CN113984350A - Lens refractive index testing system - Google Patents

Abstract

The invention provides a lens refractive index testing system. The system includes a he-ne laser, a fiber coupler, a plurality of lenses and lens sets, first and second beam splitters, first and second reflectors and first and second motorized baffles, and a first shack-hartmann wavefront sensor (SH sensor) and an interferogram acquisition sensor, wherein the first beam splitter divides the light into two paths of light which respectively enter the first reflector and the second reflector, and a first electric baffle is arranged between the first reflector and the first beam splitter, a second electric baffle is arranged between the second reflector and the first beam splitter, the sensor is controlled to respectively obtain images of the two paths of light rays by controlling the first electric baffle and the second electric baffle, so as to obtain a reference image and a tested sample image in a test system, meet the analysis requirements of the system, reduce mechanical errors and reduce the overall space size of the system through light ray turning.

Description

Lens refractive index testing system

Technical Field

The invention belongs to a lens refractive index testing system, and particularly relates to a refractive index measuring system for an aspheric lens, a free-form surface element and a special optical glass element.

Background

Refractive index measurement refers to the ratio of the speed of light in air to the speed of light in the material. The higher the refractive index of the material, the greater the ability to refract incident light. For refractive index measurement of glass lenses, conventional wavefront sensors (e.g., shack-hartmann wavefront sensors) are typically used in the prior art to measure refractive index.

As shown in fig. 1, the prior art measurement system includes a he — ne laser 101, a polarizer 102, an isolator 103, a lens 104, lens groups 106, 107, and a sensor 108. The sensor 108 is a Shack-Hartmann wavefront sensor (SH sensor), and laser is subjected to filtering, depolarization and beam expansion 110, then is incident on a sample 105 to be measured fixed in matching fluid, is modulated by an internal refractive index field (lens groups 106 and 107) and then is focused on a receiving surface of the SH sensor. The data received by the SH sensor is processed to reconstruct the wavefront information modulated by the measured sample 105, and the reference wavefront is subtracted to obtain the wavefront information modulated by the measured sample 105.

However, only a sample in which the incident surface and the exit surface are flat and parallel to each other can be measured in this manner in the prior art, and the refractive index field of the sample is constant in the light propagation direction and varies in a section perpendicular to the light propagation direction.

The development of the prior art shows that with the change of the lens shape and the change of the refractive index field, a test system with the accuracy and adaptability of the refractive index test for the aspheric lens, the free-form surface element and the special optical glass element is needed.

Disclosure of Invention

The invention aims to provide a lens refractive index testing system.

The lens refractive index test system of the invention comprises: the device comprises a laser light source adjusting component, an interference sampling light path component, an imaging component and an image analysis module; the laser light source adjusting part comprises a helium-neon laser and an external optical fiber coupler of the helium-neon laser; the helium-neon laser emits stable laser light, and the laser light enters the long-focus lens through the optical fiber coupler so as to realize beam expansion of the laser light; the expanded laser enters an interference sampling optical path component; the interference sampling optical path component comprises a first beam splitter, a second beam splitter, a first reflecting mirror, a second reflecting mirror, a first lens and a second lens, wherein the first lens and the second lens are arranged in front of the second beam splitter, the first beam splitter divides the expanded laser into two paths of parallel light, one path of parallel light is used as reference light, and the other path of parallel light is used as object light; arranging a first reflector at the tail end of the reference light to turn the vertical reference light into horizontal; arranging a second reflector at the tail end of the object light to turn the horizontal object light into vertical object light; or a first reflector is arranged at the tail end of the reference light to turn the horizontal reference light into vertical light; arranging a second reflector at the tail end of the object light to turn the vertical object light into horizontal; placing a first motorized baffle between the first beam splitter and the first mirror; placing a second motorized baffle between the first beam splitter and the second mirror; one or two beams of the reference light and the object light can be obtained by controlling the first electric baffle and the second electric baffle; and under the condition that the first or second electric baffle blocks the reference light or the object light, obtaining an image; or under the condition that the first or second electric baffle plate does not block the reference light or the object light, obtaining a reference image and a detected sample image of two paths of light; the light passing through the first reflector and the second reflector are perpendicular to each other, and the second beam splitter is respectively carried out through a first head neck and a second head neck; the light penetrating through the second beam splitter enters an imaging component; the imaging part includes first and second lens groups, wherein each lens group is composed of a long focal length lens and a small focal length lens; each beam of light passing through the second beam splitter is converged through a long-focus lens in the lens group and then expanded through the small-focus lens; an SH sensor and an interference pattern acquisition sensor are respectively arranged behind the first lens group and the second lens group; and further connected with an image analysis module;

the image analysis module comprises the following components: the refractive index deviation module is used for measuring the refractive index of the lens sample through the SH sensor, and calculating to obtain the refractive index deviation in the sample through the difference before and after the measured sample is placed; the refractive index projection module is used for collecting an interference image generated by the reference light and the object light through a CCD (charge coupled device); acquiring projections of the refractive index field of the lens sample under different angles; the phase information recovery module is used for extracting phase information of the main value interval and recovering the phase information to be a full value; the three-dimensional image generation module is used for respectively extracting phase information of each layer from the projection; the refractive index of each layer is obtained, and the reconstructed images are sequentially superimposed to form a three-dimensional image.

In still another aspect of the present invention, the refractive index deviation module further includes: the plane modulation module is used for receiving the plane modulated by the sample refractive index field by using the wavefront sensor; the reconstruction module is used for reconstructing the wavefront information of the reference light and obtaining the distribution of the refractive index field according to the thickness of the sample; and sequentially reconstructing each layer of image layer by layer.

In still another aspect of the present invention, a polarizing plate is disposed behind the fiber coupler, and the polarizing plate is adjusted to have the same polarization direction as that of the he-ne laser; a point light source was obtained by placing an isolator and an aperture stop after the polarizer.

In yet another aspect of the present invention, the image analysis module further comprises: the image reading module is used for reading the interference image to be processed; the noise reduction module is used for carrying out noise reduction processing on the interference image, identifying points in the noise-reduced image, dividing all the points in a coordinate graph by using a method of taking the most middle point of the dot matrix as an original coordinate and subtracting the coordinates of the middle point from other points to obtain the coordinate distribution of the points; the image point identification module is used for importing an image which is not placed with a sample as a reference image, identifying points in the reference image by the point identification method in the point identification step, and obtaining a coordinate function of the points; the wavefront reconstruction module is used for subtracting the coordinate function of the reference image from the coordinate function of the sample image to obtain the gravity center offset of the actual light spot, and deducing a wavefront slope according to the offset so as to reconstruct the wavefront; and the refractive index average value module is used for obtaining the refractive index average value along the optical path direction.

In another aspect of the invention, the refractive index averaging module subtracts the reference wavefront information L (x, y) from the wavefront information L (x, y) of the placed sample_rThe modulated wavefront information Δ L (x, y) is obtained, and the refractive index is obtained by using the optical path length calculation method Δ L (x, y) as Δ n (x, y) t

Wherein, delta l (x, y) is the optical path difference before and after adding the sample, namely wave surface information, delta n (x, y) is the refractive index difference between the sample and the environment (refractive index matching fluid), and t is the thickness of the lens sample.

In another aspect of the invention, in the phase information recovery module, phase information is extracted from the interferogram by Windowed Fast Fourier Transform (WFFT), then the image is filtered and translated to reduce noise and eliminate background, and then inverse fourier transform is performed to realize phase extraction; in the reconstruction module, a three-dimensional refractive index field in the measured sample is reconstructed by adopting a filtering back projection algorithm according to the obtained more continuous phase diagram; the image analysis module further comprises: and the phase unwrapping module is used for unwrapping the phase of the phase diagram recovered by the interferogram by adopting a least square method without weight and a discrete cosine method (DCT) according to multi-party algorithm comparison, and converting the obtained discontinuous phase diagram into a more continuous phase diagram.

The glass lens refractive index testing system with the structure can overcome the limitation of a wavefront sensor refractive index testing system in the prior art, improves the testing accuracy, and can be widely applied to aspheric lenses, free-form surface elements and special optical glass elements. Mechanical errors are reduced, and the overall spatial size of the system is reduced through ray bending.

Drawings

In order to more clearly illustrate the technical solution in the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly described below. It is obvious that the drawings in the following description are only examples of the invention, and that for a person skilled in the art, other drawings can be derived from them without making an inventive step.

Fig. 1 is a schematic structural diagram of a refractive index testing system for a glass lens in the prior art.

FIG. 2 is a schematic structural diagram of a refractive index testing system for glass lenses according to the present invention.

Fig. 3 is a structural diagram of an embodiment of a laser light source adjustment member of the present invention.

Fig. 4 is a partial structural view of an image analysis module of the present invention.

Fig. 5(1) is a structural diagram of a three-dimensional image reconstruction module in the image analysis module according to the present invention.

Fig. 5(2) is a structural diagram of the image analysis module according to the present invention.

Fig. 6 is a structural diagram of an image analysis module in the glass lens refractive index test system according to the present invention.

FIG. 7 is a computer product diagram of a portable or fixed storage unit of the image analysis module of the present invention.

Detailed Description

Specific embodiments of the present invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. These embodiments are provided only for the purpose of exhaustive and comprehensive description of the invention so that those skilled in the art can fully describe the scope of the invention. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention.

FIG. 2 is a schematic structural diagram of a refractive index testing system for glass lenses according to the present invention. The device comprises a laser light source adjusting component, an interference sampling light path component, an imaging component and an image analysis module. The laser light source adjusting component of the test system comprises a helium-neon laser 201 as a light source, and emits stable laser; the laser is selected as the light source by utilizing the characteristics of monochromaticity, good directivity, coherence and the like of the laser. However, the radius of the laser is too small, so that the light source is ensured to irradiate the whole sample, the detection precision is improved, and the subsequent beam expanding requirements on the laser according to different samples are facilitated, and the laser beam needs to be subjected to lens beam expanding and property adjustment. According to the floor area and the light source property, the optical fiber light source is selected as a light source, and the external optical fiber coupler 202 is used as a light source generating port. Optionally, a polarizer (not shown in fig. 2) is placed behind the beam, adjusted to the same polarization as the laser, to reduce stray light in other directions; optionally, a separator (not shown in fig. 2) is placed behind the polarizer to prevent the reflected light t from being affected by the light path; an aperture stop (not shown in fig. 2) is placed behind to ensure that a point source of light is obtained; a lens 206 with long focal length is arranged behind the point light source to achieve the purpose of beam expanding, and the lens can be replaced according to the size of a sample at the later stage and can be flexibly called.

The lenses used in the interference sampling optical path component and the imaging component in the invention are spherical or aspherical lenses, and the lenses in the same system are matched with each other in optical property. In the interference sampling optical path component of the test system, the lens 206 is used for transforming the laser beam to generate parallel light; a first beam splitter 203 is arranged in front of the lens 206 and is used for splitting the parallel light into two paths of parallel light, wherein one path of parallel light is used as reference light, and the other path of parallel light is used as object light; the reference light and the object light are almost perpendicular to each other; the reference light is in the vertical direction, and the tail end of the reference light is provided with a first reflector 208 for turning the light path to be horizontal; the object light is horizontal and a second mirror 204 is placed at the end. A first motorized shutter 207 is disposed between the first beam splitter 203 and the first mirror 208 in a direction perpendicular to the reference light; and a second electrically powered shutter 205 is placed between said first beam splitter 203 and said second mirror 204. The first and second electrically operated shutters 207 and 205 may be electrically operated shutters, and one of the reference light and the object light may be blocked by opening or closing the shutters with a button. That is to say, in the testing system of the present invention, one image can be obtained under the condition that the electric baffle blocks the reference light or the object light, or images of two paths of light can be simultaneously obtained under the condition that the electric baffle does not block the reference light or the object light, that is, a reference image and a tested sample image are obtained; images of the two paths of light can be compared to see whether the final measurement mode is accurate or not; since the reference images can be acquired simultaneously in the same system, mechanical errors due to device differences or device changes to acquire new images can be eliminated. The first and second electric baffles 207 and 205 can realize independent switching of the reference light and the object light, when the reference light and the object light are independently switched on, the first SH sensor 212 is used for comparing and judging whether the light intensity distribution of the two paths of light is consistent, and if the light intensity distribution of the two paths of light is greatly deviated, the light path is adjusted to realize calibration of the reference light and the object light without a sample. The specific working principle will be set forth in detail below.

Light rays passing through the first mirror 208 and the second mirror 204 are approximately perpendicular to each other, pass through lenses 216 and 209, respectively, and enter a second beam splitter 215; since the first reflector 208 and the second reflector 204 respectively bend the two light beams emitted from the first beam splitter 203, the two light beams emitted from the first beam splitter 203 and the two light beams entering the second beam splitter 215 through bending form an approximately "square" optical path; the sample 220 to be measured can be placed on any side length of the square; in one embodiment, only object light passes through the apparatus under the control of the first and second electric baffles 207 and 205, the sample 220 to be measured is placed between the second reflecting mirror 204 and the second beam splitter 215, the difference between the sample 220 to be measured before and after the sample is placed is obtained, the refractive index deviation in the sample is further obtained through calculation, and finally the refractive index deviation on the cross section perpendicular to the light propagation direction is obtained, so that the apparatus can flexibly switch the working mode. In the imaging component of the testing system of the present invention, before the light enters the second beam splitter 215, the two beams of light reflected by the first reflector 208 and the second reflector 204 are converged by the lenses 216 and 209, respectively; two beams of interference light are respectively emitted in the outlet direction of the second beam splitter 215, after each beam of interference light, a long-focus lens is placed to converge the light, then a small-focus lens is placed to expand the beam, and the light is matched with the window of the detector, so that the camera can perfectly shoot pictures. The first lens group 213 and the second lens group 210 are composed of a long focal length lens and a small focal length lens. A first SH sensor 212 and an interference pattern capturing sensor 211 are disposed behind the first lens group 213 and the second lens group 210, respectively. In one embodiment, the first SH sensor 212 may also be a CCD camera. The first SH sensor 212 and the interference pattern capturing sensor 211 or the CCD camera and the interference pattern capturing sensor 211 are connected to an image analyzing module 214.

Fig. 3 is a structural diagram of an embodiment of a laser light source adjustment member of the present invention. A polarizing plate 301 is arranged behind the optical fiber coupler 202 and adjusted to have the same polarization direction as the laser so as to reduce stray light in other directions; an isolator 302 is placed behind the polarizer to prevent reflected light t from passing through the optical path; an aperture diaphragm 303 is arranged behind the light source to ensure that a point light source is obtained; a lens 206 with long focal length is arranged behind the point light source to achieve the purpose of beam expanding, and the lens can be replaced according to the size of a sample at the later stage and can be flexibly called.

Fig. 4 is a partial structural view of an image analysis module of the present invention. Image parameters, such as spot maps, beam views, line views, zernike coefficients, etc., are obtained by the SH sensor. An image reading module 401 for reading an interference image to be processed; a denoising module 402, which performs denoising processing on the image by using an imtophat function and an imbothatat function in matlab, is configured to perform denoising processing on the interference image, identify a point in the denoised image, and divide all points in a coordinate graph by using a method in which a point at the middle of a dot matrix is an original coordinate and coordinates of middle points are subtracted from other points to obtain coordinate distribution of the points; an image point identification module 403 for importing an image before the sample is placed as a reference image and utilizing the components of the identification points in the noise reduction moduleIdentifying points in the reference image and obtaining a coordinate function of the points; the wavefront reconstruction module 404 is configured to subtract the coordinate function of the reference image from the coordinate function of the sample image to obtain a center-of-gravity offset of the actual light spot, and derive a wavefront slope according to the offset to reconstruct a wavefront; and a refractive index average module 405 for obtaining an average of the refractive index along the optical path. Specifically, the reference wavefront information L is subtracted from L (x, y)_rThe modulated wavefront information Δ L (x, y) is obtained, and the refractive index is obtained by using the optical path length calculation method Δ L (x, y) as Δ n (x, y) t

Wherein, Δ l (x, y) is the optical path difference before and after adding the sample, namely wave surface information, Δ n (x, y) is the refractive index difference between the sample and the environment (refractive index matching fluid), and t is the thickness of the lens or the thickness of the sample.

Fig. 5(1) is a structural diagram of a three-dimensional image reconstruction module in the image analysis module according to the present invention. Interference images are collected through a Charge Coupled Device (CCD) camera, a stepping motor is used for controlling the sample to rotate 360 degrees, and interference images of the sample to be detected in all directions are obtained. The whole system adopts a cage structure, so that the collimation of a light path is facilitated. The rotation of the sample is still performed in the system of the present invention by means of stepper motor control. In one embodiment, the motor is controlled by a drive, riding on an overhead frame of the cage structure, extending 21mm from the shaft. The clamp plays a role of opening and closing, on one hand, a groove with the length of 20mm is coaxially matched with an extending shaft of the motor, on the other hand, springs are arranged on two sides below the clamp to fix a sample, and the same sample is placed in the sample cell together. When the motor works and rotates, the clamp is driven to drive the sample to move in the sample pool. The angular step of the stepper motor is 1.8 deg., and the RS485 controller can perform a total of 15 types of sub-division control on the stepper motor, 2, 4, 8, 16, 32, 64, 128, 5, 10, 20, 25, 40, 50, 100, 125, so that, theoretically, the actual minimum angular step of the stepper motor can reach 1.8 deg./128.

The method comprises the steps of collecting interference images generated by an optical path by a CCD camera to obtain 'projections' of a refractive index field of a measured object under different angles, extracting phase information from the interference images by a window Fourier transform method, recovering the phase information in a main value interval to be a full value by a weighted least square method and a discrete cosine transform solving algorithm, extracting phase information of each layer from wave front phase 'projections', performing one-dimensional Fourier transform on projection data of each layer by a filter back-projection algorithm, performing inverse transform of two-dimensional discrete Fourier transform on the processed data to obtain the refractive index of each layer, reconstructing images of each layer by layer along the height direction, and overlapping the images in sequence to form a three-dimensional image.

The image analysis module of the present invention is part of implementing the reconstructed refractive index distribution information in the image analysis module by: in step 501, acquiring an interference image, wherein the interference image comprises a wavefront phase, and acquiring projections of a refractive index field of a measured object under different angles; at step 502, interferogram spectral analysis is performed and phase principal values are calculated: extracting phase information from the interference pattern through Windowed Fast Fourier Transform (WFFT), filtering and translating the image to realize noise reduction and background elimination, and then performing inverse Fourier transform to realize phase extraction; the phase main value can jump from-pi to pi, so that the obtained phase diagram is not continuous; in step 503, phase unwrapping is performed: according to the comparison of a multi-square algorithm, performing phase unwrapping by using a least square method without weight and a discrete cosine method (DCT) to obtain a relatively continuous phase diagram; at step 504, a Computed Tomography (CT) reconstruction is performed; respectively extracting phase information of each layer from the wavefront phase projection as input data for reconstructing the refractive index field of the layer; and reconstructing a three-dimensional refractive index field in the measured sample by adopting a filtering back projection algorithm according to the obtained more continuous phase diagram. Fig. 5(2) is a structural diagram of the image analysis module according to the present invention. The image analysis module comprises the following components: the refractive index deviation module is used for measuring the refractive index of the lens sample through the SH sensor, and calculating to obtain the refractive index deviation in the sample through the difference before and after the measured sample is placed; the refractive index projection module is used for collecting an interference image generated by the reference light and the object light through a CCD camera; acquiring projections of the refractive index field of the lens sample under different angles; the phase information recovery module is used for extracting phase information of the main value interval and recovering the phase information to be a full value; the three-dimensional image generation module is used for respectively extracting phase information of each layer from the projection; the refractive index of each layer is obtained, and the reconstructed images are sequentially superimposed to form a three-dimensional image. In the phase information recovery module, extracting phase information from an interference pattern through Windowed Fast Fourier Transform (WFFT), filtering and translating an image to realize noise reduction and background elimination, and then performing inverse Fourier transform to realize phase extraction; and in the reconstruction module, reconstructing a three-dimensional refractive index field in the measured sample by adopting a filtering back projection algorithm according to the obtained more continuous phase diagram.

By adopting the refractive index testing system, on one hand, because the system has two optical paths with the same mode, self calibration can be realized by reasonably utilizing the two optical paths, and the accuracy of an instrument is convenient to measure; on the other hand, the introduction of the system structure greatly increases the application range of the whole instrument, combines another refractive index measurement method, namely measuring the refractive index of a sample by using a Mach-Zehnder interferometer, can realize two refractive index measurement methods of one set of system through integration, and mutually calibrates the two methods to improve the measurement precision. The method comprises the steps of utilizing the principle of a refractive index measuring method of a Harck-Chartmann wavefront sensor, carrying out surface type detection on an aspheric lens according to a method for expanding a detection module by a system, respectively utilizing a Zernike coefficient and a point diagram obtained by the sensor to reconstruct the wavefront of a sample, and realizing model establishment of the refractive index distribution condition according to the wavefront diagram and the relation between the optical path difference and the refractive index; according to the appearance characteristics of the non-uniform element, the principle of measuring the refractive index by using a Mach-Zehnder interferometer is utilized, the light path interference image of the non-uniform element is obtained step by a CCD (charge coupled device) camera, and the refractive index is measured by performing phase recovery, phase unwrapping and phase reconstruction on the image; a detailed analysis method for measuring the refractive index distribution according to the change of the spatial form of the optical element is provided, and the reconstruction of the spatial structure of the sample and the model establishment of the refractive index distribution condition can be realized no matter the Mach-Zehnder interferometer or the Hack-Chartmann wavefront sensor is used.

Fig. 6 is a structural diagram of an image analysis module in the glass lens refractive index test system according to the present invention. Such as a server 601 of the image analysis module. The server of the image analysis module comprises a processor 610, here a general purpose or application specific chip (ASIC/ASIC) or FPGA or NPU etc., and a computer program product or computer readable medium in the form of a memory 620. The memory 620 may be an electronic memory such as a flash memory, an EEPROM (electrically erasable programmable read only memory), an EPROM, a hard disk, or a ROM. The memory 620 has a storage space 630 for program code for performing any of the method steps of the above-described method. For example, the memory space 630 for the program code may comprise respective program codes 631 for respectively implementing the various steps in the above method. These program codes may be read or written into the processor 610. These computer program products comprise a program code carrier such as a hard disk, a Compact Disc (CD), a memory card or a floppy disk. Such a computer program product is typically a portable or fixed storage unit as described with reference to fig. 7. FIG. 7 is a computer product diagram of a portable or fixed storage unit of the image analysis module of the present invention. The storage unit may have a storage section, a storage space, and the like arranged similarly to the memory 620 in the server of fig. 6. The program code may be compressed, for example, in a suitable form. Typically, the storage unit comprises computer readable code 631', i.e. code that can be read by a processor, such as 610, for example, which when executed by a server causes the server to perform the steps of the method described above. The codes, when executed by the server, cause the server to perform the steps of the method described above.

Reference herein to "one embodiment," "an embodiment," or "one or more embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Moreover, it is noted that instances of the word "in one embodiment" are not necessarily all referring to the same embodiment.

The above description is only for the purpose of illustrating the present invention, and any person skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of the claims should be accorded the full scope of the claims. The invention has been explained above with reference to examples. However, other embodiments than the above described are equally possible within the scope of this disclosure. The different features and steps of the invention may be combined in other ways than those described. The scope of the invention is limited only by the appended claims. More generally, those of ordinary skill in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are exemplary and that actual parameters, dimensions, materials, and/or configurations will depend upon the particular application or applications for which the teachings of the present invention is/are used.

Claims (6)

1. A lens refractive index testing system comprising:

the device comprises a laser light source adjusting component, an interference sampling light path component, an imaging component and an image analysis module; the laser light source adjusting part comprises a helium-neon laser and an external optical fiber coupler of the helium-neon laser; the helium-neon laser emits stable laser light, and the laser light enters the long-focus lens through the optical fiber coupler so as to realize beam expansion of the laser light; the expanded laser enters an interference sampling optical path component;

the interference sampling optical path component comprises a first beam splitter, a second beam splitter, a first reflecting mirror, a second reflecting mirror, a first lens and a second lens, wherein the first lens and the second lens are arranged in front of the second beam splitter, the first beam splitter divides the expanded laser into two paths of parallel light, one path of parallel light is used as reference light, and the other path of parallel light is used as object light;

arranging a first reflector at the tail end of the reference light to turn the vertical reference light into horizontal; arranging a second reflector at the tail end of the object light to turn the horizontal object light into vertical object light; or a first reflector is arranged at the tail end of the reference light to turn the horizontal reference light into vertical light; arranging a second reflector at the tail end of the object light to turn the vertical object light into horizontal;

placing a first motorized baffle between the first beam splitter and the first mirror; placing a second motorized baffle between the first beam splitter and the second mirror; one or two beams of the reference light and the object light can be obtained by controlling the first electric baffle and the second electric baffle; and under the condition that the first or second electric baffle blocks the reference light or the object light, obtaining an image; or under the condition that the first or second electric baffle plate does not block the reference light or the object light, obtaining a reference image and a detected sample image of two paths of light; the light passing through the first reflector and the second reflector are perpendicular to each other, and the second beam splitter is respectively carried out through a first head neck and a second head neck; the light penetrating through the second beam splitter enters an imaging component;

the imaging part includes first and second lens groups, wherein each lens group is composed of a long focal length lens and a small focal length lens; each beam of light passing through the second beam splitter is converged through a long-focus lens in the lens group and then expanded through the small-focus lens; an SH sensor and an interference pattern acquisition sensor are respectively arranged behind the first lens group and the second lens group; and further connected with an image analysis module;

the image analysis module comprises the following components:

the refractive index deviation module is used for measuring the refractive index of the lens sample through the SH sensor, and calculating to obtain the refractive index deviation in the sample through the difference before and after the measured sample is placed;

the refractive index projection module is used for collecting an interference image generated by the reference light and the object light through a CCD camera; acquiring projections of the refractive index field of the lens sample under different angles;

the phase information recovery module is used for extracting phase information of the main value interval and recovering the phase information to be a full value;

the three-dimensional image generation module is used for respectively extracting phase information of each layer from the projection; the refractive index of each layer is obtained, and the reconstructed images are sequentially superimposed to form a three-dimensional image.

2. The refractive index testing system of claim 1, wherein the refractive index deviation module further comprises:

the plane modulation module is used for receiving the plane modulated by the sample refractive index field by using the wavefront sensor;

the reconstruction module is used for reconstructing the wavefront information of the reference light and obtaining the distribution of the refractive index field according to the thickness of the sample; and sequentially reconstructing each layer of image layer by layer.

3. The refractive index testing system of claim 1, wherein:

a polaroid is arranged behind the optical fiber coupler, and is adjusted to have the same polarization direction as the helium-neon laser;

a point light source was obtained by placing an isolator and an aperture stop after the polarizer.

4. The refractive index testing system of claim 1, wherein the image analysis module further comprises:

the image reading module is used for reading the interference image to be processed;

the noise reduction module is used for carrying out noise reduction processing on the interference image, identifying points in the noise-reduced image, dividing all the points in a coordinate graph by using a method of taking the most middle point of the dot matrix as an original coordinate and subtracting the coordinates of the middle point from other points to obtain the coordinate distribution of the points;

the image point identification module is used for importing an image which is not placed with a sample as a reference image, identifying points in the reference image by the point identification method in the point identification step, and obtaining a coordinate function of the points;

the wavefront reconstruction module is used for subtracting the coordinate function of the reference image from the coordinate function of the sample image to obtain the gravity center offset of the actual light spot, and deducing a wavefront slope according to the offset so as to reconstruct the wavefront;

and the refractive index average value module is used for obtaining the refractive index average value along the optical path direction.

5. The refractive index testing system of claim 4, wherein

And a refractive index average module which subtracts the reference wavefront information Lr from the wavefront information L (x, y) of the placed sample to obtain modulated wavefront information delta L (x, y), and obtains the refractive index by using a calculation method delta L (x, y) as delta n (x, y) t of the optical path

Wherein, delta l (x, y) is the optical path difference before and after adding the sample, namely wave surface information, delta n (x, y) is the refractive index difference between the sample and the environment (refractive index matching fluid), and t is the thickness of the lens sample.

6. The refractive index testing system of claim 2, wherein

In the phase information recovery module, extracting phase information from an interference pattern through Windowed Fast Fourier Transform (WFFT), filtering and translating an image to realize noise reduction and background elimination, and then performing inverse Fourier transform to realize phase extraction; in the reconstruction module, a three-dimensional refractive index field in the measured sample is reconstructed by adopting a filtering back projection algorithm according to the obtained more continuous phase diagram;

the image analysis module further comprises: and the phase unwrapping module is used for unwrapping the phase of the phase diagram recovered by the interferogram by adopting a least square method without weight and a discrete cosine method (DCT) according to multi-party algorithm comparison, and converting the obtained discontinuous phase diagram into a more continuous phase diagram.

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