CN104793343B - Three-channel and single-Wollaston prism polarization imaging device and polarization information detecting method - Google Patents
Three-channel and single-Wollaston prism polarization imaging device and polarization information detecting method Download PDFInfo
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Abstract
The invention discloses a three-channel and single-Wollaston prism polarization imaging device and a polarization information detecting method and aims to solve the problem that the prior art is redundant in structure and low in resolution and cannot detect target polarization information in real time. The polarization imaging device comprises a front optical lens group (1), a polarization modulation module (2), a focusing imaging module (3) and a data processing module (4), wherein the polarization modulation module (2) is a polarization modulation structure composed of a non-polarization beam-splitting prism (21), a linear polarizer (22) and a single Wollaston prism (23), three polarization azimuth angle images of a target can be obtained by one exposure through the polarization modulation structure, and super-resolution reconstruction and registration and polarization state analysis and fusion are sequentially performed on the three polarization azimuth angle images through the data processing module (4) to obtain a target image containing the target polarization information and scene detail information. The three-channel and single-Wollaston prism polarization imaging device is simple in structure, high in space resolution and applicable to target detection and environment monitoring.
Description
Technical Field
The invention belongs to the field of photoelectric imaging detection, and particularly relates to a polarization imaging device and a polarization information detection method thereof, which are used for target detection, substance identification and environment monitoring.
Background
Polarization is another dimensional light wave property different from intensity, phase, spectrum, which provides important information on the properties of the target surface. Polarized imaging detection can improve the recognition rate of objects in a cluttered background or be used for improving the contrast and definition of images. The polarization properties of the target optical radiation are often characterized by Stokes parameters that facilitate measurement. The conventional practice for detecting the linear polarization component in the Stokes' parameters is to take four different polarization azimuth images, e.g. I0°、I45°、I90°And I135°. There are many imaging detection configurations for implementing this method.
There are three general categories of typical imaging polarization detection devices available: time-sequence type, divided-amplitude type, and divided-aperture type. The time sequence device obtains four images with different polarization azimuth angles in sequence by changing the configuration of the instrument during measurement. However, this configuration can only detect stationary scenes and requires that atmospheric disturbances in the measurements are not significant. The amplitude division type and the aperture division type belong to a simultaneous detection structure, and real-time performance is achieved. The amplitude splitting is realized mainly by means of a splitting prism, namely splitting energy. The main disadvantages of this configuration are the large size of the system, the complex structure and the high cost. The aperture division structure is used for dividing the exit pupil, and the polarizer array is used in the four azimuth image detection modules. This configuration greatly reduces the equipment volume, but degrades the spatial resolution of the imaging.
Chinese patent publication No. CN103604945A, published 2014, 26, entitled three-channel CMOS polarization imaging system, discloses a simultaneous three-channel polarization imaging device, but combines three sets of polarization detection devices to obtain polarization information of the same target. This approach is bulky, expensive, and the detection accuracy is reduced due to the performance differences of the devices. Chinese patent publication No. 102707452a, published 2012, 10 and 3, entitled dual-separation wollaston high-resolution simultaneous polarization imaging system. The utility model discloses a to have now to divide amplitude and the polarization imaging device who divides aperture system to combine together, it adopts two wollaston prisms to divide two way four direction angle images of collection, has effectively promoted resolution ratio. But the device is improved on the basis of the existing four-channel physical model. If polarization analysis of the full link is carried out on the polarization analysis device, redundancy of the device still exists.
Disclosure of Invention
The invention aims to provide a three-channel single-Wollaston prism polarization imaging device and a polarization information detection method thereof aiming at the defects of the prior art, so as to effectively reduce the volume of a detection structure, improve the resolution of an imaging space and realize the real-time detection of the polarization information of a target.
The technical idea for realizing the invention is as follows: and modeling and analyzing the polarization imaging link by using the Mueller matrix, and designing an optimized structure of the system, namely a three-channel single-Wollaston prism polarization imaging structure. Three polarization azimuth angle images I are acquired simultaneously by realizing one-time focusing imaging0°、I22.5°、I90°(ii) a Analyzing the stokes parameter, the polarization degree and the polarization angle image through the established polarization mathematical model.
The technical scheme of the invention is as follows according to the above thought:
the invention discloses a three-channel single-Wollaston prism real-time polarization imaging detection system, which comprises a preposed optical lens group 1, a polarization modulation module 2, a focusing imaging module 3 and a data processing module 4, and is characterized in that:
the front optical lens group 1 comprises a filter plate 11, a telescopic lens 12, a field mask plate 13 and a collimating lens 14, and the devices are arranged along the incident light direction in a coaxial manner;
the polarization modulation module 2 comprises a depolarizing beam splitter prism 21, a linear polarizer 22 and a wollaston prism 23; the linear polarizer 22 has a transmission axis direction of 22.5 ° and is disposed at the beam reflection end of the beam splitter prism 21; the two optical axis directions of the wollaston prism 23 are 90 ° and 180 °, respectively, and they are arranged at the beam transmission end of the beam splitter prism 21.
The focusing imaging module 3 includes a first focusing lens 311 and a second focusing lens 312, and a first area array detector 313 and a second area array detector 314 are respectively disposed on back focal planes of the two focusing lenses.
The polarization information detection method of the invention comprises the following steps:
1) the polarization imaging device is used for focusing and shooting a target object and recording a polarization azimuth angle image I0°、I22.5°And I90°And transmitted to the data processing module 4;
2) the image processing module 4 performs operation processing on the obtained three polarization azimuth angle images, and analyzes the target polarization information:
2.1) carrying out high-resolution reconstruction based on learning and sparse representation on the polarization azimuth angle image to double the resolution of the polarization azimuth angle image;
2.2) carrying out registration preprocessing based on Fourier-Mellin transformation on the polarization azimuth angle image with improved resolution;
2.3) analyzing Stokes parameters by using the polarization azimuth angle image after registration to generate a polarization degree image and a polarization angle image which can visualize polarization information;
2.3a) establishing a polarization mathematical model of the three-channel single-Wollaston prism polarization imaging detection device by using a Muller matrix and a Stokes parameter theory, wherein the polarization mathematical model comprises the following steps:
S(1)′＝C1·WP(α)·T·Si
S(2)′＝C1·WP(α+π/2)·T·Si
S(3)′＝C2·WA·R·Si
wherein: s(1)′、S(2)′、S(3)' Stokes parameters of three paths of emergent light respectively, T, R reflection Mueller matrix and transmission Mueller matrix of depolarizing beam splitter prism, WP (α) Mueller matrix of Wollaston prism, α optical axis direction angle of Wollaston prism, WA Mueller matrix of linear polarizer, C1、C2Responsivity, S, of the first and second detectors respectivelyiIs the Stokes parameter of the incident beam;
2.3b) extracting and combining the matrix of the polarization mathematical model to approximately obtain the incident beam Stokes parameters of high-resolution imaging as follows:
wherein:representing the Stokes parameter of the incident beam at high resolution imaging,representing the total intensity of the incident beam in high resolution imaging,represents linear polarization components whose polarization directions are horizontal and vertical directions in high-resolution imaging,linear polarization components representing directions of polarization of +45 ° or-45 ° in high-resolution imaging; ()KThe operation of the first row and the first three columns of the representation matrix is performed]-1Representing an operation of taking the inverse of the matrix;andindividual watchThree images obtained by performing super-resolution reconstruction on three paths of light intensity detected by the polarization imaging device are shown;
2.3c) solving a polarization degree image P and a polarization angle image psi which can visually observe the polarization characteristics of the space target by using the obtained Stokes parameters:
2.3c) solving a polarization degree image P and a polarization angle image psi which can visually observe the polarization characteristics of the space target by using the obtained Stokes parameters:
and 2.4) carrying out image fusion based on wavelet transformation on the polarization degree image, the polarization angle image and the intensity image of the target, so that the finally obtained target image not only contains target polarization information, but also contains richer background detail information.
Compared with the prior art, the invention has the following advantages:
1) the invention can obtain three polarization azimuth angle images only by one exposure, avoids the influence caused by environmental change during multiple measurements, can detect the polarization information of the target in real time and has high working efficiency.
2) The invention realizes the detection of all linear polarization components only by adopting the polarization modulation structure of the single Wollaston prism and the linear polarizer, and has simple structure, no redundancy and small volume compared with the existing amplitude-division polarization imaging structure.
3) According to the invention, the high-resolution reconstruction based on learning and sparse representation is carried out on the detected polarization azimuth angle image, so that the resolution of the detected target image is improved, and the imaging is clearer.
4) Because the invention uses the Mueller matrix to mathematically model the change of the polarization state of the incident beam which records the polarization information and is generated by the whole optical link, a new Stokes vector analytical function is established, and the invention does not depend on the traditional methodOf (a) is a four-channel (I)0°、I45°、I90°、I135°) The imaging model breaks the limitation of the traditional polarization imaging mechanism, and the polarization information of the detection target can be detected in real time through the physical process.
Drawings
Fig. 1 is a schematic structural diagram of a three-channel single wollaston prism polarization imaging device of the present invention;
fig. 2 is a flow chart of a polarization information detection method of the present invention.
Detailed Description
The structure of the three-channel single wollaston prism polarization imaging device and the detailed process of detecting and analyzing the target polarization state information are clearly and completely described in the following with the attached drawings.
Referring to fig. 1, the polarization imaging apparatus of the present invention is composed of a front optical lens group 1, a polarization modulation module 2, a focus detection module 3, and a data processing module 4, which are sequentially arranged along an incident light direction. Wherein: the preposed optical lens group 1 consists of a filter plate 11, a telescopic lens 12, a field mask plate 13 and a collimating lens 14, and the devices are arranged along the common optical axis and are sequentially arranged along the incident light direction; the focal length f of the retractable lens 12 is adjusted according to the imaging distance, and the field mask 13 is a stainless steel rectangular slit, the surface of which is coated with dark matte paint and is placed on the imaging focal plane of the retractable lens 12. The polarization modulation module 2 is composed of a depolarization beam splitter prism 21, a linear polarizer 22 and a Wollaston prism 23, wherein the depolarization beam splitter prism 21 is arranged at the light beam emergent end of the collimating lens 14, the linear polarizer 22 is arranged at the light beam reflecting end of the depolarization beam splitter prism 21, the Wollaston prism 23 is arranged at the light beam transmitting end of the depolarization beam splitter prism 21, the two optical axis directions of the Wollaston prism 23 are 90 degrees and 180 degrees in sequence, and the light transmission axis direction of the linear polarizer 22 is 22.5 degrees. The focusing imaging module 3 is composed of a first focusing lens 311, a second focusing lens 312, a first area array detector and a second area array detector, the first area array detector is placed on the back focal plane of the first focusing lens 311, the second area array detector is placed on the back focal plane of the second focusing lens 312, and the first focusing lens 311 is placed at the light beam exit end of the linear polarizer 22; a second focusing lens 312 is placed at the beam exit end of the wollaston prism 23.
The data processing module 4 includes:
the image super-resolution reconstruction submodule is used for doubling the resolution of the three polarization azimuth angle images received by the detector;
the image registration submodule is used for carrying out image correction and registration on the three polarization azimuth angle images with improved resolution;
the polarization information visualization submodule is used for calculating the three polarization azimuth angle images after the registration is finished and analyzing the polarization degree image and the polarization angle image;
and the information fusion sub-module is used for fusing the polarization degree image, the polarization angle image and the intensity image of the target to acquire an image containing richer target information.
The working principle of the device is as follows:
incident light from each point of the target enters the narrow-band filter plate 11, and image quality reduction caused by chromatic aberration introduced by the Wollaston prism is eliminated; and the image is formed on a primary image surface of the system through a telescopic transmission 12, a field mask plate 13 arranged on the primary image surface inhibits the overlapping of orthogonal polarization azimuth angle images received by a detector through the aperture of a constrained light beam, and the light beam is modulated into a parallel light beam through a collimating lens 14 and enters a depolarization beam splitter prism 21. Parallel light beams are incident from one right-angle end face of the depolarization beam splitter prism 21 and are split into two paths of reflected light and transmitted light with mutually perpendicular transmission directions on the inclined plane of the prism 21, and at the moment, the polarization states of the two paths of light beams are not changed and are consistent with the incident light beams. Because the depolarizing beam splitter prism 21 splits the light only and does not condense the light, the two outgoing beams are parallel beams and are respectively emitted from the other two right-angle end surfaces of the depolarizing prism 21; the reflected light beam passes through the linearly polarizing plate 22 having an optical axis direction of 22.5 °, and is modulated into linearly polarized light having a polarization direction of 22.5 °, which enters the focusing lens 311 and is imaged on the first area detector 312. The transmitted light beam enters the Wollaston prism 23, the transmitted light beam is modulated into two paths of linearly polarized light of o light and e light with mutually vertical vibration directions to be separately emitted due to the double refraction effect of the Wollaston prism 23, and meanwhile, the transmitted light beam enters the Wollaston prism 23 in a parallel light state, so that no monochromatic aberration is introduced into the Wollaston prism 23, and the imaging quality of the light beam is ensured. The two emitted linearly polarized light beams are simultaneously collected by the second focusing lens 321 and imaged on the second area array detector 322. The first planar array detector 312 and the planar array detector 322 receive three polarization azimuth angle images of 0 °, 90 °, and 22.5 ° at the same time, and complete polarization imaging of the three-channel single-wollaston prism.
The three polarization azimuth angle images are transmitted to a data processing module 4, the resolution of the three polarization azimuth angle images is doubled through an image super-resolution reconstruction submodule, then image registration is carried out through an image registration submodule, the three polarization azimuth angle images after registration are transmitted to a polarization information visualization submodule to finish analysis of Stokes parameters and generate a polarization degree image and a polarization angle image capable of visualizing polarization information, the polarization degree image and the polarization angle image are fused with a target intensity image through an information fusion submodule, and a target image containing target polarization information and scene detail information is obtained.
Referring to fig. 2, the polarization information detection method of the present invention is performed as follows:
step 1, shooting a polarization azimuth angle image by using the three-channel single-Wollaston prism polarization imaging device, and recording the polarization state of incident radiation of a target.
The polarization imaging device of the invention is used for focusing and shooting a target object, and incident radiation for recording target polarization information sequentially enters the preposed optical lens group 1 and the polarization modulationThree polarization azimuth angle images I obtained by the system module 2 and the focusing imaging module 30°、I22.5°And I90°And transmits the three polarization azimuth angle images to the data processing module 4.
And 2, performing super-resolution image reconstruction processing on the polarization azimuth angle image based on learning and sparse representation to double the resolution of the polarization azimuth angle image.
2.1a) creating an image library, selecting N high-resolution pictures with a resolution twice as high as that of the polarization azimuth angle image from the image libraryj ═ 1,2,.., N, will beObtaining a low-resolution image with resolution consistent with the shot polarization azimuth angle image by first degrading and then interpolatingIn the method, n groups of high-resolution and low-resolution image block pairs are randomly extracted;
2.1b) dictionary training is carried out on the extracted image block pairs to obtain a low-resolution dictionary DlAnd high resolution dictionary Dh；
2.1c) according to the obtained high-low resolution dictionary, respectively aligning the shot polarization azimuth angle images I0°、I22.5°And I90°Sparse reconstruction is carried out to obtain a polarization azimuth image with resolution doubledAnd
step 3, polarization azimuth angle image data with improved three resolutionsAndand carrying out polarization azimuth image registration.
3.1) selection of 0 ° azimuthal imageFor registering the reference images, denoted f (x, y), the ones to be registeredImage sumThe images are respectively marked as g1(x, y) and g2(x,y)；
3.2) pairs of f (x, y) and g1(x, y) fourier-transforming to obtain respective magnitude spectra | F (ζ, η) | and | G (ζ, η) | and high-pass filtering the same;
3.3) converting the two filtered amplitude spectrum images into a log-polar coordinate form, and solving a cross-power spectrum between the two images in the form to obtain a ratio transformation coefficient sigma and a rotation angle theta;
3.4) for the first image g to be registered1(x, y) rotating and scaling sequentially, then calculating the cross power spectrum between the scaled image and the reference image f (x, y) to obtain the relative displacement of the two images, and then aligning the first image g to be aligned according to the displacement1(x, y) are translated in opposite directions to obtain registrationAn image;
3.5) for the second image g to be registered2(x, y) repeating the steps 2.2) -2.4) above to obtain a registeredAnd (4) an image.
And 4, establishing a full link polarization imaging mathematical model.
4.1) describe the polarization state of the incident beam according to Stokes vector theory as follows:
Si＝[S0S1S3S4]T
wherein: s0Representing the total intensity of the light beam, S1Linear polarization component, S, representing horizontal and vertical polarization directions2A linear polarization component representing a direction of polarization of +45 ° or-45 °; s4Represents the circular polarization component of the light beam; []TRepresenting the operation of matrix transposition;
4.2) the change of the polarization state of the incident light beam by each polarization device in the imaging chain is described by using a Mueller matrix. Stokes parameter S of emergent beami' to be expressed as:
wherein: msymThe Mueller matrix representing the entire system, which is the product of the Mueller matrices for the individual polarizing devices, is denoted Msym＝M1·M2……Mn；
4.3) substituting the Mueller matrix of each polarizer into formula Msym＝Mn·Mn-1……M1In the method, a three-path detection polarization mathematical model of the imaging device is established as follows:
S(1)′＝C1·WP(α)·T·Si
S(2)′＝C1·WP(α+π/2)·T·Si
S(3)′＝C2·WA·R·Si
wherein: s(1)′、S(2)′、S(3)' Stokes parameters of emergent light passing through the system, T, R are reflection Mueller matrix and projection Mueller matrix of the depolarizing beam splitter prism, WP (α) is Mueller matrix of the Wollaston prism, α is optical axis direction angle of the Wollaston prism, WA is Mueller matrix of the linear polarizer, C1、C2Is the responsivity of the detector; siIs the Stokes parameter of the incident beam.
And 5, calculating a Stokes parameter analytic function by the polarization mathematical model.
5.1) according to the light intensity component S of the detector which can only receive Stokes parameters0And only responding to the characteristic of the linear polarization component of the polarization state, and respectively extracting the Stokes parameters S of the three paths of emergent beams(1)′、S(2)' and S(3)' the first row, the first three columns, and matrix combining, the combined polarization mathematical model is:
wherein I1、I2、I3Respectively, three detected light intensities, i.e. polarization azimuth image I0°、I90°And I22.5°；()KRepresenting the operation of the first three rows of the matrix;
5.2) A first item at the right end of the upper formula is denoted H, andand let I ═ I (I)1,I2,I3)TThe combined polarization mathematical model is represented as:
I＝Η·Si
5.3) Using the formula Si＝H-1I finding the Stokes parameter S of the incident lighti：
Wherein: []-1Representing an operation of taking the inverse of the matrix.
5.4) useIncident Stokes parameters approximating high resolution imaging
And 6, solving the polarization degree and polarization angle images.
Using the obtained Stokes parametersSolving a polarization degree image P and a polarization angle image psi which can visually observe the polarization characteristics of the space target:
and 7, carrying out image fusion based on wavelet transformation on the polarization degree image, the polarization angle image and the intensity image of the target to obtain a target image containing target polarization information and background detail information.
7.1) carrying out wavelet decomposition on the polarization degree image P or the polarization angle image psi and the target intensity image I to obtain a decomposition coefficientAnd
wherein:representing a low-frequency wavelet coefficient of the polarization characteristic image after the j-th layer wavelet decomposition;representing a high-frequency wavelet coefficient in the horizontal direction after the j-th layer of wavelet decomposition is carried out on the polarization characteristic image;high-frequency wavelet coefficient in vertical direction after j layer wavelet decomposition is carried out on the representative polarization characteristic image;after the j-th layer of wavelet decomposition is carried out on the representative polarization characteristic image, high-frequency wavelet coefficients in the diagonal direction are j equal to 1,2.. N;representing the low-frequency wavelet coefficient of the intensity image after the jth layer of wavelet decomposition;high-frequency wavelet coefficient in horizontal direction after j-th layer wavelet decomposition is carried out on the representative intensity image;after the representative intensity image is subjected to the jth layer wavelet decomposition, the high-frequency wavelet coefficient in the vertical direction is obtained;after the representative intensity image is subjected to the jth layer wavelet decomposition, the high-frequency wavelet coefficient in the diagonal direction is obtained;
7.2) for low-frequency wavelet coefficientsAndcarrying out weighted average to obtain the fused low-frequency coefficientFor high frequency wavelet coefficientAndandandrespectively carrying out fusion based on the regional energy to respectively obtain the fused high-frequency wavelet coefficients of the j-th layer in the horizontal directionHigh-frequency wavelet coefficient in vertical direction of j-th layerAnd high-frequency wavelet coefficient of j-th layer in diagonal direction
The fusion rule based on the region energy is as follows:
wherein,representing the high-frequency wavelet coefficient of the image in the horizontal, vertical or diagonal direction of the jth layer of the polarization characteristic image,representing the high-frequency wavelet coefficient of the image in the horizontal, vertical or diagonal direction of the jth layer of the intensity image,high-frequency wavelet coefficients of the fused image in the j-th layer horizontal, vertical or diagonal direction;representing the energy of the wavelet transform coefficient of the j layer horizontal, vertical or diagonal direction of the polarization characteristic image;represents the energy of the wavelet transform coefficient of the jth layer of the intensity image in the horizontal, vertical or diagonal direction,andcalculated by the following formula respectively:
wherein M represents the width value of the set region template, N represents the height value of the set region template, and M × N represents the pixel value size of the set region template;representing the high-frequency wavelet coefficient of the image in the horizontal, vertical or diagonal direction of the j-th layer of the polarization characteristic image, x represents the horizontal coordinate of the pixel value in the region calculated by the above formula, and y represents the bitIn the area, the vertical coordinate of the pixel value calculated by the above formula is carried out;image high-frequency wavelet coefficients representing the j-th layer horizontal, vertical or diagonal direction of the intensity image: Σ represents a summation operation;
7.3) carrying out wavelet reconstruction on the fused wavelet coefficient to obtain a final target image, wherein the image not only contains target polarization information, but also contains abundant background detail information.
The above description is only one specific example of the present invention and does not constitute any limitation of the present invention. It will be apparent to persons skilled in the relevant art that various modifications and changes in form and detail can be made therein without departing from the principles and arrangements of the invention, but these modifications and changes are still within the scope of the invention as defined in the appended claims.
Claims (9)
1. The utility model provides a three passageway list wollaston prism polarization image device, includes leading optical lens group (1), polarization modulation module (2), focus imaging module (3) and data processing module (4), its characterized in that:
the preposed optical lens group (1) comprises a filter plate (11), a telescopic lens (12), a field mask plate (13) and a collimating lens (14), and the devices are arranged along the common optical axis and are sequentially arranged along the incident light direction;
the polarization modulation module (2) comprises a depolarization beam splitter prism (21), a linear polarizer (22) and a Wollaston prism (23); the linear polarizer (22) has a transmission axis direction of 22.5 degrees and is arranged at the beam reflection end of the beam splitter prism (21); the two optical axis directions of the Wollaston prism (23) are respectively 90 degrees and 180 degrees, and the Wollaston prism is arranged at the light beam transmission end of the beam splitter prism (21);
the focusing imaging module (3) comprises a first focusing lens (311) and a second focusing lens (321), and a first area array detector (312) and a second area array detector (322) are respectively arranged on back focal planes of the two focusing lenses;
the data processing module (4) comprises:
the image super-resolution reconstruction submodule is used for doubling the resolution of the three polarization azimuth angle images received by the detector;
the image registration submodule is used for carrying out image correction and registration on the three polarization azimuth angle images with improved resolution;
the polarization information visualization submodule is used for calculating the three polarization azimuth angle images after the registration is finished and analyzing the polarization degree image and the polarization angle image;
and the information fusion sub-module is used for fusing the polarization degree image, the polarization angle image and the intensity image of the target to acquire an image containing richer target information.
2. The apparatus of claim 1, wherein:
the field mask plate (13) is a stainless steel rectangular slit, and the surface of the field mask plate is coated with dark matt paint; which is placed on the imaging focal plane of the retractable lens (12);
the focal length f of the retractable lens (12) is adjusted with the imaging distance.
3. The apparatus of claim 1, wherein: the first focusing lens (311) is arranged at the light beam emergent end of the linear polarizer (22); the second focusing lens (321) is arranged at the light beam exit end of the Wollaston prism (23).
4. The method for detecting polarization information by using the three-channel single-wollaston prism polarization imaging device of claim 1, comprising the following steps:
1) the polarization imaging device is used for focusing and shooting a target object and recording a polarization azimuth angle image I0°、I22.5°And I90°And transmitted to the data processing module (4);
2) the image processing module (4) performs operation processing on the obtained three polarization azimuth angle images, and analyzes the target polarization information:
2.1) carrying out high-resolution reconstruction based on learning and sparse representation on the polarization azimuth angle image to double the resolution of the polarization azimuth angle image;
2.2) carrying out registration preprocessing based on Fourier-Mellin transformation on the polarization azimuth angle image with improved resolution;
2.3) analyzing Stokes parameters by using the polarization azimuth angle image after registration to generate a polarization degree image and a polarization angle image which can visualize polarization information:
2.3a) establishing a polarization mathematical model of the three-channel single-Wollaston prism polarization imaging detection device by using a Muller matrix and a Stokes parameter theory, wherein the polarization mathematical model comprises the following steps:
S(1)′＝C1·WP(α)·T·Si
S(2)′＝C1·WP(α+π/2)·T·Si
S(3)′＝C2·WA·R·Si
wherein: s(1)′、S(2)′、S(3)' Stokes parameters of three paths of emergent light respectively, T, R reflection Mueller matrix and transmission Mueller matrix of depolarizing beam splitter prism, WP (α) Mueller matrix of Wollaston prism, α optical axis direction angle of Wollaston prism, WA Mueller matrix of linear polarizer, C1、C2Responsivity, S, of the first and second detectors respectivelyiIs the Stokes parameter of the incident beam;
2.3b) extracting and combining the matrix of the polarization mathematical model to approximately obtain the incident beam Stokes parameters of high-resolution imaging as follows:
wherein:representing the Stokes parameter of the incident beam at high resolution imaging,representing the total intensity of the incident beam in high resolution imaging,represents the difference between the horizontal and vertical linear polarization components in high resolution imaging,represents the difference between the 45 ° linear polarization component and the 135 ° linear polarization component; ()ΚThe operation of the first row and the first three columns of the representation matrix is performed]-1Representing an operation of taking the inverse of the matrix;andthree images obtained by performing super-resolution reconstruction on the three paths of light intensity detected by the polarization imaging device are respectively represented;
2.3c) solving a polarization degree image P and a polarization angle image psi which can visually observe the polarization characteristics of the space target by using the obtained Stokes parameters:
and 2.4) carrying out image fusion based on wavelet transformation on the polarization degree image, the polarization angle image and the intensity image of the target, so that the finally obtained target image not only contains target polarization information, but also contains rich background detail information.
5. The polarization information detection method according to claim 4, wherein the super-resolution image reconstruction processing based on learning and sparse representation on the polarization azimuth angle image of step 2.1) comprises the following steps:
2.1a) creating an image library, selecting N high-resolution pictures with a resolution twice as high as that of the polarization azimuth angle image from the image libraryj ═ 1,2,.., N, will beObtaining a low-resolution image with resolution consistent with the shot polarization azimuth angle image by first degrading and then interpolatingIn the method, n groups of high-resolution and low-resolution image block pairs are randomly extracted;
2.1b) dictionary training is carried out on the extracted image block pairs to obtain a low-resolution dictionary DlAnd high resolution dictionary Dh；
2.1c) according to the obtained high-low resolution dictionary, respectively aligning the shot polarization azimuth angle images I0°、I22.5°And I90°Sparse reconstruction is carried out to obtain a polarization azimuth image with resolution doubledAnd
6. the polarization information detection method according to claim 5, wherein the registration preprocessing of the polarization azimuth angle image based on Fourier-Mellin transform in step 2.2) comprises the following steps:
2.2a) selection of 0 ° azimuthal imageFor registering the reference images, denoted f (x, y), the ones to be registeredImage sumThe images are respectively marked as g1(x, y) and g2(x,y)；
2.2b) fourier transforming F (x, y) and G1(x, y) to obtain respective magnitude spectra | F (ζ, η) | and | G (ζ, η) | and high-pass filtering the same;
2.2c) converting the two filtered amplitude spectrum images into a log-polar coordinate form, and solving a cross-power spectrum between the two images in the form to obtain a ratio transformation coefficient sigma and a rotation angle theta;
2.2d) aligning the first image g to be registered1(x, y) rotating and scaling sequentially, then calculating the cross power spectrum between the scaled image and the reference image f (x, y) to obtain the relative displacement of the two images, and then aligning the first image g to be aligned according to the displacement1(x, y) are translated in opposite directions to obtain registrationAn image;
2.2e) for a second image g to be registered2(x, y) repeating the steps 2.2b) -2.2d) above to obtain a registeredAnd (4) an image.
7. The polarization information detection method according to claim 5, wherein the step 2.3a) of establishing a polarization mathematical model of the three-channel single-wollaston prism polarization imaging detection device by using the Muller matrix and the Stokes parameter theory comprises the following steps:
first, the polarization state of an incident beam is described as follows according to Stokes vector theory:
Si＝[S0S1S2S3]T，
wherein: s0Representing the total intensity of the light beam, S1Representing the difference between linearly polarized components with the polarization directions in the horizontal and vertical directions, S2Represents the difference between a linearly polarized component having a polarization direction of +45 ° and a linearly polarized component having a polarization direction of-45 °; s3Representing the difference between the right and left polarization components of the beam; []TRepresenting the operation of matrix transposition;
secondly, the change of each polarization device in the imaging link to the polarization state of the incident beam is described by using a Mueller matrix, and the Stokes parameters S of the emergent beam are obtainedi' is:
wherein: msymThe Mueller matrix, which is the product of the Mueller matrices for the individual polarizing devices, denoted M, represents the entire optical systemsym＝M1·M2……Mn；S0' represents the total intensity of the emergent beam, S1' denotes the difference between the horizontal and vertical polarization components, S2' represents the difference, S, between the 45 DEG and 135 DEG linear polarization components3' represents the difference between the right-handed circular polarization component and the left-handed circular polarization component;
finally, the Mueller matrix of each polarizer is substituted into formula Msym＝Mn·Mn-1……M1In the method, a three-path detection polarization mathematical model of the imaging device is established as follows:
8. the method for detecting polarization information according to claim 5, wherein the step 2.3b) of extracting and combining the matrix of the polarization mathematical model to obtain the analytic function of the Stokes parameters of the incident beam comprises the following steps:
firstly, according to the light intensity component S of the detector which can only receive Stokes parameters0And respectively extracting Stokes parameters S of the three paths of emergent beams only in response to the characteristics of the linear polarization components(1)′、S(2)' and S(3)' the first row, the first three columns, and matrix combining, the combined polarization mathematical model is:
the first term at the right end of the combined mathematical model expression for polarization is denoted by Η, note:
and let I ═ I (I)1,I2,I3)TThe combined polarization mathematical model is represented as: H.I.H.SiWherein: i is1、I2、I3Respectively representing the three detected light intensities, i.e. polarization azimuth images I0°、I90°And I22.5°；S0Representing the total intensity of the light beam, S1Representing the difference between linearly polarized components with the polarization directions in the horizontal and vertical directions, S2Represents the difference between a linearly polarized component having a polarization direction of +45 ° and a linearly polarized component having a polarization direction of-45 °;
then according to Si＝H-1I finding the Stokes parameter S of the incident lighti：
Wherein: []-1Representing an operation of taking the inverse of the matrix;
finally, byIncident Stokes parameters approximating high resolution imaging
9. The polarization information detection method according to claim 5, wherein the wavelet transform-based image fusion of the polarization degree image, the polarization angle image and the intensity image of the object in step 2.4) is performed by the following formula:
wherein,high frequency wavelet coefficients representing the jth layer of the polarization signature image,high frequency wavelet coefficients representing the jth layer of the intensity image,representing the j-th layer high-frequency wavelet coefficient of the fused image;representing the energy of the high-frequency wavelet coefficient of the j layer of the polarization characteristic image;representing the energy of the high frequency wavelet coefficients of the jth layer of the intensity image.
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