A super-resolution microscopic interferometry method based on broadband annular radial polarization

Abstract

The invention discloses a super-resolution microscopic interferometry method based on broadband annular radial polarized light. A wide-spectrum extended surface light source is selected, a Kohler illumination system is adopted to provide uniform illumination covering the field of view to be measured and having a certain aperture angle, a two-stage relay system is designed, and amplitude and polarization modulation of a light beam in the whole field of view is realized through a liquid crystal spatial light modulator and a vortex wave plate; the extended surface light source and a large numerical aperture microscope objective are combined to focus the broadband annular radial polarized light to realize super-resolution microscopic interferometry imaging of a sample; and a phase-shifting interferometry method is combined to realize super-resolution morphology measurement of a microstructure surface, so as to solve the problem of low efficiency caused by traditional laser point scanning, break through the lateral resolution limitation of traditional microscopic interferometry morphology measurement, and improve the morphology resolution of traditional microscopic interferometry measurement.

Description

Technical Field

[0001] The invention belongs to the field of optical microscopic interference morphology measurement, and in particular relates to a super-resolution microscopic interference measurement method based on broadband annular radial polarized light. Background Art

[0002] Micro-interference has the ability to non-destructively measure the three-dimensional morphology of microstructures. Using low-coherence vertical scanning, its axial resolution can reach 0.1nm, but its lateral resolution is limited by the diffraction limit of microscopic imaging. Even with a 100x interference microscope objective, the maximum resolution is only about 200nm.

[0003] The optical imaging system will have a diffraction-limited resolution due to the diffraction effect of the finite aperture. Under the condition of no optical aberration, i.e. diffraction-limited, according to Abbe's definition of imaging resolution, the lateral resolution limit that can be achieved by an optical microscope based on incoherent illumination is (NA is the numerical aperture of the system.) The diffraction of light waves by the finite aperture in the optical imaging system makes the resolution of optical microscopy technology limited by the diffraction limit and cannot be further improved.

[0004] In the past decade, a series of fluorescence super-resolution microscopy techniques have been developed rapidly. Currently, the more mature ones are super-resolution microscopy methods based on single-molecule imaging, including photoactivated localization microscopy (PALM), stochastic optical reconstruction microscopy (STORM), and fluorescence activated localization microscopy (FPALM); and stimulated emission depletion microscopy (STED), which improves imaging resolution by changing the point spread function of the light source, are widely used in the biomedical field. However, these techniques require the use of specific fluorescent probes to label the samples, which cannot be introduced into microscopic interferometry.

[0005] Light field control is an effective means to improve the optical resolution of the system, and its methods include annular aperture modulation and polarization state modulation. Studies have found that radially polarized light is a type of polarized light with perfect axial symmetry. Its electric field vector is symmetrically distributed along the optical axis and is radial. Its longitudinal component is significantly enhanced under large numerical aperture focusing. By increasing the annular aperture to weaken the transverse component, a smaller focus point can be produced than natural light.

[0006] At present, the light sources used in the research of radial polarized light super-resolution technology are all monochromatic laser light sources with small imaging field of view. When realizing super-resolution imaging of samples, it is necessary to use an electric displacement stage for point scanning. Peiwen Meng et al. built an experimental system in the article "Demonstration of lateral resolution enhancement by focusing amplitudemodulated radially polarized light in a confocal imaging system" to verify the super-resolution microscopy effect of radial polarized light. The light source used was a helium-neon laser with a wavelength of 632.8nm, and the electric displacement stage was used to perform point scanning on the sample. The above imaging method is inefficient, and the point scanning method has great limitations in measuring the three-dimensional morphology of microstructures. Summary of the invention

[0007] The present invention proposes a super-resolution microscopic interferometry measurement method based on broadband annular radially polarized light, which solves the low efficiency problem caused by traditional laser point scanning, breaks through the lateral resolution limitation of traditional microscopic interferometry morphology measurement, and improves the morphology resolution of traditional microscopic interferometry measurement.

[0008] The technical solution to achieve the purpose of the present invention is: a super-resolution microscopic interferometry method based on broadband annular radial polarized light, the steps are as follows:

[0009] Step 1, designing a two-stage relay system to generate broadband circular radial polarized light;

[0010] The two-stage relay system includes a light source, a polarizer, a first condenser, a first standard plane reflector, a liquid crystal spatial light modulator, a second condenser, a first cubic beam splitter, an analyzer, a third condenser, and a vortex wave plate;

[0011] The first condenser and the second condenser constitute a first-stage relay lens group;

[0012] The second condenser and the third condenser constitute a second-stage relay lens group;

[0013] The light source, the polarizer, the first relay mirror group, the first standard plane reflector, the first cubic beam splitter prism, and the liquid crystal spatial light modulator constitute a first-stage relay system;

[0014] The liquid crystal spatial light modulator, the second relay mirror group, the first cubic beam splitter prism, the polarizer, and the vortex wave plate constitute the second-stage relay system.

[0015] A light source, a polarizer, a first condenser, and a first standard plane reflector are sequentially arranged along a common first optical axis, and an angle between a reflective surface of the first standard plane reflector and the first optical axis is 45°.

[0016] A liquid crystal spatial light modulator, a second condenser, a first cubic beam splitter, an analyzer, a third condenser, and a vortex wave plate are sequentially arranged along a common second optical axis. The first cubic beam splitter is located on a reflected light path of a first standard plane reflector. Broadband annular radial polarized light is emitted from the vortex wave plate.

[0017] Step 2: Build a super-resolution microscopic interferometry system based on broadband circular radial polarized light.

[0018] The broadband annular radially polarized light-based super-resolution microscopic interferometry system comprises a two-stage relay system, a fourth condenser, a fifth condenser, a second cubic beam splitter, a first microscope objective, a sample to be measured, a piezoelectric ceramic PZT, a second microscope objective, a second standard plane reflector, a tube lens, and an industrial CCD camera; the sample to be measured is arranged on the piezoelectric ceramic PZT.

[0019] The fourth condenser, the fifth condenser, the second cubic beam splitter, the first microscope objective lens, and the sample to be measured are arranged behind the vortex wave plate along the second optical axis; there is also a third optical axis passing through the second cubic beam splitter, and the second standard plane reflector, the second microscope objective lens, the second cubic beam splitter, the tube lens, and the industrial CCD camera are sequentially distributed along the third optical axis, and the third optical axis is perpendicular to the second optical axis.

[0020] The first microscope objective lens, the sample to be tested, and the piezoelectric ceramic PZT constitute a test optical path, and the second microscope objective lens and the second standard plane reflector constitute a reference optical path.

[0021] The fourth condenser and the fifth condenser form a Kohler illumination mirror group.

[0022] Step 3, the light source emits a multi-field light beam, which is passed through a polarizer to generate linearly polarized light, which is converged to the first standard plane reflector through a first condenser, and then reflected 90° by the first standard plane reflector to the first cubic beam splitter prism. The first reflected light after being reflected by the first cubic beam splitter prism is passed through a second condenser to a liquid crystal spatial light modulator. At this time, the first reflected light is linearly polarized light, and its polarization direction is consistent with the long side direction of the liquid crystal light valve of the liquid crystal spatial light modulator. The liquid crystal spatial light modulator performs hollow annular modulation and reflection on the incident linearly polarized light, and the modulated annular light beam is the second reflected light. The second reflected light passes through the second condenser to the first cubic beam splitter prism, and then passes through the first cubic beam splitter prism and then passes through the analyzer. The polarization direction of the analyzer is perpendicular to the polarizer, and then converged to the vortex wave plate through a third condenser. The vortex wave plate performs polarization modulation on the full-field light beam to output broadband annular radial polarized light, and then passes through the Kohler illumination mirror group The light is transmitted to the second cubic beam splitter prism, and the second cubic beam splitter prism divides the light into test light and reference light. The test light is transmitted to the first microscope objective lens, and then illuminates the sample to be tested after passing through the first microscope objective lens. The third reflected light carrying the surface information of the sample to be tested after being reflected by the sample to be tested passes through the first microscope objective lens to the second cubic beam splitter prism, and then is reflected by the second cubic beam splitter prism and enters the tube lens. The tube lens focuses the third reflected light carrying the surface information of the sample to be tested on the industrial CCD camera; the reference light is reflected to the second microscope objective lens, and then illuminates the second standard plane reflector after passing through the second microscope objective lens. The fourth reflected light carrying the surface information of the second standard plane reflector after being reflected by the second standard plane reflector passes through the second microscope objective lens to the second cubic beam splitter prism, and then is transmitted through the second cubic beam splitter prism and enters the tube lens. The tube lens focuses the fourth reflected light carrying the surface information of the second standard plane reflector on the industrial CCD camera; at the same time, the reference light and the test light interfere with each other.

[0023] Step 4: Use piezoelectric ceramics PZT to control the micro-displacement of the sample to be tested along the optical axis, and use an industrial CCD camera to collect several phase-shift interference patterns of the sample to be tested within the full field of view of the first microscope objective.

[0024] Step 5: Use a vertical scanning interferometer algorithm to process the collected phase-shift interferograms to obtain the three-dimensional morphology information of the sample to be tested.

[0025] Compared with the prior art, the present invention has the following significant advantages:

[0026] (1) The light source used in the super-resolution microscopic interferometry method based on broadband annular radial polarized light described in the present invention is a wide-spectrum extended surface light source. Compared with the laser light source used in existing studies, the coherence length of the wide-spectrum light source is much smaller than the coherence length of the laser light source. The interference signal is modulated by the rapid attenuation of the coherent envelope. Only when the optical path difference between the detection light and the reference light is close to zero, an obvious interference signal will appear. At the same time, the divergence angle of the light source matches the field of view of the object to be measured. The Kohler illumination system provides uniform illumination covering the field of view to be measured and having a certain aperture angle. When the microscopic interferometry imaging is performed on the sample to be measured, the full-field interference pattern is directly obtained, and there is no need to use an electric displacement platform to perform point scanning on the sample to be measured, thus breaking the low efficiency problem caused by traditional laser point scanning.

[0027] (2) The present invention describes a two-stage relay system designed based on a super-resolution microscopic interferometry method for broadband annular radially polarized light. The liquid crystal spatial light modulator and the vortex wave plate are used to modulate the amplitude and polarization of the full-field light beam. The liquid crystal spatial light modulator modulates the light source beam into an annular hollow beam, and the vortex wave plate modulates the linear polarized light into radially polarized light. Broadband annular radially polarized light can be directly generated, and the structure is flexible and easy to adjust.

[0028] (3) The super-resolution microscopic interferometry method based on broadband annular radially polarized light described in the present invention utilizes the tight focusing characteristics of radially polarized light and combines it with a wide spectrum extended surface light source to measure the surface morphology of the microstructure through phase-shifting interferometry in the super-resolution microscopic interferometry optical path, thereby breaking through the lateral resolution limitation of traditional microscopic interferometry morphology measurement and improving the morphology resolution of traditional microscopic interferometry measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is an experimental optical path diagram of a super-resolution microscopic interferometry method based on broadband annular radially polarized light described in the present invention.

[0030] Figure 2 The present invention is a flowchart of the steps of a super-resolution microscopic interferometry method based on broadband annular radially polarized light.

[0031] Figure 3 This is a comparison of the light field distribution near the focus when lenses with different numerical apertures focus radial polarized light. From top to bottom, the numerical apertures of the focusing lenses in each row are: , , , , from left to right, each column represents the radial component, axial component, and total light intensity distribution.

[0032] Figure 4 This is a comparison of the light field distribution near the focus when focusing radial polarized light at different obstruction ratios. From top to bottom, the obstruction ratios of each row are , , , from left to right, each column represents the radial component, axial component, and total light intensity distribution.

[0033] Figure 5 This is the object-image conjugate relationship diagram of the Kohler illumination system. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In addition, in the present invention, the descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0036] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0037] In the present invention, unless otherwise clearly specified and limited, the "front" and "back" in the terms "front focal plane" and "back focal plane" are defined according to the direction of light propagation, with the lens as the reference, and the side where the light enters the lens is defined as the front, and the side where the light exits the lens is defined as the back.

[0038] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0039] The following will further introduce the specific implementation method, as well as the technical difficulties and inventive points of this invention in combination with this design example.

[0040] Combination Figure 1 The present invention provides a super-resolution microscopic interferometry method based on broadband annular radial polarized light, comprising the following steps:

[0041] Step 1: Design a two-stage relay system to generate broadband circular radially polarized light.

[0042] The two-stage relay system includes a light source 1, a polarizer 2, a first condenser 4, a first standard plane reflector 5, a liquid crystal spatial light modulator 6, a second condenser 8, a first cubic beam splitter prism 9, an analyzer 10, a third condenser 11, and a vortex wave plate 12.

[0043] The first condenser lens 4 and the second condenser lens 8 constitute a first-stage relay lens group 3 .

[0044] The second condensing mirror 8 and the third condensing mirror 11 constitute a second-stage relay lens group 7 .

[0045] The light source 1, the polarizer 2, the first relay mirror group 3, the first standard plane reflector 5, the liquid crystal spatial light modulator 6, and the first cubic beam splitter prism 9 constitute a first-stage relay system.

[0046] The liquid crystal spatial light modulator 6, the second relay lens group 7, the first cubic beam splitter prism 9, the polarizer 10, and the vortex wave plate 12 constitute a second-stage relay system.

[0047] A light source 1, a polarizer 2, a first condenser 4, and a first standard plane reflector 5 are sequentially arranged along a common first optical axis, and an angle between a reflection surface of the first standard plane reflector 5 and the first optical axis is 45°.

[0048] A liquid crystal spatial light modulator 6, a second condenser 8, a first cubic beam splitter prism 9, an analyzer 10, a third condenser 11, and a vortex wave plate 12 are arranged in sequence along the second optical axis. The first cubic beam splitter prism 9 is located on the reflected light path of the first standard plane reflector 5; the vortex wave plate 12 emits broadband annular radially polarized light.

[0049] Step 2: Build a super-resolution microscopy interferometry system based on broadband circular radial polarized light.

[0050] The super-resolution microscopic interferometry system based on broadband annular radial polarized light includes a two-stage relay system, a fourth condenser 14, a fifth condenser 15, a second cubic beam splitter prism 16, a first microscope objective 17, a sample to be measured 18, a piezoelectric ceramic PZT 19, a second microscope objective 20, a second standard plane reflector 21, a tube lens 22, and an industrial CCD camera 23; the sample to be measured 18 is arranged on the piezoelectric ceramic PZT 19.

[0051] The fourth condenser 14, the fifth condenser 15, the second cubic beam splitter prism 16, the first microscope objective lens 17, and the sample to be measured 18 are arranged on the second optical axis behind the vortex wave plate 12; there is also a third optical axis passing through the second cubic beam splitter prism 16, and the second standard plane reflector 21, the second microscope objective lens 20, the second cubic beam splitter prism 16, the tube lens 22, and the industrial CCD camera 23 are distributed in sequence along the third optical axis, and the third optical axis is perpendicular to the second optical axis.

[0052] The first microscope objective lens 17 , the sample to be tested 18 , and the piezoelectric ceramic PZT 19 constitute a test optical path, and the second microscope objective lens 20 and the second standard plane reflector 21 constitute a reference optical path.

[0053] The fourth condenser 14 and the fifth condenser 15 constitute a Kohler illumination lens assembly 13 .

[0054] Step 3, the light source 1 emits a multi-field light beam, which is passed through the polarizer 2 to generate linearly polarized light, which is converged to the first standard plane reflector 5 through the first condenser 4, and then reflected 90° by the first standard plane reflector 5 to the first cubic beam splitter prism 9. The first reflected light after being reflected by the first cubic beam splitter prism 9 is passed through the second condenser 8 to the liquid crystal spatial light modulator 6. At this time, the first reflected light is linearly polarized light, and its polarization direction is consistent with the long side direction of the liquid crystal light valve of the liquid crystal spatial light modulator 6. The liquid crystal spatial light modulator 6 is directed to the input The linearly polarized light emitted is modulated in a hollow ring and reflected. The modulated annular beam is the second reflected light. The second reflected light passes through the second condenser 8 to the first cubic beam splitter prism 9, and then passes through the first cubic beam splitter prism 9 and then passes through the analyzer 10. The polarization direction of the analyzer 10 is perpendicular to the polarizer 2. Then, it is converged to the vortex wave plate 12 through the third condenser 11. The vortex wave plate 12 performs polarization modulation on the full-field light beam to output broadband annular radial polarized light, and then passes through the Kohler illumination lens group 13 to the second cubic beam splitter prism. 16, the second cubic beam splitter prism 16 divides the light into a test light and a reference light, the test light is transmitted to the first microscope objective lens 17, and after passing through the first microscope objective lens 17, it illuminates the sample to be tested 18, and the third reflected light carrying the surface information of the sample to be tested after being reflected by the sample to be tested 18 passes through the first microscope objective lens 17 to the second cubic beam splitter prism 16, and after being reflected by the second cubic beam splitter prism 16, it enters the tube lens 22, and the tube lens 22 focuses the third reflected light carrying the surface information of the sample to be tested 18 on the industrial CCD camera 23; the reference light is The light is reflected to the second microscope objective lens 20, and then illuminates the second standard plane reflector 21 after passing through the second microscope objective lens 20. The fourth reflected light carrying the surface type information of the second standard plane reflector after being reflected by the second standard plane reflector 21 passes through the second microscope objective lens 20 to the second cubic beam splitter prism 16, and then is transmitted into the tube lens 22 through the second cubic beam splitter prism 16. The tube lens 22 focuses the fourth reflected light carrying the surface type information of the second standard plane reflector on the industrial CCD camera 23. At the same time, the reference light and the test light interfere with each other.

[0055] Step 4: Use the piezoelectric ceramic PZT19 to control the micro displacement of the sample 18 to be tested along the optical axis, and use the industrial CCD camera 23 to collect several phase-shift interference patterns of the sample 18 to be tested within the full field of view of the first microscope objective lens 17.

[0056] Step 5: Use a vertical scanning interference algorithm to process the collected phase-shifting interference patterns to obtain three-dimensional morphological information of the sample 18 to be tested.

[0057] The use of broadband annular radial polarized light is the innovation of the present invention. The polarization state of the radial polarized light is spatially non-uniformly distributed. The diffraction field is analyzed according to the Richards-wolf vector diffraction theory to obtain the electric field distribution near the focus under the illumination of broadband annular radial polarized light. and light intensity distribution It can be expressed as:

[0058] ,

[0059] ,

[0060] in, is the radial polarization component, is the axial polarization component, express The conjugation of.

[0061] ,

[0062] For observation point The position vector in image space, expressed in cylindrical coordinates, is Represents the radial distance in the cylindrical coordinate system (i.e. from the z-axis to the point Horizontal distance), Represents the axial coordinate in the cylindrical coordinate system (i.e. point height in the z direction), Represents the azimuth in the cylindrical coordinate system (i.e., point The angle relative to the positive x-axis).

[0063] is the numerical aperture, is the maximum convergence angle of light, is the refractive index, ;

[0064] is the pupil function, and the pupil function corresponding to the uniform plane wave is 1;

[0065] is the annular occlusion coefficient of radially polarized light;

[0066] is a Bessel function with the following properties:

[0067] ,

[0068] The electric field distribution near the focus of radial polarized light illumination under different NA (0.4, 0.6, 0.8, 0.9) is simulated and calculated. The results show that radial polarized light has a small numerical aperture ( ) In the case of focusing, the light field distribution at the focus is a hollow ring. At this time, the radial component mainly contributes to the total light field distribution, and the axial component of the light field is relatively small. As the focusing numerical aperture increases, the proportion of the axial component of the light field increases. The axial component of the light field at the focus plays a major role in the light field distribution. At this time, the focused light spot at the focus is an ideal circular spot, and the radius of the light spot is smaller than the expected Rayleigh radius. The larger the numerical aperture of the focusing lens, the smaller the half-height width of the transverse light intensity curve of the radially polarized light focused light spot, and the better the tight focusing characteristics. The super-resolution micro-interference measurement system of the present invention is selected Microscope objective lens.

[0069] The electric field distribution near the focus of radial polarized light illumination under different annular occlusion coefficients is calculated by simulation, and the annular occlusion coefficient is fitted using the least squares method. The half-height width of the light intensity distribution near the focus And the maximum light intensity on the focal plane The relationship between them gives the following function expression:

[0070] ,

[0071] ,

[0072] It can be seen that as the annular occlusion coefficient The half-width of the intensity distribution of radially polarized light near the focus The value will gradually decrease, and the lateral resolution of the system will increase. When the value increases to above 0.9, the light intensity of the radially polarized light at the focal plane will drop sharply. Considering the influence of factors such as the signal-to-noise ratio of the detector receiving signal, the exposure time of the detector and the dynamic response range during the experiment, the broadband annular radial polarized light of the present invention adopts an annular shielding coefficient of Circular radial polarization.

[0073] The measurement system of the present invention adopts a Linnik-type interference optical path. The test optical path and the reference optical path use two identical microscope objective lenses, combined with broadband annular radial polarized light illumination, and the interference signal actually received during the vertical scanning process is It can be expressed as:

[0074] ,

[0075]

[0076] in,

[0077] is the scanning interference signal when the diffraction effect is not considered;

[0078] is the point spread function, ;

[0079] is the surface shape function of the sample to be tested;

[0080] is the sum of the light intensities of the test arm and the reference arm;

[0081] To make the test optical path and the reference optical path equal in optical path, is the phase of the interference signal when the optical path length is equal;

[0082] is the scanning step length, is the number of scan steps and the total scan length ;

[0083] is the coherence length of light source 1;

[0084] is the central wavelength of light source 1.

[0085] According to the calibration rules for white light micro-interferometers in the guideline VDI / VDE 2655-1.1 for testing instruments, the three-dimensional resolution of the super-resolution micro-interferometer system It can be expressed as:

[0086] ,

[0087] in,

[0088] is the coefficient related to the structural characteristics of the sample 18 to be tested, and different structural characteristics correspond to different The value of The value is between 2 and 3.

[0089] is the half-height width of the light intensity distribution near the focus, which characterizes the lateral resolution of the super-resolution microscopy interferometry system;

[0090] Ring occlusion coefficient The half-width of the intensity distribution of radially polarized light near the focus The value will gradually decrease, and the lateral resolution of the super-resolution microscopy system will be improved, thereby increasing the three-dimensional resolution. promote.

[0091] Example

[0092] Combination Figure 1 In this embodiment, the light source 1 adopts a red LED light source with a central wavelength of 629nm and a bandwidth of 15nm; the focal lengths of the first condenser 4, the second condenser 8, and the third condenser 11 are all 60mm, the focal length of the fourth condenser 14 is 200mm, and the focal length of the fifth condenser 15 is 100mm; the liquid crystal spatial light modulator 6 adopts an amplitude-type reflective liquid crystal spatial light modulator; the vortex wave plate 12 adopts an LBTEK first-order vortex wave plate; the magnification of the first microscope 17 and the second microscope 20 is 100×, and the numerical aperture ; The focal length of the tube lens 22 is 200 mm; but the device described in the present invention is not limited to this.

[0093] For the selection of objective lens in the system, combined with Figure 3 , obtained through simulation calculation The axial component of the light field at the focus plays a major role in the light field distribution. At this time, the focused light spot at the focus is an ideal circular spot, and the radius of the light spot is smaller than the expected Rayleigh radius. The larger the numerical aperture of the focusing lens, the smaller the half-height width of the transverse light intensity curve of the radially polarized light focused light spot, and the better the tight focusing characteristics. In this embodiment, the microscope objective 17 and the microscope objective 20 are both selected with a magnification of 100× and a numerical aperture of Microscope objective lens.

[0094] For the selection of annular beam obstruction in the system, combined with Figure 4 , with the annular occlusion coefficient The half-width of the intensity distribution of radially polarized light near the focus The value will gradually decrease, and the lateral resolution of the system will increase. When it increases to more than 0.9, the light intensity value of the radially polarized light focusing focal plane will drop sharply. Considering the influence of factors such as the signal-to-noise ratio of the detector receiving signal, the exposure time of the detector and the dynamic response range during the experiment, the annular shielding coefficient of the broadband annular radially polarized light of the present invention is .

[0095] Specifically, in the primary relay system, the light source 1 is located at the front focal plane of the first condenser 4, the rear focal plane of the first condenser 4 coincides with the front focal plane of the second condenser 8, the liquid crystal spatial light modulator 6 is located at the rear focal plane of the second condenser 8, the first condenser 4 and the second condenser 8 form a 4f system, ensuring that the light source 1 is conjugate with the liquid crystal spatial light modulator 6, the polarizer 2 is arranged on the incident light path between the light source 1 and the first condenser 4, ensuring that the incident light beam is linearly polarized light, and the angle between the polarization direction of the incident light and the long side of the liquid crystal light valve of the liquid crystal spatial light modulator 6 is 0°, and the angle of the analyzer 10 is the same as the angle of the polarizer 2. The target image, i.e., a ring pattern with 90% center obstruction, is loaded on the liquid crystal spatial light modulator 6 to form a broadband ring beam; in the two-stage relay system, the liquid crystal spatial light modulator 6 is located at the front focal plane of the second condenser 8, the rear focal plane of the second condenser 8 coincides with the front focal plane of the third condenser 11, the vortex wave plate 12 is located at the rear focal plane of the third condenser 11, and the second condenser 8 and the third condenser 11 form a 4f system to ensure that the liquid crystal spatial light modulator 6 and the vortex wave plate 12 are conjugated, and the broadband ring beam is polarized modulated at the vortex wave plate 12 to convert the linear polarized light into radial polarized light. After the above two-stage relay system, broadband annular radially polarized light can be generated.

[0096] For the selection of condenser in the system, combined with Figure 5 To ensure the experimental effect, the theoretically calculated illumination range and aperture angle should be larger than the actual required values, that is, satisfying:

[0097] ,

[0098] in, represents the diameter of the light emitting surface of light source 1, It represents the spot diameter when the central field light beam of the light source 1 propagates to the fourth condenser 14, It represents the spot diameter when the parallel light beam emitted by the light source 1 is converged to the fifth condenser 15 through the fourth condenser 14, Indicates the range of illumination required for the sample 18 to be tested, represents the divergence angle of light source 1, and They respectively represent the convergence angles of the parallel light beam emitted by the light source 1 after passing through the fourth condenser 14 and the fifth condenser 15, represents the object aperture angle of the first microscope objective lens 17, , , They respectively represent the focal lengths of the fourth condenser 14, the fifth condenser 15, and the first microscope objective 17.

[0099] Substituting the numerical value into the calculation, we get

[0100] ,

[0101] Taking into account pupil size and aberration correction, determine , , The light source 1 is a red LED light source with a central wavelength of 629 nm and a bandwidth of 15 nm. The focal length of the fourth condenser 14 is 200 mm, and the focal length of the fifth condenser 15 is 100 mm. The condensers are all achromatic doublet lenses, and the wavelength range is the LED spectrum.

[0102] Combination Figure 1 , Figure 2 The super-resolution microscopic interferometry method based on broadband annular radial polarized light comprises the following steps:

[0103] Step 1: Design a two-stage relay system to generate broadband circular radially polarized light.

[0104] The two-stage relay system includes a light source 1, a polarizer 2, a first condenser 4, a first standard plane reflector 5, a liquid crystal spatial light modulator 6, a second condenser 8, a first cubic beam splitter prism 9, an analyzer 10, a third condenser 11, and a vortex wave plate 12.

[0105] The first condenser 4 and the second condenser 8 constitute a first-stage relay lens group 3;

[0106] The second condenser 8 and the third condenser 11 constitute a second-stage relay lens group 7;

[0107] The light source 1, the polarizer 2, the first relay mirror group 3, the first standard plane reflector 5, the liquid crystal spatial light modulator 6, and the first cubic beam splitter prism 9 constitute a first-stage relay system.

[0108] The liquid crystal spatial light modulator 6, the second relay lens group 7, the first cubic beam splitter prism 9, the polarizer 10, and the vortex wave plate 12 constitute a second-stage relay system.

[0109] A light source 1, a polarizer 2, a first condenser 4, and a first standard plane reflector 5 are sequentially arranged along a common first optical axis, and an angle between a reflection surface of the first standard plane reflector 5 and the first optical axis is 45°.

[0110] A liquid crystal spatial light modulator 6, a second condenser 8, a first cubic beam splitter prism 9, an analyzer 10, a third condenser 11, and a vortex wave plate 12 are arranged in sequence along the second optical axis. The first cubic beam splitter prism 9 is located on the reflected light path of the first standard plane reflector 5; the vortex wave plate 12 emits broadband annular radially polarized light.

[0111] Step 2: Build a super-resolution microscopy interferometry system based on broadband circular radial polarized light.

[0112] The super-resolution microscopic interferometry system based on broadband annular radial polarized light includes a two-stage relay system, a fourth condenser 14, a fifth condenser 15, a second cubic beam splitter prism 16, a first microscope objective 17, a sample to be measured 18, a piezoelectric ceramic PZT 19, a second microscope objective 20, a second standard plane reflector 21, a tube lens 22, and an industrial CCD camera 23; the sample to be measured 18 is arranged on the piezoelectric ceramic PZT 19.

[0113] The fourth condenser 14, the fifth condenser 15, the second cubic beam splitter prism 16, the first microscope objective lens 17, and the sample to be measured 18 are arranged on the second optical axis behind the vortex wave plate 12; there is also a third optical axis passing through the second cubic beam splitter prism 16, and the second standard plane reflector 21, the second microscope objective lens 20, the second cubic beam splitter prism 16, the tube lens 22, and the industrial CCD camera 23 are distributed in sequence along the third optical axis, and the third optical axis is perpendicular to the second optical axis.

[0114] The first microscope objective lens 17 , the sample to be tested 18 , and the piezoelectric ceramic PZT 19 constitute a test optical path, and the second microscope objective lens 20 and the second standard plane reflector 21 constitute a reference optical path.

[0115] The fourth condenser 14 and the fifth condenser 15 constitute a Kohler illumination lens assembly 13 .

[0116] Step 3, the light source 1 emits a multi-field light beam, which is passed through the polarizer 2 to generate linearly polarized light, which is converged to the first standard plane reflector 5 through the first condenser 4, and then reflected 90° by the first standard plane reflector 5 to the first cubic beam splitter prism 9. The first reflected light after being reflected by the first cubic beam splitter prism 9 is passed through the second condenser 8 to the liquid crystal spatial light modulator 6. At this time, the first reflected light is linearly polarized light, and its polarization direction is consistent with the long side direction of the liquid crystal light valve of the liquid crystal spatial light modulator 6. The liquid crystal spatial light modulator 6 is directed to the input The linearly polarized light emitted is modulated in a hollow ring and reflected. The modulated annular beam is the second reflected light. The second reflected light passes through the second condenser 8 to the first cubic beam splitter prism 9, and then passes through the first cubic beam splitter prism 9 and then passes through the analyzer 10. The polarization direction of the analyzer 10 is perpendicular to the polarizer 2. Then, it is converged to the vortex wave plate 12 through the third condenser 11. The vortex wave plate 12 performs polarization modulation on the full-field light beam to output broadband annular radial polarized light, and then passes through the Kohler illumination lens group 13 to the second cubic beam splitter prism. 16, the second cubic beam splitter prism 16 divides the light into a test light and a reference light, the test light is transmitted to the first microscope objective lens 17, and after passing through the first microscope objective lens 17, it illuminates the sample to be tested 18, and the third reflected light carrying the surface information of the sample to be tested after being reflected by the sample to be tested 18 passes through the first microscope objective lens 17 to the second cubic beam splitter prism 16, and after being reflected by the second cubic beam splitter prism 16, it enters the tube lens 22, and the tube lens 22 focuses the third reflected light carrying the surface information of the sample to be tested 18 on the industrial CCD camera 23; the reference light is The light is reflected to the second microscope objective lens 20, and then illuminates the second standard plane reflector 21 after passing through the second microscope objective lens 20. The fourth reflected light carrying the surface type information of the second standard plane reflector after being reflected by the second standard plane reflector 21 passes through the second microscope objective lens 20 to the second cubic beam splitter prism 16, and then is transmitted into the tube lens 22 through the second cubic beam splitter prism 16. The tube lens 22 focuses the fourth reflected light carrying the surface type information of the second standard plane reflector on the industrial CCD camera 23. At the same time, the reference light and the test light interfere with each other.

[0117] Step 4: Use the piezoelectric ceramic PZT19 to control the micro displacement of the sample 18 to be tested along the optical axis, and use the industrial CCD camera 23 to collect several phase-shift interference patterns of the sample 18 to be tested within the full field of view of the first microscope objective lens 17.

[0118] Step 5: Use a vertical scanning interference algorithm to process the collected phase-shifting interference patterns to obtain three-dimensional morphological information of the sample 18 to be tested.

Claims

1. A super-resolution microscopic interferometry method based on broadband annular radial polarized light, characterized in that: Here are the steps: Step 1, designing a two-stage relay system to generate broadband circular radial polarized light; The two-stage relay system comprises a light source (1), a polarizer (2), a first condenser (4), a first standard plane reflector (5), a liquid crystal spatial light modulator (6), a second condenser (8), a first cubic beam splitter (9), an analyzer (10), a third condenser (11), and a vortex wave plate (12); The first condenser lens (4) and the second condenser lens (8) constitute a first-stage relay lens group (3); The second condenser (8) and the third condenser (11) constitute a second-stage relay lens group (7); The light source (1), the polarizer (2), the first relay mirror group (3), the first standard plane reflector (5), the first cubic beam splitter prism (9), and the liquid crystal spatial light modulator (6) constitute a first-stage relay system; The liquid crystal spatial light modulator (6), the second relay lens group (7), the first cubic beam splitter prism (9), the polarizer (10), and the vortex wave plate (12) constitute a second-stage relay system; A light source (1), a polarizer (2), a first condenser (4), and a first standard plane reflector (5) are sequentially arranged along a common first optical axis, and the angle between the reflection surface of the first standard plane reflector (5) and the first optical axis is 45°; A liquid crystal spatial light modulator (6), a second condenser (8), a first cubic beam splitter (9), an analyzer (10), a third condenser (11), and a vortex wave plate (12) are sequentially arranged along a common second optical axis, wherein the first cubic beam splitter (9) is located on a reflection light path of a first standard plane reflector (5); broadband annular radial polarized light is emitted from the vortex wave plate (12); Step 2: Build a super-resolution microscopic interferometry system based on broadband annular radial polarized light; The broadband annular radially polarized light-based super-resolution microscopic interferometry system comprises a two-stage relay system, a fourth condenser (14), a fifth condenser (15), a second cubic beam splitter (16), a first microscope objective (17), a sample to be measured (18), a piezoelectric ceramic PZT (19), a second microscope objective (20), a second standard plane reflector (21), a tube lens (22), and an industrial CCD camera (23); the sample to be measured (18) is arranged on the piezoelectric ceramic PZT (19); A fourth condenser (14), a fifth condenser (15), a second cubic beam splitter (16), a first microscope objective lens (17), and a sample to be measured (18) are arranged on a second optical axis behind the vortex wave plate (12); a third optical axis passes through the second cubic beam splitter (16), and a second standard plane reflector (21), a second microscope objective lens (20), a second cubic beam splitter (16), a tube lens (22), and an industrial CCD camera (23) are sequentially distributed along the third optical axis, and the third optical axis is perpendicular to the second optical axis; The first microscope objective lens (17), the sample to be tested (18), and the piezoelectric ceramic PZT (19) constitute a test optical path, and the second microscope objective lens (20) and the second standard plane reflector (21) constitute a reference optical path; The fourth condenser (14) and the fifth condenser (15) form a Kohler illumination mirror group (13); Step 3, the light source (1) emits a multi-field light beam, which is passed through the polarizer (2) to generate linearly polarized light, which is then converged to the first standard plane reflector (5) through the first condenser (4), and then reflected 90° by the first standard plane reflector (5) to the first cubic beam splitter (9). The first reflected light after being reflected by the first cubic beam splitter (9) is passed through the second condenser (8) to the liquid crystal spatial light modulator (6). At this time, the first reflected light is linearly polarized light, and its polarization direction is consistent with the long side direction of the liquid crystal light valve of the liquid crystal spatial light modulator (6). The liquid crystal spatial light modulator (6) is directed into the first reflected light. The incident linearly polarized light is modulated in a hollow ring and reflected, and the modulated ring beam is the second reflected light. The second reflected light passes through the second condenser (8) to the first cubic beam splitter (9), and then passes through the first cubic beam splitter (9) and then passes through the analyzer (10). The polarization direction of the analyzer (10) is perpendicular to the polarizer (2). The second reflected light is then converged to the vortex wave plate (12) through the third condenser (11). The vortex wave plate (12) performs polarization modulation on the full-field light beam to output broadband annular radial polarized light, and then passes through the Kohler illumination lens group (13) to the second cubic beam splitter (1 6), the second cubic beam splitter (16) splits the light into test light and reference light, the test light is transmitted to the first microscope objective lens (17), and illuminates the sample to be tested (18) after passing through the first microscope objective lens (17), the third reflected light carrying the surface information of the sample to be tested (18) after being reflected by the sample to be tested (18) passes through the first microscope objective lens (17) to the second cubic beam splitter (16), and is reflected by the second cubic beam splitter (16) into the tube lens (22), and the tube lens (22) focuses the third reflected light carrying the surface information of the sample to be tested (18) on the industrial CCD camera (23); reference The light is reflected to the second microscope objective lens (20), and then illuminates the second standard plane reflector (21) after passing through the second microscope objective lens (20). The fourth reflected light carrying the surface type information of the second standard plane reflector after being reflected by the second standard plane reflector (21) passes through the second microscope objective lens (20) to the second cubic beam splitter prism (16), and is transmitted through the second cubic beam splitter prism (16) into the tube lens (22). The tube lens (22) focuses the fourth reflected light carrying the surface type information of the second standard plane reflector on the industrial CCD camera (23); at the same time, the reference light and the test light interfere with each other; Step 4: using a piezoelectric ceramic PZT (19) to control the micro displacement of the sample to be tested (18) along the optical axis direction, and using an industrial CCD camera (23) to collect a plurality of phase-shift interference patterns of the sample to be tested (18) within the full field of view of the first microscope objective lens (17); Step 5: Use a vertical scanning interference algorithm to process the collected phase-shift interference patterns to obtain three-dimensional morphological information of the sample to be tested (18).

2. The method of super-resolution micro-interference measurement based on broadband annular radial polarized light according to claim 1, characterized in that: The light source (1) is a wide-spectrum extended surface light source with a wavelength range of visible light. The coherence length of the wide-spectrum light source is much smaller than the coherence length of the laser light source. The interference signal is modulated by the rapid attenuation of the coherent envelope. Only when the optical path difference between the detection light and the reference light is close to zero, an obvious interference signal will appear. The divergence angle of the light source (1) matches the field of view of the object to be measured. The Kohler illumination system provides uniform illumination covering the field of view to be measured and having a certain aperture angle. When performing microscopic interference imaging on the sample to be measured (18), a full-field interference pattern is directly obtained. There is no need to use an electric displacement platform to perform point scanning on the sample to be measured (18), thereby breaking the inefficiency problem caused by traditional laser point scanning.

3. The method of super-resolution microscopic interferometry based on broadband annular radial polarized light according to claim 2, characterized in that: Broadband circular radial polarization satisfies the following equation: The electric field distribution E and light intensity distribution I near the focus under broadband annular radial polarized light illumination are expressed as: E=E r +E z , Among them, E r is the radial polarization component, E z is the axial polarization component, represents the conjugation of E; By simulating and calculating the electric field distribution near the focus of radial polarized light illumination under different annular shielding coefficients, the relationship between the annular shielding coefficient and the half-width of the light intensity distribution near the focus and the maximum light intensity on the focal plane is fitted using the least squares method, and the following function expression is obtained: x(m)=-0.053·m 2 -0.1529·m+0.4012, I max (m)=-0.353·m 2 -0.088·m+0.365, Among them, represents the annular occlusion coefficient, x(m) represents the half-height width of the light intensity distribution near the focus, and I max (m) represents the maximum light intensity on the focal plane.

4. The method of super-resolution micro-interference measurement based on broadband annular radial polarized light according to claim 3, characterized in that: The annular occlusion coefficient m=0.

9.

5. The method of super-resolution micro-interference measurement based on broadband annular radial polarized light according to claim 4, characterized in that: The super-resolution microscopic interferometry system based on broadband annular radial polarized light in step 2 adopts a Linnik-type interference optical path. The test optical path and the reference optical path use two identical microscope objective lenses, respectively. Combined with the illumination of broadband annular radial polarized light, the interference signal I actually received during the vertical scanning process is q,image (x,y) is represented as: I q,image (x,y)=I q (x,y)*psf(x,y), in, I q (x, y) is the scanning interference signal when the diffraction effect is not considered; psf(x,y) is the point spread function, h(x,y) is the surface function of the sample to be tested; I' is the sum of the light intensities of the test arm and the reference arm; z0 is the position where the test light path and the reference light path are equal in optical path, and φ0 is the phase of the interference signal when the optical path is equal; Δz is the scanning step length, q is the number of scanning steps, and the total scanning length z = q·Δz; l c is the coherence length of the light source (1); λ is the central wavelength of the light source (1); According to the calibration rules of white light micro-interferometers in the guideline VDI / VDE2655-1.1 for testing instruments, the three-dimensional resolution of the super-resolution micro-interferometer system is 3D (m) is expressed as: Λ 3D (m)=a·x(m)=a·(-0.053·m 2 -0.1529·m+0.4012), in, a is the coefficient related to the structural characteristics of the sample to be tested (18); x(m) is the half-height width of the light intensity distribution near the focus, which characterizes the lateral resolution of the super-resolution microscopy interferometry system; As the annular occlusion coefficient m increases, the lateral resolution of the super-resolution microscopy system increases, resulting in a three-dimensional resolution of Λ 3D promote.

6. The method of super-resolution micro-interference measurement based on broadband annular radial polarized light according to claim 5, characterized in that: The light source (1) is located on the front focal plane of the first condenser (4); the first condenser (4) and the second condenser (8) are confocal; the liquid crystal spatial light modulator (6) is located at the rear focal plane of the second condenser (8); the second condenser (8) and the third condenser (11) are confocal; the vortex wave plate (12) is located at the rear focal plane of the third condenser (11); the fourth condenser (14) and the fifth condenser (15) are confocal; the fifth condenser (15) and the first microscope objective lens (17) are confocal; the sample to be measured (18) is located at the rear focal plane of the first microscope objective lens (17); and the second standard plane reflector (21) is located at the rear focal plane of the second microscope objective lens (20).

7. The method of super-resolution micro-interference measurement based on broadband annular radial polarized light according to claim 6, characterized in that: The test light path is completely consistent with the reference light path, wherein the position of the sample to be tested (18) in the test light path corresponds to the position of the second standard plane reflector (21) in the reference light path.

8. The method of super-resolution micro-interference measurement based on broadband annular radial polarized light according to claim 7, characterized in that: The condensers are all achromatic lenses, and the wavelength range is the same as the LED spectrum.

9. The method of super-resolution micro-interference measurement based on broadband annular radial polarized light according to claim 8, characterized in that: The liquid crystal spatial light modulator is an amplitude-type reflective liquid crystal spatial light modulator, which is used to generate a ring-shaped light beam.

10. The method of super-resolution micro-interference measurement based on broadband annular radial polarized light according to claim 1, characterized in that: The first microscope objective lens (17) and the second microscope objective lens (20) are both common objective lenses with a numerical aperture NA greater than 0.85.

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