CN113899697A - Fringe image-based crystal refractive index measuring method and device and storage medium - Google Patents
Fringe image-based crystal refractive index measuring method and device and storage medium Download PDFInfo
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Abstract
The invention discloses a method, a device and a storage medium for measuring the refractive index of a crystal based on a fringe image, wherein the method comprises the steps of obtaining a reference interference image and a crystal interference image; performing gravity center point calculation on the reference interference image and the crystal interference image to obtain fringe variation; calculating the number of first average width pixel points of dark fringes and the number of second average width pixel points of bright fringes in a reference interference image so as to obtain the fringe width of the reference interference image; obtaining the refractive index according to the variation of the stripes, the width of the stripes, the thickness of the crystal and the wavelength of the source light beam; the refractive index can be directly measured without processing the crystal to change the shape of the crystal, the measurement precision is high, the measurement speed is high, and the efficiency and the accuracy of the measurement of the refractive index of the crystal are greatly improved.
Description
Technical Field
The invention relates to the field of refractive index measurement, in particular to a method and a device for measuring the refractive index of a crystal based on a fringe image and a storage medium.
Background
The refractive index is an important parameter of the crystal and can reflect the optical property and the physical property of the crystal. The prior representative methods for measuring the refractive index mainly comprise a precision goniometer method, a microscopic observation method, an oil immersion method, a total reflection law measurement method and the like. The precision goniometer method has high measurement precision, but has the problems of complex operation and time consumption, the crystal needs to be specially processed into the prism, the processing precision requirement is high, the difficulty is high, the shape of the raw material is damaged, and the recycling of the sample is limited. The microscopic observation method mainly uses a polarization microscope to observe crystals in the sheet mainly for measuring the refractive index of the film, and has relatively high requirements for the measurement process and is relatively time-consuming. The solution used in the oil immersion method is complicated to prepare, and the transparency of the crystal is reduced and the measurement accuracy is deteriorated when the solution is immersed in oil. The total reflection law measurement method is characterized in that when light enters an optically thinner medium from an optically denser medium, an incident angle when a refraction angle is equal to 90 degrees is called a total reflection critical angle, and the total reflection critical angle is calculated according to a physical relation between the critical angle and the refraction index, so that the requirement on a measurement environment is high.
Disclosure of Invention
The present invention is directed to solve at least one of the problems of the prior art, and provides a method and an apparatus for measuring a refractive index of a crystal based on a fringe image, and a storage medium.
The technical scheme adopted by the invention for solving the problems is as follows:
in a first aspect of the present invention, a method for measuring a refractive index of a crystal based on a fringe image includes:
acquiring a reference interference image and a crystal interference image, wherein the reference interference image is generated by a source light beam passing through an interferometer without a crystal placed on the interferometer, and the crystal interference image is generated by the source light beam passing through the interferometer with the crystal placed on the interferometer;
performing gravity center point calculation on the reference interference image and the crystal interference image to respectively obtain a first gravity center point coordinate of the reference interference image and a second gravity center point coordinate of the crystal interference image, and performing difference calculation on the first gravity center point coordinate and the second gravity center point coordinate to obtain a fringe variation;
calculating a first average width pixel point number of a dark fringe and a second average width pixel point number of a bright fringe in the reference interference image, and obtaining the fringe width of the reference interference image according to the first average width pixel point number and the second average width pixel point number;
and obtaining the refractive index of the crystal according to the fringe variation, the fringe width, the thickness of the crystal and the wavelength of the source light beam.
According to the first aspect of the present invention, before the center of gravity calculation of the reference interference image and the crystal interference image, the method further includes:
and carrying out image binarization processing on the reference interference image and the crystal interference image.
According to the first aspect of the present invention, the center of gravity point calculation includes processing the image to obtain a gray value of a pixel point and calculating the center of gravity point coordinates of the image using the gray value of the pixel point as the quality of the pixel point.
According to the first aspect of the present invention, the stripe change amount is represented by the following equation:
wherein s (r) is the variation of the stripes, m is the number of pixels of the image, and yijThe ordinate, g, of a pixel point representing the ith row and the jth column of the reference interference imageijGray value y0 representing a pixel point of the ith row and the jth column of the reference interference imageijOrdinate, g0, of a pixel point representing the ith row and the jth column of the crystal interference imageijAnd expressing the gray value of the pixel point of the ith row and the jth column of the crystal interference image.
According to the first aspect of the present invention, the calculating the number of first average width pixels of dark fringes and the number of second average width pixels of bright fringes in the reference interference image includes:
calculating the total width pixel points of all the dark stripes and the number of the dark stripes, and dividing the total width pixel points of all the dark stripes and the number of the dark stripes to obtain first average width pixel points;
and calculating the total width pixel points of all the bright stripes and the number of the bright stripes, and dividing the total width pixel points of all the bright stripes and the number of the bright stripes to obtain the second average width pixel points.
According to the first aspect of the present invention, the obtaining the fringe width of the reference interference image according to the number of the first average width pixel points and the number of the second average width pixel points includes:
carrying out average calculation on the first average width pixel point number and the second average width pixel point number to obtain the stripe width pixel number;
and multiplying the number of the fringe width pixels by the camera pixels to obtain the fringe width of the reference interference image.
According to the first aspect of the present invention, the refractive index of the crystal is represented by the following formula:
where n is the refractive index of the crystal, s (r) is the fringe variation, l is the fringe width of the reference interference image, λ is the wavelength of the source beam, and D is the thickness of the crystal.
In a second aspect of the present invention, a fringe image-based crystal refractive index measuring apparatus is applied to the crystal refractive index measuring method according to the first aspect of the present invention; the device comprises:
an interferometer;
the system comprises an interference image acquisition module, a crystal interference image acquisition module and a control module, wherein the interference image acquisition module is used for acquiring a reference interference image and a crystal interference image, the reference interference image is generated by a source light beam passing through the interferometer without a crystal placed, and the crystal interference image is generated by the source light beam passing through the interferometer with the crystal placed;
the gravity center point calculation module is used for performing gravity center point calculation on the reference interference image and the crystal interference image to respectively obtain a first gravity center point coordinate of the reference interference image and a second gravity center point coordinate of the crystal interference image, and calculating the difference of the first gravity center point coordinate and the second gravity center point coordinate to obtain a fringe variation;
the fringe width calculating module is used for calculating a first average width pixel point number of a dark fringe and a second average width pixel point number of a bright fringe in the reference interference image and obtaining the fringe width of the reference interference image according to the first average width pixel point number and the second average width pixel point number;
and the refractive index calculation module is used for obtaining the refractive index of the crystal according to the fringe variation, the fringe width, the thickness of the crystal and the wavelength of the source light beam.
In a third aspect of the present invention, a fringe image-based crystal refractive index measurement apparatus includes a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor implements the crystal refractive index measurement method according to the first aspect of the present invention when executing the computer program.
In a fourth aspect of the present invention, a storage medium stores executable instructions that when executed by a processor implement the crystal refractive index measurement method according to the first aspect of the present invention.
The scheme at least has the following beneficial effects: the refractive index can be directly measured without processing the crystal to change the shape of the crystal, the measurement precision is high, the measurement speed is high, and the efficiency and the accuracy of the measurement of the refractive index of the crystal are greatly improved.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
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The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a flow chart of a method for measuring the refractive index of a crystal based on fringe images according to an embodiment of the invention;
FIG. 2 is a diagram of a crystal refractive index measuring apparatus according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the structure of an interferometer and an interferometric image acquisition module;
FIG. 4 is a binarized image of a reference interference image;
fig. 5 is a binarized image of a crystal interference image.
Detailed Description
Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.
In the description of the present invention, it should be understood that the orientation or positional relationship referred to in the description of the orientation, such as the upper, lower, front, rear, left, right, etc., is based on the orientation or positional relationship shown in the drawings, and is only for convenience of description and simplification of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
In the description of the present invention, the meaning of a plurality of means is one or more, the meaning of a plurality of means is two or more, and larger, smaller, larger, etc. are understood as excluding the number, and larger, smaller, inner, etc. are understood as including the number. If the first and second are described for the purpose of distinguishing technical features, they are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.
In the description of the present invention, unless otherwise explicitly limited, terms such as arrangement, installation, connection and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above terms in the present invention in combination with the specific contents of the technical solutions.
Referring to fig. 1, an embodiment of a first aspect of the present invention provides a fringe image-based crystal refractive index measurement method.
The crystal refractive index measuring method comprises the following steps:
step S100, acquiring a reference interference image and a crystal interference image, wherein the reference interference image is generated by the source light beam passing through the interferometer 100 without the crystal placed, and the crystal interference image is generated by the source light beam passing through the interferometer 100 with the crystal placed.
In step S100, the interferometer 100 generates a dual beam by a partial amplitude method to achieve interference, and the interferometer 100 is specifically a mach-zehnder interferometer 100.
Referring to fig. 3, the interferometer 100 includes a source beam generator 10, a first lens 21, a second lens 22, a first beam splitter 31, a second beam splitter 32, an attenuation sheet 40, and a crystal placing stage 50; the source light beam generated by the source light beam generator 10 passes through the first lens 21, the second lens 22 and the first beam splitter 31 in sequence, one of the light beams split by the first beam splitter 31 passes through the attenuation sheet 40 and the second beam splitter 32, and the other light beam split by the first beam splitter 31 passes through the crystal placing table 50 and the second beam splitter 32. Interferometer 100 may also be provided with a mirror 60 to adjust the direction of propagation of the light beam.
Specifically, the source beam generator 10 is a helium-neon laser; the source beam is laser emitted by a helium-neon laser. The helium-neon laser is a gas laser which takes neutral atomic gases such as helium and neon as working substances; the continuous laser light is output in a continuous excitation manner. The gas atoms have a determined energy level structure, and are excited by external electrons to generate energy level transition to generate excited radiation to emit laser, so that the helium-neon laser wavelength is pure monochromatic light, the line width is extremely narrow, the wavelength error is only a few nanometers, and the helium-neon laser has an extremely large coherence length. The atomic level structure is determined, and thus the laser is not affected by temperature fluctuation. The effect of the resonant cavity ensures that the laser output has good collimation property, and the divergence angle is small and is only a few milliradians.
When the crystal is not placed on the crystal placing stage 50, a reference interference image can be obtained by the light beam generated by the interferometer 100. When the crystal is placed on the crystal stage 50 with one of the beams passing through the crystal, an interference image of the crystal can be obtained by the beams generated by the interferometer 100.
The light beam generated by the interferometer 100 enters the CCD camera, and a reference interference image and a crystal interference image can be obtained.
Before step S200, image binarization processing needs to be performed on the reference interference image and the crystal interference image.
It should be noted that, the image binarization is to set the gray level of a pixel point on the image to 0 or 255, so that the whole image exhibits an obvious black-and-white effect. In digital image processing, image binarization greatly reduces the data volume of an image, thereby making it possible to highlight the contour of a target. The gradation value of the pixel having the gradation greater than or equal to the set threshold is represented by 255, and the gradation value of the pixel having the gradation smaller than the set threshold is represented by 0.
Step S200, performing gravity center point calculation on the reference interference image and the crystal interference image to respectively obtain a first gravity center point coordinate of the reference interference image and a second gravity center point coordinate of the crystal interference image, and calculating a difference between the first gravity center point coordinate and the second gravity center point coordinate to obtain a fringe variation.
In step S200, since the optical path difference changes after the light beam passes through the crystal, the interference image has significant interference fringe movement and fringe width change. In the image processing process, a single pixel point of the image is regarded as an area, and the gray value of the pixel point is taken as the quality of the pixel point, so that the center of gravity of the interference image can be solved.
And performing gravity center point calculation on the reference interference image and the crystal interference image, wherein the ordinate of the gravity center point coordinate of the images is represented by the following formula:
in the formula, Y is the vertical coordinate of the gravity center point, m is the number of pixel points of the image, and YijThe ordinate, g, of a pixel point representing the ith row and the jth column of the imageijAnd expressing the gray value of the pixel point of the ith row and the jth column of the image.
And calculating the gravity center point of the reference interference image and the crystal interference image according to the formula to obtain a first gravity center point coordinate corresponding to the reference interference image and a second gravity center point coordinate corresponding to the crystal interference image. Obtaining a fringe variation s (r) by subtracting the first gravity center point coordinate and the second gravity center point coordinate, that is
G and G0 are total gray scale values of the reference interference image and the crystal interference image respectively; gyAnd Gy0Multiplying the vertical coordinate distance of each pixel point coordinate of the reference interference image and the crystal interference image by the gray value of the pixel point; g and g0 are represented as gray values for each pixel point of the reference interference image and the crystal interference image, respectively.
Step S300, calculating a first average width pixel point number of a dark fringe and a second average width pixel point number of a bright fringe in the reference interference image, and obtaining the fringe width of the reference interference image according to the first average width pixel point number and the second average width pixel point number.
For step S300, wherein the number of first average width pixel points of dark fringes and the number of second average width pixel points of bright fringes in the reference interference image are calculated, the method includes, but is not limited to, the following steps:
calculating the gray values of all the pixel points of the first row of the dark stripes, and judging whether the gray values are larger than or equal to a set detection threshold of the dark stripes, wherein the detection threshold of the dark stripes can be set according to historical experience, if so, calculating the number of the width pixel points of the row of the dark stripes, and if not, calculating the gray values of the desired pixel points of the next row of the dark stripes and judging the gray values. And judging whether a bright stripe area is met, if so, adding one to the number of the dark stripes, otherwise, calculating the gray value of the desired pixel point of the next row of stripes and judging the gray value. And judging whether the gray value exceeds the image area, if so, finishing, and if not, calculating the gray value of the desired pixel point of the next row of stripes and judging the gray value.
And calculating the total width pixel point number of all the dark stripes and the number of the dark stripes according to the method.
And dividing the total width pixel point number of all the dark stripes and the number of the dark stripes to obtain the first average width pixel point number.
Calculating the gray values of all pixel points of the first row of bright stripes, and judging whether the gray values are greater than or equal to a set detection threshold of the bright stripes, wherein the detection threshold of the bright stripes can be set according to historical experience, if so, calculating the number of width pixel points of the row of bright stripes, and if not, calculating the gray values of desired pixel points of the next row of bright stripes and judging the gray values. And judging whether a bright stripe area is met, if so, adding one to the number of the bright stripes, otherwise, calculating the gray value of the desired pixel point of the next row of stripes and judging the gray value. And judging whether the gray value exceeds the image area, if so, finishing, and if not, calculating the gray value of the desired pixel point of the next row of stripes and judging the gray value.
And calculating the total width pixel point number of all the bright stripes and the number of the bright stripes according to the method.
And dividing the total width pixel point number of all the bright stripes with the number of the bright stripes to obtain the second average width pixel point number.
Obtaining the fringe width of the reference interference image according to the number of the first average width pixel points and the number of the second average width pixel points, wherein the method comprises the following steps of:
carrying out average calculation on the first average width pixel point number and the second average width pixel point number to obtain the stripe width pixel number; and multiplying the number of the fringe width pixels by the camera pixels to obtain the fringe width of the reference interference image.
And step S400, obtaining the refractive index of the crystal according to the fringe variation, the fringe width, the thickness of the crystal and the wavelength of the source light beam.
In step S400, nD ═ Δ k λ is given according to the relationship between the optical path difference and the fringe movement amount generated by the crystal whose refractive index is expressed by the following equation:
where n is the refractive index of the crystal, s (r) is the fringe variation, l is the fringe width of the reference interference image, λ is the wavelength of the source beam, and D is the thickness of the crystal.
Referring to fig. 4 and 5, fig. 4 is a binarized image of the reference interference image; fig. 5 is a binarized image of a crystal interference image. The wavelength of the he-ne laser is 632.8nm, the measured thickness of the crystal is 3.9mm, the measured refractive index of the crystal is 2.0964 by processing the crystal shown in the figures 4 and 5 by the method for measuring the refractive index of the crystal, the actual refractive index of the crystal is 2.0974, the error of the measured refractive index is 0.046%, and the two are basically similar.
By the crystal refractive index measuring method, the refractive index can be directly measured without processing the crystal and changing the shape of the crystal, the measuring precision is high, the measuring speed is high, and the crystal refractive index measuring efficiency and accuracy are greatly improved.
Referring to fig. 2, an embodiment of a second aspect of the present invention provides a crystal refractive index measurement apparatus based on fringe images. The crystal refractive index measuring apparatus employs the crystal refractive index measuring method as an embodiment of the first aspect of the present invention.
The crystal refractive index measuring apparatus includes an interferometer 100, an interference image acquisition module 200, a gravity center point calculation module 300, a fringe width calculation module 400, and a refractive index calculation module 500.
Wherein the interference image obtaining module 200 is configured to obtain a reference interference image and a crystal interference image, the reference interference image is generated by passing a source light beam through the interferometer without a crystal placed thereon, and the crystal interference image is generated by passing the source light beam through the interferometer with the crystal placed thereon. Specifically, the interference image acquisition module 200 is a CCD camera.
The gravity center point calculation module 300 is configured to perform gravity center point calculation on the reference interference image and the crystal interference image, respectively obtain a first gravity center point coordinate of the reference interference image and a second gravity center point coordinate of the crystal interference image, and obtain a fringe variation by subtracting the first gravity center point coordinate and the second gravity center point coordinate.
The fringe width calculating module 400 is configured to calculate a first average width pixel point number of a dark fringe and a second average width pixel point number of a bright fringe in the reference interference image, and obtain a fringe width of the reference interference image according to the first average width pixel point number and the second average width pixel point number.
The refractive index calculation module 500 is configured to obtain the refractive index of the crystal according to the fringe variation, the fringe width, the thickness of the crystal, and the wavelength of the source light beam.
It should be noted that, the crystal refractive index measuring apparatus adopted in the embodiment of the second aspect of the present invention adopts the crystal refractive index measuring method as the embodiment of the first aspect of the present invention, has the same technical solution, solves the same technical problems, and achieves the same technical effects, and is not described in detail herein.
Embodiments of a third aspect of the invention provide a fringe image-based crystal refractive index measurement apparatus. The crystal refractive index measuring device comprises a memory, a processor and a computer program stored on the memory and capable of running on the processor, and is characterized in that the processor implements the crystal refractive index measuring method according to the first aspect of the invention when executing the computer program.
An embodiment of a fourth aspect of the invention provides a storage medium. The storage medium has stored therein executable instructions which, when executed by the processor, implement the crystal refractive index measurement method according to the first aspect of the invention.
One of ordinary skill in the art will appreciate that all or some of the steps, systems, and methods disclosed above may be implemented as software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components may be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on computer readable media, which may include computer storage media (or non-transitory media) and communication media (or transitory media). The term computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, as is well known to those of ordinary skill in the art. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can accessed by a computer. In addition, communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media as known to those skilled in the art.
The above description is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiment, and the present invention shall fall within the protection scope of the present invention as long as the technical effects of the present invention are achieved by the same means.
Claims (10)
1. The crystal refractive index measuring method based on the fringe image is characterized by comprising the following steps:
acquiring a reference interference image and a crystal interference image, wherein the reference interference image is generated by a source light beam passing through an interferometer without a crystal placed on the interferometer, and the crystal interference image is generated by the source light beam passing through the interferometer with the crystal placed on the interferometer;
performing gravity center point calculation on the reference interference image and the crystal interference image to respectively obtain a first gravity center point coordinate of the reference interference image and a second gravity center point coordinate of the crystal interference image, and performing difference calculation on the first gravity center point coordinate and the second gravity center point coordinate to obtain a fringe variation;
calculating a first average width pixel point number of a dark fringe and a second average width pixel point number of a bright fringe in the reference interference image, and obtaining the fringe width of the reference interference image according to the first average width pixel point number and the second average width pixel point number;
and obtaining the refractive index of the crystal according to the fringe variation, the fringe width, the thickness of the crystal and the wavelength of the source light beam.
2. The method of claim 1, further comprising, before the calculating the center of gravity of the reference interference image and the crystal interference image:
and carrying out image binarization processing on the reference interference image and the crystal interference image.
3. The fringe image-based crystal refractive index measurement method of claim 1, wherein the center of gravity point calculation comprises processing the image to obtain gray values of pixel points and calculating the coordinates of the center of gravity point of the image by using the gray values of the pixel points as the quality of the pixel points.
4. The fringe image-based crystal refractive index measurement method according to claim 3, wherein the amount of fringe change is expressed by the following equation:
wherein s (r) is the variation of the stripes, m is the number of pixels of the image, and yijThe ordinate, g, of a pixel point representing the ith row and the jth column of the reference interference imageijGray value y0 representing a pixel point of the ith row and the jth column of the reference interference imageijOrdinate, g0, of a pixel point representing the ith row and the jth column of the crystal interference imageijAnd expressing the gray value of the pixel point of the ith row and the jth column of the crystal interference image.
5. The method of claim 1, wherein the calculating the number of pixels with the first average width of dark fringes and the number of pixels with the second average width of bright fringes in the reference interference image comprises:
calculating the total width pixel points of all the dark stripes and the number of the dark stripes, and dividing the total width pixel points of all the dark stripes and the number of the dark stripes to obtain first average width pixel points;
and calculating the total width pixel points of all the bright stripes and the number of the bright stripes, and dividing the total width pixel points of all the bright stripes and the number of the bright stripes to obtain the second average width pixel points.
6. The method for measuring the refractive index of the crystal based on the fringe image as claimed in claim 1 or 5, wherein the obtaining the fringe width of the reference interference image according to the number of the first average width pixel points and the number of the second average width pixel points comprises:
carrying out average calculation on the first average width pixel point number and the second average width pixel point number to obtain the stripe width pixel number;
and multiplying the number of the fringe width pixels by the camera pixels to obtain the fringe width of the reference interference image.
7. The fringe image-based crystal refractive index measurement method according to claim 1, wherein the refractive index of the crystal is represented by the following equation:
where n is the refractive index of the crystal, s (r) is the fringe variation, l is the fringe width of the reference interference image, λ is the wavelength of the source beam, and D is the thickness of the crystal.
8. A crystal refractive index measuring apparatus based on a fringe image, characterized in that the crystal refractive index measuring method according to any one of claims 1 to 7 is applied; the device comprises: an interferometer;
the system comprises an interference image acquisition module, a crystal interference image acquisition module and a control module, wherein the interference image acquisition module is used for acquiring a reference interference image and a crystal interference image, the reference interference image is generated by a source light beam passing through the interferometer without a crystal placed, and the crystal interference image is generated by the source light beam passing through the interferometer with the crystal placed;
the gravity center point calculation module is used for performing gravity center point calculation on the reference interference image and the crystal interference image to respectively obtain a first gravity center point coordinate of the reference interference image and a second gravity center point coordinate of the crystal interference image, and calculating the difference of the first gravity center point coordinate and the second gravity center point coordinate to obtain a fringe variation;
the fringe width calculating module is used for calculating a first average width pixel point number of a dark fringe and a second average width pixel point number of a bright fringe in the reference interference image and obtaining the fringe width of the reference interference image according to the first average width pixel point number and the second average width pixel point number;
and the refractive index calculation module is used for obtaining the refractive index of the crystal according to the fringe variation, the fringe width, the thickness of the crystal and the wavelength of the source light beam.
9. A crystal refractive index measurement device based on fringe images, comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the crystal refractive index measurement method according to any one of claims 1 to 7 when executing the computer program.
10. A storage medium having stored therein executable instructions which, when executed by a processor, carry out a crystal refractive index measurement method according to any one of claims 1 to 7.
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