CN115052091B - Transmission type double-channel compression imaging method and system based on crystal line polarizer - Google Patents
Transmission type double-channel compression imaging method and system based on crystal line polarizer Download PDFInfo
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Abstract
The invention discloses a transmission type double-channel compression imaging method and system based on a crystal line polarizer, and belongs to the technical field of computational imaging. According to the invention, through double-channel common image plane compression imaging, single exposure is realized, double-channel images are captured at the same time, the time resolution is doubled under the condition of the same detector, and the data size is doubled under the requirement of the same imaging time resolution precision. According to the invention, the mixed images acquired by the two-channel shared image plane are separated in a frequency domain compression mode, and the imaging view field is enlarged without adding a scanning device. The invention solves the contradiction between the optical imaging visual field and the focal length by the transmission type double-channel compression imaging based on the crystal line polarizer, realizes the concurrent imaging of the large visual field and the long focal length, remarkably improves the effect of the target identification probability of the monitoring tracking system, can acquire the polarization information of the target, and has the advantages of high resolution, narrow bandwidth, simple adjustment, high processing feasibility, compact structure, high stability and good economy of the imaging system.
Description
Technical Field
The invention belongs to the technical field of computational imaging, and relates to a transmission type double-channel compression imaging method and system based on a crystal line polarizer.
Background
Along with the continuous development of science and technology, the requirements of the fields of target detection, identification, tracking and the like on an optical system are higher and higher, and the current optical system is gradually developed towards the directions of large field of view and long focal length. The long focal length is used for higher resolution, the longer the focal length is, the higher the resolution is, the more pixels the target occupies in the image, and the more favorable the detection and recognition of the target are; the larger the field of view, the more target space information can be acquired, and the larger the monitoring range is, so that the monitoring, observation and tracking of the high maneuvering target are facilitated, and the target is prevented from being lost. However, the field of view and the focal length are a pair of contradictory quantities, and the improvement of the field of view and the focal length can rapidly increase the image plane of the optical system, but is limited by the semiconductor processing technology, and the CCD and the CMOS with large target surfaces are very difficult to obtain, so that the common methods for solving the problems are methods of detector splicing, compound eyes, scanning and the like. However, the middle spliced part can leak the view field and the like due to the detector splicing, and the cost of the infrared detector is quite high. Compound eyes can greatly increase the volume, weight and data volume of the system. Scanning requires complex optical scanning mechanisms and motors, which can reduce the reliability and time resolution of the device.
In 2021, ke Jun et al at Beijing university of technology in High-resolution fast mid-wave infrared compressive imaging propose to use a compressed sensing method to improve the resolution of the acquired low-resolution image, but the field of view and focal length of the optical system still conform to the conventional imaging theory, and multiple images are needed to calculate and recover a single image, so that the time resolution is reduced.
Disclosure of Invention
In order to solve the contradiction problem of the visual field and the focal length in the traditional optical design method, the invention discloses a transmission type double-channel compression imaging method and a transmission type double-channel compression imaging system based on a crystal line polarizer, which can improve the visual field and the focal length simultaneously. The technical problems to be solved are as follows: through transmission type double-channel common image plane compression imaging based on a crystal line polarizer, single exposure is realized, an image of an object space scene corresponding to a double-channel view field is captured at the same time, the image processing data volume is reduced, the contradiction between an optical imaging view field and a focal length is solved, concurrent imaging of a large view field and a long focal length is realized, polarization information of a target can be obtained, and the method has the advantages of high imaging resolution, narrow bandwidth, simple adjustment, high processing feasibility, compact structure, high stability and good economy.
The invention aims at realizing the following technical scheme:
according to the transmission type double-channel compression imaging method based on the crystal line polarizer, single exposure is realized through double-channel common image plane compression imaging, double-channel images are captured at the same time, the time resolution is doubled under the condition of the same detector, and the data size is doubled under the requirement of the same imaging time resolution precision. The mixed image acquired by the two-channel shared image surface is separated in a frequency domain compression mode, and the imaging view field is enlarged without adding a scanning device, so that the structural compactness, stability and economy of the imaging system are improved. In summary, the invention solves the contradiction between the optical imaging field of view and the focal length by the transmission type double-channel compression imaging based on the crystal linear polarizer, realizes concurrent imaging of a large field of view and a long focal length, can acquire the polarization information of a target, and has the advantages of high resolution, narrow bandwidth, simple adjustment, high processing feasibility, compact structure, high stability and good economy of an imaging system.
The invention discloses a transmission type double-channel compression imaging method based on a crystal line polarizer, which expands transmission type double-channel compression imaging based on the crystal line polarizer into transmission type multi-channel compression imaging based on the crystal line polarizer, further expands imaging view field, improves the structural compactness, economy and resolution of an imaging system and compresses the bandwidth of the imaging system.
The transmission type double-channel compression imaging method based on the crystal line polarizer is realized by the following steps:
step one: and carrying out frequency domain coding on the imaging light beam obtained by the transmission type double-channel compression imaging light path based on the crystal polarizer according to the following four constraint conditions, wherein the coding modulation is realized by adding a special phase on the secondary mirror, and the imaging light beam after the frequency domain coding is obtained.
Condition one: the MTF of the transmission type dual-channel compression imaging optical system based on the crystal line polarizer cannot be enabled to have zero before the characteristic frequency by the phase coding, otherwise, information is lost;
condition II: PSF of the transmission type double-channel compression imaging optical system based on the crystal line polarizer enables sampling positions of respective OTFs on an image frequency domain to be different, so that image information is guaranteed not to be aliased on the frequency domain, and recovery by a recovery algorithm is facilitated;
and (3) a third condition: PSFs after different view field phase codes of each channel of the transmission type dual-channel compression imaging optical system based on the crystal line polarizer are the same as much as possible, so that an image restoration algorithm is simplified greatly;
condition four: the PSF after the phase encoding of the transmission type double-channel compression imaging optical system based on the crystal line polarizer enables the OTF sampling area to be as large as possible, so that the information of frequency domain sampling is increased, and the image restoration is facilitated.
Step two: and (3) exposing the frequency-domain coded imaging light beam obtained in the step (A) through a double-channel shared image plane to obtain a double-channel shared image plane mixed image.
The dual-channel shared image plane refers to that the dual channels share one area array photoelectric detector to capture a mixed image.
The intensity information i (x, y) of the mixed image captured by the area array photodetector is simplified as follows:
wherein ,
representing convolution, f 1 (x,y)、f 2 (x, y) represents object space information captured by two channels of a transmission type dual-channel compression imaging optical system based on a crystal line polarizer, PSF 1 (x,y)、PSF 2 (x, y) represents the point spread function of two channels of a crystal line polarizer based transmissive two-channel compression imaging optical system.
Step three: and (3) carrying out Fourier transform on the transmission type double-channel common image surface mixed image based on the crystal line polarizer obtained in the step (II) to obtain a spectrogram of the common image surface mixed image, carrying out image restoration on the spectrogram through a compressed sensing restoration algorithm, and respectively restoring object side images of two imaging channels from one image, namely realizing frequency domain compression mode separation imaging.
And (3) carrying out Fourier transform on the two-channel shared image surface mixed image obtained in the step (2) to obtain a spectrogram of the shared image surface mixed image as shown in the formula (2).
The inverse problem of the transmission type dual-channel frequency domain compression imaging based on the crystal line polarizer is converted into the compressed sensing restoration problem on the frequency domain:
and (3) taking the frequency domain compressed sensing restoration problem shown in the formula (3) as an objective function of image restoration, carrying out image restoration on the spectrogram through a compressed sensing restoration algorithm, and respectively restoring object side images of two imaging channels from one image, namely realizing frequency domain compression mode separation imaging.
By adopting the frequency domain compression mode for separation imaging, two separation images can be obtained, and preferably, the two separation images are spliced according to the double-channel view field relation, so that the visual effect of imaging is improved on the basis of expanding the view field.
The invention also discloses a transmission type double-channel compression imaging system based on the crystal line polarizer, which is used for realizing the transmission type double-channel compression imaging method based on the crystal line polarizer. The transmission type double-channel compression imaging system based on the crystal linear polarizer comprises a first phase plate, a second phase plate, a first afocal beam shrinking lens group, a second afocal beam shrinking lens group, a first polaroid, a second polaroid, the crystal linear polarizer, an imaging objective lens, an area array photoelectric detector and an image restoration system. In the light propagation direction, the components are arranged in sequence.
The first phase plate is positioned at the pupil of the first afocal beam shrinking lens group, forms a first channel together with the first afocal beam shrinking lens group and the first polaroid, and modulates and codes imaging light beams passing through the first front group beam shrinking lens group. The phase plate is a glass plate with a predetermined face that encodes the imaging beam to modulate the PSF and OTF of the optical first channel in the dual channel compression imaging system. The phase plate profile should be matched to the amount and phase of modulation of the desired phase modulation, which modulates the sampling characteristics of the optical first channel so that it meets the four conditions of step one.
The second phase plate is positioned at the pupil of the second afocal beam shrinking lens group, and forms a second channel together with the second afocal beam shrinking lens group and the second polaroid to modulate and encode imaging light beams passing through the second front group beam shrinking lens group. The phase plate is a glass plate with a predetermined profile that encodes the imaging beam to modulate the PSF and OTF of the optical second channel in the dual channel compression imaging system. The phase plate profile should be matched to the amount and phase of modulation of the desired phase modulation, which modulates the sampling characteristics of the optical second channel so that it meets the four conditions of step one.
The first phase plate and the second phase plate perform phase modulation on the imaging light beam through the surface type parameters, the modulation of the imaging light beam meets the relevant rule of compressed sensing, so that a subsequent image restoration system can restore an acquired image, and the specific rule meets four conditions in the step one.
The first afocal beam shrinking lens group is positioned at the rear end of the first phase plate, the front end of the first polaroid is used for shrinking the imaging light beam passing through the first phase plate, the imaging caliber of the system is enlarged, the resolution is improved, and the afocal beam shrinking lens group can adopt a Galilean type structure, can also adopt a kepler type structure and can also be omitted.
The second afocal beam shrinking lens group is positioned at the rear end of the second phase plate, the front end of the second polaroid is used for shrinking the imaging light beam passing through the second phase plate, the imaging caliber of the system is enlarged, the energy passing through the system is increased, the resolution is improved, and the imaging lens group can adopt a Galilean type structure, can also adopt a kepler type structure and can also be omitted.
The first polaroid is positioned in front of the crystal line polarizer, the polarization direction allowed to pass through the first afocal beam shrinking lens group is the same as the polarization direction of e light (o light when the rear crystal line polarizer is a Wollaston prism and a Luo Xiong prism, and o light is needed here) of the rear crystal line polarizer, the o light is filtered (o light is needed here when the rear crystal line polarizer is a Wollaston prism and a Luo Xiong prism), stray light crosstalk in an optical system is reduced, and imaging quality is improved. And combined with a subsequent crystal line polarizer to realize the beam combination of the two-channel imaging light beams.
The second polarizer is located in front of the crystal line polarizer, and behind the second afocal beam-shrinking lens group, the polarization direction allowed to pass through the second polarizer should be the same as the o-light (e-light should be here) polarization direction of the rear crystal line polarizer (e-light should be here) when the rear crystal line polarizer is a wollaston prism and a Luo Xiong prism, and o-light should be here) when the rear crystal line polarizer is a wollaston prism and a Luo Xiong prism, so that parasitic light crosstalk in an optical system is reduced, and imaging quality is improved. And combined with a subsequent crystal line polarizer to realize the beam combination of the two-channel imaging light beams.
The crystal linear polarizer is positioned at the rear ends of the first polaroid and the second polaroid, and combines the light beams passing through the first polaroid and the second polaroid, so that the subsequent imaging objective lens can simultaneously image the imaging light beams of the two channels. The traditional crystal line polarizer is used for dividing one beam of light into two beams of light with orthogonal polarization directions, and combining the two beams of light with orthogonal polarization directions into one beam of light through the crystal line polarizer according to the principle of reversibility of an optical path.
The imaging objective lens is positioned behind the crystal line polarizer and is used for converging and imaging the imaging light beam passing through the crystal line polarizer onto an image plane.
The area array photoelectric detector is positioned behind the imaging objective lens, is a CCD or CMO, and the photosensitive surface of the area array photoelectric detector coincides with the image surface of the imaging objective lens, converts optical signals into electric signals and transmits the electric signals to the image restoration module.
The image restoration module is used for respectively calculating the information of the two optical channels from the image captured by the area array photoelectric detector. The image restoration module is provided with a calculation storage terminal and an image restoration algorithm, the image restoration algorithm adopts a traditional compressed sensing restoration algorithm to restore a mixed image captured by CCD or CMOS, firstly, problems are converted into a frequency domain according to the coding principle and the formula deduction described in the step three, and the image is restored by using the compressed sensing restoration algorithm in the frequency domain.
The beneficial effects are that:
1. the transmission type double-channel compression imaging method and system based on the crystal line polarizer, disclosed by the invention, adopt the common use of two channel image planes, can simultaneously improve the focal length and the view field of an optical system under the condition of limited detector area array, realize wide-area high-resolution monitoring of a target scene, capture more target details with high resolution, greatly improve the target recognition probability, greatly improve the monitoring range with wide area, be beneficial to target tracking, and especially aim at targets with high maneuvering performance, so that the method has the effect of obviously improving the target recognition probability of a monitoring tracking system.
2. According to the transmission type double-channel compression imaging method and system based on the crystal line polarizer, the images of the two channels are separated from the single Zhang Gongyong image plane mixed image through the frequency domain compression perception restoration algorithm, so that the contradiction between the focal length and the visual field in the traditional optical design can be broken through, the visual field and the focal length are improved simultaneously, the time resolution of the system is not reduced, and the effect of remarkably improving the target tracking efficiency of a monitoring tracking system is achieved.
3. According to the transmission type double-channel compression imaging method and system based on the crystal line polarizer, the two channels share one image plane and work simultaneously, and the images of the two channels are separated from the mixed image by means of subsequent image resolving, so that the effect of reducing the data quantity by half is achieved. The method can effectively solve the defects of high bandwidth requirement of the existing high-definition lens and short storage time of the monitoring video, and provides a new solution for a video transmission scheme of large-view-field high-definition monitoring.
4. The invention discloses a transmission type double-channel compression imaging method and a transmission type double-channel compression imaging system based on a crystal line polarizer, which adopt frequency domain coding at a pupil instead of intensity coding at an intermediate image plane, so that coding can be realized without secondary imaging, the volume, the weight and the cost of an optical system are obviously reduced, and the adjustment difficulty is reduced.
5. The transmission type double-channel compression imaging method and system based on the crystal line polarizer, disclosed by the invention, adopt the polarizer and the crystal line polarizer to combine two channel imaging light beams, can acquire certain object space polarization information, can acquire the sufficient polarization information of the object space through the simultaneous operation of a plurality of systems, and perform polarization imaging, thereby having the advantages of weak light detection, obviously improving the target recognition probability, anti-camouflage, acquiring the target material information and the like.
Drawings
FIG. 1 is a flow chart of a transmission type dual-channel compression imaging method based on a crystal line polarizer;
FIG. 2 is a flowchart of an image restoration algorithm for implementing the method of the present invention;
FIG. 3 is a schematic diagram of a dual-channel compression imaging system based on a nicol prism according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a dual channel compression imaging system based on a glaring prism.
Fig. 5 is a schematic structural diagram of a two-channel compression imaging system based on a wollaston prism.
Fig. 6 is a schematic structural diagram of a dual-channel compression imaging system based on a Luo Xiong prism.
FIG. 7 is an image for algorithm simulation in an embodiment of the present invention, which represents object information collected by two channels, respectively; obtained by coding plates
FIG. 8 is a PSF obtained by encoding plates for each of two channels in an embodiment of the present invention;
FIG. 9 is a blended image obtained by two channels operating simultaneously in which information collected by the two channels is blended together in an embodiment of the present invention;
fig. 10 illustrates object information captured by two channels recovered from fig. 9 by an image recovery module according to an embodiment of the present invention.
Wherein: the device comprises a first phase plate, a second phase plate, a first 3-afocal beam shrinking lens group, a second 4-afocal beam shrinking lens group, a first 5-polaroid, a second 6-polaroid, a 7-crystal linear polarizer, an 8-imaging objective lens, a 9-area array photoelectric detector and a 10-image restoration module.
Detailed Description
For a better description of the objects and advantages of the present invention, the following description will be given with reference to the accompanying drawings and examples.
Example 1:
as shown in fig. 1, the transmission type dual-channel compression imaging method based on the crystal line polarizer disclosed in this embodiment includes the following specific implementation steps:
step one: and carrying out frequency domain coding on the imaging light beam acquired by the transmission type double-channel imaging light path based on the crystal polarizer according to the following four constraint conditions, wherein the coding modulation is realized by adding a special phase on the secondary mirror, and the imaging light beam after the frequency domain coding is obtained. The object information carried by the two-channel imaging beam is shown in fig. 7.
Condition one: the MTF of the transmission type dual-channel imaging optical system based on the crystal line polarizer cannot be enabled to have zero before the characteristic frequency by the phase coding, otherwise, information is lost;
condition II: PSF of the transmission type double-channel compression imaging optical system based on the crystal line polarizer enables sampling positions of respective OTFs on an image frequency domain to be different, so that image information is guaranteed not to be aliased on the frequency domain, and recovery by a recovery algorithm is facilitated;
and (3) a third condition: PSFs after different view field phase codes of each channel of the transmission type dual-channel imaging optical system based on the crystal line polarizer are the same as much as possible, so that an image restoration algorithm is simplified greatly;
condition four: the PSF after the phase encoding of the transmission type double-channel imaging optical system based on the crystal line polarizer enables the OTF sampling area to be as large as possible, so that the frequency domain sampling information is increased, and the image restoration is facilitated.
The PSFs of the two channels of the wide-band dual-channel compression imaging optical system encoded in this embodiment are shown in fig. 8.
Step two: and (3) exposing the frequency-domain coded imaging light beam obtained in the step (A) through a double-channel shared image plane to obtain a double-channel shared image plane mixed image.
The dual-channel shared image plane refers to that the dual channels share one area array photoelectric detector to capture a mixed image, as shown in fig. 9.
The intensity information i (x, y) of the mixed image captured by the area array photodetector is simplified as follows:
wherein ,
representing convolution, f 1 (x,y)、f 2 (x, y) represents object space information captured by two channels of a transmission type dual-channel compression imaging optical system based on a crystal line polarizer, PSF 1 (x,y)、PSF 2 (x, y) represents the point spread function of two channels of a crystal line polarizer based transmissive two-channel compression imaging optical system.
Step three: and (3) carrying out Fourier transform on the transmission type double-channel common image surface mixed image based on the crystal line polarizer obtained in the step (II) to obtain a spectrogram of the common image surface mixed image, carrying out image restoration on the spectrogram through a compressed sensing restoration algorithm, and respectively restoring object side images of two imaging channels from one image, namely realizing frequency domain compression mode separation imaging. Algorithm restoration flowchart as shown in fig. 2, the restoration algorithm adopted in the present embodiment is a TWIST algorithm.
And (3) carrying out Fourier transform on the two-channel shared image surface mixed image obtained in the step (II) to obtain a spectrogram of the shared image surface mixed image as shown in the formula (5).
The inverse problem of the transmission type dual-channel frequency domain compression imaging based on the crystal line polarizer is converted into the compressed sensing restoration problem on the frequency domain:
and (3) taking the frequency domain compressed sensing restoration problem shown in the formula (6) as an objective function of image restoration, carrying out image restoration on the spectrogram through a compressed sensing restoration algorithm, and respectively restoring object side images of two imaging channels from one image, namely realizing frequency domain compression mode separation imaging. In this embodiment, the TWIST algorithm is adopted to recover the problem, and other convex optimization algorithms can also be adopted. The image restoration result is shown in fig. 10.
By adopting the frequency domain compression mode for separation imaging, two separation images can be obtained, and preferably, the two separation images are spliced according to the double-channel view field relation, so that the visual effect of imaging is improved on the basis of expanding the view field. In this embodiment, the system field of view is discontinuous, so no image stitching is performed.
The invention also discloses a transmission type double-channel compression imaging system based on the crystal line polarizer, which is used for realizing the transmission type double-channel compression imaging method based on the crystal line polarizer. The transmission type double-channel compression imaging system based on the crystal linear polarizer comprises a first phase plate, a second phase plate, a first afocal beam shrinking lens group, a second afocal beam shrinking lens group, a first polaroid, a second polaroid, the crystal linear polarizer, an imaging objective lens, an area array photoelectric detector and an image restoration system. In the light propagation direction, the components are arranged in sequence. The system structure diagram is shown in fig. 3, 4, 5 and 6 according to the selection of different crystal line polarizers.
The first phase plate is positioned at the pupil of the first afocal beam shrinking lens group, forms a first channel together with the first afocal beam shrinking lens group and the first polaroid, and modulates and codes imaging light beams passing through the first front group beam shrinking lens group. The phase plate is a glass plate with a predetermined face that encodes the imaging beam to modulate the PSF and OTF of the optical first channel in the dual channel compression imaging system. The phase plate profile should be matched to the amount and phase of modulation of the desired phase modulation, which modulates the sampling characteristics of the optical first channel so that it meets the four conditions of step one.
The second phase plate is positioned at the pupil of the second afocal beam shrinking lens group, and forms a second channel together with the second afocal beam shrinking lens group and the second polaroid to modulate and encode imaging light beams passing through the second front group beam shrinking lens group. The phase plate is a glass plate with a predetermined profile that encodes the imaging beam to modulate the PSF and OTF of the optical second channel in the dual channel compression imaging system. The phase plate profile should be matched to the amount and phase of modulation of the desired phase modulation, which modulates the sampling characteristics of the optical second channel so that it meets the four conditions of step one.
The first phase plate and the second phase plate perform phase modulation on the imaging light beam through the surface type parameters, the modulation of the imaging light beam meets the relevant rule of compressed sensing, so that a subsequent image restoration system can restore an acquired image, and the specific rule meets four conditions in the step one.
The first afocal beam shrinking lens group is positioned at the rear end of the first phase plate, the front end of the first polaroid is used for shrinking the imaging light beam passing through the first phase plate, the imaging caliber of the system is enlarged, the resolution is improved, and the afocal beam shrinking lens group can adopt a Galilean type structure, can also adopt a kepler type structure and can also be omitted.
The second afocal beam shrinking lens group is positioned at the rear end of the second phase plate, the front end of the second polaroid is used for shrinking the imaging light beam passing through the second phase plate, the imaging caliber of the system is enlarged, the energy passing through the system is increased, the resolution is improved, and the imaging lens group can adopt a Galilean type structure, can also adopt a kepler type structure and can also be omitted.
The first polaroid is positioned in front of the crystal line polarizer, the polarization direction allowed to pass through the first afocal beam shrinking lens group is the same as the polarization direction of e light (o light when the rear crystal line polarizer is a Wollaston prism and a Luo Xiong prism, and o light is needed here) of the rear crystal line polarizer, the o light is filtered (o light is needed here when the rear crystal line polarizer is a Wollaston prism and a Luo Xiong prism), stray light crosstalk in an optical system is reduced, and imaging quality is improved. And combined with a subsequent crystal line polarizer to realize the beam combination of the two-channel imaging light beams.
The second polarizer is located in front of the crystal line polarizer, and behind the second afocal beam-shrinking lens group, the polarization direction allowed to pass through the second polarizer should be the same as the o-light (e-light should be here) polarization direction of the rear crystal line polarizer (e-light should be here) when the rear crystal line polarizer is a wollaston prism and a Luo Xiong prism, and o-light should be here) when the rear crystal line polarizer is a wollaston prism and a Luo Xiong prism, so that parasitic light crosstalk in an optical system is reduced, and imaging quality is improved. And combined with a subsequent crystal line polarizer to realize the beam combination of the two-channel imaging light beams.
The crystal linear polarizer is positioned at the rear ends of the first polaroid and the second polaroid, and combines the light beams passing through the first polaroid and the second polaroid, so that the subsequent imaging objective lens can simultaneously image the imaging light beams of the two channels. The traditional crystal line polarizer is used for dividing one beam of light into two beams of light with orthogonal polarization directions, and combining the two beams of light with orthogonal polarization directions into one beam of light through the crystal line polarizer according to the principle of reversibility of an optical path.
The imaging objective lens is positioned behind the crystal line polarizer and is used for converging and imaging the imaging light beam passing through the crystal line polarizer onto an image plane.
The area array photoelectric detector is positioned behind the imaging objective lens, is a CCD or CMO, and the photosensitive surface of the area array photoelectric detector coincides with the image surface of the imaging objective lens, converts optical signals into electric signals and transmits the electric signals to the image restoration module.
The image restoration module is used for respectively calculating the information of the two optical channels from the image captured by the area array photoelectric detector. The image restoration module is provided with a calculation storage terminal and an image restoration algorithm, the image restoration algorithm adopts a traditional compressed sensing restoration algorithm to restore a mixed image captured by CCD or CMOS, firstly, problems are converted into a frequency domain according to the coding principle and the formula deduction described in the step three, and the image is restored by using the compressed sensing restoration algorithm in the frequency domain.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
Claims (5)
1. A transmission type double-channel compression imaging method based on a crystal line polarizer is characterized in that: the double-channel common image plane compression imaging is adopted, so that single exposure is realized, double-channel images are captured at the same time, the time resolution is doubled under the condition of the same detector, and the data size is doubled under the requirement of the same imaging time resolution precision; the mixed image acquired by the two-channel shared image surface is separated in a frequency domain compression mode, and the imaging view field is enlarged without adding a scanning device, so that the structural compactness, stability and economy of an imaging system are improved; through transmission type double-channel compression imaging based on a crystal line polarizer, the contradiction between an optical imaging view field and a focal length is solved, and concurrent imaging of a large view field and a long focal length is realized;
the transmission type double-channel compression imaging method based on the crystal line polarizer comprises the following steps,
step one: the method comprises the steps of carrying out frequency domain coding on imaging light beams obtained by a transmission type double-channel compression imaging light path based on a crystal line polarizer according to the following four constraint conditions, wherein the coding modulation is realized by adding a special phase on a secondary mirror, and the imaging light beams after the frequency domain coding are obtained;
condition one: the MTF of the transmission type dual-channel compression imaging optical system based on the crystal line polarizer cannot be enabled to have zero before the characteristic frequency by the phase coding, otherwise, information is lost;
condition II: PSF of the transmission type double-channel compression imaging optical system based on the crystal line polarizer enables sampling positions of respective OTFs on an image frequency domain to be different, so that image information is guaranteed not to be aliased on the frequency domain, and recovery by a recovery algorithm is facilitated;
and (3) a third condition: PSFs after different view field phase codes of each channel of the transmission type dual-channel imaging optical system based on the crystal line polarizer are the same as much as possible, so that an image restoration algorithm is simplified greatly;
condition four: PSF after phase encoding of a transmission type double-channel imaging optical system based on a crystal line polarizer enables an OTF sampling area to be as large as possible, so that frequency domain sampling information is increased, and image restoration is facilitated;
step two: exposing the obtained imaging light beam after the frequency domain coding in the step one through a double-channel shared image plane to obtain a double-channel shared image plane mixed image;
step three: and (3) carrying out Fourier transform on the transmission type double-channel common image surface mixed image based on the crystal line polarizer obtained in the step (II) to obtain a spectrogram of the common image surface mixed image, carrying out image restoration on the spectrogram through a compressed sensing restoration algorithm, and respectively restoring object side images of two imaging channels from one image, namely realizing frequency domain compression mode separation imaging.
2. The transmission type double-channel compression imaging method based on the crystal line polarizer as claimed in claim 1, wherein the method comprises the following steps of: in the second step, the second step is to carry out the process,
the dual-channel shared image plane refers to a dual-channel shared area array photoelectric detector for capturing a mixed image;
the intensity information i (x, y) of the mixed image captured by the area array photodetector is simplified as follows:
wherein ,
representing convolution, f 1 (x,y)、f 2 (x, y) represents object space information captured by two channels of a transmission type dual-channel compression imaging optical system based on a crystal line polarizer, PSF 1 (x,y)、PSF 2 (x, y) represents the point spread function of two channels of a crystal line polarizer based transmissive two-channel compression imaging optical system.
3. The transmission type double-channel compression imaging method based on the crystal line polarizer as claimed in claim 2, wherein the method comprises the following steps of: performing Fourier transform on the two-channel shared image surface mixed image obtained in the step two to obtain a spectrogram of the shared image surface mixed image as shown in the formula (2);
the inverse problem of the transmission type dual-channel frequency domain compression imaging based on the crystal line polarizer is converted into the compressed sensing restoration problem on the frequency domain:
and (3) taking the frequency domain compressed sensing restoration problem shown in the formula (3) as an objective function of image restoration, carrying out image restoration on the spectrogram through a compressed sensing restoration algorithm, and respectively restoring object side images of two imaging channels from one image, namely realizing frequency domain compression mode separation imaging.
4. A transmission type dual-channel compression imaging method based on a crystal line polarizer as claimed in claim 3, wherein: through the adoption of the frequency domain compression mode for separation imaging, two separation images can be obtained, the two separation images are spliced according to the double-channel view field relation, and the visual effect of imaging is improved on the basis of expanding the view field.
5. A transmission type dual-channel compression imaging system based on a crystal line polarizer, for implementing a transmission type dual-channel compression imaging method based on a crystal line polarizer as set forth in claim 3 or 4, characterized in that: the system comprises a first phase plate, a second phase plate, a first afocal beam shrinking lens group, a second afocal beam shrinking lens group, a first polaroid, a second polaroid, a crystal line polarizer, an imaging objective lens, an area array photoelectric detector and an image restoration system; in the light propagation direction, the components are arranged in sequence;
the first phase plate is positioned at the pupil of the first afocal beam shrinking lens group, forms a first channel together with the first afocal beam shrinking lens group and the first polaroid, and modulates and codes imaging light beams passing through the first front group beam shrinking lens group; the phase plate is a glass plate with a preset surface, and encodes an imaging light beam to modulate PSF and OTF of an optical first channel in the dual-channel compression imaging system; the phase plate type is matched with the modulation quantity and the phase of the required phase modulation, and modulates the sampling characteristic of the optical first channel so as to enable the sampling characteristic to meet the four conditions in the first step;
the second phase plate is positioned at the pupil of the second afocal beam shrinking lens group, and forms a second channel together with the second afocal beam shrinking lens group and the second polaroid to modulate and encode imaging light beams passing through the second front group beam shrinking lens group; the phase plate is a glass plate with a preset surface, and encodes the imaging light beam to modulate PSF and OTF of an optical second channel in the dual-channel compression imaging system; the phase plate type is matched with the modulation quantity and the phase of the required phase modulation, and modulates the sampling characteristic of the optical second channel so as to enable the sampling characteristic to meet the four conditions in the first step;
the first phase plate and the second phase plate carry out phase modulation on the imaging light beam through the surface type parameters, the modulation of the imaging light beam meets the relevant rule of compressed sensing, so that a subsequent image restoration system can restore an acquired image, and the specific rule meets four conditions in the step one;
the first afocal beam shrinking lens group is positioned at the rear end of the first phase plate and at the front end of the first polaroid, and is used for shrinking the imaging beam passing through the first phase plate, enlarging the imaging caliber of the system and improving the resolution;
the second afocal beam shrinking lens group is positioned at the rear end of the second phase plate, the front end of the second polaroid is used for shrinking the imaging beam passing through the second phase plate, and the imaging caliber of the system is enlarged;
the first polaroid is positioned in front of the crystal linear polarizer, and the polarization direction allowed to pass through the first afocal beam shrinking lens group is the same as the e-light polarization direction of the crystal linear polarizer at the rear, so that o-light is filtered, stray light crosstalk in an optical system is reduced, and imaging quality is improved; and combining with a subsequent crystal line deflector to realize the beam combination of the two-channel imaging light beams;
the second polaroid is positioned in front of the crystal line polarizer, and the polarization direction allowed to pass through the second afocal beam shrinking lens group is the same as the o-ray polarization direction of the crystal line polarizer at the rear, so that e-ray is filtered, stray light crosstalk in an optical system is reduced, and imaging quality is improved; and combining with a subsequent crystal line deflector to realize the beam combination of the two-channel imaging light beams;
the crystal linear polarizer is positioned at the rear ends of the first polaroid and the second polaroid, and is used for combining the light beams passing through the first polaroid and the second polaroid, so that the subsequent imaging objective lens can simultaneously image the imaging light beams of the two channels; the traditional crystal line polarizer is used for dividing one beam of light into two beams of light with orthogonal polarization directions, and combining the two beams of light with orthogonal polarization directions into one beam of light through the crystal line polarizer according to the light path reversibility principle;
the imaging objective lens is positioned behind the crystal line polarizer and is used for converging and imaging the imaging light beam passing through the crystal line polarizer onto an image plane;
the area array photoelectric detector is positioned behind the imaging objective lens, is a CCD or CMO, and has a photosensitive surface coincident with the image surface of the imaging objective lens, converts optical signals into electric signals, and transmits the electric signals to the image restoration module;
the image restoration module is used for respectively calculating the information of the two optical channels from the image captured by the area array photoelectric detector; the image restoration module is provided with a calculation storage terminal and an image restoration algorithm, the image restoration algorithm adopts a traditional compressed sensing restoration algorithm to restore a mixed image captured by CCD or CMOS, firstly, problems are converted into a frequency domain according to the coding principle and the formula deduction described in the step three, and the image is restored by using the compressed sensing restoration algorithm in the frequency domain.
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