Variable view field Linnik interference microscopic system and measurement method thereof

Abstract

The invention discloses a variable view field Linnik interference microscopic system and a measurement method thereof, and belongs to the field of laser measurement instruments, and a variable diaphragm is introduced into a reference arm of an interference system to realize matching of objective lenses of different test arms, so that light field spatial correlation under speckle illumination is maintained; meanwhile, a light source system with a delay line structure is adopted to accurately compensate the optical path difference introduced by the asymmetric objective lens configuration, so that the acquisition of a high-contrast interference pattern is realized. The method can effectively improve the quality of an interference image, has a depth selection function, and is suitable for dynamic phase imaging in different view field ranges. The technical scheme of the invention shows good imaging effect and adaptability in the aspects of dynamic imaging and depth layering.

Description

Technical Field

[0001] The invention belongs to the field of laser measuring instruments, and in particular relates to a variable-field Linnik interference microscopy system and a measuring method thereof. Background Art

[0002] Interferometry microscopy has significantly expanded the capabilities and applications of microscopic imaging in life sciences and precision metrology. To achieve high-contrast interferograms while maintaining flexible system configurations, laser sources with high spatiotemporal coherence are often employed. However, the inherent high spatial coherence of laser illumination can easily lead to speckle noise caused by optical component imperfections, and parasitic fringes generated by reflections from multilayer interfaces within the sample can further reduce the system's axial resolution.

[0003] Dynamic speckle illumination effectively suppresses coherent noise by adding a temporal variation factor to the speckle field. Temporal averaging of multiple speckle patterns significantly reduces speckle noise in the image. Simultaneously, the decorrelation of the speckle field during defocusing reduces interference contrast, thereby improving depth selection. However, the low spatiotemporal coherence of speckle illumination requires extremely high optical matching between the reference and sample arms to achieve optimal interferometry.

[0004] Existing reflective dynamic speckle interferometry microscopy techniques typically use identical objective lenses in both the reference and sample arms to ensure highly consistent exit pupil wavefronts. However, when measurements are required at different fields of view or resolutions, the reference arm objective must be replaced to match the sample arm configuration, complicating system commissioning and significantly increasing costs. Furthermore, manufacturing tolerances mean that the wavefronts of any two "identical" objectives may not be completely identical, requiring careful selection from a large selection pool of identical lenses, further increasing costs and complexity.

[0005] In order to balance the flexibility of the system and high-contrast interferometric imaging, some schemes have attempted to design interchangeable or adjustable objective lens groups in the reference arm to match the objectives of different sample arms. However, this method is only effective for specific lens combinations, and the matching process is cumbersome. Some schemes compensate for the optical path difference by translating the objective lens and sample as a whole, but the difference in wavefront curvature will introduce curved fringes. There are also schemes that use a high temporal coherence, low spatial coherence laser-diffuser combination. Although it can tolerate large optical path differences, it makes the system's axial resolution completely dependent on the numerical aperture of the objective lens, making it difficult to obtain good depth resolution in low numerical aperture applications. Summary of the Invention

[0006] The present invention aims to provide a variable-field-of-view Linnik interferometry microscopy system and a measurement method thereof, so as to solve the technical problem in existing Linnik interferometry microscopy systems in which the low coherence of the light source leads to high consistency requirements for the objective lens and thus limited objective lens selection. The system can achieve highly sensitive phase imaging under different field-of-view and resolution conditions without replacing the reference arm objective lens.

[0007] The technical solution for achieving the purpose of the present invention is: a variable-field Linnik interference microscopy system, the entire system is divided into three parts, including a delay compensation light source subsystem, a rotating ground glass and an asymmetric interference subsystem arranged in sequence along the optical path, wherein the delay compensation light source subsystem includes a short coherence laser, a half-wave plate, a first polarization beam splitter prism, a first quarter-wave plate, a first corner cube prism, a second quarter-wave plate, a second corner cube prism, and a translation stage; the asymmetric interference subsystem includes a beam expander lens, a collimating lens, a second polarization beam splitter prism, a third quarter-wave plate, a test arm microscope objective, a measurement sample, a reference arm microscope objective, a reference mirror, a variable aperture, a fourth quarter-wave plate, a fifth quarter-wave plate, a tube lens and a polarization CMOS camera.

[0008] A half-wave plate, a first polarization beam splitter, a first quarter-wave plate, and a first corner cube are sequentially arranged along the central vertical optical axis of the common delay compensation light source subsystem; a first polarization beam splitter, a second quarter-wave plate, and a second corner cube are arranged along the central horizontal optical axis of the common delay compensation light source subsystem; the central vertical optical axis of the delay compensation light source subsystem and the central horizontal optical axis of the delay compensation light source subsystem intersect perpendicularly at the first polarization beam splitter prism; the second corner cube is arranged on a translation stage; the direction of the outgoing light beam of the short coherence laser is the same as the central vertical optical axis of the delay compensation light source subsystem, and the lateral offset distance is d, where d is not greater than half of the aperture of the first corner cube; the direction of the outgoing light beam of the delay compensation light source subsystem is the same as the central horizontal optical axis of the delay compensation light source subsystem, and the lateral offset distance is also d.

[0009] A beam expander lens, a collimating lens, a second polarization beam splitter prism, a third quarter-wave plate, a test arm microscope objective, and a measurement sample are sequentially arranged on the central horizontal optical axis of the co-asymmetric interference subsystem; a polarization CMOS camera, a tube lens, a fifth quarter-wave plate, a second polarization beam splitter prism, a fourth quarter-wave plate, a variable aperture, a reference arm microscope objective, and a reference mirror are sequentially arranged on the central vertical optical axis of the co-asymmetric interference subsystem; the central horizontal optical axis of the co-asymmetric interference subsystem and the central vertical optical axis of the co-asymmetric interference subsystem intersect perpendicularly at the second polarization beam splitter prism.

[0010] The collimated light emitted by the short coherence laser passes through the half-wave plate and is incident on the splitting surface of the first polarization beam splitter at a 45° angle. The splitting surface of the first polarization beam splitter is divided into reflected light and transmitted light with mutually perpendicular polarization directions, wherein the reflected light is the high spatial coherence test light and the transmitted light is the high spatial coherence reference light; the high spatial coherence reference light passes through the first quarter-wave plate and is incident on the first corner cube prism. The light reflected by the first corner cube prism passes through the first quarter-wave plate and is reflected on the splitting surface of the first corner cube prism, and is transmitted along the output beam direction of the delay compensation light source subsystem. The high spatial coherence test light passes through the second quarter-wave plate and is incident on the second corner cube placed on the translation stage. The light reflected by the second corner cube passes through the second quarter-wave plate and then passes through the beam splitting surface of the first corner cube, and is emitted to the rotating ground glass along the output beam direction of the delay compensation light source subsystem. The high spatial coherence test light and the high spatial coherence reference light with mutually orthogonal polarization directions are incident on the same position of the rotating ground glass, and after passing through the rotating ground glass, they form speckle test light and speckle reference light respectively, and then enter the asymmetric interference subsystem.

[0011] In the asymmetric interferometer system, the speckle test light and the speckle reference light pass through the beam expander lens and the collimator lens to reach the second polarization beam splitter prism. After the speckle test light passes through the beam splitting surface of the second polarization beam splitter prism, it passes through the third quarter-wave plate and the test arm microscope objective lens, reaches the surface of the measurement sample and is reflected. The speckle test light carrying the surface information of the measurement sample passes through the test arm microscope objective lens and the third quarter-wave plate to reach the second polarization beam splitter prism, is reflected at the beam splitting surface of the second polarization beam splitter prism, passes through the fifth quarter-wave plate and the tube lens to reach the target surface of the polarization CMOS camera. The speckle reference light, after reflecting from the beam splitting surface of the second polarization beam splitter prism, passes through the fourth quarter-wave plate, the variable aperture, and the reference arm microscope objective lens to reach the surface of the reference mirror. After being reflected by the reference mirror, it passes through the reference arm microscope objective lens and the fourth quarter-wave plate to reach the second polarization beam splitter prism, passes through the beam splitting surface of the second polarization beam splitter prism, passes through the fifth quarter-wave plate and the tube lens to reach the target surface of the polarization CMOS camera, and interferes with the speckle test light carrying the surface information of the measurement sample.

[0012] A measurement method for a variable field-of-view Linnik interferometry microscope system, comprising the following steps:

[0013] Step 1: After the polarization direction of the linearly polarized light beam emitted by the short coherence laser is adjusted by a half-wave plate, it is split into a high spatial coherence reference light and a high spatial coherence measurement light with polarization directions perpendicular to each other on the splitting surface of the first polarization splitting prism (3).

[0014] Step 2: Adjust the measurement sample and reference mirror in sequence so that the measurement sample and reference mirror are clearly imaged on the polarization CMOS camera.

[0015] Step 3: Adjust the size of the variable aperture to maximize the correlation between the speckle test light and the speckle reference light reaching the polarization CMOS camera.

[0016] Step 4: Adjust the translation stage so that the phase delay between the high spatial coherence reference light and the high spatial coherence measurement light just compensates for the optical path difference between the reference arm and the arm to be measured due to the different microscope objectives, so that the high spatial coherence measurement light and the high spatial coherence reference light form a stable interference pattern on the surface of the polarization CMOS camera.

[0017] Step 5: The polarization CMOS camera collects multiple frames of interference patterns for analysis to achieve surface morphology detection of the measured sample.

[0018] Compared with the prior art, the present invention has the following significant advantages:

[0019] (1) The asymmetric optical structure can be used to match the spatial coherence of the test arm objective lens by adjusting the adjustable aperture of the reference arm, so that microscope objective lenses with different magnifications can be selected according to measurement requirements.

[0020] (2) A delay-compensated light source subsystem is used for illumination. The reference arm and test arm light beams are separated by a polarization beam splitter. The corner cube prism on the adjustable linear platform is used to achieve temporal coherence matching of objective lenses with different parameters, thereby obtaining a high-contrast interference pattern under short-coherence light source illumination.

[0021] (3) A polarization phase-shift interferometer module, including a quarter-wave plate and a polarization camera, is introduced to simultaneously acquire four phase-shift interferograms through a single exposure, thus achieving real-time synchronous measurement and further improving the imaging speed and phase measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the optical path diagram of the Linnik interference microscopy system of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the accompanying drawings.

[0024] Combine Figure 1A variable-field Linnik interferometry microscopy system is described. The system consists of three parts: a delay compensation light source subsystem, a rotating ground glass 9, and an asymmetric interferometry subsystem, all arranged sequentially along the optical path. The delay compensation light source subsystem includes a short-coherence laser 1, a half-wave plate 2, a first polarization beam splitter prism 3, a first quarter-wave plate 4, a first corner cube prism 5, a second quarter-wave plate 6, a second corner cube prism 7, and a translation stage 8. The asymmetric interferometry subsystem includes a beam expander lens 10, a collimating lens 11, a second polarization beam splitter prism 12, a third quarter-wave plate 13, a test arm microscope objective 14, a measurement sample 15, a reference arm microscope objective 16, a reference mirror 17, a variable aperture 18, a fourth quarter-wave plate 19, a fifth quarter-wave plate 20, a tube lens 21, and a polarization CMOS camera 22.

[0025] When a traditional Linnik interferometry microscopy system uses a low-coherence light source for illumination, in order to ensure the contrast of the interference pattern, it is necessary to use exactly the same reference arm microscope objective lens 16 and test arm microscope objective lens 14 to achieve coherence matching between the reference arm and the test arm. The present invention decomposes the consistency requirement of the low-coherence light source for the reference arm microscope objective lens 16 and the test arm microscope objective lens 14 into the requirement for spatial coherence matching and the requirement for temporal coherence matching, and satisfies both requirements simultaneously by placing a variable aperture 18 on the entrance pupil plane of the reference arm microscope objective lens 16 and using a delay compensation light source subsystem, so that the test arm microscope objective lens 14 can be switched arbitrarily while the reference arm microscope objective lens 16 remains unchanged.

[0026] A half-wave plate 2, a first polarization beam splitter prism 3, a first quarter-wave plate 4, and a first corner cube prism 5 are sequentially arranged along the central vertical optical axis of the common delay compensation light source subsystem; a first polarization beam splitter prism 3, a second quarter-wave plate 6, and a second corner cube prism 7 are arranged along the central horizontal optical axis of the common delay compensation light source subsystem; the central vertical optical axis of the delay compensation light source subsystem and the central horizontal optical axis of the delay compensation light source subsystem intersect perpendicularly at the first polarization beam splitter prism 3; the second corner cube prism 7 is arranged on a translation stage 8; the direction of the outgoing light beam of the short coherent laser 1 is the same as the central vertical optical axis of the delay compensation light source subsystem, and the lateral offset distance is d, where d is not greater than half of the aperture of the first corner cube prism 5; the direction of the outgoing light beam of the delay compensation light source subsystem is the same as the central horizontal optical axis of the delay compensation light source subsystem, and the lateral offset distance is d; the second corner cube prism 7 is installed on a translation stage 8, and the position of the second corner cube prism 7 can be moved by moving the translation stage 8.

[0027] The central horizontal optical axis of the co-asymmetric interference subsystem is sequentially provided with a beam expander lens 10, a collimating lens 11, a second polarization beam splitter prism 12, a third quarter-wave plate 13, a test arm microscope objective lens 14, and a measurement sample 15. The central vertical optical axis of the co-asymmetric interference subsystem is sequentially provided with a polarization CMOS camera 22, a tube lens 21, a fifth quarter-wave plate 20, a second polarization beam splitter prism 12, a fourth quarter-wave plate 19, a variable aperture 18, a reference arm microscope objective lens 16, and a reference mirror 17. The central horizontal optical axis of the co-asymmetric interference subsystem and the central vertical optical axis of the co-asymmetric interference subsystem intersect perpendicularly at the second polarization beam splitter prism 12.

[0028] The collimated light emitted by the short coherence laser 1 passes through the half-wave plate 2 and is incident on the splitting surface of the first polarization beam splitter prism 3 at a 45° angle. The splitting surface of the first polarization beam splitter prism 3 is divided into reflected light and transmitted light with mutually perpendicular polarization directions, wherein the reflected light is the high spatial coherence test light and the transmitted light is the high spatial coherence reference light; the high spatial coherence reference light passes through the first quarter-wave plate 4 and is incident on the first corner cube prism 5. The light reflected by the first corner cube prism 5 passes through the first quarter-wave plate 4 and is reflected on the splitting surface of the first corner cube prism 5, and is transmitted along the output beam direction of the delay compensation light source subsystem. The high spatial coherence test light passes through the second quarter-wave plate 6 and is incident on the second corner cube 7 placed on the translation stage 8. The light reflected by the second corner cube 7 passes through the second quarter-wave plate 6 and then passes through the splitting surface of the first corner cube 5. It is emitted to the rotating ground glass 9 along the output beam direction of the delay compensation light source subsystem; the high spatial coherence test light and the high spatial coherence reference light with mutually orthogonal polarization directions are incident on the same position of the rotating ground glass 9, and after passing through the rotating ground glass 9, they form speckle test light and speckle reference light respectively, and then enter the asymmetric interference subsystem.

[0029] In the asymmetric interferometer system, the speckle test light and the speckle reference light pass through the beam expander lens 10 and the collimator lens 11 to reach the second polarization beam splitter prism 12. The speckle test light passes through the beam splitting surface of the second polarization beam splitter prism 12, passes through the third quarter-wave plate 13 and the test arm microscope objective lens 14, reaches the surface of the measurement sample 15 and is reflected. The speckle test light carrying the surface information of the measurement sample 15 passes through the test arm microscope objective lens 14 and the third quarter-wave plate 13 to reach the second polarization beam splitter prism 12, is reflected at the beam splitting surface of the second polarization beam splitter prism 12, passes through the fifth quarter-wave plate 20 and the tube lens 21, and is reflected. 1 reaches the target surface of the polarization CMOS camera 22, and the speckle reference light is reflected at the splitting surface of the second polarization beam splitter prism 12, and then passes through the fourth quarter-wave plate 19, the variable aperture 18, and the reference arm microscope objective 16 to reach the surface of the reference mirror 17. After being reflected by the reference mirror 17, it passes through the reference arm microscope objective 16 and the fourth quarter-wave plate 19 to reach the second polarization beam splitter prism 12, passes through the splitting surface of the second polarization beam splitter prism 12, passes through the fifth quarter-wave plate 20 and the tube lens 21 to reach the target surface of the polarization CMOS camera 22, and interferes with the speckle test light carrying the surface information of the measurement sample 15.

[0030] The rotating frosted glass 9 is conjugate with the back focal planes of the test arm microscope objective lens 14 and the reference arm microscope objective lens 16, and the spot size on the frosted glass 9 illuminated by the light source should be able to fill the back focal planes when it reaches the back focal planes of the test arm microscope objective lens 14 and the reference arm microscope objective lens 16 through the optical system, so that the microscope objective lens can fully utilize its NA.

[0031] The difference between the wavefronts emitted by the test arm microscope objective lens 14 and the reference arm microscope objective lens 16 does not exceed λ / 10.

[0032] The test arm microscope objective lens 14 and the reference arm microscope objective lens 16 are infinity corrected, the focal length of the tube lens 21 is 200 mm, and the target surface of the CMOS camera 22 is placed at the rear focal plane of the tube lens 21 .

[0033] The fast axes of the first quarter wave plate 4 , the second quarter wave plate 6 , the third quarter wave plate 13 , and the fourth quarter wave plate 19 form an angle of 45° with the horizontal direction.

[0034] When the variable iris 18 is fully opened and does not block the light beam, the entrance pupil diameter of the reference arm microscope objective lens 16 should be larger than the entrance pupil diameter of the test arm microscope objective lens 16 .

[0035] The test arm microscope objective lens 14 can be switched to microscope objectives of different magnifications, but the entrance pupil diameter of the switched microscope objective lens must be smaller than the entrance pupil diameter of the reference arm microscope objective lens 16, so that the variable aperture 18 can adjust the entrance pupil diameter of the reference arm microscope objective lens 16 to be the same as the entrance pupil diameter of the test arm microscope objective lens 14.

[0036] Combine Figure 1 A measurement method for a variable field-of-view Linnik interferometry microscope system is provided, wherein the steps are as follows:

[0037] Step 1: After the linearly polarized beam emitted by the short coherence laser 1 is polarized by the half-wave plate 2, it is split into a high spatial coherence reference beam and a high spatial coherence measurement beam with mutually perpendicular polarization directions at the splitting surface of the first polarization beam splitter prism 3.

[0038] Step 2: sequentially adjust the measurement sample 15 and the reference mirror 17 so that the measurement sample 15 and the reference mirror 17 are clearly imaged on the polarization CMOS camera 22 .

[0039] Step 3: Adjust the size of the variable aperture 18 so that the speckle test light and the speckle reference light reaching the polarization CMOS camera 22 achieve maximum correlation, as follows:

[0040] When the reference arm microscope objective lens 16 and the test arm microscope objective lens 14 have different focal lengths, the complex amplitudes U of the speckle test light and the speckle reference light at the camera plane are s O (r) and U s R (r) are respectively expressed as:

[0041]

[0042] Among them, U d (r) represents the complex amplitude distribution of the rotating ground glass (9), λ is the central wavelength of the short coherent laser 1, represents Fourier transform, f TL is the focal length of the tube lens 21, r represents the vertical axis coordinate, P E.P O (r), P E.P R (r) are the entrance pupil aperture functions of the test arm microscope objective 14 and the reference arm microscope objective 16, respectively, and are written as:

[0043]

[0044] where r E.P O 、r E.P R are the entrance pupil radii of the test arm microscope objective 14 and the reference arm microscope objective 16 limited by the variable aperture 18, respectively. The correlation Cor between the speckle test light and the speckle reference light is expressed as:

[0045]

[0046] When the clear aperture of the variable iris 18 is controlled so that the entrance pupil radii of the test arm microscope objective 14 and the reference arm microscope objective 16 are the same, the correlation between the speckle test light and the speckle reference light reaches a maximum value, ie, Cor=1.

[0047] Step 4: Adjust the translation stage 8 so that the phase delay between the high spatial coherence reference light and the high spatial coherence measurement light just compensates for the optical path difference between the reference arm and the arm to be measured due to the different microscope objective lenses, so that the high spatial coherence measurement light and the high spatial coherence reference light form a stable interference pattern on the surface of the polarization CMOS camera 22.

[0048] The reference arm refers to the optical path composed of the first polarization beam splitter prism 3, the first quarter-wave plate 4, the first corner cube prism 5, the rotating ground glass 9, the beam expander lens 10, the collimating lens 11, the second polarization beam splitter prism 12, the fourth quarter-wave plate 19, the variable aperture 18, the reference arm microscope objective 16, the reference mirror 17, the fifth quarter-wave plate 20, the tube lens 21, and the polarization CMOS camera 22 through which the reference light passes.

[0049] The test arm refers to the optical path composed of the first polarization beam splitter prism 3, the second quarter-wave plate 6, the second corner cube prism 7, the translation stage 8, the rotating ground glass 9, the beam expander lens 10, the collimating lens 11, the second polarization beam splitter prism 12, the third quarter-wave plate 14, the test arm microscope objective 14, the measurement sample 15, the fifth quarter-wave plate 20, the tube lens 21, and the polarization CMOS camera 22 through which the test light passes.

[0050] Step 5: The polarization CMOS camera collects multiple frames of interference patterns for analysis to achieve surface morphology detection of the measured sample.

[0051] The short coherent laser 1 has a central wavelength of 632.8 nm and a coherent length of 100 μm.

[0052] The polarization CMOS camera 22 simultaneously collects four interference patterns and calculates the height information of the surface to be measured:

[0053]

[0054] Wherein H is the surface height of the sample 15 to be measured, I1, I2, I3, and I4 are the intensities of the four interference patterns, and λ is the central wavelength of the short coherent laser 1.

Claims

1. A variable-field Linnik interferometry microscopy system, characterized by: The invention comprises a delay compensation light source subsystem, a rotating frosted glass (9) and an asymmetric interference subsystem which are sequentially arranged along an optical path, wherein the delay compensation light source subsystem comprises a short coherent laser (1), a half-wave plate (2), a first polarization beam splitter prism (3), a first quarter-wave plate (4), a first corner cube prism (5), a second quarter-wave plate (6), a second corner cube prism (7) and a translation stage (8); and the asymmetric interference subsystem comprises a beam expander lens (10), a collimating lens (11), a second polarization beam splitter prism (12), a third quarter-wave plate (13), a test arm microscope objective lens (14), a measurement sample (15), a reference arm microscope objective lens (16), a reference mirror (17), a variable aperture (18), a fourth quarter-wave plate (19), a fifth quarter-wave plate (20), a tube lens (21) and a polarization CMOS camera (22); A half-wave plate (2), a first polarization beam splitter prism (3), a first quarter-wave plate (4), and a first corner cube prism (5) are sequentially arranged on the central vertical optical axis of the common delay compensation light source subsystem; a first polarization beam splitter prism (3), a second quarter-wave plate (6), and a second corner cube prism (7) are arranged on the central horizontal optical axis of the common delay compensation light source subsystem; the central vertical optical axis of the delay compensation light source subsystem and the central horizontal optical axis of the delay compensation light source subsystem intersect perpendicularly at the first polarization beam splitter prism (3); and the second corner cube prism (7) is arranged on a translation stage (8); the direction of an outgoing light beam of the short coherent laser (1) is the same as the central vertical optical axis of the delay compensation light source subsystem, and the lateral offset distance is d, which is no greater than half the aperture of the first corner cube prism (5); the direction of an outgoing light beam of the delay compensation light source subsystem is the same as the central horizontal optical axis of the delay compensation light source subsystem, and the lateral offset distance is also d; The central horizontal optical axis of the co-asymmetric interference subsystem is sequentially provided with a beam expander lens (10), a collimating lens (11), a second polarization beam splitter prism (12), a third quarter wave plate (13), a test arm microscope objective lens (14), and a measurement sample (15); the central vertical optical axis of the co-asymmetric interference subsystem is sequentially provided with a polarization CMOS camera (22), a tube lens (21), a fifth quarter wave plate (20), a second polarization beam splitter prism (12), a fourth quarter wave plate (19), a variable aperture (18), a reference arm microscope objective lens (16), and a reference mirror (17); the central horizontal optical axis of the co-asymmetric interference subsystem and the central vertical optical axis of the co-asymmetric interference subsystem intersect perpendicularly at the second polarization beam splitter prism (12); The collimated light emitted by the short coherence laser (1) passes through a half-wave plate (2) and is incident on the splitting surface of the first polarization beam splitter (3) at an angle of 45 degrees. The splitting surface of the first polarization beam splitter (3) is divided into reflected light and transmitted light with polarization directions perpendicular to each other, wherein the reflected light is high spatial coherence test light and the transmitted light is high spatial coherence reference light; the high spatial coherence reference light passes through a first quarter-wave plate (4) and is incident on a first corner cube prism (5). The light reflected by the first corner cube prism (5) passes through the first quarter-wave plate (4) and is reflected on the splitting surface of the first corner cube prism (5), and is emitted along the output of the delay compensation light source subsystem. The light beam is emitted to the rotating frosted glass (9); the high spatial coherence test light passes through the second quarter wave plate (6) and is incident on the second corner cube prism (7); the light reflected by the second corner cube prism (7) passes through the second quarter wave plate (6) and then passes through the beam splitting surface of the first corner cube prism (5), and is emitted to the rotating frosted glass (9) along the output light beam direction of the delay compensation light source subsystem; the high spatial coherence test light and the high spatial coherence reference light with mutually orthogonal polarization directions are incident on the same position of the rotating frosted glass (9), and after passing through the rotating frosted glass (9), they form speckle test light and speckle reference light respectively, and then enter the asymmetric interference subsystem; In the asymmetric interference subsystem, the speckle test light and the speckle reference light pass through the beam expander lens (10) and the collimator lens (11) and arrive at the second polarization beam splitter prism (12). The speckle test light passes through the beam splitting surface of the second polarization beam splitter prism (12), passes through the third quarter wave plate (13) and the test arm microscope objective lens (14), and arrives at the surface of the measurement sample (15) and is reflected. The speckle test light carrying the surface information of the measurement sample (15) passes through the test arm microscope objective lens (14) and the third quarter wave plate (13) and arrives at the second polarization beam splitter prism (12), is reflected at the beam splitting surface of the second polarization beam splitter prism (12), passes through the fifth quarter wave plate (20), the tube lens (21) and the tube lens (22). ) reaches the target surface of the polarization CMOS camera (22); the speckle reference light is reflected at the splitting surface of the second polarization beam splitter prism (12), then passes through the fourth quarter wave plate (19), the variable aperture (18), and the reference arm microscope objective lens (16), reaches the surface of the reference mirror (17), and then reflects from the reference mirror (17) and passes through the reference arm microscope objective lens (16) and the fourth quarter wave plate (19) to reach the second polarization beam splitter prism (12), passes through the splitting surface of the second polarization beam splitter prism (12), passes through the fifth quarter wave plate (20), and the tube lens (21) to reach the target surface of the polarization CMOS camera (22), and interferes with the speckle test light carrying the surface information of the measurement sample (15).

2. The variable field-of-view Linnik interferometry microscopy system according to claim 1, characterized in that: The rotating frosted glass (9) is conjugated with the back focal planes of the test arm microscope objective lens (14) and the reference arm microscope objective lens (16) relative to the 4f system composed of the beam expander lens (10) and the collimator lens (11), and the spot size of the rotating frosted glass (9) illuminated by the light source should be able to fill the back focal planes of the test arm microscope objective lens (14) and the reference arm microscope objective lens (16) when it reaches the back focal planes of the test arm microscope objective lens (14) and the reference arm microscope objective lens (16) through the 4f system composed of the beam expander lens (10) and the collimator lens (11), so that the microscope objective lens can fully utilize its own NA.

3. The variable field-of-view Linnik interferometry microscopy system according to claim 1, wherein: The translation stage (8) in the delayed light source compensation system can be translated along the optical axis, and the translation distance thereof is greater than the optical path difference between the test arm microscope objective lens (14) and the reference arm microscope objective lens (16).

4. The variable field-of-view Linnik interferometry microscopy system according to claim 1, wherein: The variable iris (18) is placed on the entrance pupil plane of the reference arm microscope objective lens (16), and when the clear aperture of the variable iris (18) is at its maximum, the entrance pupil diameter of the reference arm microscope objective lens (16) is greater than or equal to the entrance pupil diameter of the test arm microscope objective lens (14).

5. The variable field-of-view Linnik interferometry microscopy system according to claim 1, wherein: The entrance pupil diameter of the reference arm microscope objective lens (16) can be controlled by controlling the clear aperture of the variable iris (18) so that the entrance pupil diameter is the same as that of the test arm microscope objective lens (14). The test arm microscope objective lens (14) can arbitrarily switch microscope objective lenses of different magnifications without switching the reference arm microscope objective lens (16).

6. A measurement method based on the variable field of view Linnik interferometry microscopy system according to any one of claims 1 to 5, characterized in that: Here are the steps: Step 1: After the polarization direction of the linearly polarized light beam emitted by the short coherence laser (1) is adjusted by the half-wave plate (2), it is split into a high spatial coherence reference light and a high spatial coherence measurement light with mutually perpendicular polarization directions on the splitting surface of the first polarization splitting prism (3); Step 2: sequentially adjust the measurement sample (15) and the reference mirror (17) so that the measurement sample (15) and the reference mirror (17) are clearly imaged on the polarization CMOS camera (22); Step 3: Adjust the size of the variable aperture (18) so that the speckle test light and the speckle reference light reaching the polarization CMOS camera (22) achieve maximum correlation; Step 4: Adjust the translation stage (8) so that the phase delay between the high spatial coherence reference light and the high spatial coherence measurement light just compensates for the optical path difference between the reference arm and the arm to be measured due to the different microscope objective lenses, so that the high spatial coherence measurement light and the high spatial coherence reference light form a stable interference pattern on the surface of the polarization CMOS camera (22); Step 5: The polarization CMOS camera (22) collects multiple frames of interference patterns for analysis to achieve surface morphology detection of the measurement sample (15).

7. The measurement method of a variable field-of-view Linnik interferometry microscopy system according to claim 6, characterized in that: In step 3, the size of the variable aperture (18) is adjusted to maximize the correlation between the speckle test light and the speckle reference light reaching the polarization CMOS camera, as follows: When the reference arm microscope objective lens (16) and the test arm microscope objective lens (14) have different focal lengths, the complex amplitudes U of the speckle test light and the speckle reference light on the camera plane are s O (r) and U s R (r) are respectively expressed as: Among them, U d (r) represents the complex amplitude distribution of the rotating ground glass (9), λ is the central wavelength of the short coherent laser (1), represents Fourier transform, f TL is the focal length of the tube lens (21), r represents the vertical axis coordinate, P E.P O (r), P E.P R (r) are the entrance pupil aperture functions of the test arm microscope objective (14) and the reference arm microscope objective (16), respectively, and are written as: where r E.P O 、r E.P R are the entrance pupil radii of the test arm microscope objective (14) and the reference arm microscope objective (16) limited by the variable aperture (18), respectively. The correlation Cor between the speckle test light and the speckle reference light is expressed as: When the clear aperture of the variable iris (18) is controlled so that the entrance pupil radii of the test arm microscope objective (14) and the reference arm microscope objective (16) are the same, the correlation between the speckle test light and the speckle reference light reaches a maximum value, that is, Cor=1.

8. The measurement method of a variable field-of-view Linnik interferometry microscopy system according to claim 6, characterized in that: In step 5, the polarization CMOS camera (22) simultaneously collects four interference patterns and calculates the height information of the surface to be measured: Wherein H is the surface height of the sample to be measured (15), I1, I2, I3, and I4 are the intensities of the four interference patterns, and λ is the central wavelength of the short coherent laser (1).

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