Scanning quantitative phase microscopy device and method based on polarization multiplexing modulation

Abstract

The present invention discloses a scanning quantitative phase microscopy device based on polarization multiplexing modulation, comprising a laser focus scanning module, a polarization multiplexing modulation module and an image acquisition module, wherein the laser focus scanning module generates a collimated light beam for point-by-point scanning illumination of a sample to be measured; the polarization multiplexing modulation module performs polarization modulation on the collimated light beam along the X-axis direction and the Y-axis direction, and uses a phase-type spatial light modulator to modulate the linear polarized light along the Y-axis direction, and obtains reflected light carrying complex reflectivity information at different points of the sample by loading a predetermined phase modulation pattern that generates shear offset along the X-axis direction or along the Y-axis direction on the phase-type spatial light modulator; the image acquisition module obtains multiple scanning differential interference phase shift images along the X-axis shear direction and along the Y-axis shear direction. The present invention realizes scanning differential interference measurement by combining the phase-type spatial light modulator with the laser focus scanning illumination, and effectively avoids the problem of spatial diffraction crosstalk.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical microscopic imaging, and in particular relates to a scanning quantitative phase microscopy device and method based on polarization multiplexing modulation, which is used for performing label-free, high-contrast quantitative phase detection on opaque samples. Background Art

[0002] Quantitative Phase Microscopy (QPM) is a high-resolution and highly sensitive label-free detection technology that can detect the sample in situ without fluorescent labeling. It has a very broad application prospect. For example, in life and medical research, it can capture the dynamics and interactions of organelles to study the mechanism of life phenomena; and in industrial detection, it can detect the surface morphology of micro-nano devices to characterize the processing accuracy. Quantitative phase microscopy technology can image the sample with high contrast by restoring the phase change that occurs when the illumination beam passes through the sample.

[0003] In the past decade of development, different phase recovery algorithms and imaging systems have been proposed for quantitative detection of transparent and opaque samples, such as digital holographic microscopy, quantitative phase microscopy based on the light intensity transmission equation, quantitative phase microscopy based on asymmetric illumination and deconvolution, Fourier stacking microscopy, quantitative phase contrast microscopy, and quantitative differential interference contrast microscopy. These well-known quantitative phase microscopy techniques are all based on wide-field imaging, that is, a planar array camera is used to simultaneously record the light intensity information at each point of the sample. Therefore, quantitative phase microscopy imaging technology based on wide-field imaging inevitably has the problem of spatial diffraction crosstalk. This will not only affect the contrast of the imaging, but also produce image artifacts, thereby affecting the detection accuracy.

[0004] In order to avoid the spatial diffraction crosstalk problem in wide-field imaging, researchers proposed a scanning digital holographic microscopy technology based on off-axis interference, which realized scanning quantitative phase imaging for the first time and performed high-precision detection of micro devices on the surface of silicon wafers. Subsequently, researchers combined scanning digital holographic microscopy with atomic force microscopy to achieve higher-resolution scanning quantitative phase imaging. However, the optical structure of off-axis interference makes the scanning quantitative phase imaging technology very immune to external disturbances, so the imaging quality is easily affected. In order to improve the stability of scanning quantitative phase imaging, researchers proposed a scanning confocal digital holographic microscopy technology based on Mirau interferometer objective, which causes the object light and the reference light to interfere in the same path, greatly improving the system's immunity to external interference. However, the use of Mirau interferometer objective not only increases the cost of the system, but also greatly limits the coupling of the imaging system with other imaging modes, limiting its scope of application.

[0005] Recently, researchers have proposed a scanning quantitative phase microscopy technique based on Nomarski prism and Wollaston prism (Wollaston). This microscopy technique not only avoids the problem of spatial diffraction crosstalk, but also ensures the stability of imaging. At the same time, this microscopy technique also inherits the characteristics of high axial resolution of differential interference contrast microscopy. However, this imaging technique requires a Nomarski prism and a Wollaston prism for precise matching, which not only greatly increases the difficulty of system construction and maintenance, but also makes it impossible to effectively couple with other imaging modes. In addition, this imaging technique can only achieve shear interference in a single direction, and complex image processing is required to remove image artifacts. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the present invention provides a scanning quantitative phase microscopy device and method based on polarization multiplexing modulation. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0007] The present invention provides a scanning quantitative phase microscopy device based on polarization multiplexing modulation, comprising a laser focus scanning module, a polarization multiplexing modulation module and an image acquisition module, wherein:

[0008] The laser focus scanning module is used to generate a collimated light beam capable of performing point-by-point scanning illumination on the sample to be tested;

[0009] The polarization multiplexing modulation module is used to perform polarization modulation on the collimated light beam along mutually perpendicular X-axis and Y-axis directions, and to modulate the linear polarized light polarized along the Y-axis direction by using a phase-type spatial light modulator, and to obtain reflected light carrying complex reflectivity information at different points of the sample by loading a predetermined phase modulation pattern shear-shifted along the X-axis direction or along the Y-axis direction on the phase-type spatial light modulator, wherein the plane where the X-axis direction and the Y-axis direction are located is perpendicular to the optical axis direction of the polarization multiplexing modulation module;

[0010] The image acquisition module is used to obtain multiple scanning differential interference phase shift images along the X-axis shear direction and multiple scanning differential interference phase shift images along the Y-axis shear direction using the reflected light carrying the complex reflectivity information at different points of the sample.

[0011] In one embodiment of the present invention, the laser focus scanning module includes a laser and a first thin lens, a second thin lens, a scanning galvanometer, a third thin lens, a fourth thin lens and a non-polarizing beam splitter prism arranged in sequence along the optical axis direction of the laser, wherein:

[0012] The first thin lens and the second thin lens form a confocal system, which is used to expand the aperture of the collimated light beam emitted by the laser;

[0013] The scanning galvanometer is used to control the propagation direction of the collimated light beam from the second thin lens, so as to perform point-by-point scanning illumination on the sample to be tested within the imaging field of view;

[0014] The third thin lens and the fourth thin lens form a confocal system for forming a collimated light beam with a larger aperture, and the working center of the scanning galvanometer is located at the front focal plane of the third thin lens;

[0015] The non-polarization beam splitter prism is used to reflect the collimated light beam with a larger aperture from the fourth thin lens to the polarization multiplexing modulation module.

[0016] In one embodiment of the present invention, the scanning galvanometer is a two-dimensional linear galvanometer system including two reflecting mirrors; and the non-polarizing beam splitter prism is a beam splitter cube with a beam splitting ratio of 50:50.

[0017] In one embodiment of the present invention, the polarization multiplexing modulation module comprises a linear polarizer, a phase-type spatial light modulator, a fifth thin lens, a sixth thin lens and a microscope objective lens which are sequentially arranged along the optical axis direction of the light beam emitted by the laser focus scanning module, wherein:

[0018] The linear polarizer can divide the collimated light beam from the laser focus scanning module into a collimated light beam linearly polarized along the X-axis direction and a collimated light beam linearly polarized along the Y-axis direction with equal power;

[0019] The phase-type spatial light modulator is located at the common focal plane of the fourth thin lens and the fifth thin lens, and can modulate the collimated light beam linearly polarized along the Y-axis direction to obtain collimated light polarized along the Y-axis direction and with a shifted propagation direction;

[0020] The fifth thin lens and the sixth thin lens form a confocal system, and the collimated light polarized along the Y-axis direction and shifted in the propagation direction is focused at the confocal plane of the fifth thin lens and the sixth thin lens to form Y-polarized focused light;

[0021] The sixth thin lens and the microscope objective lens form a confocal system, the sample to be tested is set on the object focal plane of the microscope objective lens, the Y polarized focused light passes through the confocal system formed by the sixth thin lens and the microscope objective lens to collect complex reflectivity information at a point on the sample to be tested, and is collected by the microscope objective lens in the form of divergent light to form a Y polarized point complex amplitude;

[0022] The collimated light beam linearly polarized along the X-axis direction directly passes through the phase-type spatial light modulator and is focused on the confocal plane of the fifth thin lens and the sixth thin lens to form X-polarized focused light; the X-polarized focused light passes through the confocal system composed of the sixth thin lens and the microscope objective lens to collect complex reflectivity information at another point on the sample to be measured, and is collected by the microscope objective lens in the form of divergent light to form an X-polarized point complex amplitude.

[0023] In one embodiment of the present invention, the phase-type spatial light modulator is further used to: re-modulate the collimated light derived from the complex amplitude of the Y polarization point reflected from the sample to be tested;

[0024] After being modulated again by the phase-type spatial light modulator, the collimated light derived from the complex amplitude of the Y polarization point can completely overlap with the collimated light derived from the complex amplitude of the X polarization point, and single-point differential interference detection is realized on the image acquisition module through the focusing effect of the seventh thin lens (14).

[0025] In one embodiment of the present invention, a predetermined phase modulation pattern that generates a shear offset along the X-axis direction is loaded on the phase-type spatial light modulator, and phase values ​​of 0π, 0.25π, 0.5π and 0.75π are sequentially added to the predetermined phase modulation pattern that generates a shear offset along the X-axis direction;

[0026] A predetermined phase modulation pattern that generates a shearing offset along the Y-axis direction is loaded on the phase-type spatial light modulator, and phase values ​​of 0π, 0.25π, 0.5π and 0.75π are sequentially added to the predetermined phase modulation pattern that generates a shearing offset along the Y-axis direction; and,

[0027] When each phase modulation pattern is loaded on the phase-type spatial light modulator, the scanning galvanometer can be controlled to perform point-by-point scanning illumination on the sample to be tested within the imaging field of view, and the image acquisition module performs global exposure, thereby obtaining four scanning differential interference phase shift images along the X-axis shear direction and four scanning differential interference phase shift images along the Y-axis shear direction on the image acquisition module.

[0028] In one embodiment of the present invention, the phase-type spatial light modulator is a transmissive phase-type spatial light modulator or a reflective phase-type spatial light modulator.

[0029] In one embodiment of the present invention, when scanning illumination is performed on the sample to be tested, the collimated light beam between the sixth thin lens and the microscope objective lens always fills the pupil aperture of the microscope objective lens, and the pupil aperture of the microscope objective lens is located at the confocal plane of the microscope objective lens and the sixth thin lens.

[0030] Another aspect of the present invention provides a scanning quantitative phase microscopy method based on polarization multiplexing modulation, comprising:

[0031] S1: using the scanning quantitative phase microscopy device based on polarization multiplexing modulation described in any one of the above embodiments to obtain four scanning differential interference phase shift images along the X-axis shear direction and four scanning differential interference phase shift images along the Y-axis shear direction;

[0032] S2: using the four scanning differential interference phase shift images in the X-axis shear direction to obtain the phase gradient distribution of the sample to be tested along the X-axis shear direction;

[0033] S3: using the four scanning differential interference phase shift images in the Y-axis shear direction to obtain the phase gradient distribution of the sample to be tested along the Y-axis shear direction;

[0034] S4: Obtaining phase distribution information of the sample to be tested according to the phase gradient distribution along the X-axis shear direction and the phase gradient distribution along the Y-axis shear direction.

[0035] In one embodiment of the present invention, the S1 includes:

[0036] Loading a predetermined phase modulation pattern that generates a shear offset along the X-axis direction on the phase-type spatial light modulator, and sequentially adding phase values ​​of 0π, 0.25π, 0.5π and 0.75π to the predetermined phase modulation pattern that generates a shear offset along the X-axis direction;

[0037] A predetermined phase modulation pattern that generates a shearing offset along the Y-axis direction is loaded on the phase-type spatial light modulator, and phase values ​​of 0π, 0.25π, 0.5π and 0.75π are sequentially added to the predetermined phase modulation pattern that generates a shearing offset along the Y-axis direction; and,

[0038] When each phase modulation pattern is loaded on the phase-type spatial light modulator, the scanning galvanometer is controlled to perform point-by-point scanning illumination on the sample to be tested within the imaging field of view, and the image acquisition module performs global exposure, thereby obtaining four scanning differential interference phase shift images along the X-axis shear direction and four scanning differential interference phase shift images along the Y-axis shear direction on the image acquisition module.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention proposes a scanning quantitative phase microscopy device and method based on polarization multiplexing modulation, which has the following advantages: first, the device does not require special prisms and special objective lenses, and realizes quantitative phase imaging of point-by-point scanning illumination by combining laser focus scanning illumination with the polarization modulation characteristics of a phase-type spatial light modulator; in the proposed device, the two polarized light beams used to realize scanning differential interference measurement pass through exactly the same optical devices, so the device of the present invention has very good resistance to external disturbances; second, the point-by-point scanning detection method avoids the spatial diffraction crosstalk problem existing in wide-field imaging, avoids image artifacts, and improves the signal-to-noise ratio and detection accuracy. Therefore, the scanning quantitative phase microscopy device proposed by the present invention can be easily coupled with fluorescence microscopy technology and other quantitative phase microscopy technologies to realize multi-mode imaging.

[0041] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of the optical path structure of a scanning quantitative phase microscopy device based on polarization multiplexing modulation provided by an embodiment of the present invention;

[0043] Figure 2 It is a schematic diagram of the optical path structure of another scanning quantitative phase microscopy device based on polarization multiplexing modulation provided by an embodiment of the present invention;

[0044] Figure 3 These are four phase modulation patterns loaded by the phase-type spatial light modulator when shear offset occurs along the X-axis direction;

[0045] Figure 4 These are the four phase modulation patterns loaded by the phase-type spatial light modulator when shear offset is generated along the Y-axis direction;

[0046] Figure 5 It is a real phase distribution and amplitude distribution of a simulated sample provided by an embodiment of the present invention;

[0047] Figure 6 It is the sample phase gradient distribution obtained by using the traditional wide-field reflection quantitative differential interference microscopy technique;

[0048] Figure 7 It is the phase distribution of the sample obtained using traditional wide-field reflection quantitative differential interference microscopy;

[0049] Figure 8 The phase gradient distribution of the sample is obtained by using the scanning quantitative phase microscopy device based on polarization multiplexing modulation proposed in an embodiment of the present invention;

[0050] Fig. 9The phase distribution of the sample is obtained by using the scanning quantitative phase microscopy device based on polarization multiplexing modulation proposed in an embodiment of the present invention;

[0051] Fig.10 It is along Figure 7 (dashed line) and Fig. 9 (solid line) phase distribution of horizontal center line;

[0052] Fig.11 It is a quantitative phase image of the silicon wafer surface obtained by using traditional reflective quantitative differential interference microscopy under laser wide-field illumination;

[0053] Fig.12 It is a quantitative phase image of the silicon wafer surface obtained by using traditional reflective quantitative differential interference microscopy under LED wide-field illumination;

[0054] Fig.13 The quantitative phase image of the silicon wafer surface is obtained by using the scanning quantitative phase microscope device based on polarization multiplexing modulation proposed in the embodiment of the present invention.

[0055] Description of reference numerals:

[0056] 1-laser; 2-first thin lens; 3-second thin lens; 4-scanning galvanometer; 5-third thin lens; 6-fourth thin lens; 7-non-polarizing beam splitter; 8-linear polarizer; 9-phase-type spatial light modulator; 10-fifth thin lens; 11-sixth thin lens; 12-microscope objective; 13-sample to be tested; 14-seventh thin lens; 15-image acquisition module. DETAILED DESCRIPTION

[0057] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, a scanning quantitative phase microscopy device and method based on polarization multiplexing modulation proposed by the present invention are described in detail below in combination with the accompanying drawings and specific implementation methods.

[0058] The above and other technical contents, features and effects of the present invention are clearly presented in the following detailed description of the specific implementation modes in conjunction with the accompanying drawings. Through the description of the specific implementation modes, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the attached drawings are only for reference and explanation purposes and are not used to limit the technical solutions of the present invention.

[0059] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements that are not explicitly listed. In the absence of more restrictions, the elements defined by the statement "including one..." do not exclude the existence of other identical elements in the article or device including the elements.

[0060] Embodiment 1

[0061] See also Figure 1 , Figure 1 This is a schematic diagram of the optical path structure of a scanning quantitative phase microscope device based on polarization multiplexing modulation provided by an embodiment of the present invention. The scanning quantitative phase microscope device includes a laser focus scanning module, a polarization multiplexing modulation module and an image acquisition module, wherein the laser focus scanning module is used to generate a collimated light beam that can perform point-by-point scanning illumination on the sample to be tested; the polarization multiplexing modulation module is used to polarize the collimated light beam along mutually perpendicular X-axis and Y-axis directions, and modulate the linear polarized light polarized along the Y-axis direction using a phase-type spatial light modulator, and obtain the reflected light carrying the complex reflectivity information at different points of the sample by loading a predetermined phase modulation pattern that is shear-shifted along the X-axis direction or along the Y-axis direction on the phase-type spatial light modulator, wherein the plane where the X-axis direction and the Y-axis direction are located is perpendicular to the optical axis direction of the polarization multiplexing modulation module; the image acquisition module is used to obtain multiple scanning differential interference phase shift images along the X-axis shear direction and multiple scanning differential interference phase shift images along the Y-axis shear direction using the reflected light carrying the complex reflectivity information at different points of the sample.

[0062] In this embodiment, the laser focus scanning module includes a laser 1 and a first thin lens 2, a second thin lens 3, a scanning galvanometer 4, a third thin lens 5, a fourth thin lens 6 and a non-polarizing beam splitter prism 7 arranged in sequence along the optical axis direction of the laser 1, wherein the first thin lens 2 and the second thin lens 3 constitute a confocal system for expanding the aperture of the collimated light beam emitted by the laser 1; the scanning galvanometer 4 is used to control the propagation direction of the collimated light beam from the second thin lens 3 so as to perform point-by-point scanning illumination on the sample to be measured 13 within the imaging field of view, the third thin lens 5 and the fourth thin lens 6 constitute a confocal system for forming a collimated light beam with a larger aperture, and the working center of the scanning galvanometer 4 is located at the front focal plane of the third thin lens 5; the non-polarizing beam splitter prism 7 is used to reflect the collimated light beam with a larger aperture from the fourth thin lens 6 to the polarization multiplexing modulation module.

[0063] Specifically, the small-aperture collimated light emitted by the laser 1 passes through the confocal system composed of the first thin lens 2 and the second thin lens 3 to generate a large-aperture collimated light beam. After the large-aperture collimated light beam enters the scanning galvanometer 4, its propagation direction is controlled by the scanning galvanometer 4. The collimated light beam emitted from the scanning galvanometer 4 passes through the confocal system composed of the third thin lens 5 and the fourth thin lens 6 to generate a larger-aperture collimated light beam, and is injected into the non-polarizing beam splitter prism 7. The working center of the scanning galvanometer 4 is located at the front focal plane of the third thin lens 5, that is, the center of the slow axis reflector of the scanning galvanometer 4 is located at the front focal plane of the third thin lens 5.

[0064] The laser 1 of this embodiment uses a blue laser with a central wavelength of 488 nanometers. In order to obtain a sufficiently small focal point, the first thin lens 2 uses an achromatic objective lens with a magnification of 20 times and a numerical aperture of 0.4, and the second thin lens 3 uses a double-cemented achromatic lens with a focal length of 125 mm. The scanning galvanometer 4 is a two-dimensional high-speed linear galvanometer system, including two reflectors. The third thin lens 5 is a two-inch double-cemented achromatic lens with a focal length of 75 mm. The fourth thin lens 6 is a two-inch double-cemented achromatic lens with a focal length of 300 mm. The non-polarizing beam splitter prism 7 is a beam splitting cube with a beam splitting ratio of 50:50.

[0065] Furthermore, the polarization multiplexing modulation module of this embodiment includes a linear polarizer 8, a phase-type spatial light modulator 9, a fifth thin lens 10, a sixth thin lens 11 and a microscope objective 12, which are arranged in sequence along the optical axis direction of the light beam emitted by the laser focus scanning module. After being reflected by the non-polarizing beam splitter prism 7, 50% of the collimated light is reflected into the polarization multiplexing modulation module. The reflected collimated light passes through the linear polarizer 8 and then enters the phase-type spatial light modulator 9 located at the confocal plane of the fourth thin lens 6 and the fifth thin lens 10. The polarization direction of the linear polarizer 8 is parallel to the positive direction of the X-axis ( Figure 1 The positive direction of the Y axis ( Figure 1 Therefore, the linear polarizer 8 can divide the collimated light beam from the laser focus scanning module into a collimated light beam linearly polarized along the X-axis direction and a collimated light beam linearly polarized along the Y-axis direction with equal power.

[0066] The phase-type spatial light modulator 9 is located at the confocal plane of the fourth thin lens 6 and the fifth thin lens 10. The modulation of the light field by the phase-type spatial light modulator 9 is polarization selective. In this embodiment, the phase-type spatial light modulator 9 only acts on the linearly polarized light along the Y-axis direction (fast axis). Therefore, the collimated light linearly polarized along the X-axis direction will not be modulated by the phase-type spatial light modulator 9. After passing through the phase-type spatial light modulator 9 directly, it is focused on the confocal plane ( ) between the fifth thin lens 10 and the sixth thin lens 11 under the converging effect of the fifth thin lens 10. Figure 1(shown by solid lines in the figure). For the convenience of description, this focused light beam is referred to as X-polarized focused light. After propagating through the confocal system composed of the sixth thin lens 11 and the microscope objective 12, the X-polarized focused light is focused on the sample to be tested 13 on the object focal plane of the microscope objective 12, and collects the complex reflectivity information at a certain point on the sample to be tested 13, and then is collected by the microscope objective 12 in the form of divergent light. For the convenience of description, the complex amplitude generated at this point is referred to as the X-polarized point complex amplitude.

[0067] At the same time, the collimated light incident on the phase-type spatial light modulator 9 along the Y-axis direction is modulated by the phase-type spatial light modulator 9, and its propagation direction is shifted, such as Figure 1 As shown by the dotted line in the middle. After the converging effect of the fifth thin lens 10, the collimated light polarized along the Y-axis direction and offset in the propagation direction is focused on the confocal plane of the fifth thin lens 10 and the sixth thin lens 11. For the convenience of description, this focused light beam is referred to as Y-polarized focused light. At this time, compared with the aforementioned X-polarized focused light, the Y-polarized focused light undergoes a shear offset. The direction and distance of the shear offset are controlled by a predetermined phase modulation pattern loaded on the phase-type spatial light modulator 9, generally in the X direction and the Y direction. Similarly, after the Y-polarized focused light propagates through the confocal system composed of the sixth thin lens 11 and the microscope objective 12, it is focused on the sample to be tested 13 on the object side focal plane of the microscope objective 12, and the complex reflectivity information at a certain point on the sample to be tested 13 is collected, and then collected by the microscope objective 12 in the form of divergent light. For the convenience of description, at this time, the complex amplitude generated at this point is referred to as the Y-polarization point complex amplitude.

[0068] It should be noted that, since the Y polarized focused light has a shear offset relative to the X polarized focused light, the Y polarized point complex amplitude also has a shear offset relative to the X polarized point complex amplitude. This means that the X polarized point complex amplitude and the Y polarized point complex amplitude respectively carry the complex reflectivity information at two different points on the surface of the sample to be measured, and the position between these two points is determined by the predetermined phase modulation pattern loaded on the phase-type spatial light modulator 9. It should be noted that in order to achieve effective differential interference detection, the distance of the shear offset is set to half of the lateral spatial resolution of the scanning quantitative phase microscope under vertical illumination.

[0069] In this embodiment, the wavefront deformation of the light wave after passing through the linear polarizer 8 is less than 1 / 4 wavelength. The liquid crystal switching time of the phase-type spatial light modulator 9 is 2 milliseconds, and its phase modulation resolution is 8 bits. The fifth thin lens 10 is a two-inch double-cemented achromatic lens with a focal length of 250 mm. The sixth thin lens 11 is a tube lens with a focal length of 200 mm. The microscope objective lens 12 is a plan achromatic objective lens with a magnification of 20X.

[0070] The phase-type spatial light modulator 9 of this embodiment is a transmissive phase-type spatial light modulator. In another embodiment of the present invention, the phase-type spatial light modulator 9 is selected to be a reflective phase-type spatial light modulator, such as Figure 2 All other devices are Figure 1 Therefore, all the light beams modulated by the transmissive phase-type spatial light modulator 9 are Figure 2 is reflected and modulated by the reflective phase spatial light modulator 9, and Figure 2 The beam propagation between all other devices in Figure 1 Completely consistent. Therefore, Figure 2 The beam propagation in will not be described in detail.

[0071] Furthermore, the phase-type spatial light modulator 9 is also used to: re-modulate the collimated light derived from the complex amplitude of the Y polarization point reflected from the sample 13 to be tested; the collimated light derived from the complex amplitude of the Y polarization point can completely overlap with the collimated light derived from the complex amplitude of the X polarization point after being re-modulated by the phase-type spatial light modulator 9.

[0072] Specifically, on the surface of the sample to be measured, two divergent lights with complex amplitudes of the X polarization point and the Y polarization point are collimated, converged and collimated by the microscope objective 12, the sixth thin lens 11 and the fifth thin lens 10, and then are emitted into the phase-type spatial light modulator 9. Among them, the collimated light derived from the complex amplitude of the X polarization point ( Figure 1 The collimated light (shown by the solid line in the middle) directly passes through the phase-type spatial light modulator 9 and is not modulated by it. Figure 1 The light beams (shown by the dashed line in the middle) are modulated by the phase-type spatial light modulator 9 again, and then completely overlap with the collimated light that directly passes through the phase-type spatial light modulator 9 and is derived from the complex amplitude of the X polarization point. They pass through the linear polarizer 8 and the non-polarization beam splitter prism 7 at the same time, and then are focused to the rear focal plane by the seventh thin lens 14. At this time, they completely overlap and coherently superimpose, and then are detected by the image acquisition module 15 at the rear focal plane of the seventh thin lens 14 to achieve single-point differential interference detection. It should be noted that at this time, the image acquisition module 15 only collects the intensity value at a certain position, and the intensity value is the differential interference intensity value between the two points on the sample surface with shear offset when the scanning galvanometer 4 is at a certain angle, that is, the interference intensity value between the complex amplitude of the X polarization point and the complex amplitude of the Y polarization point. The seventh thin lens 14 is a two-inch double-cemented achromatic lens with a focal length of 300 mm. The image acquisition module 15 is selected as a sCOMS camera, and the size of a single pixel is 6.5 microns × 6.5 microns.

[0073] In order to obtain the differential interference intensity value at each position on the surface of the sample to be tested within the imaging field of view, the predetermined phase modulation pattern loaded by the phase-type spatial light modulator 9 remains unchanged within the exposure time of the image acquisition module. At the same time, the scanning galvanometer 4 is controlled to perform point-by-point scanning illumination on the sample to be tested within the imaging field of view. In this way, point-by-point scanning differential interference measurement of the sample to be tested is achieved within the imaging field of view. It is worth noting that at this time, the intensity distribution recorded by the image acquisition module 15 only contains the cosine value of the sample phase gradient along the X-axis direction or along the Y-axis direction. In order to quantitatively obtain the phase gradient distribution of the sample, the phase-type spatial light modulator 9, while loading a predetermined phase modulation pattern that produces a shear offset along the X-axis direction or along the Y-axis direction, has all its pixels additionally added with phase values ​​of 0, 0.25π, 0.5π and 0.75π respectively.

[0074] Specifically, a predetermined phase modulation pattern that generates a shear offset along the X-axis direction is loaded on the phase-type spatial light modulator 9, and phase values ​​of 0π, 0.25π, 0.5π and 0.75π are sequentially added to the predetermined phase modulation pattern that generates a shear offset along the X-axis direction; a predetermined phase modulation pattern that generates a shear offset along the Y-axis direction is loaded on the phase-type spatial light modulator 9, and phase values ​​of 0π, 0.25π, 0.5π and 0.75π are sequentially added to the predetermined phase modulation pattern that generates a shear offset along the Y-axis direction; and, when each phase modulation pattern is loaded on the phase-type spatial light modulator 9, the scanning galvanometer 4 is controlled to perform point-by-point scanning illumination on the sample 13 to be tested within the imaging field of view, and the image acquisition module performs global exposure, so as to obtain four scanning differential interference phase shift images along the X-axis shear direction and four scanning differential interference phase shift images along the Y-axis shear direction on the image acquisition module.

[0075] That is to say, in the case of shear offset along the X-axis direction, the phase-type spatial light modulator 9 loads four phase modulation patterns in sequence: a predetermined phase modulation pattern for shear offset along the X-axis direction, a predetermined phase modulation pattern for shear offset along the X-axis direction +0.25π, a predetermined phase modulation pattern for shear offset along the X-axis direction +0.5π, and a predetermined phase modulation pattern for shear offset along the X-axis direction +0.75π. While the phase-type spatial light modulator 9 loads these four phase modulation patterns respectively, the scanning galvanometer 4 is controlled to perform point-by-point scanning illumination on the sample to be tested within the imaging field of view, and the image acquisition module 15 performs global exposure, thereby obtaining four scanning differential interference phase shift images along the X-axis shear direction. Then, through simple trigonometric function calculations, the phase gradient distribution of the sample along the X-axis shear direction can be quantitatively obtained.

[0076] In the case of shear offset along the Y-axis direction, the phase-type spatial light modulator 9 successively loads four phase modulation patterns: a predetermined phase modulation pattern for shear offset along the Y-axis direction, a predetermined phase modulation pattern for shear offset along the Y-axis direction +0.25π, a predetermined phase modulation pattern for shear offset along the Y-axis direction +0.5π, and a predetermined phase modulation pattern for shear offset along the Y-axis direction +0.75π. While the phase-type spatial light modulator 9 loads these four phase modulation patterns respectively, the scanning galvanometer 4 is controlled to perform point-by-point scanning illumination on the sample to be tested within the imaging field of view, and the image acquisition module 15 performs global exposure, thereby obtaining four scanning differential interference phase shift images along the Y-axis shear direction. Then, through simple trigonometric function calculations, the phase gradient distribution of the sample along the Y-axis shear direction can be quantitatively obtained. After obtaining the phase gradient distribution of the sample along the X-axis shear direction and the Y-axis shear direction, the Frankot-Chellappa formula can be used to quantitatively obtain the phase distribution information of the sample to be tested.

[0077] It should be noted that, in the process of scanning and illuminating the sample to be tested, the collimated light beam between the sixth thin lens 11 and the microscope objective lens 12 always fills the pupil aperture of the microscope objective lens 12. Figure 1 In addition, the pupil aperture of the microscope objective 12 is located on the confocal plane of the microscope objective 12 and the sixth thin lens 11. After being imaged by the confocal system composed of the sixth thin lens 11 and the fifth thin lens 10, the pupil aperture of the microscope objective 12 is completely covered by the working surface of the phase-type spatial light modulator 9.

[0078] Embodiment 2

[0079] Based on the first embodiment, this embodiment further provides a scanning quantitative phase microscopy method based on polarization multiplexing modulation, including:

[0080] S1: Four scanning differential interference phase shift images along the X-axis shear direction and four scanning differential interference phase shift images along the Y-axis shear direction are obtained using a scanning quantitative phase microscopy device based on polarization multiplexing modulation.

[0081] S2: Use four scanning differential interference phase shift images in the X-axis shear direction to obtain the phase gradient distribution of the sample to be tested along the X-axis shear direction.

[0082] S3: Use four scanning differential interference phase shift images in the Y-axis shear direction to obtain the phase gradient distribution of the sample to be tested along the Y-axis shear direction.

[0083] S4: Obtaining phase distribution information of the sample to be tested according to the phase gradient distribution along the X-axis shear direction and the phase gradient distribution along the Y-axis shear direction.

[0084] Further, step S1 includes:

[0085] A predetermined phase modulation pattern that generates a shear offset along the X-axis direction is loaded on the phase-type spatial light modulator, and phase values ​​of 0π, 0.25π, 0.5π and 0.75π are sequentially added to the predetermined phase modulation pattern that generates a shear offset along the X-axis direction; a predetermined phase modulation pattern that generates a shear offset along the Y-axis direction is loaded on the phase-type spatial light modulator, and phase values ​​of 0π, 0.25π, 0.5π and 0.75π are sequentially added to the predetermined phase modulation pattern that generates a shear offset along the Y-axis direction; and when each phase modulation pattern is loaded on the phase-type spatial light modulator, the scanning galvanometer is controlled to perform point-by-point scanning illumination on the sample to be tested within the imaging field of view, and the image acquisition module performs global exposure, so as to obtain four scanning differential interference phase shift images along the X-axis shear direction and four scanning differential interference phase shift images along the Y-axis shear direction on the image acquisition module.

[0086] Further, for the scanning quantitative phase microscopy device based on polarization multiplexing modulation of the embodiment of the present invention, its detailed imaging mechanism is described as follows. In order to simplify the analysis and facilitate expression, let the focal length of all lenses (the first lens to the seventh lens) and the microscope objective be f, that is, let the magnification of each part of the imaging system be 1, and let the axis of the optical system be the Z axis (horizontally to the left in the paper is the positive direction). Take the intersection of the Z axis and the sample surface as the origin, and establish an XY plane coordinate system on the sample surface, wherein the positive direction of the X axis is perpendicular to the paper surface, and the positive direction of the Y axis is vertically upward in the paper surface. Take the intersection of the working surface of the phase-type spatial light modulator 9 and the Z axis as the origin, and establish an X'-Y' plane coordinate system on the working surface of the phase-type spatial light modulator 9, wherein the positive direction of the X' axis is perpendicular to the paper surface, and the positive direction of the Y' axis is vertically upward in the paper surface. Taking the intersection of the working surface of the image acquisition module 15 and the Z axis as the origin, an X"-Y" plane coordinate system is established on the working surface of the image acquisition module 15, wherein the positive direction of the X" axis is perpendicular to the paper surface and the positive direction of the Y" axis is vertically upward in the paper surface. Taking the intersection of the pupil plane of the microscope objective 12 and the Z axis as the origin, an X"'-Y"' plane coordinate system is established on the pupil plane of the microscope objective 12, wherein the positive direction of the X"' axis is perpendicular to the paper surface and the positive direction of the Y"' axis is vertically upward in the paper surface.

[0087] In order to ensure that the scanning focus on the sample surface has a sufficiently small size, the light source used in the embodiment of the present invention is a laser with very good coherence, and its central wavelength is λ. The scanning system composed of the laser 1, the first thin lens 2, the second thin lens 3, the scanning galvanometer 4, the third thin lens 5, and the fourth thin lens 6 is used to generate collimated light propagating in different directions. Therefore, the specific light beam propagation process between the laser 1 and the fourth thin lens 6 is no longer analyzed in the principle analysis.

[0088] After being reflected by the non-polarizing beam splitter prism 7 and polarized by the linear polarizer 8, the collimated light reaching the working surface of the phase-type spatial light modulator 9 can be expressed by the Jones matrix:

[0089]

[0090] in, represents the lateral spatial coordinate on the working plane of the phase-type spatial light modulator 9, and j represents an imaginary unit. represents the transverse wave vector of the collimated light reaching the working surface of the phase-type spatial light modulator 9; φ represents the angle between the wave vector of the collimated light reflected by the non-polarized beam splitter prism 7 and the positive direction of the Z axis; θ represents the angle between the projection of the wave vector of the collimated light reflected by the non-polarized beam splitter prism 7 in the X'-Y' plane and the X' axis. φ and θ are controlled by the scanning system composed of the laser 1 to the fourth thin lens 6. At the same time, the phase modulation pattern loaded by the phase-type spatial light modulator 9 is expressed as:

[0091]

[0092] in, f represents the focal length of the fifth thin lens 10, (x0, y0) represents the shear offset vector generated by the phase-type spatial modulator 9 at the confocal plane between the fifth thin lens 10 and the sixth thin lens 11, and Here, NA represents the numerical aperture of the microscope objective lens 12 . As mentioned above, the phase-type spatial light modulator 9 in the embodiment of the present invention only acts on linearly polarized light along the Y-axis direction. Therefore, after the polarization modulation effect of the phase-type spatial light modulator 9, the light field represented by formula (1) becomes:

[0093]

[0094] Wherein, j represents an imaginary unit. Subsequently, the light field shown in formula (3) propagates through the confocal system composed of the fifth thin lens 10 and the sixth thin lens 11, and reaches the confocal plane of the microscope objective lens 12 and the sixth thin lens 11. The light field at this time is expressed as:

[0095]

[0096] Here, (x′″, y′″) represents the lateral spatial coordinates on the pupil plane of the microscope objective 12 .

[0097] Next, after the spatial Fourier transform of the microscope objective lens 12, the spectrum distribution of the light field shown in formula (4) is displayed on the object focal plane of the microscope objective lens 12, which is expressed as:

[0098]

[0099] in, represents the transverse spatial coordinate of the sample surface, m = sin(φ)·cos(θ), n = sin(φ)·sin(θ). It can be seen from the light field distribution shown in formula (5) that after the polarization modulation of the phase-type spatial light modulator 9 and the spatial Fourier transform of the microscope objective 12, two separate focal points are generated on the object focal plane of the microscope objective 12. Specifically, relative to the focal point polarized along the X-axis, the focal point polarized along the Y-axis has a shear offset of (x0, y0) and The position of the focal point along the X-axis polarization is determined by the scanning system and the focal length of the microscope objective 12. Therefore, by controlling the scanning system, the focus scanning at different positions of the sample surface can be achieved. At the same time, an opaque sample 13 to be tested is placed on the object focal plane of the microscope objective 12, and its complex reflectivity is expressed as:

[0100]

[0101] Wherein, (x, y) represents the amplitude information of the sample 13 to be tested, represents the phase information of the sample to be tested 13. After the light field shown in formula (5) is irradiated to the sample to be tested 13, a new light field is generated, which is expressed as:

[0102]

[0103] Since the embodiment of the present invention is applied to an opaque sample, the light field shown in formula (7) propagates in the opposite direction of the Z axis and is collected by the microscope objective 12. After the spatial Fourier transform of the microscope objective 12, the spectrum distribution of the light field shown in formula (7) is displayed at the pupil plane of the microscope objective 12, that is:

[0104]

[0105] Then, the light field shown in formula (8) propagates through the confocal system composed of the sixth thin lens 11 and the fifth thin lens 10 and reaches the working surface of the phase-type spatial light modulator 9 (i.e., the confocal surface of the fifth thin lens 10 and the seventh thin lens 14). The light field at this time is expressed as:

[0106]

[0107] As mentioned above, the phase-type spatial light modulator 9 in the embodiment of the present invention only acts on linearly polarized light along the Y-axis direction. Therefore, the light field represented by formula (9) will be polarized again when passing through the phase-type spatial light modulator 9. At this time, the light field represented by formula (9) becomes:

[0108]

[0109] Finally, after being modulated by the linear polarizer 8 and the Fourier transform of the seventh thin lens 14, the light field at the rear focal plane of the seventh thin lens 14 is expressed as:

[0110]

[0111] At this time, the intensity distribution recorded by the image acquisition module 15 at the rear focal plane of the seventh thin lens 14 is expressed as:

[0112]

[0113] Among them, A0=a(-f·m, -f·n) and B0=a(-f·m-x0, -f·n-y0). Analyzing formulas (5) to (12), it can be seen that at a certain moment, the scanning focus along the X-axis polarization is located at the sample surface (-f·m, -f·n), and the scanning focus along the Y-axis polarization is located at the sample surface (-f·m-x0, -f·n-y0). At this time, the image acquisition module 15 only collects the light intensity value at its working surface (-f·m, -f·n). The light intensity value is related to the complex reflectivity at (-f·m, -f·n) and (-f·m-x0, -f·n-y0) on the sample surface.

[0114] It should be noted that in the actual imaging system, the microscope objective 12 has a limited numerical aperture. Therefore, in the object focal plane of the microscope objective 12, the two focus points with shear offset represented by formula (5) are actually two Airy diffraction spots with shear offset. The Airy diffraction spot consists of a central peak and a series of concentric rings with decreasing amplitudes, and its half-height full width is the lateral spatial resolution of the microscope system under vertical illumination. After the two Airy diffraction spots with shear offset detect the complex reflectivity information of the sample at the corresponding position, they completely overlap on the working surface of the image acquisition module 15 and coherent superposition occurs at the corresponding position. As far as the image acquisition module 15 is concerned, each detection point is a square pixel of a certain size. Therefore, from the perspective of imaging, the Airy diffraction spots on the sample surface can be regarded as multiple discrete point sources with different amplitudes. That is to say, the multiple pixel positions covered by the Airy diffraction spot on the image acquisition module 15 simultaneously obtain the light intensity values ​​expressed by formula (12), but these light intensity values ​​have certain differences. In addition to being related to the complex reflectivity at the corresponding position on the sample surface, they are also related to the amplitude of the Airy diffraction spot at the corresponding position. Therefore, considering that the microscope objective 12 has a finite numerical aperture, the light intensity at the multiple pixel positions covered by the Airy diffraction spot on the working surface of the image acquisition module 15 can still be uniformly expressed by formula (12).

[0115] During one exposure time of the image acquisition module 15, the phase modulation pattern loaded by the phase-type spatial light modulator 9 remains unchanged, that is, (x0, y0) and Remain unchanged, and at the same time, under the control of the scanning galvanometer 4, the sample to be tested 13 within the imaging field of view is scanned and illuminated point by point. Here, the lateral distance between two adjacent X-polarized scanning points is set to one-third of the lateral spatial resolution of the system under vertical illumination. Therefore, after one exposure by the image acquisition module 15, all pixels on the working surface of the image acquisition module 15 collect corresponding light intensity values, which are related to the complex reflectivity of the corresponding position on the sample surface. Therefore, after one exposure by the image acquisition module, the collected light intensity distribution can be uniformly written as:

[0116]

[0117] Where A = a(x″, y″) and B = a(x″-x0, y″-y0). When y0 in the phase modulation function shown in formula (2) is 0, and When the phases are 0, 0.25π, 0.5π, and 0.75π respectively, the phase-type spatial light modulator 9 is loaded with four phase patterns respectively, such as Figure 3 As shown. Since the phase range that each pixel of the phase-type spatial light modulator 9 can modulate is 0 to 2π, therefore, Figure 3 The phase modulation distribution shown is the result obtained by phase wrapping the original phase modulation function, so that all phases are distributed between 0 and 2π. At this time, the image acquisition module 15 records four intensity images: I0(x″, y″, x0, 0), I 0.5π (x″,y″,x0,0),I π (x″,y″,x0,0) and I 1.5π (x″,y″,x0,0). Therefore, under the premise of x0= / NA / 2, the gradient distribution of the sample phase along the X-axis direction can be approximately calculated as:

[0118]

[0119] Here, atan represents the inverse tangent function.

[0120] When x0 in the phase modulation function shown in formula (2) is 0, and When the phases are 0, 0.25π, 0.5π, and 0.75π respectively, the phase-type spatial light modulator 9 is loaded with four phase patterns respectively, such as Figure 4 As shown. Since the phase range of each pixel of the phase-type spatial light modulator can be modulated is 0 to 2π, Figure 4 The phase modulation distribution shown is the result of phase wrapping processing of the original phase modulation function, so that all phases are distributed between 0 and 2π. At this time, the image acquisition module records four intensity images: I0(x″,y″,0,y0), I 0.5π(x″,y″,0,y0),I π (x″,y″,0,y0) and I 1.5π (x″,y″,0,y0). Therefore, under the premise of y0= / NA / 2, the gradient distribution of the sample phase along the Y-axis direction can be calculated as:

[0121]

[0122] Here, atan represents the inverse tangent function.

[0123] Finally, the phase distribution of the sample to be tested can be quantitatively obtained using the Frankot-Chellappa phase integration algorithm:

[0124]

[0125] in, represents the two-dimensional Fourier transform operation, It represents the two-dimensional inverse Fourier transform operation, (ρ,γ) represents the frequency domain coordinates, and ε represents the regularization coefficient, which defaults to 0.0001.

[0126] It can be seen from formula (1) to formula (16) that the scanning quantitative phase microscopy device based on polarization multiplexing modulation of the present invention realizes scanning differential interference measurement by combining a phase-type spatial light modulator with laser scanning illumination, and realizes four-step phase shift detection by using the same phase-type spatial light modulator, thereby realizing reflective quantitative phase imaging based on scanning illumination for the sample to be tested. This effectively avoids the spatial diffraction crosstalk problem existing in wide-field imaging, so that the collected image has high image quality; in addition, the scanning quantitative phase microscopy device can realize shear offsets in different directions and to different degrees through the phase-type spatial modulator, and is suitable for different types of objective lenses and samples. Therefore, high-quality quantitative phase images can be obtained without complex image processing; secondly, the optical structure of common path interference makes the scanning quantitative phase microscopy device of the present invention have very strong immunity to external disturbances; finally, the device of the present invention has high axial resolution, can perform artifact-free three-dimensional quantitative phase imaging of the sample to be tested, and can be coupled with any microscopic imaging technology to realize multi-mode imaging. Therefore, the proposed scanning quantitative phase microscopy device based on polarization multiplexing modulation can perform label-free, high-quality in-situ quantitative detection of the samples to be tested, and has very good scalability in structure and function, and has great application value in fields such as industrial detection.

[0127] The following is a further description of the effect of the scanning quantitative phase microscopy device based on polarization multiplexing modulation proposed by the present invention through specific experiments. First, a numerical simulation is performed, such as Figures 5 to 10In the simulation process, the sample to be tested is set as a non-pure phase object, and its actual phase distribution and amplitude distribution are shown in Figure 5 First, a conventional wide-field reflective quantitative differential interference microscope was used for simulation, in which case the illumination of the sample to be tested was vertically uniform collimated light. Figure 6 The results shown are the phase gradient distribution of the sample along the X-axis and Y-axis directions obtained using a traditional wide-field reflection quantitative differential interference microscope. Figure 6 Parasitic diffraction patterns can be clearly observed in the phase gradient distribution shown, which will seriously affect the phase recovery quality of the sample. Figure 7 The results shown are obtained using Figure 6 The phase image of the sample is reconstructed from the phase gradient distribution shown. Figure 7 It can be clearly seen that there are serious image artifacts both inside and outside the sample, and the recovered sample phase value is also quite different from the theoretical value. Therefore, the spatial diffraction crosstalk problem in traditional wide-field quantitative phase imaging directly affects the quality and accuracy of phase recovery.

[0128] Next, the scanning quantitative phase microscopy device based on polarization multiplexing modulation proposed in the embodiment of the present invention is used to Figure 5 The samples shown were reconstructed by simulation. Figure 8 The results shown are obtained by using the scanning quantitative phase microscopy device based on polarization multiplexing modulation proposed in the embodiment of the present invention to obtain the phase gradient distribution of the sample along the X-axis direction and along the Y-axis direction. Figure 8 It can be seen that there is no parasitic diffraction pattern in the obtained phase gradient distribution, which shows that the device proposed by the present invention effectively avoids the spatial diffraction crosstalk problem existing in wide-field imaging. Fig. 9 The results shown are obtained using Figure 8 The phase image of the sample is reconstructed from the phase gradient distribution shown. Fig. 9 It can be seen that by using the scanning quantitative phase microscopy device based on polarization multiplexing modulation proposed in the present invention, high-quality and high-precision phase images can be obtained without any special prisms and objective lenses. Therefore, the obtained phase image has no image artifacts and has a very high signal-to-noise ratio and detection accuracy.

[0129] Further, Fig.10 Given along the Figure 7 (dashed line) and Fig. 9 (Solid line) The phase distribution of the horizontal center line further demonstrates the advantages of the device of the present invention in avoiding image artifacts and improving the signal-to-noise ratio and detection accuracy. It should be noted that in the simulation process, we took into account the reality that the system objective lens has a limited numerical aperture. Therefore, Figure 7 and Fig. 9The phase distribution shown is relative to Figure 5 The actual phase distributions shown all suffer from the problem of reduced resolution.

[0130] Subsequently, based on the above-listed devices, quantitative phase imaging experiments were performed on microdevices on the surface of silicon wafers, e.g. Figure 11-13 First, the traditional reflective quantitative differential interference microscopy technique under laser wide-field illumination was used to perform reflective quantitative phase imaging on the silicon wafer. The obtained quantitative phase image is shown in Fig.11 Subsequently, the traditional reflective quantitative differential interference microscopy technique under LED wide-field illumination was used to perform reflective quantitative phase imaging of the silicon wafer in the same field of view. The obtained quantitative phase image is shown in Fig.12 Finally, the scanning quantitative phase microscopy device based on polarization multiplexing modulation proposed in the embodiment of the present invention is used to perform reflective quantitative phase imaging of the silicon wafer in the same field of view, and the obtained quantitative phase image is as shown in FIG. Fig.13 As shown. Fig.11 , Fig.12 and Fig.13 It can be seen that laser wide-field illumination will bring serious speckle noise and harmful interference patterns to the image; although LED wide-field illumination avoids speckle noise, the spatial diffraction crosstalk problem in wide-field imaging reduces the image contrast, signal-to-noise ratio and detection accuracy; in comparison, the scanning quantitative phase microscopy device based on polarization multiplexing modulation proposed in the present invention can provide high-contrast and high-quality quantitative phase images, and can accurately measure fine structures with a diameter of 1.2 microns on the surface of silicon wafers, such as Fig.13 As shown in the upper right corner. In summary, the proposed scanning quantitative phase microscopy device based on polarization multiplexing modulation does not require special prisms or special objective lenses, can perform label-free, high-quality scanning quantitative phase imaging on the sample to be tested, and has very good scalability in structure and function, and has great application value in the fields of industrial detection and so on. The above numerical simulations and real experiments prove that the device proposed in the present invention is feasible and effective.

[0131] In the several embodiments provided by the present invention, it should be understood that the apparatus and method disclosed by the present invention can be implemented in other ways. For example, the apparatus embodiments described above are only illustrative, for example, the division of the modules is only a logical function division, and there may be other division methods in actual implementation, for example, multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0132] In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of hardware plus software functional modules.

[0133] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A scanning quantitative phase microscopy device based on polarization multiplexing modulation, characterized in that: It includes a laser focus scanning module, a polarization multiplexing modulation module and an image acquisition module, wherein: The laser focus scanning module is used to generate a collimated light beam capable of performing point-by-point scanning illumination on the sample to be tested; The polarization multiplexing modulation module is used to perform polarization modulation on the collimated light beam along mutually perpendicular X-axis and Y-axis directions, and to modulate the linear polarized light polarized along the Y-axis direction by using a phase-type spatial light modulator, and to obtain reflected light carrying complex reflectivity information at different points of the sample by loading a predetermined phase modulation pattern shear-shifted along the X-axis direction or along the Y-axis direction on the phase-type spatial light modulator, wherein the plane where the X-axis direction and the Y-axis direction are located is perpendicular to the optical axis direction of the polarization multiplexing modulation module; The image acquisition module is used to obtain multiple scanning differential interference phase shift images along the X-axis shear direction and multiple scanning differential interference phase shift images along the Y-axis shear direction using the reflected light carrying the complex reflectivity information at different points of the sample; The laser focus scanning module comprises a laser (1) and a first thin lens (2), a second thin lens (3), a scanning galvanometer (4), a third thin lens (5), a fourth thin lens (6) and a non-polarizing beam splitter prism (7) which are sequentially arranged along the optical axis direction of the laser (1), wherein: The first thin lens (2) and the second thin lens (3) form a confocal system, which is used to expand the aperture of the collimated light beam emitted by the laser (1); The scanning galvanometer (4) is used to control the propagation direction of the collimated light beam from the second thin lens (3) so as to perform point-by-point scanning illumination on the sample to be measured (13) within the imaging field of view; The third thin lens (5) and the fourth thin lens (6) form a confocal system for forming a collimated light beam with a larger aperture, and the working center of the scanning galvanometer (4) is located at the front focal plane of the third thin lens (5); The non-polarization beam splitter prism (7) is used to reflect the collimated light beam with a larger aperture from the fourth thin lens (6) to the polarization multiplexing modulation module; The polarization multiplexing modulation module comprises a linear polarizer (8), a phase-type spatial light modulator (9), a fifth thin lens (10), a sixth thin lens (11) and a microscope objective lens (12) which are sequentially arranged along the optical axis direction of the light beam emitted by the laser focus scanning module.

2. The scanning quantitative phase microscopy device based on polarization multiplexing modulation according to claim 1, characterized in that: The scanning galvanometer (4) is a two-dimensional linear galvanometer system, comprising two reflecting mirrors; the non-polarizing beam splitting prism (7) is a beam splitting cube with a beam splitting ratio of 50:

50.

3. The scanning quantitative phase microscopy device based on polarization multiplexing modulation according to claim 1, characterized in that: The linear polarizing plate (8) is capable of dividing the collimated light beam from the laser focus scanning module into a collimated light beam linearly polarized along the X-axis direction and a collimated light beam linearly polarized along the Y-axis direction with equal power; The phase-type spatial light modulator (9) is located at the common focal plane of the fourth thin lens (6) and the fifth thin lens (10), and is capable of modulating the collimated light beam linearly polarized along the Y-axis direction to obtain collimated light polarized along the Y-axis direction and with a shifted propagation direction; The fifth thin lens (10) and the sixth thin lens (11) form a confocal system, and the collimated light polarized along the Y-axis direction and with a shifted propagation direction is focused at the confocal plane between the fifth thin lens (10) and the sixth thin lens (11) to form Y-polarized focused light; The sixth thin lens (11) and the microscope objective lens (12) form a confocal system, the sample to be measured (13) is arranged on the object focal plane of the microscope objective lens (12), the Y polarized focused light passes through the confocal system formed by the sixth thin lens (11) and the microscope objective lens (12) to collect complex reflectivity information at a point on the sample to be measured (13), and is collected by the microscope objective lens (12) in the form of divergent light to form a Y polarized point complex amplitude; The collimated light beam linearly polarized along the X-axis direction directly passes through the phase-type spatial light modulator (9) and is focused on the confocal plane of the fifth thin lens (10) and the sixth thin lens (11), forming X-polarized focused light; the X-polarized focused light passes through the confocal system composed of the sixth thin lens (11) and the microscope objective lens (12), collects complex reflectivity information at another point on the sample to be measured (13), and is collected by the microscope objective lens (12) in the form of divergent light, forming an X-polarized point complex amplitude.

4. The scanning quantitative phase microscopy device based on polarization multiplexing modulation according to claim 3, characterized in that: The phase-type spatial light modulator (9) is also used to: re-modulate the collimated light derived from the complex amplitude of the Y polarization point reflected from the sample to be tested (13); After being modulated again by the phase-type spatial light modulator (9), the collimated light derived from the complex amplitude of the Y polarization point can completely overlap with the collimated light derived from the complex amplitude of the X polarization point, and single-point differential interference detection is realized on the image acquisition module through the focusing action of the seventh thin lens (14).

5. The scanning quantitative phase microscopy device based on polarization multiplexing modulation according to claim 3, characterized in that: Loading a predetermined phase modulation pattern that generates a shearing offset along the X-axis direction onto the phase-type spatial light modulator (9), and sequentially adding phase values ​​of 0π, 0.25π, 0.5π and 0.75π to the predetermined phase modulation pattern that generates a shearing offset along the X-axis direction; A predetermined phase modulation pattern that generates a shearing offset along the Y-axis direction is loaded onto the phase-type spatial light modulator (9), and phase values ​​of 0π, 0.25π, 0.5π and 0.75π are sequentially added to the predetermined phase modulation pattern that generates a shearing offset along the Y-axis direction; and When each phase modulation pattern is loaded on the phase-type spatial light modulator (9), the scanning galvanometer (4) is controlled to perform point-by-point scanning illumination on the sample to be tested (13) within the imaging field of view, and the image acquisition module performs global exposure, thereby obtaining four scanning differential interference phase shift images along the X-axis shear direction and four scanning differential interference phase shift images along the Y-axis shear direction on the image acquisition module.

6. The scanning quantitative phase microscopy device based on polarization multiplexing modulation according to claim 3, characterized in that: The phase-type spatial light modulator (9) is a transmissive phase-type spatial light modulator or a reflective phase-type spatial light modulator.

7. The scanning quantitative phase microscopy device based on polarization multiplexing modulation according to claim 3, characterized in that: When scanning illumination is performed on the sample to be tested (13), the collimated light beam between the sixth thin lens (11) and the microscope objective lens (12) always fills the pupil aperture of the microscope objective lens (12), and the pupil aperture of the microscope objective lens (12) is located at the confocal plane of the microscope objective lens (12) and the sixth thin lens (11).

8. A scanning quantitative phase microscopy method based on polarization multiplexing modulation, characterized in that: include: S1: using the scanning quantitative phase microscopy device based on polarization multiplexing modulation according to any one of claims 1 to 7 to obtain four scanning differential interference phase shift images along the X-axis shear direction and four scanning differential interference phase shift images along the Y-axis shear direction; S2: using the four scanning differential interference phase shift images in the X-axis shear direction to obtain the phase gradient distribution of the sample to be tested along the X-axis shear direction; S3: using the four scanning differential interference phase shift images in the Y-axis shear direction to obtain the phase gradient distribution of the sample to be tested along the Y-axis shear direction; S4: Obtaining phase distribution information of the sample to be tested according to the phase gradient distribution along the X-axis shear direction and the phase gradient distribution along the Y-axis shear direction.

9. The scanning quantitative phase microscopy method based on polarization multiplexing modulation according to claim 8, characterized in that: The S1 includes: Loading a predetermined phase modulation pattern that generates a shear offset along the X-axis direction on the phase-type spatial light modulator, and sequentially adding phase values ​​of 0π, 0.25π, 0.5π and 0.75π to the predetermined phase modulation pattern that generates a shear offset along the X-axis direction; A predetermined phase modulation pattern that generates a shearing offset along the Y-axis direction is loaded on the phase-type spatial light modulator, and phase values ​​of 0π, 0.25π, 0.5π and 0.75π are sequentially added to the predetermined phase modulation pattern that generates a shearing offset along the Y-axis direction; and, When each phase modulation pattern is loaded on the phase-type spatial light modulator, the scanning galvanometer is controlled to perform point-by-point scanning illumination on the sample to be tested within the imaging field of view, and the image acquisition module performs global exposure, thereby obtaining four scanning differential interference phase shift images along the X-axis shear direction and four scanning differential interference phase shift images along the Y-axis shear direction on the image acquisition module.

Images