CN110888177A - Novel dark and weak target detection device under strong sky light background - Google Patents

Abstract

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.

Description

A new type of detection device for dim and weak targets in the background of strong sky light

technical field

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

Background technique

Optical search and tracking technology is a widely used general technology, which can be used for precise pointing of laser beams, maintaining the position and attitude of flying platforms, and high-precision tracking and aiming of large-diameter optoelectronic telescopes. A star tracking device, usually called a star sensor, obtains the position and attitude information of the aircraft (satellite, etc.) by detecting the distribution of the star field in a large area.

The existing optical search and tracking device is affected by the background of the sun and sky light, and its detection period, detection capability and measurement accuracy are severely restricted. However, the existing methods for suppressing skylight background noise (mainly including: field of view control method, spectral filtering method, polarization filtering method, etc.) have their limitations, which are mainly reflected in the following points: For the field of view control method, the disadvantage is that the visual field The field is small, and the suppression ability is not good in the strong sky light background; for the spectral filtering method, the disadvantage is that it is difficult to distinguish the spectral energy peaks of the target light and the sky light background when the spectra of the target and the sky light background are similar; for the polarization filtering method, generally The difference between the polarization states of the target light and the sky light background needs to be estimated in advance. Since the difference of polarization states changes with the change of the orbital motion and attitude of the target and the altitude angle of the sun, etc., the specific implementation is relatively complicated and also has certain implications for the application period and scene. Must request. Therefore, the dim target detectors based on the existing methods of suppressing the background noise of sky light often have problems such as low detection magnitude and poor adaptability to the application environment.

SUMMARY OF THE INVENTION

Based on this, it is necessary to provide a new type of weak target detection device under the background of strong sky light to solve the problems of low detection magnitude and poor adaptability to the application environment of the existing weak target detectors.

In order to solve the above problems, the present invention adopts the following technical solutions:

A new type of detection device for dim and weak targets under the background of strong sky light, comprising:

The shearing interferometer is used to form two transverse shearing beams from the incident beams including the target light and the sky light background light, and periodically modulate the shearing amount of the two transverse shearing beams, so that the two transverse shearing beams are The target light in the cut beam forms moving shear interference fringes;

The detector is used to convert the optical signals of the two transverse shear beams into electrical signals, and send the electrical signals to a weak signal detection device;

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

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

The novel detection device for dim and weak targets in the background of strong sky light proposed by the present invention uses a shearing interferometer to receive the incident beam including the target light and the background light of the sky light, and forms the incident beam into two transverse shear beams. The large coherent region in the far-field of the target realizes the interference of the target light in the two transverse shearing beams, and at the same time introduces a periodically changing optical path difference in the two shearing optical paths, thereby periodically modulating the two transverse shearing beams The shearing amount of the beam makes the target light in the two transverse shearing beams form moving shearing interference fringes. The detector converts the changed optical signal into an electrical signal, and then detects the target light through the subsequent weak signal detection equipment. with extraction. The invention cleverly utilizes the difference in spatial coherence between the target and the sky light background, and amplifies the difference through modulation and demodulation methods, so as to realize the detection of dim and weak targets under the strong sky light background, and due to the two-way lateral shearing The shearing amount of the beam can be adjusted to be very small, and the sheared interference fringes are clearer, so the interference detection of targets at different distances and different sizes can be realized. Therefore, the energy in the far-field coherent region of the target can be fully utilized, and the energy utilization rate is relatively high (close to 100%). Therefore, the novel detection device for dim and weak targets in the background of strong sky light proposed by the present invention can overcome the difficulty of close-range targets. The problem of interference can greatly improve the energy utilization rate, improve the detection of the magnitude of the dim target and the suppression of the sky light background. The novel detection device for dim and weak targets in the background of strong sky light proposed by the present invention can be placed on ground-based, sea-based, air-based or space-based platforms for use, and can realize the discovery and tracking of dim and small targets in the whole sky for large telescopes, and the laser beam All-day precise pointing, all-day attitude control of the aircraft, etc., have a wide range of applications and strong practicability.

Description of drawings

1 is a schematic structural diagram of a novel dark and weak target detection device under the background of strong sky light in one of the embodiments of the present invention;

Figure 2 is a shear interference fringe diagram;

FIG. 3 is a schematic structural diagram of a novel dark and weak target detection device under the background of strong sky light according to another embodiment of the present invention.

Detailed ways

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

In one of the embodiments, as shown in FIG. 1 , the present invention discloses a novel detection device for dim and weak targets under the background of strong sky light, including a shearing interferometer 10 , a detector 30 and a weak signal detection device 40 . The device utilizes shearing The interferometer 10 realizes the interference of the target light to form shearing interference fringes, and uses the shearing interferometer 10 to realize the periodic reciprocating motion of the shearing interference fringes, thereby realizing the frequency modulation of the target light signal, and then using the detector 30 to convert the shearing interference fringes. The optical signals of the two transverse shear beams formed by the interferometer 10 are converted into electrical signals, and finally the modulated target signal is detected by the weak signal detection device 40 and the influence of the main noise including the sky light background is suppressed, so as to realize the detection of dim and weak signals. Detection of target signals.

Specifically, in this embodiment, the incident light beam including the sky light background light and the target light emitted by the dim target 50 is incident on the shearing interferometer 10, and the shearing interferometer 10 forms the incident light beam into two transverse shearing beams. Both beams are ideal replicas of the target beam (that is, the wavefront distribution characteristics of the two beams are exactly the same). There is a certain center distance (that is, the distance between the centers of the two beam sections); the shearing interferometer 10 can introduce a periodically changing optical path difference in the two shearing optical paths, thereby periodically modulating the two transverse shearing beams The shearing amount of the two transverse shearing beams causes the target light in the two transverse shearing beams to form moving shearing interference fringes, while the sky light background light in the two transverse shearing beams cannot interfere, and an 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 . The regions 60 and 70 in FIG. 2 are the cross sections of the two transverse shearing beams formed by the shearing interferometer 10 (generally In this case, the cross-sectional shape of the shearing beam is the same as that of the incident light), and the region 80 is a shearing interference fringe formed in the overlapping region of the two transverse shearing beams.

The detector 30 is used to convert the 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 can be selected from a photodiode array (Photo-diode Array, PDA) detector, an avalanche photo-diode array (Avalanche Photo-diode Array, APDA) detector, and a photomultiplier tube array detector (Photomultiplier tube Array). , PMTA) or microchannel plate (Microchannel Plate, MCP) detectors and other analog output area array detectors. In order to improve the detection ability of dim targets, a light intensity multiplying device similar to an image intensifier can also be placed in front of the area array detector. Indicators such as detection sensitivity, working spectral width, resolution and pixel size of the detector 30 should be selected according to specific application requirements.

The weak signal detection device 40 is used for detecting and extracting the target signal corresponding to the target light from the electrical signal. The weak signal detection device 40 in this embodiment can be selected as a weak periodic signal detection device based on a phase-locked (lock-in) amplifier or a sampling integrator as the core device, and the number of processing channels of the weak periodic signal detection device should be equal to the number of detectors The number of pixels is 30, so as to realize the simultaneous detection and extraction of the target signal in the entire field of view of the detector. Weak signal detection equipment is a mature detection equipment used to extract periodic signals from an input signal overwhelmed by noise (the signal-to-noise ratio may be lower than 1). The present invention generates a periodic signal of the target light by introducing the modulation of the target light, while the sky light background light cannot be modulated, so random noise is generated, and then the periodic target signal is extracted by using the existing weak signal detection equipment, and finally the detection of the target light is realized. Detection of target light with dim target signal.

The novel detection device for dim and weak targets in the background of strong sky light proposed in this embodiment uses a shearing interferometer to receive the incident beam including the target light and the background light of the sky light, and forms two transverse shear beams from the incident beam. The far-field coherence area of the target is relatively large, and the interference of the target light in the two transverse shear beams is realized, and a periodically changing optical path difference is introduced in the two shear light paths, thereby periodically modulating the two transverse shear beams. The shearing amount of the cut beam makes the target light in the two transverse shear beams form moving shear interference fringes. The detector converts the changed optical signal into an electrical signal, and then realizes the target light through the subsequent weak signal detection equipment. Detection and extraction. The dim target detection device cleverly utilizes the difference in spatial coherence between the target and the sky light background, and amplifies the difference between the two through modulation and demodulation methods, so as to realize the detection of dim targets under the strong sky light background. The shearing amount of the transverse shearing beam can be adjusted to be very small, and the shearing interference fringes are clearer, so the interference detection of targets at different distances and different sizes can be realized. In addition, the center distance of the two transverse shearing beams can be very small. (can be close to zero), so the energy in the far-field coherent region of the target can be fully utilized, and the energy utilization rate is relatively high (close to 100%). The problem that the short-range target is difficult to interfere with can greatly improve the energy utilization rate, and improve the detection accuracy and accuracy of the dim target. The new type of detection device for dim and weak targets in the background of strong sky light proposed in this embodiment can be placed on ground-based, sea-based, space-based or space-based platforms, and can realize the discovery and tracking of small and dim targets in the whole sky of large telescopes. It has a wide range of applications and strong practicability.

When the width of the interference fringes formed by the shearing interferometer 10 does not match the pixel size of the detector 30 , in order to further improve the detection sensitivity of the detector 30 , a beam-reducing lens can be added between the shearing interferometer 10 and the detector 30 . 20, as shown in FIG. 3, the beam-reducing lens 20 is used to compress the coverage area of the fringe field of the two transverse shear beams, so as to improve the energy concentration of the fringes and make the interference fringe width match the pixel unit of the detector (if the detection If the detector 30 can directly and significantly detect the movement of the fringes, the beam-reducing lens 20 may not be added to the new type of detection device for dim and weak targets under the background of strong sky light. The beam reducing lens 20 is an afocal optical system with the function of compressing the beam diameter, which can 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. To eliminate chromatic aberration (caused by broad-spectrum light sources), each of the above lenses can be selected in the form of a doublet or a combination lens. Of course, other types of optical systems, such as catadioptric or total reflection capable of realizing the beam-shrinking function, can also be used as optional types of the beam-shrinking lens 20 .

The shearing interferometer 10 in the present invention can be of various types, for example: (1) a shearing interferometer comprising a spectroscopic film (or other devices with spectroscopic functions, such as a spectroscopic plate or a spectroscopic prism, etc.) and a mirror; ( 2) Shearing interferometer including shearing plate structure (two-way optical shearing by front and rear surfaces); (3) Shearing interferometer including double grating structure; (4) Shearing interferometer including birefringent prism structure Interferometer, etc. The shearing interferometer 10 used in this embodiment is not limited to a specific form, and any shearing interferometer that can realize the transverse shearing function of the two beams can be used.

As a specific implementation manner, the shearing interferometer 10 includes a reflector 11 and a spectroscopic element located in front of the reflector 11 , wherein the spectroscopic element can be any one of a beam-splitting film 12 , a beam-splitting plate, and a beam-splitting prism. Taking the shearing interferometer 10 including the reflecting mirror 11 and the beam splitting film 12 as an example, a schematic structural diagram of the dim target detection device of the present invention is given. By selecting the shear amount reasonably, the target light can form shear interference fringes, while the sky light background light cannot form interference fringes. There are many choices for the shearing amount of the two transverse shearing beams. For example, the shearing amount is equal to the center distance of the two transverse shearing beams by changing the distance between the beam splitting element and the mirror 11 . By changing the distance between the splitting element and the mirror 11, the shearing amount of the two transverse shearing beams (0-cm level) can be easily adjusted, and by choosing a smaller shearing amount (for example, 0.1 mm), a clearer beam can be formed. (according to the theory of partially coherent light, the closer the two regions participating in the interference are, the stronger the coherence will be, and the interference fringes with higher contrast can be formed); when the shear amount is very small (for example, 0.1mm), the two-way The overlapping area of the transverse shearing beam is very large, which is approximately equal to the cross section of a single beam (cm ² level), so the shearing interference method has a higher energy utilization rate (close to 100%). Since the width of the interference fringes formed by two perfectly parallel plane waves is infinite, in order to form a few fringes in the overlapping area of the shear beam (in order to improve the effective target signal intensity concentrated in a single fringe, generally 1 to 3 fringes) , a small inclination angle needs to be introduced between the beam splitting element of the shearing interferometer 10 and the mirror 11 , and the period and orientation of the shearing interference fringes can be adjusted by changing the size and direction of the inclination angle.

In order to make the target light in the two transverse shearing beams form moving shearing interference fringes, it is necessary to introduce periodic modulation of the optical path difference (or phase difference) between the two transverse shearing beams in the shearing interferometer 10, That is, a periodically varying optical path difference (or phase difference) is introduced into the two transverse shear beams. For the shearing interferometer 10 including the mirror 11 and the beam splitting element, the actuator 13 can be placed at the rear end of the mirror 11. As shown in FIG. 1, the actuator 13 is fixedly installed on the back of the mirror 11, and The actuator 13 performs periodic linear reciprocating motion, and the periodic linear reciprocating motion of the actuator 13 can periodically stretch the mirror 11 to periodically modulate the shear amount of the two transverse shear beams. amount to achieve the motion of shearing interference fringes. For schemes using other types of shearing interferometers, the method of introducing periodic modulation of the optical path difference (or phase difference) may be different from the modulation method of shearing interferometers including mirrors and beam splitting elements. The skilled person can select a suitable modulation method according to the specific structure adopted.

Further, the actuator 13 is a piezoelectric ceramic actuator or a voice coil motor actuator. The actuator 13 in this embodiment can be selected from any actuator that can realize the function of periodic linear (linear) reciprocating motion. In order to avoid the interference of low-frequency noise, high-frequency (above 50Hz) reciprocating motion is required. Piezoelectric ceramic actuators or voice coil motor actuators are devices with higher frequency reciprocating motion capabilities.

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims (10)

1. a dark and weak target detection device under the background of a novel strong sky light, is characterized in that, comprises: The shearing interferometer (10) is used to form two transverse shearing beams from the incident light beams including the target light and the sky light background light, and periodically modulate the shearing amount of the two transverse shearing beams, so that the two paths are all The target light in the transverse shear beam forms moving shear interference fringes; the detector (30) for converting the optical signals of the two transverse shear beams into electrical signals, and sending the electrical signals to a weak signal detection device (40); The weak signal detection device (40) is used for detecting and extracting a target signal corresponding to the target light from the electrical signal. 2. The novel dark and weak target detection device under strong sky light background according to claim 1, characterized in that, further comprising a beam reducing lens (20) located between the shearing interferometer (10) and the detector (30) ; The beam reduction lens (20) is used for compressing the coverage area of the fringe field of the two transverse shear beams. 3. The device for detecting dim and weak targets under the background of novel strong sky light according to claim 1 or 2, is characterized in that, The shearing interferometer (10) comprises a reflector (11) and a light-splitting element located in front of the reflector (11), the light-splitting element being any one of a light-splitting film (12), a light-splitting plate and a light-splitting prism . 4. The novel dark and weak target detection device under strong sky light background according to claim 3, wherein the shearing interferometer (10) further comprises an actuator (13); The actuator (13) is fixedly mounted on the back of the reflector (11), and the actuator (13) performs periodic linear reciprocating motion to periodically modulate the two-way transverse shear beams. amount of shear. 5. The device for detecting dim and weak targets under the background of novel strong sky light according to claim 4, is characterized in that, The actuator (13) is a piezoelectric ceramic actuator or a voice coil motor actuator. 6. The device for detecting dim and weak targets under the background of novel strong sky light according to claim 1 or 2, characterized in that, The detector (30) is any one of a photodiode array detector, an avalanche photodiode array detector, a photomultiplier tube array detector and a microchannel plate detector. 7. The device for detecting dim and weak targets under the background of novel strong sky light according to claim 1 or 2, characterized in that, The weak signal detection device (40) adopts a weak periodic signal detection device based on a lock-in amplifier or a sampling integrator as a core device, and the number of processing channels of the weak periodic signal detection device is equal to the detector (30) the number of pixels. 8. The device for detecting dim and weak targets under the background of novel strong sky light according to claim 1, is characterized in that, The shearing interferometer (10) includes a shearing plate structure. 9. The novel dark and weak target detection device under the background of strong sky light according to claim 1, is characterized in that, The shearing interferometer (10) includes a birefringent prism structure. 10. The novel dark and weak target detection device under the background of strong sky light according to claim 1, characterized in that, The shearing interferometer (10) includes a double grating structure.

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