Annular Common-Path Shear Speckle Interferometry System and Method

Abstract

This invention provides a ring-shaped common-path shearing speckle interferometry system and method, relating to an optical measurement system, including a beam generating device that generates light that illuminates the surface of the object being measured and forms reflected light; part of the reflected light passes sequentially through an imaging objective lens and a first Fourier lens before illuminating a polarizing beam splitter, where it is split into reflected light and transmitted light; part of the reflected light is reflected sequentially by a first reflecting mirror, an adjustable reflecting mirror, a second reflecting mirror, and the polarizing beam splitter, and then sequentially passes through a quarter-wave plate and a second Fourier lens before illuminating the imaging surface of a polarizing camera; part of the transmitted light is reflected sequentially by a second reflecting mirror, an adjustable reflecting mirror, and a first reflecting mirror, and then sequentially passes through the polarizing beam splitter, a quarter-wave plate, and a second Fourier lens before illuminating the imaging surface of the polarizing camera; this application can effectively achieve arbitrary adjustment of the shearing amount.

Description

Technical Field

[0001] This invention relates to an optical measurement system, specifically to a ring common-path shear speckle interferometry system and method. Background Technology

[0002] Shearing speckle interferometry is an optical measurement technique based on laser speckle phenomena and interference principles. It is primarily used to measure the displacement derivatives of an object's surface, such as the first derivative (slope) of out-of-plane displacement. Its principle is as follows: When coherent light (such as laser light) irradiates a rough surface, due to the microscopic irregularities of the surface, the coherent light is reflected and scattered, producing scattered light. This scattered light interferes with each other in space, forming a random intensity distribution pattern, i.e., a speckle field. Passing a portion of this speckle field through an optical shearing device causes a certain lateral displacement in that portion (i.e., lateral shearing). Then, the portion with the lateral displacement is superimposed on another portion of the speckle field (without lateral displacement) on the imaging plane, causing interference (i.e., shearing speckle interferometry). The phase of the resulting interference field changes, and the amount of phase change between the undeformed and deformed object is related to the displacement derivative of the object's surface.

[0003] Common optical path shearing devices include those based on Michelson interferometers and Mach-Zehnder interferometers. These devices split the object beam into two independent propagating paths, and the lateral displacement of each path is independently adjusted using optical elements such as mirrors. In these devices, vibrations and other factors in the propagation path can cause inconsistent optical path difference disturbances between the original and sheared object beam fields, thus affecting the measurement results. Common-path shearing devices can avoid these problems. Currently, common-path shearing methods include those based on flat plates, gratings, and Wollaston prisms. However, these common-path shearing devices have the disadvantage of inconvenient shearing adjustment. The shearing amount of a flat plate-based shearing device is determined by the thickness of the plate; the shearing amount of a Wollaston prism-based shearing device is determined by the prism size and its birefringence characteristics, making continuous adjustment impossible; and the shearing amount of a grating-based shearing device is determined by the grating position. Although continuous adjustment is possible, the grating position needs to be changed over a large range, and the adjustment range is limited, with the minimum shearing amount not approaching zero. In addition, the above three common-path shearing devices require the entire plate, grating, and Wollaston prism to be rotated when changing the shearing direction, which is inconvenient to adjust. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a ring-shaped common-path shear speckle interferometry system and method to solve the technical problem that the shear amount cannot be continuously adjusted in existing technologies.

[0006] (II) Technical Solution

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

[0008] In a first aspect, the present invention provides a ring common-path shear speckle interferometry system, including a beam generating device, wherein the light generated therefrom irradiates the surface of the object under test and forms reflected light;

[0009] Part of the reflected light passes through the imaging objective lens and the Fourier lens in sequence before shining on the polarizing beam splitter, where it is split into reflected light and transmitted light.

[0010] Part of the reflected light is reflected in sequence by mirror one, adjustable mirror, mirror two and polarizing beam splitter, and then passes through quarter wave plate and Fourier lens two to illuminate the imaging plane of polarizing camera.

[0011] Part of the transmitted light is reflected in sequence by mirror two, adjustable mirror and mirror one, and then passes through polarizing beam splitter, quarter wave plate and Fourier lens two in sequence to illuminate the imaging surface of polarizing camera.

[0012] in:

[0013] Fourier lens 1 and Fourier lens 2 form a 4f system, and the back focal plane of the imaging objective lens coincides with the front focal plane of Fourier lens 1, while the back focal plane of Fourier lens 2 coincides with the imaging plane of the polarization camera.

[0014] The adjustable mirror can rotate arbitrarily around point A on its reflecting surface, and point A is located on the optical axis and spectral plane of the 4f system.

[0015] Furthermore, the adjustable reflector includes a third reflector and a driving structure. The third reflector is mounted on the driving structure, which is used to drive the third reflector to rotate arbitrarily around point A.

[0016] Furthermore, the beam generating device includes a laser and a beam expander, wherein the beam generated by the laser is irradiated onto the surface of the object being measured by the beam expander.

[0017] Furthermore, the polarizing beam splitter is replaced with a semi-transparent and semi-reflective prism, and a polarizer is also provided between the semi-transparent and semi-reflective prism and the first reflector, a polarizer is also provided between the semi-transparent and semi-reflective prism and the second reflector, and a half-wave plate is also provided between the first reflector and the adjustable reflector.

[0018] A second aspect of the present invention also provides a method for measuring surface deformation of an object using the above-described annular common-path shear speckle interferometry system, the method comprising:

[0019] Before the object under test undergoes out-of-plane deformation, the speckle interferogram obtained on the imaging plane of the polarization camera corresponds to the image. And recorded as

[0020] After the object under test undergoes out-of-plane deformation, the deformed speckle interferogram obtained on the imaging plane of the polarization camera corresponds to... And recorded as

[0021] Depend on Obtain the deformation derivative of point (x,y) along the z-axis. Used for calculating out-of-plane deformation;

[0022] Among them, the shearing amount between the two beams of light illuminating the imaging plane of the polarization camera before and after the deformation of the object under test is δ. s , To correspond to the phase difference between the reflected and transmitted light in the speckle interferogram I(x,y), and Obtained from the following formula:

[0023] I m (x,y) represents the intensity of the modulated light in the corresponding speckle interferogram, (x,y) represents the coordinates of a point on the imaging plane of the polarization camera, and i is the imaginary unit. Let λ be the carrier phase introduced by the polarizer array in the polarization camera at point (x,y), and let λ be the wavelength of the light emitted by the beam generator. For δ s The corresponding shearing direction vector.

[0024] (III) Beneficial Effects

[0025] The present invention provides a ring-shaped common-path shear speckle interferometry system and method, which, compared with the prior art, has the following advantages:

[0026] 1. By setting an adjustable reflector, the shear position can be adjusted arbitrarily according to the needs, which improves the adjustment efficiency.

[0027] 2. The object beam and the sheared object beam are transmitted in the same path, which helps to resist the influence of environmental disturbances on the measurement results.

[0028] 3. Using polarization phase shift technology, a phase shift is introduced between two object beams that are transmitted in the same path to achieve high-precision phase measurement. Attached Figure Description

[0029] 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.

[0030] Figure 1A schematic diagram of the optical path structure of a ring common-path shear speckle interferometer system provided in Embodiment 1 is shown;

[0031] Figure 2 A schematic diagram of the light propagation path in the annular common-path shear speckle interferometer system shown in Example 1 is illustrated.

[0032] Figure 3 A schematic diagram of the polarizer array in the polarization camera shown in Embodiment 1 is illustrated.

[0033] Figure 4 A schematic diagram of the optical path structure of a ring common-path shear speckle interferometer system provided in Embodiment 2 is shown.

[0034] In the picture:

[0035] 1. Beam generating device; 2. Imaging objective lens; 3. Polarizing beam splitter; 4. Mirror 1; 5. Adjustable mirror; 6. Mirror 2; 7. Quarter wave plate; 8. Fourier lens 2; 9. Polarizing camera; 10. Semi-transparent and semi-reflective prism; 11. Polarizer 1; 12. Polarizer 2; 13. Half wave plate; 14. Fourier lens 1. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] Combined with appendix Figure 1 This embodiment provides a ring common-path shear speckle interferometer system, which includes a beam generator 1, an imaging objective lens 2, a Fourier lens 14, a polarizing beam splitter 3, a reflector 4, an adjustable reflector 5, a second reflector 6, a quarter-wave plate 7, a second Fourier lens 8, and a polarizing camera 9.

[0039] in:

[0040] 1. The imaging objective 2 and the Fourier lens-14 are coaxially distributed, and the back focal plane of the imaging objective 2 coincides with the front focal plane of the Fourier lens-14. The surface that coincides with the two is the intermediate image plane. Light emitted from any point on the intermediate image plane is parallel light after passing through the Fourier lens-14.

[0041] 2. A polarizing beam splitter, 3. a first reflector, 4. an adjustable reflector, 5. and a second reflector, 6 form a ring optical path;

[0042] 3. The quarter-wave plate 7, the Fourier lens 8, and the polarization camera 9 are coaxially distributed, and the outgoing light from the ring optical path passes through the quarter-wave plate 7 and the Fourier lens 8 in sequence before illuminating the imaging surface of the polarization camera 9.

[0043] 4. The back focal plane of Fourier lens 8 coincides with the imaging plane of polarization camera 9.

[0044] 5. Fourier lens 14 and Fourier lens 28 constitute a 4f system, and point A on the reflecting surface of the adjustable mirror 5 is located on the spectral surface of the 4f system and also on the optical axis of the 4f system.

[0045] 6. The adjustable reflector 5 can rotate arbitrarily around point A.

[0046] Based on the location distribution of the above-mentioned system components, this embodiment forms the following optical path:

[0047] The light generated by the beam generator 1 first shines on the surface of the object being measured, forming scattered light;

[0048] Some of the scattered light passes through the imaging objective lens 2 and the Fourier lens-14 in sequence and then shines on the polarizing beam splitter 3, where it is split into reflected light and transmitted light, with the reflected light being S-light and the transmitted light being P-light.

[0049] Part of the reflected light is reflected in sequence by mirror 4, adjustable mirror 5, mirror 6 and polarizing beam splitter 3, and then passes through quarter wave plate 7 and Fourier lens 8 before illuminating the imaging surface of polarizing camera 9.

[0050] Part of the transmitted light is reflected in sequence by mirror 6, adjustable mirror 5 and mirror 4, and then passes through polarizing beam splitter 3, quarter wave plate 7 and Fourier lens 8 before illuminating the imaging surface of polarizing camera 9.

[0051] The two beams of light illuminating the imaging plane of the polarization camera 9 are both emitted from the polarization beam splitter 3. They are first converted into two circularly polarized beams with opposite rotation directions by the quarter-wave plate 7, and then imaged on the imaging plane of the polarization camera 9 by the Fourier lens 8. They interfere with each other and form a ring common-path shear speckle interferometer system, which is then used for related measurements.

[0052] In this embodiment, the polarization beam splitter 3 makes the polarization states of the reflected light and transmitted light entering the annular optical path perpendicular to each other. By adjusting the adjustable mirror 5, the reflected light and transmitted light in the annular optical path can be laterally misaligned, thereby adjusting the shearing amount. The adjustment amount can be arbitrarily adjusted according to the needs, which greatly improves the convenience of adjustment. Secondly, the setting of point A in the adjustable mirror 5, which is located on both the spectral plane and the optical axis of the 4f system, ensures that the principal ray of the object light in the system is always perpendicular to the imaging plane of the polarization camera 9 during any rotation, thus preventing additional spatial carrier waves and helping to improve the later spectrum utilization rate.

[0053] In this embodiment, the beam generating device 1 is used to generate a beam that illuminates the surface of the object being measured. It may include a laser and a beam expander. The beam generated by the laser is illuminated on the surface of the object being measured by the beam expander to form reflected light.

[0054] In this embodiment, the adjustable reflector 5 may include a reflector three and a driving structure. The reflector three is mounted on the driving structure, and the driving structure is used to drive the reflector three to rotate arbitrarily around point A.

[0055] The principle of measuring surface deformation based on the annular common-path shear speckle interferometry system provided in this embodiment is as follows:

[0056] Reference Appendix Figure 2 When the adjustable mirror 5 is not rotated (at which point the reflected light undergoes a displacement with a shearing amount of 0):

[0057] The propagation path of the transmitted light is 0→1→2→3→0 in the figure, and the propagation path of the reflected light is 0→3→2→1 in the figure. At this time, the transmitted light and the reflected light are imaged to the same position by the Fourier lens 8.

[0058] When rotating the adjustable mirror 5 (at this time, the reflected light undergoes a displacement with a non-zero shearing):

[0059] The propagation path of the transmitted light is 0→1→2→4→5→6 in the figure, and the propagation path of the reflected light is 0→3→2→7→8→9 in the figure. At this time, the reflected light and the transmitted light are imaged by the Fourier lens and are offset by the same distance in opposite directions.

[0060] Based on the above, the principle of phase measurement is as follows:

[0061] Rotate the adjustable mirror 5 so that the shearing between the two beams of light incident on the imaging plane of the polarizing camera is δ. s δ s The components along the x-axis and y-axis are δ x and δ y For the sake of simplicity in the derivation process, let δ be... y =0, only retain δx Then the complex amplitudes A1(x,y) of the reflected light and A2(x,y) of the transmitted light incident on the imaging plane of the polarization camera are respectively:

[0062]

[0063] Where i is the imaginary unit, (x,y) are the coordinates of a point on the imaging plane of the polarization camera, and the origin of the coordinate system containing this point is located on the optical axis of the 4f system, A0(x,y). δ x The complex amplitude and phase of the reflected light incident on the imaging plane of the polarization camera when the amplitude is 0.

[0064] The resulting speckle interference pattern I(x,y) after the reflected and transmitted light interfere on the imaging plane of the polarization camera is as follows:

[0065]

[0066] I0(x,y) represents the background light intensity, which does not carry carrier information and remains constant before and after deformation of the object being measured (where the shearing amount of the reflected light is always δ). s The x-δ value remains unchanged and is therefore a fixed value, unaffected by whether the object being measured is deformed. Furthermore, I0(x,y)=|A0(x-δ ... x ,y)| 2 +|A0(x+δ x ,y)| 2 ;

[0067] I m (x,y) represents the intensity of the modulated light, I m (x,y)=2|A0(v-δ x ,y)A0(x+δ x ,y)|;

[0068] Let be the phase difference between the reflected and transmitted light incident on the imaging plane of the polarization camera, and:

[0069]

[0070] The carrier phase introduced by the polarizer array in the polarization camera, since the polarizer array in the polarization camera consists of four (2×2) polarization arrays with polarization directions of 0°, 45°, 90° and 135° respectively. Figure 3The structure obtained by arranging polarizers in a matrix of micro-polarizers introduces an additional carrier phase because right-handed and left-handed circularly polarized light interfere with each other through the polarizer array, resulting in a phase shift twice the rotation angle of the polarizers. Therefore, the two object beams entering the imaging plane of the polarizing camera have different rotation directions. The carrier phase introduced by the polarizer array in the polarizing camera is as follows:

[0071]

[0072] (m,n) are the coordinates of the micro-polarizers in the polarizer array of the polarizer camera;

[0073] To separate the modulated light spectrum from the background light spectrum, the speckle interferogram acquired by the polarization camera needs to be processed as follows:

[0074] make

[0075] visible It consists of three parts, among which A portion of the spectrum carries no carrier phase and is located in the center, i.e., the low-frequency region, while the other two portions carry carrier phase and are located in the peripheral regions of the spectrum. This latter portion of the information can be extracted using a Fourier transform combined with a bandpass filter. That is:

[0076]

[0077] thereby obtaining

[0078] The above formula specifically means: First, perform a Fourier transform on the obtained speckle interferogram to obtain a spectrum, then use a low-pass filter to filter it, and finally use an inverse Fourier transform to obtain intensity information without any carrier phase; where FFT is used to calculate the Fourier transform, converting the image from the spatial domain (time domain) to the frequency domain. After applying FFT, the center of the image's spectrum is low frequency, and the surrounding area is high frequency. IFFT is the inverse transform of FFT, converting the frequency domain data back to the spatial domain, so that the processed data can be restored to the image. LPF represents a low-pass filter, which allows low-frequency signals to pass through while suppressing high-frequency signals.

[0079] Then, acquire one speckle interferogram before and after deformation, and extract the corresponding data respectively. Data collected before the object under test is deformed for Data collected after the object under test is deformed for Subtracting the two values ​​yields the phase difference Δψ between the reflected and transmitted light illuminating the polarization camera's imaging surface before and after the object's deformation. In this embodiment, the angle between the illumination direction and the observation direction is close to zero (default is 0). Therefore, Δψ is only related to the first derivatives of the object's out-of-plane deformation function w(x,y) in the x-axis and y-axis directions, and thus:

[0080] λ is the wavelength of the light emitted by the beam generating device 1;

[0081] In the above derivation process, to simplify the derivation process, let δ s The component δ in the y-axis direction y =0 and the component δ in the x-axis direction x ≠0, however, in actual shearing processes, δ y It can be set according to needs, and is not always zero. Therefore, the shearing amount between two beams of light illuminating the imaging plane of the polarization camera is δ. s When the measured object deforms, the relationship between Δψ obtained at point (x,y) before and after deformation and the deformation function w(x,y) of that point in the z-axis direction is as follows:

[0082]

[0083] Where, δ s The magnitude and its corresponding shear direction vector The relationship is as follows:

[0084]

[0085] Based on the foregoing, in order to obtain the out-of-plane deformation of the object after deformation, the following methods can be used:

[0086] Step 1: Before the object under test undergoes out-of-plane deformation, obtain the shearing amount δ between the two beams of light illuminating the imaging plane of the polarization camera. s (δ s When the image is directly obtained from the adjustable mirror (using the adjustment device), the pre-deformation speckle interferogram is obtained on the imaging plane of the polarization camera, and the corresponding speckle pattern is obtained from this pre-deformation speckle interferogram. And recorded as

[0087] Step 2: After the object under test undergoes out-of-plane deformation, obtain the shearing amount δ between the two beams of light illuminating the imaging plane of the polarization camera. s (δ s When the image is directly obtained from the adjustable mirror (using the adjustment device), the deformed speckle interferogram is obtained on the imaging plane of the polarization camera, and the corresponding speckle interferogram is obtained from this deformed speckle interferogram. And recorded as

[0088] Then by achievable Used for calculating out-of-plane deformation.

[0089] Based on the above, this embodiment also provides a method for measuring surface deformation using the aforementioned annular common-path shear speckle interferometry system. The method specifically comprises:

[0090] Step 1: Obtain the speckle interferogram before deformation on the imaging plane of the polarization camera before the object under test undergoes out-of-plane deformation. And recorded as

[0091] Step 2: Obtain the deformed speckle interferogram corresponding to the image surface of the polarization camera after the object undergoes out-of-plane deformation. And recorded as

[0092] Step 3, from Obtain the deformation derivative of point (x,y) along the z-axis. Used for calculating out-of-plane deformation;

[0093] Among them, the shearing amount between the two beams of light illuminating the imaging plane of the polarization camera before and after the deformation of the object under test is δ. s , To correspond to the phase difference between the reflected and transmitted light in the speckle interferogram I(x,y), and Obtained from the following formula:

[0094] I m (x,y) represents the intensity of the modulated light in the corresponding speckle interferogram, (x,y) represents the coordinates of a point on the imaging plane of the polarization camera, and i is the imaginary unit. Let λ be the carrier phase introduced by the polarizer array in the polarization camera at point (x,y), and let λ be the wavelength of the light emitted by the beam generator. For δ s The corresponding shearing direction vector.

[0095] Example 2

[0096] like Figure 4 This embodiment provides a ring-shaped common-path shear speckle interferometry system. The main difference between this system and Embodiment 1 is:

[0097] The polarizing beam splitter prism 3 in Example 1 is replaced with a semi-transparent and semi-reflective prism 10. A polarizer 11 is also provided between the semi-transparent and semi-reflective prism 10 and the first reflector 4. A polarizer 12 is also provided between the semi-transparent and semi-reflective prism 10 and the second reflector 6. A half-wave plate 13 is also provided between the first reflector 4 and the adjustable reflector 5.

[0098] In this embodiment, the formed optical path is as follows:

[0099] The light generated by the beam generator 1 first shines on the surface of the object being measured, forming scattered light;

[0100] Some of the scattered light passes through the imaging objective lens 2 and the Fourier lens-14 in sequence and then shines on the semi-transparent and semi-reflective prism 10, where it is divided into reflected light and transmitted light.

[0101] Part of the reflected light first passes through polarizer 11 and is reflected by mirror 4. After passing through half-wave plate 13, it is reflected in sequence by adjustable mirror 5 and mirror 6. Then it passes through polarizer 12 and is reflected by semi-transparent prism 10. After passing through quarter-wave plate 7 and Fourier lens 8, it illuminates the imaging surface of polarizing camera 9.

[0102] Part of the transmitted light first passes through polarizer 12, and after being reflected in sequence by mirror 6 and adjustable mirror 5, it passes through half-wave plate 13 and is reflected by mirror 4. Then it passes in sequence through polarizer 11, semi-transparent and semi-reflective prism 10, quarter-wave plate 7 and Fourier lens 8 before illuminating the imaging surface of polarizing camera 9.

[0103] In this design, the optical axes of polarizer 11 and polarizer 2 12 are perpendicular, and the optical axis of half-wave plate 13 forms an angle of 45° with both polarizer 11 and polarizer 2 12. Based on this structure, the polarization states of the two beams (reflected light and transmitted light) emitted from the semi-transparent prism 10 are perpendicular to each other. By adjusting the adjustable mirror 5, the two beams entering the annular optical path can be laterally misaligned, i.e., the shearing amount can be adjusted. Furthermore, point A on the adjustable mirror 5 is located on the spectral plane and optical axis of the 4f system. Therefore, regardless of the shearing amount adjustment, the principal ray of the object beam is always perpendicular to the imaging plane of the polarization camera, thus preventing additional spatial carrier waves and improving spectral utilization. The two beams emitted from the semi-transparent prism 10 are transformed into two circularly polarized beams with opposite rotation directions after passing through the half-wave plate. They are then imaged onto the imaging plane of the polarization camera 9 by Fourier lens 2 8, interfering with each other to form a common-path sheared speckle interference system of the annular interferometer.

[0104] The remaining principles are the same as in Example 1, and will not be repeated here.

[0105] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0106] 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 method for measuring surface deformation of an object using a ring-shaped common-path shear speckle interferometry system, characterized in that, The system includes a beam generator that generates light that illuminates the surface of the object being measured and forms reflected light. Part of the reflected light passes through the imaging objective lens and the Fourier lens in sequence before shining on the polarizing beam splitter, where it is split into reflected light and transmitted light. Part of the reflected light is reflected in sequence by mirror one, adjustable mirror, mirror two and polarizing beam splitter, and then passes through quarter wave plate and Fourier lens two to illuminate the imaging plane of polarizing camera. Part of the transmitted light is reflected in sequence by mirror two, adjustable mirror and mirror one, and then passes through polarizing beam splitter, quarter wave plate and Fourier lens two in sequence to illuminate the imaging surface of polarizing camera. in: Fourier lens 1 and Fourier lens 2 form a 4f system, and the back focal plane of the imaging objective lens coincides with the front focal plane of Fourier lens 1, while the back focal plane of Fourier lens 2 coincides with the imaging plane of the polarization camera. The adjustable mirror can rotate arbitrarily around point A on its reflecting surface, and point A is located on the optical axis and spectral plane of the 4f system; The method includes: Before the object under test undergoes out-of-plane deformation, the speckle interferogram obtained on the imaging plane of the polarization camera corresponds to the image. , and record as ; After the object under test undergoes out-of-plane deformation, the deformed speckle interferogram obtained on the imaging plane of the polarization camera corresponds to... , and record as ; Depend on Gain points exist Deformation derivative in the axial direction , used for calculating out-of-plane deformation; Among them, the shearing amount between the two beams of light illuminating the imaging plane of the polarization camera before and after the deformation of the object under test is both , For the corresponding speckle interferogram The phase difference between reflected and transmitted light, and Obtained from the following formula: ; To correspond to the modulated light intensity in the speckle interferogram, The coordinates of a point on the imaging plane of the polarization camera. The imaginary unit, For point The carrier phase introduced by the polarizer array in the polarization camera, The wavelength of the light emitted by the beam generator. for The corresponding shearing direction vector; Indicates Fourier transform, yes inverse transform, This indicates a low-pass filter.

2. The method according to claim 1, characterized in that, The adjustable reflector includes a third reflector and a driving structure. The third reflector is mounted on the driving structure, which is used to drive the third reflector to rotate arbitrarily around point A.

3. The method according to claim 1, characterized in that, The beam generating device includes a laser and a beam expander, and the beam generated by the laser is irradiated onto the surface of the object being measured by the beam expander.

4. The method according to claim 1, characterized in that, The polarizing beam splitter is replaced with a semi-transparent and semi-reflective prism, and a polarizer is also provided between the semi-transparent and semi-reflective prism and the first reflector. A polarizer is also provided between the semi-transparent and semi-reflective prism and the second reflector. A half-wave plate is also provided between the first reflector and the adjustable reflector.

Images