CN111257226A - Dark field confocal microscopic measurement device and method based on polarization autocorrelation - Google Patents
Dark field confocal microscopic measurement device and method based on polarization autocorrelation Download PDFInfo
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- G02B21/0024—Confocal scanning microscopes (CSOMs) or confocal "macroscopes"; Accessories which are not restricted to use with CSOMs, e.g. sample holders
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- G01N21/84—Systems specially adapted for particular applications
- G01N21/88—Investigating the presence of flaws or contamination
- G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
- G01N2021/8887—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges based on image processing techniques
Abstract
The invention discloses a dark field confocal microscopic measuring device and method based on polarization autocorrelation, wherein the device comprises a polarized annular light illuminating module, a polarized annular light scanning module and a confocal polarization detection module; through the shaping of the illuminating light beam and the shielding detection of the complementary aperture, the reflected signal of the surface of the sample and the scattered signal of the sub-surface are effectively separated, the three-dimensional distribution information of defects such as nano-scale surface scratches, abrasion, sub-surface cracks, bubbles and the like can be simultaneously obtained, and the integrated detection function of the defects of the surface and the sub-surface is realized; meanwhile, the asymmetry of the sample structure is utilized to excite the single wave vector illumination light field in different directions to generate the difference of the polar scattering and the autocorrelation cumulant of adjacent observation points, so that the super-resolution measurement is realized. The invention has the advantage of realizing the detection of the nanometer-scale subsurface three-dimensional defects.
Description
Technical Field
The invention relates to the technical field of optical precision measurement, in particular to a dark field confocal microscopic measurement device and method based on polarization autocorrelation.
Background
High-performance optical elements and micro-electromechanical elements are core components of modern high-end equipment, and surface appearance measurement and subsurface defect detection are required for guaranteeing the processing quality and service reliability of the high-performance optical elements and the micro-electromechanical elements, and no equipment can simultaneously realize the functions at home and abroad at present.
The existing surface topography nondestructive measurement technology at home and abroad mainly comprises the following steps: confocal microscopy, white light interference microscopy and zoom microscopy. Compared with the other two technologies, the confocal microscopic measurement technology has the characteristics of wide applicability of measurement samples and capability of measuring complex sample structures, and is widely applied to the field of industrial detection. The sub-surface defect nondestructive detection technology mainly comprises the following steps: laser modulation scattering technology, total internal reflection microscopy, optical coherence tomography, high frequency scanning acoustic microscopy, and X-ray microscopy. The method has the defects of low depth positioning precision, low signal-to-noise ratio, low detection efficiency, limited detection samples and the like.
Therefore, how to realize the detection of a complex sample structure and improve the wide applicability, the depth positioning precision and the detection efficiency of the sample detection are problems to be solved urgently by those skilled in the art.
Disclosure of Invention
In view of the above, the present invention provides a dark field confocal microscopy measurement device and method based on polarization autocorrelation, which can effectively separate a sample surface reflection signal and a sub-surface scattering signal through illumination beam shaping and complementary aperture shielding detection, can simultaneously obtain three-dimensional distribution information of defects such as nano-scale surface scratches, abrasion, sub-surface cracks, bubbles, and the like, and has a surface and sub-surface defect integrated detection function.
In order to achieve the purpose, the invention adopts the following technical scheme:
a dark field confocal microscopy measuring device based on polarization autocorrelation comprises: the device comprises a polarized annular light illumination module, a polarized annular light scanning module and a confocal polarization detection module;
the polarized annular light illumination module sequentially comprises the following components in the light beam transmission direction: the device comprises a laser, a beam expander, a polarizer I, a polarization splitting film, a quarter wave plate, a conical lens, a plane reflector and a semi-reflecting and semi-transmitting film, wherein light beams are reflected by the plane reflector after passing through the polarization splitting film, the quarter wave plate and the conical lens to generate reflected light beams; the reflected light beam is shaped into an annular light beam after passing through the conical lens again, and the polarization direction changes by 90 degrees after passing through the quarter-wave plate again to obtain a linear polarization annular light beam which is reflected by the polarization splitting film; the linear polarization annular light beam transmits the semi-reflecting and semi-transmitting film and enters the polarization annular light scanning module;
the polarized annular light scanning module sequentially comprises the following components in the light beam transmission direction: the linear polarization annular light beam forms a focusing light spot on the surface of the sample, the reflected light and the scattered light of the sample return to the two-dimensional scanning galvanometer in a primary path, and the light beam reflected by the two-dimensional scanning galvanometer enters the confocal polarization detection module after being reflected by the semi-reflecting and semi-transparent film;
the confocal analyzing and detecting module sequentially comprises the following components according to the light beam propagation direction: the device comprises a diaphragm, a polarizing plate II, a focusing lens, a pinhole and a camera; the diaphragm receives the light beam reflected by the semi-reflecting and semi-transmitting film.
Preferably, the polarization direction of the first polarizer is subjected to 360-degree azimuth angle rotation control, the rotation angle of each time is 360 degrees/N, and the linear polarization annular beams in different linear polarization states illuminate the sample by adjusting different polarization directions of the first polarizer; the polarization direction of the second polarizing plate is matched with the polarization direction of the first polarizing plate.
Preferably, the combination of the cone lens and the plane mirror shapes the linearly polarized light beam generated by the first polarizer into a linearly polarized annular light beam with adjustable inner and outer diameters; the beam expander is placed at the front end of the optical path of the cone lens and used for adjusting the inner diameter of the linear polarization annular light beam, and the larger the diameter of an output light spot of the beam expander is, the larger the thickness of the linear polarization annular light beam is, and the smaller the inner diameter is; the outer diameter of the linear polarization annular light beam is adjusted through the relative distance between the conical lens and the plane reflector, the farther the relative distance is, the larger the outer diameter is, otherwise, the smaller the outer diameter is; the outer diameter of the linear polarization annular light beam is matched with the entrance pupil of the objective lens, and the observation requirement on the sample is met.
Preferably, the working surface of the scanning lens is arranged at the front focal plane of the tube mirror.
Preferably, the aperture of the diaphragm is the same as the inner diameter of the linear polarization annular beam; the diaphragm completely blocks a reflected light beam from the sample, only allows scattered light carrying the sample information to enter the confocal polarization detection module, and then enters the diaphragm and a subsequent light path, so that a reflected signal and a scattered signal from the sample are effectively separated.
Preferably, the light path from the polarized annular light illumination module passes through the semi-reflecting and semi-transmitting film, and is semi-transmitted and semi-reflected above the light path; the light path from the polarized annular light scanning module passes through the semi-reflecting and semi-transparent film and is partially reflected to the diaphragm.
A dark field confocal microscopic measurement device method based on polarization autocorrelation comprises the following specific steps:
step 1: shaping the parallel laser beams into linear polarized annular beams by a polarized annular illumination module, and transmitting the linear polarized annular beams to a polarized annular light scanning module to perform polarized annular light illumination on a sample to form a focusing light spot on the sample;
the polarized annular light illumination module sequentially comprises the following components in the light transmission direction: the device comprises a laser, a beam expander, a first polaroid, a polarization beam splitting film, a quarter-wave plate, a conical lens, a plane reflector and a semi-reflecting and semi-transmitting film; the polarized annular light scanning module sequentially comprises the following components in the light propagation direction: the two-dimensional scanning galvanometer, the scanning lens, the tube lens, the objective lens and the sample;
the beam diameter of the parallel laser beam emitted by the laser is amplified through the beam expander, the parallel laser beam is changed into a linearly polarized light beam through the polarizer I, the linearly polarized light beam passes through the polarization splitting film, the quarter-wave plate and the conical lens in sequence and is reflected and transmitted back by the plane reflector, the reflected linearly polarized light beam passes through the conical lens again and is shaped into a linearly polarized annular beam, the polarization direction of the linearly polarized annular beam changes by 90 degrees after passing through the quarter-wave plate again and is reflected to the semi-reflecting and semi-transmitting film by the polarization splitting film, the linearly polarized annular beam transmits through the semi-reflecting and semi-transmitting film I, is reflected by the two-dimensional scanning vibrating mirror, is focused to the front focal plane of the tube mirror through the scanning lens, and then generates a parallel linearly polarized annular beam incidence linear polarization objective lens through the tube mirror to form a focusing spot on the sample, effecting said linearly polarized annular beam illumination of said sample;
step 2: the polarized annular light scanning module performs two-dimensional scanning on the sample by using the focusing light spot to generate scattered light and reflected light carrying the sample information;
controlling the deflection of the two-dimensional scanning galvanometer to enable the focusing light spot to perform two-dimensional scanning on the sample, wherein a scattered light beam and a reflected light beam of the sample sequentially pass through the objective lens, the tube lens, the scanning lens and the two-dimensional scanning galvanometer and are reflected to the confocal detection module by the semi-reflecting and semi-transparent film, so that the linear polarization annular light beam of the sample is scanned;
and step 3: a confocal polarization detection module collects the scattered light from the sample to realize confocal polarization detection of the sample;
the confocal polarization detection module sequentially comprises the following components in the light propagation direction: the diaphragm, the second polarizing film, the focusing lens, the pinhole and the camera;
the scattered light beam and the reflected light beam of the sample reflected by the semi-reflecting and semi-transparent film pass through the diaphragm, the reflected light beam of the sample is shielded and filtered, the scattered light carrying the internal defect information of the sample passes through the second polaroid, is focused to the center of the pinhole by the focusing lens and is finally collected by the camera tightly attached to the pinhole, and the interference light from the objective lens except the focusing light spot is shielded and filtered by the pinhole to realize confocal polarization detection of the sample;
and 4, step 4: controlling the polarization direction of a polarizing film I (3) of the polarization annular illumination module to rotate, wherein the rotation angle is 360 DEG/N, and once every rotation, a camera (18) of the confocal polarization detection module collects a two-dimensional scanning image of the sample (13) to obtain N to-be-detected sample images I under the illumination of the linear polarization annular light beamsi(x, y), i is 1, 2, 3, …, N, where x is the row number of the image pixel of the sample to be tested, y is the column number of the image pixel, and (x, y) represents the pixel point position;
and 5: performing m-order autocorrelation quantity calculation on each pixel point at the same position of the N to-be-detected sample images obtained in the step (4) to obtain a super-resolution image C with improved resolutionmThe calculation formula is as follows:
wherein (x, y) represents the pixel point position, IiRepresenting the images of the sample to be detected acquired under the illumination of the annular beams in different linear polarization states, wherein N is the number of the images acquired by one (3) 360-degree circumferential rotation of the polaroid, m represents the calculation order, and m is a positive integer not greater than 4.
Step 6: for the super-resolution image C obtained in the step 5mPerforming iterative deconvolution operation, and then taking
Eliminating the nonlinear effect by the power, obtaining a measurement image with resolution improved by m times, and completing super resolution; the calculation formula of the iterative deconvolution operation is as follows:
wherein h is a system point spread function, y is an image after deconvolution operation, and y is the first iteration1＝CmI 1, 2, 3, …, N, FFT and iFFT are fast fourier transform and fast inverse fourier transform, respectively, j is the number of iterations, j isA maximum value of 100;
and 7: and moving the sample in the vertical direction, performing transverse two-dimensional scanning on different axial positions of the sample, repeating the step 4 to the step 6, obtaining the measurement images of different axial positions, and realizing the three-dimensional super-resolution microscopic measurement of the sample.
The technical scheme shows that compared with the prior art, the device comprises a polarized annular light illumination module, a polarized annular light scanning module and a confocal polarization detection module, the polarized annular light illumination module shapes an illumination light beam by using the combination of a cone lens and a plane reflector to obtain a linear polarized annular light beam with adjustable inner and outer diameters, the linear polarized annular light beam irradiates the polarized annular light scanning module and the confocal polarization detection module, the polarized annular light scanning module scans a sample and feeds back a scanning light signal to the confocal polarization detection module, the diaphragm of the confocal polarization detection module controls the circular light space of the linear polarized annular light beam to be strictly complementary and matched to shield a sample reflected light beam in the fed-back scanning light signal, only receiving the scattered light beam carrying the sample information, thereby effectively separating the sample surface reflection signal and the sub-surface scattering signal and realizing the sub-surface defect detection of the high-performance optical element and the micro-electro-mechanical element. And the asymmetry of the sample structure is utilized to excite the single wave vector illumination light field in different directions to generate polar scattering and the autocorrelation cumulant difference of adjacent observation points, so that the measurement of the nanometer defects on the sub-surface of the sample is realized.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a dark field confocal microscopy measurement device based on polarization autocorrelation, provided by the invention;
FIG. 2 is a flow chart of a dark field confocal microscopy imaging method based on polarization autocorrelation provided by the invention.
In fig. 1: the device comprises a 1-laser, a 2-polaroid I, a 3-polaroid I, a 4-polarization beam splitting film, a 5-quarter wave plate, a 6-cone lens, a 7-plane reflector, an 8-semi-reflecting and semi-transmitting film, a 9-two-dimensional scanning galvanometer, a 10-scanning lens, an 11-tube lens, a 12-objective lens, a 13-sample, a 14-diaphragm, a 15-polaroid II, a 16-focusing lens, a 17-pinhole and an 18-camera.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a dark field confocal microscopic measuring device based on polarization autocorrelation, which comprises: the device comprises a polarized annular light illumination module, a polarized annular light scanning module and a confocal polarization detection module;
the polarized annular light illumination module comprises the following components in sequence according to the light beam propagation direction: the device comprises a laser 1, a beam expander 2, a polarizer I3, a polarization splitting film 4, a quarter wave plate 5, a conical lens 6, a plane reflector 7 and a semi-reflecting and semi-permeable film 8, wherein light beams are reflected by the plane reflector 7 after passing through the polarization splitting film 4, the quarter wave plate 5 and the conical lens 6 to generate reflected light beams; the reflected light beam is shaped into an annular light beam after passing through the conical lens 6 again, the polarization direction changes by 90 degrees after passing through the quarter-wave plate 5 again, and the linear polarization annular light beam is obtained and reflected by the polarization splitting film 4; the linear polarization annular light beam transmits the semi-reflecting and semi-transmitting film 8 and enters the polarization annular light scanning module;
the polarized annular light scanning module sequentially comprises the following components in the light beam propagation direction: the linear polarization annular light beam forms a focusing light spot on the surface of the sample 13, and the reflected light and scattered light of the sample 13 return to the two-dimensional scanning galvanometer 9; the light beam reflected by the two-dimensional scanning galvanometer 9 enters the confocal polarization detection module after being reflected by the semi-reflecting and semi-transmitting film 8;
the confocal analyzing and detecting module comprises the following components in sequence according to the light beam propagation direction: a diaphragm 14, a second polarizing plate 15, a focusing lens 16, a pinhole 17 and a camera 18; the diaphragm 14 receives the light beam reflected by the transflective film 8.
In order to further optimize the technical scheme, the polarization direction of the polarizer I3 is subjected to 360-degree azimuth angle rotation control, the rotation angle at each time is 360 degrees/N, and linear polarization annular beams in different linear polarization states illuminate the sample 13 by adjusting different polarization directions of the polarizer I3; the polarization direction of the second polarizer 15 matches the polarization direction of the first polarizer 3.
In order to further optimize the technical scheme, the linearly polarized light beam generated by the first polarizing plate is shaped into a linearly polarized annular light beam with adjustable inner and outer diameters by the combination of the cone lens 6 and the plane reflecting mirror 7; the beam expander 2 placed at the front end of the light path of the conical lens 6 is used for adjusting the inner diameter of the linearly polarized annular light beam, and the larger the diameter of the light spot output by the beam expander 2 is, the larger the thickness of the linearly polarized annular light beam is, and the smaller the inner diameter is; the outer diameter of the linear polarization annular light beam is adjusted through the relative distance between the conical lens 6 and the plane reflector 7, the larger the relative distance is, the larger the outer diameter is, otherwise, the smaller the outer diameter is; the outer diameter of the linear polarization annular light beam is matched with the entrance pupil of the objective lens 12, and the requirement for observing the sample is met.
In order to further optimize the above solution, the working surface of the scanning lens 10 is placed at the front focal plane of the tube mirror 11.
In order to further optimize the technical scheme, the aperture of the diaphragm 14 is the same as the inner diameter of the linear polarization annular beam; the diaphragm 14 completely blocks the reflected light beam from the sample 13, and only allows the scattered light carrying the information of the sample 13 to enter the confocal polarization detection module, enter the diaphragm 14 and the subsequent optical path, so as to effectively separate the reflected signal from the sample 13 from the scattered signal.
A dark field confocal microscopic measurement device method based on polarization autocorrelation comprises the following specific steps:
s1: the parallel laser beams are shaped into linear polarized annular beams by a polarized annular illumination module and transmitted to a polarized annular light scanning module to carry out polarized annular light illumination on the sample 13, and a focusing light spot is formed on the sample 13;
the polarized annular light illumination module comprises the following components in sequence according to the light propagation direction: the device comprises a laser 1, a beam expander 2, a polarizer I3, a polarization splitting film 4, a quarter-wave plate 5, a conical lens 6, a plane reflector 7 and a semi-reflecting and semi-transmitting film 8; the polarized annular light scanning module comprises the following components in sequence according to the light propagation direction: a two-dimensional scanning galvanometer 9, a scanning lens 10, a tube lens 11, an objective lens 12 and a sample 13;
the beam diameter of the parallel laser beam emitted by the laser 1 is amplified through the beam expander 2, the parallel laser beam is changed into a linearly polarized light beam through the polarizer I3, the linearly polarized light beam passes through the polarization splitting film 4, the quarter wave plate 5 and the cone lens 6 in sequence, reflected and returned by the plane reflector 7, the reflected linearly polarized light beam is shaped into a linearly polarized annular light beam after passing through the conical lens 6 again, the polarization direction changes by 90 degrees after passing through the quarter-wave plate 5 again, and is reflected to the semi-reflecting and semi-transmitting film 8 by the polarization beam splitting film 4, the linear polarization annular light beam transmits the semi-reflecting and semi-transmitting film 8 and is reflected by the two-dimensional scanning galvanometer 9, is focused to the front focal plane of a tube lens 11 through a scanning lens 10, and then generates a parallel linear polarization annular light beam through the tube lens 11 to enter a linear polarization objective lens 12, forming a focusing light spot on the sample 13 to realize linear polarization annular beam illumination on the sample 13;
s2: the polarized annular light scanning module performs two-dimensional scanning on the sample 13 by adopting a focusing light spot to generate scattered light and reflected light carrying information of the sample 13;
the two-dimensional scanning galvanometer 9 is controlled to deflect to enable a focusing light spot to perform two-dimensional scanning on a sample 13, and a scattered light beam and a reflected light beam of the sample 13 sequentially pass through the objective lens 12, the tube lens 11, the scanning lens 10 and the two-dimensional scanning galvanometer 9 and are reflected to the confocal polarization detection module by the semi-reflecting and semi-permeable film 8, so that linear polarization annular light beam scanning of the sample 13 is realized;
s3: the confocal polarization detection module collects the scattered light from the sample 13 to realize confocal polarization detection on the sample 13;
the confocal analyzing and detecting module comprises the following components in sequence according to the light propagation direction: a diaphragm 14, a second polarizing plate 15, a focusing lens 16, a pinhole 17 and a camera 18;
the scattered light beam and the reflected light beam of the sample 13 reflected by the semi-reflecting and semi-transparent film 8 pass through the diaphragm 14, the reflected light beam of the sample 13 is shielded and filtered, the scattered light carrying the internal defect information of the sample 13 passes through the second polarizing film 15, is focused to the center of the pinhole 17 by the focusing lens 16, and is finally collected by the camera 18 closely attached to the pinhole 17, and the interference light from the objective lens 12 except the focusing light spot is shielded and filtered by the pinhole 17, so that the confocal polarization detection of the sample 13 is realized;
s4: controlling the polarization direction of a polarizer I3 of the polarization annular illumination module to rotate, wherein the rotation angle is 360 DEG/N each time, and once rotating, a camera 18 of the confocal polarization detection module collects a two-dimensional scanning image of a sample 13 to obtain N images I of the sample to be detected under the illumination of annular beams in different linear polarization statesi(x, y), i is 1, 2, 3, …, N, where x is the row number of the image pixel of the sample to be tested, y is the column number of the image pixel, and (x, y) represents the pixel point position;
s5: performing m-order autocorrelation quantity calculation on each pixel point at the same position of the N to-be-detected sample images obtained in the step S4 to obtain a super-resolution image C with improved resolutionmThe calculation formula is as follows:
wherein (x, y) represents the pixel point position, IiThe method comprises the steps of representing images of a sample to be detected obtained under illumination of annular beams in different linear polarization states, wherein N is the number of images obtained by one 3-time 360-degree circumferential rotation of a polaroid, m represents a calculation order, and m is a positive integer not greater than 4.
S6: for super-resolution image C obtained in S5mPerforming iterative deconvolution operation, and then taking
Eliminating nonlinear effect to the power to obtain a measurement diagram with resolution increased by m timesImage, finish the super resolution; the calculation formula of the iterative deconvolution operation is as follows:
wherein h is a system point spread function, y is an image after deconvolution operation, and y is the first iteration1＝CmI is 1, 2, 3, …, N, FFT and iFFT are fast fourier transform and fast inverse fourier transform, respectively, j is the number of iterations, and the maximum value of j is 100;
s7: and moving the sample 13 in the vertical direction, performing transverse two-dimensional scanning on different axial positions of the sample 13, repeating S4-S6, obtaining measurement images of different axial positions, and realizing three-dimensional super-resolution microscopic measurement on the sample 13.
Has the advantages that:
1) the linear polarized light beam is shaped into a linear polarized annular light beam by using the combination of the conical lens and the plane reflecting mirror, the inner and outer diameters of the linear polarized annular light beam can be adjusted, the complementary aperture of the diaphragm is shielded and detected, the reflected signal of the surface of the sample and the sub-surface scattering signal are effectively separated, and the sub-surface defect detection of the high-performance optical element and the micro-electro-mechanical element is realized.
2) The asymmetry of the sample structure is utilized to excite single wave vector illumination light fields in different directions to generate polar scattering and autocorrelation cumulant difference of adjacent observation points, m times of transverse resolution improvement can be obtained according to different orders m, and the nanoscale defect measurement of the sub-surface of the sample can be realized.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (9)
1. A dark field confocal microscopy measuring device based on polarization autocorrelation is characterized by comprising: the device comprises a polarized annular light illumination module, a polarized annular light scanning module and a confocal polarization detection module;
the polarized annular light illumination module sequentially comprises the following components in the light beam transmission direction: the device comprises a laser (1), a beam expander (2), a polarizer I (3), a polarization splitting film (4), a quarter-wave plate (5), a cone lens (6), a plane reflector (7) and a semi-reflecting and semi-transmitting film (8); after the light beam transmits through the polarization splitting film (4), the quarter-wave plate (5) and the conical lens (6), the light beam is reflected by the plane reflector (7) to generate a reflected light beam; the reflected light beam is shaped into an annular light beam after passing through the conical lens (6) again, and the polarization direction changes by 90 degrees after passing through the quarter-wave plate (5) again to obtain a linear polarization annular light beam which is reflected by the polarization splitting film (4); the linear polarization annular light beam transmits the semi-reflecting and semi-transmitting film (8) and enters the polarization annular light scanning module;
the polarized annular light scanning module sequentially comprises the following components in the light beam transmission direction: the linear polarization annular light beam forms a focusing light spot on the surface of the sample (13), the reflected light and the scattered light of the sample (13) return to the two-dimensional scanning galvanometer (9) in a primary path, and the light beam reflected by the two-dimensional scanning galvanometer (9) enters the confocal polarization detection module after being reflected by the semi-reflecting and semi-transparent film (8);
the confocal analyzing and detecting module sequentially comprises the following components according to the light beam propagation direction: a diaphragm (14), a second polarizing plate (15), a focusing lens (16), a pinhole (17) and a camera (18); the diaphragm receives the light beam reflected by the semi-reflecting and semi-transmitting film (8).
2. The dark-field confocal microscopy measurement device based on polarization autocorrelation is characterized in that the polarization direction of the polarizer I (3) is subjected to 360-degree azimuth angle rotation control, the angle of each rotation is 360 degrees/N, and the linear polarization annular beam in different linear polarization states is used for illuminating the sample (13) by adjusting the polarization direction of the polarizer I (3); the polarization direction of the second polarizer (15) is matched with the polarization direction of the first polarizer (3).
3. The polarization autocorrelation based dark-field confocal microscopy apparatus as claimed in claim 1 characterized in that the combination of the axicon lens (6) and the plane mirror (7) shapes the beam into an annular beam with adjustable inner and outer diameters; the beam expander (2) is placed at the front end of the light path of the conical lens (6) and used for adjusting the inner diameter of the annular light beam, and the larger the diameter of the output light spot of the beam expander (2) is, the larger the thickness of the annular light beam is, and the smaller the inner diameter is; the outer diameter of the annular light beam is adjusted through the relative distance between the conical lens (6) and the plane mirror (7), the farther the relative distance is, the larger the outer diameter is, and the smaller the outer diameter is otherwise; the outer diameter of the annular beam is matched with the entrance pupil of the objective lens (12).
4. The polarization autocorrelation based dark-field confocal microscopy apparatus according to claim 1, characterized in that the scanning lens (10) working surface is placed at the front focal plane of the tube lens (11).
5. The polarization autocorrelation based dark field confocal microscopy measurement device according to claim 1 characterized in that the aperture of the diaphragm (14) is the same as the inner diameter of the ring beam; the diaphragm (14) completely blocks the reflected light beam from the sample (13) and only allows scattered light carrying information about the sample (13) to enter the confocal analytical detection module.
6. The dark-field confocal microscopy method based on polarization autocorrelation according to any one of claims 1 to 5, characterized by comprising the following specific steps:
step 1: the method comprises the steps that parallel laser beams are shaped into linear polarized annular beams by a polarized annular illumination module and transmitted to a polarized annular light scanning module to conduct polarized annular illumination on a sample (13), and a focusing light spot is formed on the sample (13);
step 2: the polarized annular light scanning module performs two-dimensional scanning on the sample (13) by using the focusing light spot to generate scattered light and reflected light carrying information of the sample (13);
and step 3: a confocal polarization detection module collects the scattered light from the sample (13) to realize confocal polarization detection of the sample (13);
and 4, step 4: controlling the polarization direction of a polarizing film I (3) of the polarization annular illumination module to rotate, wherein the rotation angle is 360 DEG/N, and once every rotation, a camera (18) of the confocal polarization detection module collects a two-dimensional scanning image of the sample (13) to obtain N images I of the sample to be detected under the illumination of the linear polarization annular light beami(x, y), i is 1, 2, 3, …, N, where x is the row number of the image pixel of the sample to be tested, y is the column number of the image pixel, and (x, y) represents the pixel point position;
and 5: performing m-order autocorrelation quantity calculation on each pixel point at the same position of the N to-be-detected sample images obtained in the step 4 to obtain a super-resolution image with improved resolution, wherein the calculation formula is as follows:
wherein (x, y) represents the pixel point position, IiRepresenting the images of the sample to be detected acquired under the illumination of the annular beams in different linear polarization states, wherein N is the number of the images acquired by one (3) 360-degree circumferential rotation of the polaroid, m represents the calculation order, and m is a positive integer not greater than 4.
Step 6: for the super-resolution image C obtained in the step 5mPerforming iterative deconvolution operation, and then taking
Eliminating the nonlinear effect by the power, obtaining a measurement image with resolution improved by m times, and completing super resolution; the calculation formula of the iterative deconvolution operation is as follows:
wherein h is a system point spread function, y is an image after deconvolution operation, and y is the first iteration1＝CmI is 1, 2, 3, …, N, FFT and iFFT are fast fourier transform and fast inverse fourier transform, respectively, j is the number of iterations, and j has a maximum value of 100.
And 7: and moving the sample (13) in the vertical direction, performing transverse two-dimensional scanning on different axial positions of the sample (13), repeating the step 4 to the step 6, obtaining the measurement images of different axial positions, and realizing the three-dimensional super-resolution microscopic measurement on the sample (13).
7. The dark-field confocal microscopy method based on polarization autocorrelation as claimed in claim 6, wherein the polarized annular light illumination module comprises in sequence according to the light propagation direction: the device comprises a laser (1), a beam expander (2), a polarizer I (3), a polarization splitting film (4), a quarter-wave plate (5), a cone lens (6), a plane reflector (7) and a semi-reflecting and semi-transmitting film (8); the polarized annular light scanning module sequentially comprises the following components in the light propagation direction: a two-dimensional scanning galvanometer (9), a scanning lens (10), a tube lens (11), an objective lens (12) and the sample (13);
in the step 1, the beam diameter of the parallel laser beam emitted by the laser (1) is enlarged through the beam expander (2), the parallel laser beam is changed into a linearly polarized light beam through the polarizer I (3), the linearly polarized light beam passes through the polarization splitting film (4), the quarter wave plate (5) and the cone lens (6) in sequence and is reflected and transmitted back by the plane reflector (7), the reflected linearly polarized light beam passes through the cone lens (6) again and is shaped into a linearly polarized annular beam, the polarization direction of the linearly polarized annular beam is changed by 90 degrees after passing through the quarter wave plate (5) again and is reflected to the semi-reflecting and semi-transmitting film (8) by the polarization splitting film (4), the linearly polarized annular beam transmits the semi-reflecting and semi-transmitting film I (8), is reflected by the two-dimensional scanning vibration mirror (9) and is focused to the front focal plane of the tube mirror (11) through the scanning lens (10), and then parallel linear polarization annular light beams are generated by the tube lens (11) to enter the linear polarization objective lens (12), and a focusing light spot is formed on the sample (13), so that the linear polarization annular light beams of the sample (13) are illuminated.
8. The dark-field confocal microscopy method based on polarization autocorrelation as claimed in claim 7, characterized in that in the step 2, the two-dimensional scanning galvanometer (9) is controlled to deflect so that the focused light spot performs two-dimensional scanning on the sample (13), and a scattered light beam and a reflected light beam of the sample (13) sequentially pass through the objective lens (12), the tube lens (11), the scanning lens (10) and the two-dimensional scanning galvanometer (9) and are reflected to the confocal analyzing and detecting module by the semi-reflecting and semi-transparent film (8) so as to realize the linear polarization annular light beam scanning on the sample (13).
9. The dark field confocal microscopy method based on polarization autocorrelation as claimed in claim 8, wherein the confocal analyzing detection module comprises in sequence according to the light propagation direction: a diaphragm (14), a second polarizing plate (15), a focusing lens (16), a pinhole (17) and the camera (18);
the scattered light beam and the reflected light beam of the sample (13) reflected by the semi-reflecting and semi-transparent film (8) in the step 3 pass through the diaphragm (14), the reflected light beam of the sample (13) is shielded and filtered, the scattered light carrying the internal defect information of the sample (13) passes through the second polaroid (15), is focused to the center of the pinhole (17) by the focusing lens (16) and is finally collected by the camera (18) arranged close to the pinhole (17), and the interference light out of the focused light spot from the objective lens (12) is shielded and filtered by the pinhole (17), so that confocal polarization detection of the sample (13) is realized.
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