新型强天光背景下暗弱目标探测装置,属于光学搜索跟踪设备及星敏感器技术领域,该装置利用剪切干涉仪实现目标光的干涉,形成剪切干涉条纹,并且利用剪切干涉仪实现剪切干涉条纹的周期性往返运动,进而实现目标光信号的频率调制,然后利用探测器将两路横向剪切光束的光信号转换为电信号,最后利用微弱信号检测设备对受调制的目标信号进行检测并抑制包含天光背景在内的主要噪声的影响,实现对暗弱目标信号的探测。本发明所提出的新型强天光背景下暗弱目标探测装置能够克服近距离目标难以干涉的问题并且能够大大提升能量利用率,提高了暗弱目标探测星等和对天光背景的抑制能力。(The invention relates to a novel dark and weak target detection device under a strong skylight background, which belongs to the technical field of optical search tracking equipment and star sensors. The novel device for detecting the dim and weak targets under the strong skylight background can overcome the problem that the close-range targets are difficult to interfere, greatly improve the energy utilization rate and improve the capabilities of detecting stars and the like of the dim and weak targets and inhibiting the skylight background.)

1. A novel dark and weak target detection device under strong sky light background is characterized by comprising:

the shearing interferometer (10) is used for forming two transverse shearing light beams by incident light beams containing target light and skylight background light, and periodically modulating the shearing amount of the two transverse shearing light beams to enable the target light in the two transverse shearing light beams to form moving shearing interference fringes;

the detector (30) is used for converting the optical signals of the two transverse shearing light beams into electric signals and sending the electric signals to weak signal detection equipment (40);

the weak signal detection device (40) is used for detecting and extracting a target signal corresponding to the target light from the electric signal.

2. The new dark and weak target detection device under strong skylight background as claimed in claim 1, further comprising a beam shrinking lens (20) between the shearing interferometer (10) and the detector (30);

the beam shrinking lens (20) is used for compressing the coverage area of the fringe field of the two transverse shearing light beams.

3. A novel dark and weak object detection device under strong daylight background according to claim 1 or 2,

the shearing interferometer (10) comprises a reflecting mirror (11) and a light splitting element positioned in front of the reflecting mirror (11), wherein the light splitting element is any one of a light splitting film (12), a light splitting flat plate and a light splitting prism.

4. The new dark and weak target detection device under strong daylight background as claimed in claim 3, characterized in that said shearing interferometer (10) further comprises an actuator (13);

the actuator (13) is fixedly arranged on the back surface of the reflecting mirror (11), and the actuator (13) does periodic linear reciprocating motion so as to periodically modulate the shearing amount of the two transverse shearing light beams.

5. The novel dark and weak object detection device under strong skylight background is characterized in that,

the actuator (13) is a piezoelectric ceramic actuator or a voice coil motor actuator.

6. A novel dark and weak object detection device under strong daylight background according to claim 1 or 2,

the detector (30) is any one of a photodiode array detector, an avalanche photodiode array detector, a photomultiplier array detector and a microchannel plate detector.

7. A novel dark and weak object detection device under strong daylight background according to claim 1 or 2,

the weak signal detection equipment (40) adopts weak periodic signal detection equipment based on a phase-locked amplifier or a sampling integrator as a core device, and the number of processing channels of the weak periodic signal detection equipment is equal to the number of pixels of the detector (30).

8. The novel dark and weak object detection device under strong skylight background is characterized in that,

the shearing interferometer (10) comprises a shearing plate structure.

9. The novel dark and weak object detection device under strong skylight background is characterized in that,

the shearing interferometer (10) comprises a birefringent prism structure.

10. The novel dark and weak object detection device under strong skylight background is characterized in that,

the shearing interferometer (10) comprises a double grating structure.

Technical Field

The invention relates to the technical field of optical search tracking equipment and star sensors, in particular to a novel device for detecting dark and weak targets under a strong sky light background.

Background

The optical search tracking technology is a widely applied general technology and can be used for precise pointing of laser beams, position and attitude keeping of a flying platform, high-precision tracking of a large-aperture photoelectric telescope and the like. Star tracking devices, commonly referred to as star sensors, acquire position and attitude information of an aircraft (satellites, etc.) by detecting the star field distribution over a large area.

The existing optical searching and tracking device is influenced by the background of the sun and the sky light, and the detection time period, the detection capability and the measurement accuracy of the existing optical searching and tracking device are severely restricted. The existing methods for suppressing the background noise of the sky light (mainly including a field control method, a spectral filtering method, a polarization filtering method and the like) have limitations, and are mainly embodied in the following points: for the visual field control method, the visual field is small, and the inhibition capability under the background of strong sky light is poor; for the spectral filtering method, the disadvantage is that it is difficult to distinguish the spectral energy peaks of the target light and the skylight background when the target and the skylight background have similar spectra; for the polarization filtering method, the difference of the polarization states of the target light and the skylight background generally needs to be estimated in advance, and the difference of the polarization states changes along with the changes of the target orbit motion, the attitude, the solar altitude angle and the like, so the specific implementation is more complex and certain requirements are also provided for the application time interval and the scene. Therefore, the dim and weak target detector based on the existing method for suppressing the background noise of the sky light has the problems of low dim and weak target detection star and the like, poor adaptability to the application environment and the like.

Disclosure of Invention

Therefore, it is necessary to provide a novel device for detecting a dim and weak target under a strong daylight background, aiming at the problems of low dim and weak target detection stars and the like, poor adaptability to an application environment and the like of the existing dim and weak target detector.

In order to solve the problems, the invention adopts the following technical scheme:

a novel dark and weak target detection device under strong sky light background comprises:

the shearing interferometer is used for forming two transverse shearing light beams by incident light beams comprising target light and skylight background light, and periodically modulating the shearing amount of the two transverse shearing light beams to enable the target light in the two transverse shearing light beams to form moving shearing interference fringes;

the detector is used for converting the optical signals of the two transverse shearing light beams into electric signals and sending the electric signals to weak signal detection equipment;

the weak signal detection device is used for detecting and extracting a target signal corresponding to the target light from the electric signal.

Compared with the prior art, the invention has the following beneficial effects:

the novel dark and weak target detection device under the strong skylight background utilizes the shearing interferometer to receive the incident light beam containing the target light and the skylight background light, the incident light beam is formed into two transverse shearing light beams, the interference of the target light in the two transverse shearing light beams is realized by utilizing the characteristic that the far field coherent region of the target with the size far smaller than the skylight background range is larger, and meanwhile, the periodically changed optical path difference is introduced into the two shearing light paths, so that the shearing quantity of the two transverse shearing light beams is periodically modulated, the target light in the two transverse shearing light beams forms moving shearing interference fringes, the detector converts the changed optical signals into electric signals, and then the detection and extraction of the target light are realized through subsequent signal detection equipment. The invention skillfully utilizes the difference of the target and the background of the sky light on the spatial coherence and amplifies the difference of the target and the background of the sky light by a modulation and demodulation method, thereby realizing the detection of dark and weak targets under the background of strong sunlight, and because the shearing amount of the two transverse shearing light beams can be adjusted to be very small and the shearing interference fringes are clearer, the interference detection of targets with different distances and different sizes can be realized, in addition, because the center distance of the two transverse shearing light beams can be very small (can be close to zero), the energy in a target far-field coherent region can be fully utilized, the energy utilization rate is higher (close to 100%), therefore, the novel device for detecting the dim and weak targets under the strong skylight background can overcome the problem that the close-range targets are difficult to interfere, greatly improve the energy utilization rate and improve the capabilities of detecting stars and the like and inhibiting the skylight background. The novel device for detecting the dim and weak targets under the strong sky light background can be placed on a foundation, a sea foundation, an air foundation or a space foundation platform for use, can realize the discovery and tracking of the dim and weak targets in the whole day of a large telescope, the accurate pointing in the whole day of a laser beam, the control of the attitude of an aircraft in the whole day, and the like, and has wide application range and strong practicability.

Drawings

FIG. 1 is a schematic structural diagram of a device for detecting dark and weak objects under a strong sky-light background according to an embodiment of the present invention;

FIG. 2 is a shear interference fringe pattern;

fig. 3 is a schematic structural diagram of a dark and weak target detection device under a strong sky-light background in another embodiment of the present invention.

Detailed Description

The technical solution of the present invention will be described in detail with reference to the accompanying drawings and preferred embodiments.

In one embodiment, as shown in fig. 1, the present invention discloses a novel dark and weak target detection device under a strong sky-light background, which includes a shearing interferometer 10, a detector 30 and a weak signal detection device 40, and the device uses the shearing interferometer 10 to realize interference of target light to form shearing interference fringes, and uses the shearing interferometer 10 to realize periodic back-and-forth movement of the shearing interference fringes, so as to realize frequency modulation of target light signals, then uses the detector 30 to convert two paths of optical signals of transverse shearing light beams formed by the shearing interferometer 10 into electrical signals, and finally uses the weak signal detection device 40 to detect the modulated target signals and suppress the influence of main noise including the sky-light background, so as to realize detection of the dark and weak target signals.

Specifically, in the present embodiment, an incident light beam including a celestial background light and a target light emitted by a dim and dim target 50 is incident on the shearing interferometer 10, the shearing interferometer 10 forms the incident light beam into two lateral shearing light beams, both of which are ideal replicas of the target light (i.e., the wave surface distribution characteristics of the two light beams are completely the same), the propagation directions of the two light beams after passing through the shearing interferometer 10 are the same, and only a certain center distance (i.e., the distance between the centers of the cross sections of the two light beams) exists in the lateral direction (i.e., in the plane perpendicular to the propagation direction); the shearing interferometer 10 can introduce a periodically-changed optical path difference into the two shearing optical paths, so that the shearing amount of the two transverse shearing optical beams is periodically modulated, target light in the two transverse shearing optical beams forms moving shearing interference fringes, sunlight background light in the two transverse shearing optical beams cannot interfere with the target light, and approximately uniform strong light distribution is formed after superposition. The shearing interference fringes formed after the target light passes through the shearing interferometer 10 are shown in fig. 2, where a region 60 and a region 70 in fig. 2 are the cross sections of the two transverse shearing beams formed by the shearing interferometer 10 (generally, the cross section of the shearing beam is the same as that of the incident light), and a region 80 is the shearing interference fringes formed in the overlapping region of the two transverse shearing beams.

The detector 30 is configured to convert an optical signal of the compressed light beam into an electrical signal, and send the electrical signal to the weak signal detection device 40. The detector 30 in this embodiment may be an area Array detector for analog output, such as a photodiode Array (PDA) detector, an Avalanche photodiode Array (APDA) detector, a Photomultiplier tube Array (PMTA) detector, or a Microchannel Plate (MCP) detector. In order to improve the detection capability of dark and weak targets, a light intensity multiplier similar to an image intensifier can be placed in front of the area array detector. The detection sensitivity, the operating spectral width, the resolution, the pixel size, and other parameters of the detector 30 are selected according to the specific application requirements.

The weak signal detecting device 40 is configured to detect and extract a target signal corresponding to the target light from the electrical signal. The weak signal detection device 40 in this embodiment may select a weak periodic signal detection device based on a phase-locked (locked) amplifier or a sampling integrator, etc. as a core device, and the number of processing channels of the weak periodic signal detection device should be equal to the number of pixels of the detector 30, so as to realize simultaneous detection and extraction of a target signal in the entire detector field. Weak signal detection devices are currently mature detection devices that extract periodic signals from input signals (signal-to-noise ratio may be below 1) that are drowned out by noise. The invention generates periodic signals of target light by introducing modulation of the target light, and sky light background light cannot be modulated, so random noise is generated, and then the periodic target signals are extracted by using the existing weak signal detection equipment, and finally the detection of the target light of the dark and weak target signals is realized.

The novel dark and weak target detection device under the strong skylight background provided by the embodiment utilizes the shearing interferometer to receive the incident light beam containing the target light and the skylight background light, the incident light beam is formed into two paths of transverse shearing light beams, the interference of the target light in the two paths of transverse shearing light beams is realized by utilizing the characteristic that the far field coherent region of the target with the size far smaller than the skylight background range is larger, and meanwhile, the periodically changed optical path difference is introduced into the two shearing light paths, so that the shearing quantity of the two paths of transverse shearing light beams is periodically modulated, the target light in the two paths of transverse shearing light beams forms moving shearing interference fringes, the detector converts the changed optical signal into an electric signal, and then the detection and extraction of the target light are realized through subsequent weak signal detection equipment. The dark and weak target detection device skillfully utilizes the difference of the target and the sky light background on the spatial coherence and amplifies the difference of the target and the sky light background by a modulation and demodulation method, thereby realizing the detection of dark and weak targets under the background of strong sunlight, and because the shearing amount of the two transverse shearing light beams can be adjusted to be very small and the shearing interference fringes are clearer, the interference detection of targets with different distances and different sizes can be realized, in addition, because the center distance of the two transverse shearing light beams can be very small (can be close to zero), the energy in a target far-field coherent region can be fully utilized, the energy utilization rate is higher (close to 100%), therefore, the device for detecting the dim and weak targets under the background of the strong sky light provided by the embodiment can overcome the problem that the close-range targets are difficult to interfere, can greatly improve the energy utilization rate, and improves the detection precision and accuracy of the dim and weak targets. The novel dark and weak target detection device under the strong sky light background that this embodiment provided can place and use on ground, sea bed, air base or sky base platform, can realize the discovery and the tracking of the dark and weak target of large-scale telescope during the whole day, and the accurate sensing during the whole day of laser beam, the attitude control during the whole day of aircraft etc. and the range of application is wide, and the practicality is strong.

When the width of the interference fringes formed by the shearing interferometer 10 is not matched with the pixel size of the detector 30, in order to further improve the detection sensitivity of the detector 30, a beam shrinking lens 20 may be added between the shearing interferometer 10 and the detector 30, as shown in fig. 3, the beam shrinking lens 20 is used to compress the coverage area of the fringe field of the two transverse shearing light beams, so as to improve the energy concentration of the fringes and match the width of the interference fringes with the pixel unit of the detector (if the detector 30 can directly and significantly detect the movement of the fringes, the beam shrinking lens 20 may not be added in the novel dim and weak target detection device under the strong sky light background), and the two transverse shearing light beams compressed by the beam shrinking lens 20 are incident to the detector 30. The reduction lens 20 is an afocal optical system having a function of compressing the beam diameter, and may be composed of two positive (convex) lenses, and the ratio of the input and output beam diameters is approximately the ratio of the focal lengths of the front and rear lenses. In order to eliminate chromatic aberration (caused by a wide-spectrum light source), each lens can be selected to be in the form of double-cemented or combined lenses. Of course, other types of optical systems, such as catadioptric or total-reflection, capable of performing the beam-reducing function may be used as an alternative type of the beam-reducing lens 20.

The shearing interferometer 10 of the present invention may be of various types, for example: (1) a shearing interferometer including a spectroscopic film (or other device having a spectroscopic function such as a spectroscopic plate or a spectroscopic prism) and a reflecting mirror; (2) a shearing interferometer comprising a shearing flat plate structure (two-way optical shearing is realized by front and back surfaces); (3) a shearing interferometer comprising a dual grating structure; (4) shearing interferometers including birefringent prism structures, and the like. The shearing interferometer 10 used in the present embodiment is not limited to a specific form, and any shearing interferometer capable of performing the lateral shearing function of two beams may be used.

As a specific implementation manner, the shearing interferometer 10 includes a reflecting mirror 11 and a light splitting element located in front of the reflecting mirror 11, where the light splitting element may be any one of a light splitting film 12, a light splitting plate and a light splitting prism, and fig. 1 shows a schematic structural diagram of the weak light and dark object detection apparatus by taking only the example that the shearing interferometer 10 includes the reflecting mirror 11 and the light splitting film 12. Through reasonable selection of scissorsThe cut amount can make the target light form a shearing interference fringe, and the sky light background light can not form the interference fringe. The shearing amount of the two transverse shearing light beams can be selected in various ways, for example, the shearing amount is equal to the center distance of the two transverse shearing light beams by changing the distance between the light splitting element and the reflecting mirror 11. The shearing amount (0-cm level) of two paths of transverse shearing light beams can be conveniently adjusted by changing the distance between the light splitting element and the reflecting mirror 11, and clearer shearing interference fringes can be formed by selecting smaller shearing amount (for example, 0.1mm) (according to the theory of partial coherent light, the closer two areas participating in interference, the stronger coherence is, and the interference fringes with higher contrast can be formed); when the shearing amount is small (for example 0.1mm), the overlapping area of the two transverse shearing light beams is large and is approximately equal to the section (cm) of a single light beam²Stage), there is a higher energy utilization (close to 100%) with the shearing interference method. Since the width of the interference fringes formed by two completely parallel plane waves is infinite, in order to form a few fringes in the overlapping region of the shearing beams (to improve the effective target signal intensity concentrated in a single fringe, generally 1-3 fringes), a small tilt angle needs to be introduced between the beam splitting element of the shearing interferometer 10 and the reflecting mirror 11, and the period and orientation of the shearing interference fringes can be adjusted by changing the size and direction of the tilt angle.

In order to form moving shearing interference fringes for the target light in the two transverse shearing light beams, it is necessary to introduce periodic modulation of an optical path difference (or phase difference) between the two transverse shearing light beams in the shearing interferometer 10, that is, to introduce a periodically changing optical path difference (or phase difference) in the two transverse shearing light beams. For the shearing interferometer 10 comprising the reflecting mirror 11 and the light splitting element, an actuator 13 may be disposed at the rear end of the reflecting mirror 11, as shown in fig. 1, the actuator 13 is fixedly mounted on the back surface of the reflecting mirror 11, and the actuator 13 performs a periodic linear reciprocating motion, and the periodic linear reciprocating motion of the actuator 13 can periodically stretch the reflecting mirror 11 to periodically modulate the shearing amount of the two transverse shearing light beams, so as to realize the motion of shearing interference fringes by periodically modulating the shearing amount. For schemes employing other types of shearing interferometers, the method of introducing periodic modulation of the optical path difference (or phase difference) may differ from the modulation method of a shearing interferometer comprising mirrors and beam splitting elements, and one skilled in the art may select an appropriate modulation method depending on the particular configuration employed.

Further, the actuator 13 is a piezoelectric ceramic actuator or a voice coil motor actuator. The actuator 13 in this embodiment may be any actuator capable of performing a periodic linear reciprocating motion, and in order to avoid interference of low-frequency noise, a high-frequency reciprocating motion (above 50 Hz) is required, and a device having a higher reciprocating motion capability, such as a piezoelectric ceramic actuator or a voice coil motor actuator, should be selected.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.