High resolution snapshot polarimetric interferometric imaging detection system and method

Abstract

This invention relates to a high-resolution snapshot polarization interferometric imaging detection system and method, belonging to the field of optical imaging detection technology. The invention reduces the number of channels, suppresses data aliasing between demodulation channels, and improves the accuracy of polarization detection. The invention uses a light source to illuminate the target, and the reflected signal light is collected and collimated by a front-end optical system. Subsequently, a polarization grating spatially modulates and modulates the polarization state of the reflected light, resulting in two sheared beams with circular polarization states. A polarization beam splitter decomposes the sheared beams into p-components and s-components, where the p-component is transmitted and the s-component is reflected. The two components are collected by imaging lenses and imaged onto an array detector, resulting in two inverse polarization interferograms. The interference fringes of the inverse interferograms are complementary; data superposition yields the full-resolution polarization parameters of the target. Based on this, the DC component in the interferogram is removed, eliminating the interference of the polarization parameters on the demodulation of other polarization parameters and improving the accuracy of polarization parameter demodulation.

Description

Technical Field

[0001] This invention relates to the field of optical imaging detection technology, specifically to a high-resolution snapshot polarization interferometry imaging detection system and method. Background Technology

[0002] Polarization imaging technology is a novel optical detection technique that can simultaneously measure and image the polarization state of a target. Compared to traditional optical intensity imaging, this technique, in addition to acquiring conventional information such as the target's shape and color, can also extract full-dimensional polarization characteristic information such as polarization state, degree of polarization, polarization angle, and ellipticity by calculating the target's Stokes parameters, greatly expanding the information dimension and data capacity of optical detection. Furthermore, polarization imaging technology has the advantages of high imaging contrast and strong environmental resistance, and is minimally affected by external environmental factors.

[0003] Traditional spatial modulation polarization imaging technology typically uses polarization modulation elements in conjunction with an analyzer to form a polarization interferogram, encoding the Stokes parameters of the target scene onto different spatial carrier frequencies. Subsequently, a matching demodulation algorithm is used to invert and reconstruct the polarization information. The core function of the analyzer is to unify the polarization state of the interferometric beam, ensuring the system meets the coherence conditions for polarization interference. However, only specific polarization components allowed to pass through the analyzer can ultimately be incident on the detector image plane. This process inevitably leads to a loss of system optical flux, causing a decrease in the signal-to-noise ratio and directly negatively impacting the demodulation accuracy of polarization parameters. Currently, the most widely used demodulation method in this technology is the frequency domain channel demodulation algorithm. Its core idea is to map different Stokes parameters to discrete frequency domain channels, and extract and separate the target signals in each channel through frequency domain filtering. However, signal aliasing and crosstalk exist between frequency domain channels and cannot be eliminated by filtering. This introduces additional demodulation errors, further reducing the accuracy of polarization parameter inversion.

[0004] The existing invention patent, patent number 202410616044.0, patent name: Wideband snapshot type breast tumor polarization interferometry imaging detection system and method. This method modulates the polarization state of shear light separately, but it still uses the traditional frequency domain channel demodulation algorithm. Channel data crosstalk still limits the polarization detection accuracy of the instrument.

[0005] Therefore, the present invention provides a high-resolution snapshot polarization interferometry imaging detection system and method to solve the problems existing in the above-mentioned technologies. Summary of the Invention

[0006] This invention aims to provide a high-resolution snapshot polarization interferometric imaging detection system and method. The system shears the light emitted from the target into two beams with different polarization states. A polarization beam splitter then separates the s-component and p-component of the sheared light and images them separately. This yields two inverse polarization interferograms without the use of an analyzer. A demodulation algorithm is then used to demodulate the target's high-precision Stokes parameters. Because an analyzer is not used, the system's light throughput and signal-to-noise ratio are effectively improved. Simultaneously, the inverse interferograms allow for the extraction of the complete parameter S0. Reducing the number of channels suppresses data aliasing between demodulation channels, thereby improving the accuracy of polarization detection.

[0007] A high-resolution snapshot polarization interferometric imaging detection system, the detection system comprising a front optical system, a beam modulation and shaping unit, a polarization beam splitter, a first imaging lens, a second imaging lens, a first array detector, a second array detector, a first demodulation processor, and a second demodulation processor;

[0008] A light source generates a beam that illuminates the target. The reflected light from the target enters the front optical system for collimation, generating collimated light. The beam modulation and shaping unit performs spatial shearing and polarization state modulation on the collimated light, obtaining two circularly polarized beams with orthogonal polarization states at different spatial positions. The polarization beam splitter divides the circularly polarized light into p-components and s-components. The p-component is transmitted and imaged onto the first array detector by the first imaging lens, while the s-component is reflected and imaged onto the second array detector by the second imaging lens. The first and second array detectors respectively obtain polarization interferograms containing target polarization information, and the interference fringes of the two polarization interferograms are complementary. The polarization interferograms are transmitted to the corresponding demodulation processor for polarization interferometry data processing to obtain high-precision Stokes parameters of the target.

[0009] The present invention also provides a high-resolution snapshot polarization interferometry imaging detection method, which is implemented by the aforementioned high-resolution snapshot polarization interferometry imaging detection system. The specific steps of the detection method are as follows:

[0010] Step S1. Align the pixels of the polarization interferograms obtained from the first area array detector and the second area array detector, and then directly superimpose them to obtain the Stokes parameters of the target. ;

[0011] Step S2. The polarization interferogram contains the target Stokes parameters. , and Remove parameters It can remove the zero-frequency channel in the frequency domain of the interferogram, eliminating the data interference of the zero-frequency channel to the other channels;

[0012] Step S3. Position the light source with known Stokes parameters. , and The reference light directly illuminates the front optical system, and the Stokes parameters of the reference light are obtained by the demodulation processor. Interferogram and corresponding frequency domain channels ;

[0013] Step S4. After depolarizing the light source, illuminate the target and process it in the demodulation processor to obtain the Stokes parameters of the target. The interferogram and the corresponding frequency domain channel C;

[0014] Step S5. Based on the frequency domain channel of the reference light By analyzing the frequency domain channel C of the target, the spatial modulation factor coupled with the Stokes parameters is obtained, and thus the Stokes parameters of the target are derived. and This enables polarization imaging detection of the target.

[0015] The beneficial effects of this invention are:

[0016] The detection system described in this invention utilizes a beam modulation and shaping unit and a polarization beam splitter to shear, convert the polarization state, and separate the p and s components of the target signal light, thereby obtaining an anti-phase polarization interference image of the target. The use of an analyzer is avoided during the interference process, which can effectively improve the signal-to-noise ratio of the polarization image, thereby improving the demodulation accuracy.

[0017] The detection method described in this invention can obtain an inverse polarization interferogram. By superimposing the inverse polarization interferogram data, the full-resolution parameter S0 can be obtained. Subsequently, the parameter S0 in the polarization interferogram can be removed, and channels containing the parameter S0 in the frequency domain can also be removed, thereby reducing data aliasing between frequency domain channels and further improving demodulation accuracy.

[0018] This invention does not use an analyzer, which can effectively improve the instrument's light throughput and signal-to-noise ratio. It also has the advantages of snapshot, no moving parts, easy assembly and adjustment, and compact structure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the high-resolution snapshot polarization interferometry imaging detection system described in this invention;

[0020] Figure 2 The images are Fourier transform results of polarization interference images; where (a) is the Fourier transform result of the polarization interference image obtained by the first array detector; and (b) is the Fourier transform result of the polarization interference image obtained by the second detector. and These are the spatial frequency coordinates of the position coordinates x and y after Fourier transform, respectively.

[0021] Explanation of reference numerals in the attached figures: 1. Light source; 2. Front optical unit; 201. Objective lens; 202. Aperture stop; 203. Collimating lens; 3. Light modulation and shaping unit; 301. First polarization grating; 302. Second polarization grating; 4. Polarization beam splitter; 5. First imaging lens; 6. First array detector; 7. First demodulation processor; 8. Second imaging lens; 9. Second array detector; 10. Second demodulation processor; 11. Detection target. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0023] Specific Implementation Method 1: Combination Figure 1 This embodiment describes a high-resolution snapshot polarization interferometric imaging detection system, which includes a light source 1, a front optical system 2, a beam modulation and shaping unit 3, a polarization beam splitter 4, an imaging lens 5, a first array detector 6, a demodulation processor 7, an imaging lens 8, a second array detector 9, a demodulation processor 10, and a detection target 11. The front optical system 2 includes an objective lens 201, an aperture 202, and a collimating lens 203. The beam modulation and shaping unit 3 includes a first polarization grating 301 and a second polarization grating 302.

[0024] The light source can be used as an illumination source and a reference source. The light source 1 is first used as a reference source. It is converted into light with a known polarization state by a polarizer and directly incident on the high-resolution snapshot polarization interferometry imaging detection system to obtain the anti-phase polarization interferogram of the reference light and the demodulation channel data of the reference light.

[0025] Subsequently, polarization imaging detection of the target is performed. Light source 1 illuminates the target as an unpolarized light source. The signal light reflected from the target is collected by the objective lens 201, and after passing through the aperture 202 and collimating lens 203, collimated signal light is emitted. The beam modulation and shaping unit 3 performs spatial modulation and polarization state conversion on the collimated light to obtain two circularly polarized sheared beams with orthogonal polarization states and different spatial positions. Since the first polarization grating 301 and the second polarization grating 302 have the same structural parameters, are parallel to each other and placed perpendicular to the optical axis, the diffraction effects of the two gratings cancel each other out, and the two emitted sheared beams are parallel to each other. The polarization beam splitter 4 further divides the sheared light into p-components and s-components. The p-component passes through the polarization beam splitter 4 and is imaged onto the first array detector 6 by the imaging lens 5. The s-component is reflected and imaged onto the second array detector 9 by the imaging lens 8. Both the first array detector 6 and the second array detector 9 can obtain polarization interferogram data, and the interference fringes of the two are complementary. Finally, the polarization interferogram data is processed by the demodulation processor 7 and the demodulation processor 10 to obtain the full-resolution polarization parameter S0 of the target and the high-resolution other polarization parameters.

[0026] In this embodiment, the beam modulation and shaping unit 3 can shear the incident light into two circularly polarized beams. The distance between these two circularly polarized beams is called the shearing distance Δ. The shearing distance Δ is positively correlated with the spacing t between the first polarization grating and the second polarization grating, and negatively correlated with the grating period d. The specific relationship is as follows:

[0027]

[0028] Where m represents the diffraction order of the first polarization grating 301, λ is the incident light wavelength, and β ±1 The +1st and -1st order diffraction angles of the first polarization grating 301 are represented by α, and α represents the incident angle of the first polarization grating 301.

[0029] Specific Implementation Method Two: Combination Figure 2 This embodiment describes the detection method of the high-resolution snapshot polarization interferometric imaging detection system described in Specific Embodiment 1. This method removes parameter S0 from the interferogram to reduce the number of frequency domain channels and eliminate data interference from the zero-frequency channel to the remaining channels. Fourier transform calculations are performed on the interferogram with parameter S0 removed to convert it to the frequency domain, obtaining the frequency domain demodulation channel distribution. The required demodulation channels are extracted using a frequency domain filter, and then an inverse Fourier transform is performed on the selected demodulation channels. Finally, using the corresponding reference light data, high-precision Stokes parameters of the remaining target are obtained, achieving polarization imaging detection of the target. The specific implementation steps are as follows:

[0030] Step S1. Align the pixels of the polarization interferograms obtained by the first area array detector 6 and the second area array detector 10, and then directly superimpose them to obtain the Stokes parameters of the target. ;

[0031] In this embodiment, the expression for the interference light intensity obtained by the first array detector 6 is:

[0032]

[0033] The expression for the interference light intensity obtained by the second array detector 9 is:

[0034]

[0035] Where j is an imaginary number, For phase, , , Stokes parameters for the target.

[0036] By directly superimposing the polarization interferogram data of the first array detector 6 and the second array detector 9, the Stokes parameters of the target at full resolution can be obtained. :

[0037]

[0038] Step S2. The polarization interferogram contains the target Stokes parameters. , and Remove parameters It can remove the zero-frequency channel in the frequency domain of the interferogram, eliminating the data interference of the zero-frequency channel to the other channels;

[0039] Step S3. The light source uses known Stokes parameters. , and The reference light directly illuminates the front optical system, and the Stokes parameters of the reference light are obtained by the demodulation processor. Interferogram and corresponding frequency domain channels ;

[0040] When the reference light is incident, the corresponding demodulation channel obtained is:

[0041]

[0042] in, For the frequency domain channel of the reference light;

[0043] Step S4. After the light source is depolarized, it illuminates the detection target, and the demodulation processor processes the data to obtain the Stokes parameters of the target. The interferogram and the corresponding frequency domain channel C;

[0044] In this embodiment, since the parameters are obtained Then the polarization interferograms obtained by the first array detector 6 and the second array detector 9 can be compared. This process removes and reduces demodulation channels while improving the fringe contrast of the polarization interferogram. (This is done in the area array detector.) Remove the target channel and perform an inverse Fourier transform to obtain the frequency domain channel distribution. Use a frequency shift filter to extract the demodulation channel, obtaining the target's frequency domain channel C. Perform an inverse Fourier transform on the target's frequency domain channel C to obtain:

[0045]

[0046] in, This is the inverse Fourier transform, where U represents the carrier frequency generated by beam modulation and shaping unit 3. and All are Stokes parameters of the target, where f is the focal length of the first imaging lens 5 and the second imaging lens 8. is the x-axis of the interferogram.

[0047] Step S5. Based on the frequency domain channel of the reference light By analyzing the frequency domain channel C of the target, the spatial modulation factor coupled with the Stokes parameters is obtained, and thus the Stokes parameters of the target are derived. and This enables polarization imaging detection of the target.

[0048] In this embodiment, the target light and reference light channel data have similar compositions, and the Stokes parameters of the reference light are... and Since the two are known quantities, we divide them to remove the spatial modulation factor. Then, by substituting the Stokes parameter data of the reference light, the Stokes parameters of the target are finally obtained. The complete Stokes parameter demodulation process for the target is as follows:

[0049]

[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A high resolution snapshot polarimetric interferometric imaging detection system characterized by: The detection system includes a front optical system, a beam modulation and shaping unit, a polarization beam splitter, a first imaging lens, a second imaging lens, a first array detector, a second array detector, a first demodulation processor, and a second demodulation processor. A light source generates a beam that illuminates the target. The reflected light from the target enters the front optical system for collimation, generating collimated light. The beam modulation and shaping unit performs spatial shearing and polarization state modulation on the collimated light, obtaining two circularly polarized beams with orthogonal polarization states at different spatial positions. The polarization beam splitter divides the circularly polarized light into a p-component and an s-component. The p-component is transmitted and imaged onto the first array detector by the first imaging lens, while the s-component is reflected and imaged onto the second array detector by the second imaging lens. The first and second array detectors respectively obtain polarization interferograms containing target polarization information, and the interference fringes of the two polarization interferograms are complementary. The polarization interferograms are transmitted to the corresponding demodulation processor for polarization interferometry data processing to obtain high-precision Stokes parameters of the target.

2. The high resolution snapshot polarimetric interferometric imaging detection system of claim 1, wherein: The beam modulation and shaping unit includes a first polarization grating and a second polarization grating. The first polarization grating and the second polarization grating are placed perpendicular to the optical axis and parallel to each other, and the grating periods of the first polarization grating and the second polarization grating are the same. The first polarization grating and the second polarization grating shear the collimated light and perform polarization state conversion to obtain two circularly polarized beams.

3. The high resolution snapshot polarimetric interferometric imaging detection system of claim 1, wherein: The front optical system includes an objective lens, an aperture stop, and a collimating lens; the objective lens receives the reflected light from the target, the aperture stop limits the reflected light, and after collimation by the collimating lens, the collimated light is obtained and incident on the beam modulation and shaping unit.

4. A high-resolution snapshot polarimetric interferometric imaging detection method, applicable to the high-resolution snapshot polarimetric interferometric imaging detection system as claimed in any one of claims 1 to 3, characterized in that: The detection method includes the following steps: Step S1. Aligning the polarimetric interference image pixel of the first area array detector and the second area array detector directly superimposed to obtain the Stokes parameter of the target ; Step S2. The polarized interferogram contains target Stokes parameters , and , removing parameters The frequency domain zero frequency channel of the interferogram can be removed to eliminate the data interference of the zero frequency channel on the remaining channels. Step S3. Position the light source with known Stokes parameters. , and The reference light directly illuminates the front optical system, and the Stokes parameters of the reference light are obtained by the demodulation processor. Interferogram and corresponding frequency domain channels ; Step S4. After the light source is depolarized, it illuminates the detection target, and the demodulation processor processes the data to obtain the Stokes parameters of the target. The interferogram and the corresponding frequency domain channel C; Step S5. Based on the frequency domain channel of the reference light By analyzing the frequency domain channel C of the target, the spatial modulation factor coupled with the Stokes parameters is obtained, and thus the Stokes parameters of the target are derived. and This enables polarization imaging detection of the target.

5. The high resolution snapshot polarimetric interferometric imaging detection method of claim 4, wherein: In steps S3 and S4, the frequency domain channel C and C are respectively determined by removing parameters and remove parameters The interference pattern is obtained by performing Fourier transform calculation and frequency domain filtering.

6. The high-resolution snapshot polarimetric interferometric imaging detection method of claim 4, wherein: In the step S5, the frequency domain channels and C are inverse Fourier transformed, the inverse Fourier transformed results are divided to remove the spatial modulation factor, and the polarization parameter data of the reference light are substituted to obtain the target polarization parameter.

7. The high-resolution snapshot polarization interferometry imaging detection method according to claim 4, characterized in that: In step five, the final target Stokes parameters , and are calculated as ； where I FPA1 and I FPA2 denote the polarimetric interferograms obtained on the two detectors, denotes the inverse Fourier transform, j denotes the imaginary unit, Real denotes the real calculation, Imag denotes the imaginary calculation, denote the decoupling spatial modulation factor and the target polarimetric parameters.

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