Low-noise speckle interferometry system and method based on polarization camera

Abstract

The present invention provides a low-noise speckle interferometry system and method based on a polarization camera, relating to the technical field of speckle interferometry. The low-noise speckle interferometry system combines a polarization camera with a speckle interferometry system, enabling a single speckle interferogram to contain four channels with different polarization states. During image processing, the complex amplitude differences before and after deformation are averaged to achieve information fusion of the four channels. This reduces the standard deviation of the speckle interferometry noise to the original value of #imgabs0#, significantly improving the effectiveness of suppressing speckle interferometry noise. Furthermore, compared to traditional speckle interferometry techniques, data processing only requires one averaging operation, which has a minimal impact on overall measurement speed and excellent flexibility. Furthermore, by reducing the standard deviation of the speckle noise, the requirements for filtering algorithms used in speckle interferometry are reduced, thereby improving the practicality of the technique.

Description

Technical Field

[0001] The present invention relates to the field of speckle interferometry technology, and in particular to a low-noise speckle interferometry system and method based on a polarization camera. Background Art

[0002] Originating from digital holography, speckle pattern interferometry (Speckle Pattern Interferometry) observes the speckle patterns produced by coherent light on an object's surface and compares the phase variations of these patterns under different object conditions, effectively deriving the deformation of the object's surface. Due to its advantages of full-field non-contact and real-time detection, Speckle Pattern Interferometry is now widely used in measuring the mechanical properties of materials.

[0003] Because the phase obtained by speckle interferometry is wrapped in [-pi, pi], it is presented as a phase fringe pattern. When calculating surface deformation, a phase unwrapping algorithm is required to unwrap the phase to obtain the phase directly corresponding to the deformation. This is then combined with the displacement sensitivity factor to calculate the deformation information. However, like other coherent light illumination techniques, the phase image obtained by speckle interferometry contains significant speckle noise. This speckle noise can seriously interfere with the stability of the unwrapping algorithm, affecting the accuracy of the unwrapped phase and, consequently, damaging the measurement of object deformation.

[0004] A common method for suppressing speckle noise is to use image filtering algorithms in computer vision to filter out speckle noise. Considering that the edges of phase fringe patterns are relatively sharp, the filtering algorithm needs to be improved to protect the edges. The sine and cosine transform combined with the spatial filtering algorithm is the most common filtering algorithm, which has good filtering effects and fast filtering speeds. However, when faced with high-density stripes, spatial filtering will inevitably cause aliasing between stripes, affecting the phase distribution. As a representative of frequency domain filtering, the windowed Fourier transform is a filtering algorithm that is recognized to have good filtering effects. It has good filtering performance for high-density stripes or high-intensity noise. However, on the one hand, its filtering speed is slow. For modern industrial cameras with a pixel resolution of tens of millions, the filtering time can reach several minutes. On the other hand, it has many parameters, and multiple attempts are required to obtain good filtering quality. The combination of these two factors results in very poor flexibility of the windowed Fourier filter, making it difficult to apply to actual dynamic measurements.

[0005] Reducing speckle noise distribution through optical path design and combining it with simple filtering algorithms may achieve better overall results. However, current optical path designs focus on destroying the temporal coherence of the illumination beam, for example, by transmitting the beam through a rotating frosted glass to illuminate the object under test, resulting in complex optical paths and control. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the present invention provides a low-noise speckle interferometry system and method based on a polarization camera, which solves the problems of poor noise suppression effect and poor flexibility of speckle interferometry.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A low-noise speckle interferometry system based on a polarization camera, comprising: a laser source, a beam expander, a first plane mirror, a first beam splitter, a test object, a second plane mirror, a quarter-wave plate, a second beam splitter, a third plane mirror, and an imaging system;

[0009] The laser beam emitted by the laser source passes through the beam expander and is reflected by the first plane mirror to the first beam splitter, and the laser beam is split into a first beam and a second beam by the first beam splitter;

[0010] The first light beam is irradiated on the surface of the test object to generate diffuse reflection, and the diffusely reflected scattered light enters the imaging system as object light;

[0011] The second light beam is reflected by the second plane mirror, modulated by the quarter-wave plate, reflected by the second beam splitter, and reflected by the third plane mirror, and then enters the imaging system as a reference light;

[0012] A piezoelectric ceramic is installed behind the third plane mirror, and the piezoelectric ceramic drives the third plane mirror to perform regular reciprocating motion;

[0013] The imaging system includes: a first Fourier lens, a second Fourier lens, a polarization camera and a third beam splitter;

[0014] The first Fourier lens and the second Fourier lens have the same focal length, both f; the distance between the first Fourier lens and the second Fourier lens is 2f, the distance between the first Fourier lens and the test object is f, the distance between the second Fourier lens and the polarization camera is f, and the third beam splitter is disposed between the second Fourier lens and the polarization camera;

[0015] After entering the imaging system, the object light sequentially passes through the first beam splitter, the first Fourier lens, the second Fourier lens, and the third beam splitter and then is emitted to the polarization camera;

[0016] The reference light enters the imaging system, passes through the second beam splitter, is reflected by the third beam splitter, and then is emitted to the polarization camera;

[0017] The object light and the reference light are combined at the third beam splitter and interfere on the polarization camera.

[0018] Preferably, the laser beam emitted by the laser source is a linearly polarized beam.

[0019] Preferably, the beam expander is used to expand the beam diameter while keeping the beam collimated.

[0020] Preferably, the quarter wave plate is used to convert linearly polarized light into circularly polarized light.

[0021] Preferably, the imaging system is a 4f system with a magnification ratio of 1:1, and an aperture is provided on the spectrum plane of the imaging system.

[0022] Preferably, each pixel of the polarization camera is equipped with a corresponding polarizer, and all polarizers are arranged in the same 2×2 matrix array and spread throughout the entire polarization camera.

[0023] Preferably, a coordinate system is established with the upper left corner of the polarization camera as the origin, and a superpixel is defined as a 2×2 matrix. Each pixel of the polarization camera has its corresponding superpixel and serves as the upper left corner element in the superpixel.

[0024] A low-noise speckle interferometry method based on a polarization camera, the low-noise speckle interferometry method comprising:

[0025] A linearly polarized laser beam emitted by a laser source is expanded in diameter by a beam expander and then split into a first beam and a second beam by a first beam splitter. The laser beam emitted by the laser source and the first and second beams split therefrom are reflected by a plurality of plane mirrors to plan paths.

[0026] The first light beam strikes the surface of the test object along its path, causing diffuse reflection to generate speckle. The diffusely reflected scattered light, as object light, passes through the first Fourier lens, the aperture, and the second Fourier lens, and then passes through the third beam splitter to the polarization camera.

[0027] The second light beam is modulated by a quarter wave plate on its path and reflected by a third plane mirror, and then is emitted as a reference light through a third beam splitter to a polarization camera;

[0028] A piezoelectric ceramic is installed behind the third plane mirror, and the piezoelectric ceramic drives the third plane mirror to perform regular reciprocating motion, introducing periodic phase changes to the third plane mirror;

[0029] The first Fourier lens and the second Fourier lens have the same focal length, both f; the distance between the first Fourier lens and the second Fourier lens is 2f, the distance between the first Fourier lens and the test object is f, the distance between the second Fourier lens and the polarization camera is f, and the third beam splitter is disposed between the second Fourier lens and the polarization camera;

[0030] The object light and the reference light are combined at the third beam splitter and interfere on the polarization camera.

[0031] Preferably, the interference pattern light intensity expression obtained on the target surface of the polarization camera (13) is:

[0032] I(x,y)=I0(x,y)+I m (x,y)cos(φ(x,y)+φ p (x,y));

[0033] Where, I0(x,y) is the background light intensity;

[0034] I m (x,y) is the modulated light intensity;

[0035] φ(x,y) is the phase difference between the object light and the reference light;

[0036] φ p (x, y) is the phase introduced by the polarizer on the polarization camera (13);

[0037] Deduced with four-step phase shift, the intensity of the four speckle interferograms obtained is:

[0038]

[0039] in, And it can be calculated by the following formula:

[0040]

[0041] Using the four-step phase shifting technique, four speckle interferograms are collected before deformation to calculate the phase Collect four speckle interferograms before deformation to calculate phase The phase difference before and after deformation is:

[0042]

[0043] in, Indicates the phase difference caused by deformation; speckle interferometry requires subtracting the phase before deformation from the phase after deformation, and calculating the deformation based on the phase difference, so φ p (x,y) is eliminated during subtraction and does not affect the measurement and can be ignored;

[0044] Taking the interference light waves corresponding to the pixels at coordinate positions (1,1) and (2,2) as the reference, before deformation, the complex amplitudes of the light waves corresponding to these two pixels are:

[0045]

[0046] Among them, φ 1,1 and φ 2,2 for The specific values ​​at the pixels at coordinate positions (1,1) and (2,2);

[0047] According to the Jones matrix or vector superposition principle, the complex amplitudes of the other two pixels in the superpixel are expressed as:

[0048]

[0049] assumed If the signal remains unchanged within a super-pixel, then after deformation, the complex amplitudes of the two reference light waves are:

[0050]

[0051] The complex amplitudes of the other two pixels in this superpixel are expressed as:

[0052]

[0053] Among them, ε1 and ε2 are the speckle noises introduced by the pixels at positions (1,1) and (2,2) in the coordinate system. The polarization states corresponding to these two speckle noises are perpendicular to each other, so they have the characteristics of independent and identical distribution. In order to ensure To remain constant within a superpixel, the average size d of the speckle must be greater than 4 pixels; the average size of the speckle is affected by the aperture diameter D of the system, and its law is expressed as follows: Perform conjugate multiplication on the complex light field before and after deformation to obtain:

[0054]

[0055] Where * is a conjugate operation. The four complex amplitude differences in the superpixel are averaged to obtain the averaged complex amplitude difference:

[0056]

[0057]

[0058] The phase introduced by the deformation can be obtained by calculating the angle of the complex amplitude difference after the above average. Add the averaged speckle noise; let the averaged speckle noise be ε, then:

[0059]

[0060] Among them, angle represents the argument of the complex number;

[0061] The speckle noise ε is a random variable. Considering that the speckle noise ε1 and ε2 are independent and identically distributed, their standard deviation is defined as σ(ε n ), the averaged speckle noise standard deviation can be obtained:

[0062]

[0063] Finally, the speckle noise is suppressed.

[0064] The present invention provides a low-noise speckle interferometry system and method based on a polarization camera. Compared with the existing technology, it has the following advantages:

[0065] In the present invention, the low-noise speckle interferometry system combines a polarization camera with a speckle interferometry system, so that a single speckle interferogram contains four channels with different polarization states. During the image processing, the complex amplitude difference before and after deformation is averaged to achieve information fusion of the four channels, which can reduce the standard deviation of the speckle interferometry noise to the original value. The suppression effect of speckle interferometry noise is greatly improved; and in terms of data processing, only one averaging operation is added compared to traditional speckle interferometry technology, which has little impact on the overall measurement speed and excellent flexibility; in addition, by reducing the standard deviation of speckle noise, the requirements of speckle interferometry technology on the filtering algorithm are reduced, thereby improving the practicality of speckle interferometry technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0067] Figure 1 Schematic diagram of the structure of a low-noise speckle interferometry system in an embodiment of the present invention.

[0068] The reference numerals in the figure are set as: laser source 1, beam expander 2, first plane mirror 3, first beam splitter 4, test object 5, second plane mirror 6, quarter wave plate 7, second beam splitter 8, third plane mirror 9, piezoelectric ceramic 10, first Fourier lens 11, second Fourier lens 12, polarization camera 13, third beam splitter 14, aperture 15. DETAILED DESCRIPTION

[0069] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0070] The embodiments of the present application provide a low-noise speckle interferometry system and method based on a polarization camera, thereby solving the problem of poor noise suppression effect and poor flexibility of speckle interferometry.

[0071] In order to better understand the above technical solution, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0072] Example:

[0073] like Figure 1 As shown, the present invention provides a low-noise speckle interferometry system based on a polarization camera, the low-noise speckle interferometry system comprising: a laser source 1, a beam expander 2, a first plane mirror 3, a first beam splitter 4, a test object 5, a second plane mirror 6, a quarter-wave plate 7, a second beam splitter 8, a third plane mirror 9 and an imaging system;

[0074] The laser beam emitted by the laser source 1 passes through the beam expander 2 and is reflected by the first plane mirror 3 to the first beam splitter 4. The laser beam is split into a first beam and a second beam by the first beam splitter 4 through reflection and transmission.

[0075] The first light beam is irradiated onto the surface of the test object 5, causing diffuse reflection to generate speckle, and the diffusely reflected scattered light enters the imaging system as object light;

[0076] The second light beam is reflected by the second plane mirror 6, modulated by the quarter wave plate 7, reflected by the second beam splitter 8, and reflected by the third plane mirror 9, and then enters the imaging system as a reference light;

[0077] A piezoelectric ceramic 10 is installed behind the third plane mirror 9. The piezoelectric ceramic 10 drives the third plane mirror 9 to perform regular reciprocating motion, thereby introducing periodic phase changes to the third plane mirror 9.

[0078] The imaging system includes: a first Fourier lens 11, a second Fourier lens 12, a polarization camera 13 and a third beam splitter 14;

[0079] The first Fourier lens 11 and the second Fourier lens 12 have the same focal length, both f; the distance between the first Fourier lens 11 and the second Fourier lens 12 is 2f, the distance between the first Fourier lens 11 and the test object 5 is f, the distance between the second Fourier lens 12 and the polarization camera 13 is f, and the third beam splitter 14 is disposed between the second Fourier lens 12 and the polarization camera 13;

[0080] After entering the imaging system, the object light sequentially passes through the first beam splitter 4, the first Fourier lens 11, the second Fourier lens 12 and the third beam splitter 14 and then is emitted to the polarization camera 13;

[0081] After entering the imaging system, the reference light passes through the second beam splitter 8, is reflected by the third beam splitter 14, and then is emitted to the polarization camera 13;

[0082] The object light and the reference light are combined at the first beam splitter 14 and interfere with each other at the polarization camera 13 .

[0083] The laser beam emitted by the laser source 1 is a linearly polarized beam.

[0084] The beam expander 2 is used to expand the beam diameter while keeping the beam collimated.

[0085] The quarter wave plate 7 is used to convert linearly polarized light into circularly polarized light to prevent the light from being extinct in a specific polarization state of the polarization camera 13 .

[0086] like Figure 1 As shown, the imaging system is a 4f system with a magnification of 1:1. An aperture 15 is provided on the spectrum surface of the imaging system for adjusting the size of the speckle.

[0087] like Figure 1 As shown, each pixel of the polarization camera 13 is equipped with a corresponding polarizer, and all polarizers are arranged in the same 2×2 matrix array and spread throughout the entire polarization camera 13 .

[0088] A coordinate system (i, j) is established with the upper left corner of the polarization camera 13 as the origin, and a superpixel is defined as a 2×2 matrix. Each pixel of the polarization camera 13 has its corresponding superpixel and serves as the upper left corner element in the superpixel.

[0089] The present invention provides a low-noise speckle interferometry method based on a polarization camera, the low-noise speckle interferometry method comprising:

[0090] The linearly polarized laser beam emitted by the laser source 1 is expanded in diameter by the beam expander 2 and then split into a first beam and a second beam by the first beam splitter 4. The laser beam emitted by the laser source 1 and the first and second beams are reflected by a plurality of plane mirrors to plan paths.

[0091] The first light beam strikes the surface of the test object 5 along its path, causing diffuse reflection to generate speckles. The diffusely reflected scattered light, as object light, passes through the first Fourier lens 11, the aperture 15, and the second Fourier lens 12, and then passes through the third beam splitter 14 to the polarization camera 13.

[0092] The second light beam is modulated by the quarter wave plate 7 and reflected by the third plane mirror 9 on its path, and then passes through the third beam splitter 14 as the reference light to the polarization camera 13;

[0093] A piezoelectric ceramic 10 is installed behind the third plane mirror 9. The piezoelectric ceramic 10 drives the third plane mirror 9 to perform regular reciprocating motion, thereby introducing periodic phase changes to the third plane mirror 9.

[0094] The first Fourier lens 11 and the second Fourier lens 12 have the same focal length, both f; the distance between the first Fourier lens 11 and the second Fourier lens 12 is 2f, the distance between the first Fourier lens 11 and the test object 5 is f, the distance between the second Fourier lens 12 and the polarization camera 13 is f, and the third beam splitter 14 is disposed between the second Fourier lens 12 and the polarization camera 13;

[0095] The object light and the reference light are combined by transmission and reflection at the third beam splitter 14 and interfere with each other at the polarization camera 13 .

[0096] The interference pattern intensity expression obtained on the target surface of the polarization camera 13 is:

[0097] I(x,y)=I0(x,y)+I m (x,y)cos(φ(x,y)+φ p (x,y)); (1)

[0098] Where, I0(x,y) is the background light intensity;

[0099] I m (x,y) is the modulated light intensity;

[0100] φ(x,y) is the phase difference between the object light and the reference light;

[0101] φ p (x, y) is the phase introduced by the polarizer on the polarization camera 13;

[0102] Taking the four-step phase shift as an example for derivation, the intensity of the four speckle interferograms obtained is:

[0103]

[0104] in, And it can be calculated by the following formula:

[0105]

[0106] Using the four-step phase shifting technique, four speckle interferograms are collected before deformation to calculate the phase Collect four speckle interferograms before deformation to calculate phase The phase difference before and after deformation is:

[0107]

[0108] in, Indicates the phase difference caused by deformation; speckle interferometry requires subtracting the phase before deformation from the phase after deformation, and calculating the deformation based on the phase difference, so φ p (x,y) is eliminated during subtraction and does not affect the measurement and can be ignored;

[0109] The phase φ introduced by the polarization camera 13 p Since (x, y) remains unchanged at any time, it is eliminated in the subtraction process and thus does not affect the overall phase distribution. For simplicity and without loss of generality, the discussion is based on the principle of speckle noise suppression by polarization diversity. Figure 1 The first superpixel shown in the figure is analyzed. For the pixels at coordinate positions (1,1) and (2,2), the polarization states of the corresponding interference light are perpendicular to each other. Since speckles with perpendicular polarization states are not statistically correlated, the interference light waves corresponding to these two pixels are used as the reference for discussion. Before deformation, the complex amplitudes of the light waves corresponding to these two pixels are:

[0110]

[0111] Among them, φ 1,1 and φ 2,2 for The specific values ​​at the pixels at coordinate positions (1,1) and (2,2);

[0112] Considering that the phase has been directly solved by formula (3), the complex amplitude is set to 1 to simplify the discussion. According to the Jones matrix or vector superposition principle, the complex amplitudes of the other two pixels in the superpixel are expressed as:

[0113]

[0114] assumed If the signal remains unchanged within a super-pixel, then after deformation, the complex amplitudes of the two reference light waves are:

[0115]

[0116] The complex amplitudes of the other two pixels in this superpixel are expressed as:

[0117]

[0118] Among them, ε1 and ε2 are the speckle noises introduced by the pixels at positions (1,1) and (2,2) in the coordinate system. The polarization states corresponding to these two speckle noises are perpendicular to each other, so they have the characteristics of independent and identical distribution. In order to ensure To remain constant within a superpixel, the average size d of the speckle must be greater than 4 pixels; the average size of the speckle is affected by the aperture diameter D of the system, and its law is expressed as follows: Perform conjugate multiplication on the complex light field before and after deformation to obtain:

[0119]

[0120] Where * is a conjugate operation. The four complex amplitude differences in the superpixel are averaged to obtain the averaged complex amplitude difference:

[0121]

[0122] The phase introduced by the deformation can be obtained by calculating the angle of the complex amplitude difference after the above average. Add the averaged speckle noise; let the averaged speckle noise be ε, then:

[0123]

[0124] Among them, angle represents the argument of the complex number;

[0125] The speckle noise ε is a random variable. Considering that the speckle noise ε1 and ε2 are independent and identically distributed, their standard deviation is defined as σ(ε n ), the averaged speckle noise standard deviation can be obtained:

[0126]

[0127] Finally, the speckle noise is suppressed.

[0128] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0129] In an embodiment of the present invention, the low-noise speckle interferometry system combines a polarization camera with a speckle interferometry system, so that a single speckle interferogram contains four channels with different polarization states. During the image processing, the complex amplitude difference before and after deformation is averaged to achieve information fusion of the four channels, which can reduce the standard deviation of the speckle interferometry noise to the original value. The suppression effect of speckle interferometry noise is greatly improved; and in terms of data processing, only one averaging operation is added compared to traditional speckle interferometry technology, which has little impact on the overall measurement speed and excellent flexibility; in addition, by reducing the standard deviation of speckle noise, the requirements of speckle interferometry technology on the filtering algorithm are reduced, thereby improving the practicality of speckle interferometry technology.

[0130] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0131] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A low-noise speckle interferometry system based on a polarization camera, characterized in that: The low-noise speckle interferometry system comprises: a laser source (1), a beam expander (2), a first plane mirror (3), a first beam splitter (4), a test object (5), a second plane mirror (6), a quarter-wave plate (7), a second beam splitter (8), a third plane mirror (9) and an imaging system; The laser beam emitted by the laser source (1) passes through the beam expander (2) and is reflected by the first plane mirror (3) to the first beam splitter (4), and the laser beam is split into a first beam and a second beam by the first beam splitter (4); The first light beam is irradiated onto the surface of the test object (5) to generate diffuse reflection, and the diffusely reflected scattered light enters the imaging system as object light; The second light beam is sequentially reflected by the second plane mirror (6), modulated by the quarter-wave plate (7), reflected by the second beam splitter (8), and reflected by the third plane mirror (9), and then enters the imaging system as reference light; A piezoelectric ceramic (10) is installed behind the third plane mirror (9), and the piezoelectric ceramic (10) drives the third plane mirror (9) to perform regular reciprocating motion; The imaging system comprises: a first Fourier lens (11), a second Fourier lens (12), a polarization camera (13) and a third beam splitter (14); The first Fourier lens (11) and the second Fourier lens (12) have the same focal length, both being f; the distance between the first Fourier lens (11) and the second Fourier lens (12) is 2f, the distance between the first Fourier lens (11) and the test object (5) is f, the distance between the second Fourier lens (12) and the polarization camera (13) is f, and the third beam splitter (14) is arranged between the second Fourier lens (12) and the polarization camera (13); After entering the imaging system, the object light sequentially passes through the first beam splitter (4), the first Fourier lens (11), the second Fourier lens (12), and the third beam splitter (14) and then is emitted to the polarization camera (13); After entering the imaging system, the reference light passes through the second beam splitter (8), is reflected by the third beam splitter (14), and then is directed toward the polarization camera (13); The object light and the reference light are combined at the third beam splitter (14) and interfere on the polarization camera (13).

2. The low-noise speckle interferometry system based on a polarization camera according to claim 1, wherein: The laser beam emitted by the laser source (1) is a linearly polarized beam.

3. The low-noise speckle interferometry system based on a polarization camera according to claim 1, wherein: The beam expander (2) is used to expand the beam diameter while keeping the beam collimated.

4. The low-noise speckle interferometry system based on a polarization camera according to claim 1, wherein: The quarter-wave plate (7) is used to convert linearly polarized light into circularly polarized light.

5. The low-noise speckle interferometry system based on a polarization camera according to claim 1, wherein: The imaging system is a 4f system with a magnification of 1:1, and a diaphragm (15) is provided on the spectrum surface of the imaging system.

6. The low-noise speckle interferometry system based on a polarization camera according to claim 1, wherein: Each pixel of the polarization camera (13) is equipped with a corresponding polarizer, and all polarizers are arranged in the same 2×2 matrix array and spread throughout the entire polarization camera (13).

7. The low-noise speckle interferometry system based on a polarization camera according to claim 6, wherein: A coordinate system is established with the upper left corner of the polarization camera (13) as the origin, and a superpixel is defined as a 2×2 matrix. Each pixel of the polarization camera (13) has its corresponding superpixel and serves as the upper left corner element in the superpixel.

8. A low-noise speckle interferometry method based on a polarization camera, characterized in that: The low-noise speckle interferometry method comprises: A linearly polarized laser beam emitted by a laser source (1) is expanded in diameter by a beam expander (2) and then split into a first beam and a second beam by a first beam splitter (4); the laser beam emitted by the laser source (1) and the first beam and the second beam split into them are reflected by a plurality of plane mirrors to plan paths; The first light beam strikes the surface of the test object (5) along its path, causing diffuse reflection to generate speckles, and the diffusely reflected scattered light passes through the first Fourier lens (11), the aperture (15), and the second Fourier lens (12) as object light, and then passes through the third beam splitter (14) to the polarization camera (13); The second light beam is modulated by a quarter wave plate (7) and reflected by a third plane mirror (9) on its path, and then passes through a third beam splitter (14) as a reference light and is directed to a polarization camera (13); A piezoelectric ceramic (10) is installed behind the third plane mirror (9), and the piezoelectric ceramic (10) drives the third plane mirror (9) to perform regular reciprocating motion, thereby introducing a periodic phase change into the third plane mirror (9); The first Fourier lens (11) and the second Fourier lens (12) have the same focal length, both being f; the distance between the first Fourier lens (11) and the second Fourier lens (12) is 2f, the distance between the first Fourier lens (11) and the test object (5) is f, the distance between the second Fourier lens (12) and the polarization camera (13) is f, and the third beam splitter (14) is arranged between the second Fourier lens (12) and the polarization camera (13); The object light and the reference light are combined at the third beam splitter (14) and interfere on the polarization camera (13).

9. The low-noise speckle interferometry method based on a polarization camera according to claim 8, wherein: The interference pattern intensity expression obtained on the target surface of the polarization camera (13) is: ； in, is the background light intensity; is the modulated light intensity; is the phase difference between the object light and the reference light; is the phase introduced by the polarizer on the polarization camera (13); Deduced with four-step phase shift, the intensity of the four speckle interferograms obtained is: ； in, , and can be calculated by the following formula: ； Using the four-step phase shifting technique, four speckle interferograms are collected before deformation to calculate the phase , before deformation, four speckle interferograms are collected to calculate the phase ;The phase difference before and after deformation is: ； in, = Indicates the phase difference caused by deformation; Speckle interferometry requires subtracting the phase before deformation from the phase after deformation, and calculating the deformation based on the phase difference, so It is eliminated during subtraction and does not affect the measurement and can be ignored; The coordinate system position is and Taking the interference light waves corresponding to the pixels as the reference, before deformation, the complex amplitudes of the light waves corresponding to these two pixels are: ； ； in, and for The coordinate position is and The specific value of the pixel; A coordinate system is established with the upper left corner of the polarization camera (13) as the origin, and a superpixel is defined as a 2×2 matrix. Each pixel of the polarization camera (13) has its corresponding superpixel and is used as the upper left corner element in the superpixel. According to the Jones matrix or vector superposition principle, the complex amplitudes of the other two pixels in the superpixel are expressed as: ； ； assumed If the signal remains unchanged within a super-pixel, then after deformation, the complex amplitudes of the two reference light waves are: ； ； The complex amplitudes of the other two pixels in this superpixel are expressed as: ； ； in, and The position of the deformation in the coordinate system is and The speckle noise introduced by the pixels of the two speckle noises, the polarization states corresponding to the two speckle noises are perpendicular to each other, so they have the characteristics of independent and identical distribution; in order to ensure The average size of the speckle remains unchanged within a superpixel. Must be larger than 4 pixels; the average size of the speckle is affected by the system aperture diameter The influence is expressed as ; Perform conjugate multiplication on the complex light field before and after deformation to obtain: ； ； ； ； in, For the conjugate operation, the four complex amplitude differences in the superpixel are averaged to obtain the averaged complex amplitude difference: ； The phase introduced by the deformation can be obtained by calculating the angle of the complex amplitude difference after the above average. Add the averaged speckle noise; let the averaged speckle noise be ,but: ； in, It means finding the argument of a complex number; Speckle noise is a random variable; considering the speckle noise and Independent and identically distributed, their standard deviation is defined as , the standard deviation of the averaged speckle noise can be obtained: ； Finally, the speckle noise is suppressed.

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