WO2023045351A1 - 基于条纹图像的晶体折射率测量方法、装置及存储介质 - Google Patents

基于条纹图像的晶体折射率测量方法、装置及存储介质 Download PDF

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WO2023045351A1
WO2023045351A1 PCT/CN2022/092452 CN2022092452W WO2023045351A1 WO 2023045351 A1 WO2023045351 A1 WO 2023045351A1 CN 2022092452 W CN2022092452 W CN 2022092452W WO 2023045351 A1 WO2023045351 A1 WO 2023045351A1
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crystal
interference image
pixels
refractive index
fringe
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French (fr)
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张建民
杜梓浩
龙佳乐
黄克森
孙瑞
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Wuyi University Fujian
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Wuyi University Fujian
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
    • G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods

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  • the invention relates to the field of refractive index measurement, in particular to a crystal refractive index measurement method, device and storage medium based on fringe images.
  • Refractive index is an important parameter of crystal, which can reflect the optical and physical properties of crystal.
  • the representative methods for measuring the refractive index mainly include precision goniometer method, microscopic observation method, oil immersion method and total reflection law measurement method, etc.
  • the precision goniometer method has high measurement accuracy, but it has the problem of complex and time-consuming operations. It needs to special process the crystal into a prism. The processing accuracy is high and difficult, which destroys the shape of the raw material and limits the reuse of samples.
  • the microscopic observation method is mainly to use a polarizing microscope to observe the crystals in the thin film, which is mainly used to measure the refractive index of the thin film, and the requirements for the measurement process are relatively high and time-consuming.
  • the preparation of the solution used in the oil immersion method is complicated, and the crystal transparency will be reduced during oil immersion, and the measurement accuracy will be deteriorated.
  • the total reflection law measurement method is that when light is incident from an optically dense medium to an optically sparse medium, the incident angle when the refraction angle is equal to 90° is called the critical angle of total reflection, which is calculated according to the physical relationship between the critical angle and the refractive index. Higher requirements.
  • the purpose of the present invention is to solve at least one of the technical problems in the prior art, and provide a method, device and storage medium for measuring the refractive index of crystals based on fringe images.
  • a method for measuring the refractive index of a crystal based on a fringe image includes:
  • the reference interference image is generated by the source beam passing through an interferometer without placing a crystal
  • the crystal interference image is generated by the source beam passing through an interferometer placing the crystal
  • the center of gravity point calculation is performed on the reference interference image and the crystal interference image to obtain the first center of gravity coordinates of the reference interference image and the second center of gravity point coordinates of the crystal interference image respectively, and calculate the first center of gravity
  • the difference between the point coordinates and the second center of gravity point coordinates is obtained to obtain the amount of variation of the stripes;
  • the refractive index of the crystal is obtained according to the variation of the fringe, the width of the fringe, the thickness of the crystal and the wavelength of the source light beam.
  • the first aspect of the present invention before calculating the center of gravity point of the reference interference image and the crystal interference image, it also includes:
  • Image binarization processing is performed on the reference interference image and the crystal interference image.
  • the center of gravity point calculation includes processing the image to obtain the gray value of the 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.
  • the amount of variation of the stripes is represented by the following formula:
  • s(r) is the fringe change amount
  • m is the number of pixels in the image
  • y ij represents the ordinate of the pixel point in row i and column j of the reference interference image
  • g ij represents the reference
  • y0 ij represents the ordinate of the pixel point in the i-th row and j-column of the crystal interference image
  • g0 ij represents the i-th pixel point of the crystal interference image
  • the calculation of the number of pixels of the first average width of dark fringes and the number of pixels of the second average width of bright fringes in the reference interference image includes:
  • the obtaining the fringe width of the reference interference image according to the number of pixels of the first average width and the number of pixels of the second average width includes:
  • the number of pixels of the fringe width is multiplied by the camera pixels to obtain the fringe width of the reference interference image.
  • the refractive index of the crystal is represented by the following formula:
  • n is the refractive index of the crystal
  • s(r) is the variation of the fringe
  • l is the fringe width of the reference interference image
  • ⁇ is the wavelength of the source beam
  • D is the thickness of the crystal .
  • a device for measuring the refractive index of a crystal based on a fringe image uses the method for measuring the refractive index of a crystal as described in the first aspect of the present invention; the device includes:
  • the interference image acquisition module is used to acquire a reference interference image and a crystal interference image, the reference interference image is generated by the source beam passing through the interferometer without placing a crystal, and the crystal interference image is generated by the source beam passing through a placed produced by said interferometer of said crystal;
  • a center-of-gravity point calculation module configured to calculate the center-of-gravity point of the reference interference image and the crystal interference image, and respectively obtain the first center-of-gravity point coordinates of the reference interference image and the second center-of-gravity point coordinates of the crystal interference image, and calculating the difference between the coordinates of the first center of gravity point and the coordinates of the second center of gravity point to obtain the amount of variation of the stripes;
  • the fringe width calculation module is used to calculate the first average width pixels of the dark fringes and the second average width pixels of the bright fringes in the reference interference image, according to the first average width pixels and the second average width The number of pixels obtains the fringe width of the reference interference image;
  • the refractive index calculation module is used to obtain the refractive index of the crystal according to the variation of the fringe, the width of the fringe, the thickness of the crystal and the wavelength of the source light beam.
  • the device for measuring the refractive index of crystals based on fringe images includes a memory, a processor, and a computer program stored in the memory and operable on the processor, wherein the processor executes the computer program
  • the program implements the method for measuring the refractive index of a crystal as described in the first aspect of the present invention.
  • a storage medium stores executable instructions, and when the executable instructions are executed by a processor, the method for measuring the refractive index of a crystal according to the first aspect of the present invention is implemented.
  • the refractive index can be directly measured without processing the crystal to change the shape of the crystal, and has high measurement accuracy and high measurement rate, which greatly improves the efficiency and accuracy of crystal refractive index measurement.
  • Fig. 1 is a flow chart of the method for measuring the refractive index of crystals based on fringe images according to an embodiment of the present invention
  • Fig. 2 is a structural diagram of a crystal refractive index measuring device according to an embodiment of the present invention.
  • Fig. 3 is the structural representation of interferometer and interferometric image acquisition module
  • Fig. 4 is the binary image of reference interference image
  • Fig. 5 is a binarized image of a crystal interference image.
  • orientation descriptions such as up, down, front, back, left, right, etc. indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, and are only In order to facilitate the description of the present invention and simplify the description, it 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.
  • an embodiment of the first aspect of the present invention provides a method for measuring the refractive index of crystals based on fringe images.
  • Crystal refractive index measurement methods include:
  • Step S100 acquiring a reference interference image and a crystal interference image.
  • the reference interference image is generated by the source beam passing through the interferometer 100 without crystals, and the crystal interference image is generated by the source beam passing through the interferometer 100 placed on the crystal.
  • step S100 the interferometer 100 generates two beams by the partial amplitude method to achieve interference, and the interferometer 100 is specifically the Mach-Zehnder interferometer 100 .
  • interferometer 100 comprises source beam generator 10, first lens 21, second lens 22, first beam splitter mirror 31, second beam splitter mirror 32, attenuation sheet 40 and crystal placement table 50; Source beam generator The source beam generated by the device 10 passes through the first lens 21, the second lens 22 and the first beam splitter 31 in sequence, and one of the beams obtained by splitting the first beam splitter 31 passes through the attenuation sheet 40 and the second beam splitter 32, Another beam split by the first beam splitter 31 passes through the crystal placement table 50 and the second beam splitter 32 .
  • the interferometer 100 can also be provided with a mirror 60 to adjust the propagation direction of the light beam.
  • the source beam generator 10 is a He-Ne laser; the source beam is the laser emitted by the He-Ne laser.
  • the helium-neon laser is a gas laser with neutral atomic gases helium and neon as the working substance; it outputs continuous laser light in a continuous excitation mode. Gas atoms have a definite energy level structure, which is excited by external electrons to undergo energy level transitions to generate stimulated radiation and emit laser light. Therefore, the wavelength of helium-neon laser is pure monochromatic light, the line width is extremely narrow, and the wavelength error is only a few nanometers. large coherence length. The atomic energy level structure is determined, so the laser is not affected by temperature fluctuations. In addition, the role of the resonant cavity ensures that the laser output has good collimation, and the divergence angle is small, only a few milliradians.
  • a reference interference image can be obtained through the light beam generated by the interferometer 100 .
  • the crystal interference image can be obtained by the beam generated by the interferometer 100.
  • the light beam generated by the interferometer 100 enters the CCD camera, and then a reference interference image and a crystal interference image can be obtained.
  • step S200 image binarization processing needs to be performed on the reference interference image and the crystal interference image.
  • image binarization is to set the gray value of the pixels on the image to 0 or 255, so that the whole image presents an obvious black and white effect.
  • image binarization greatly reduces the amount of data in the image, thereby highlighting the outline of the target.
  • the grayscale value of the pixel whose grayscale is greater than or equal to the set threshold is represented by 255, and the grayscale value of the pixel whose grayscale is smaller than the set threshold is represented by 0.
  • Step S200 calculate the center of gravity point of the reference interference image and the crystal interference image, respectively obtain the first center of gravity point coordinates of the reference interference image and the second center of gravity point coordinates of the crystal interference image, and calculate the The difference between the coordinates of the first center of gravity and the coordinates of the second center of gravity is obtained to obtain the variation of the stripes.
  • step S200 since the optical path difference changes after the light beam passes through the crystal, the interference image has obvious interference fringe movement and fringe width change.
  • a single pixel of the image is regarded as a region, and the gray value of the pixel is taken as the quality of the pixel, so that the center of gravity of the interference image can be obtained.
  • the center of gravity point calculation is performed on both the reference interference image and the crystal interference image, and the ordinate of the center of gravity point coordinates of the image is expressed by the following formula:
  • Y is the ordinate of the center of gravity
  • m is the number of pixels in the image
  • y ij represents the ordinate of the pixel in row i and column j of the image
  • g ij represents the pixel of the image
  • the center of gravity point calculation is performed on the reference interference image and the crystal interference image according to the above formula, and the coordinates of the first center of gravity point corresponding to the reference interference image and the second center of gravity point coordinates of the corresponding crystal interference image can be obtained.
  • the difference between the coordinates of the first center of gravity point and the coordinates of the second center of gravity point can be used to obtain the amount of variation s(r) of the stripes, namely G and G0 are the total gray value of the reference interference image and the crystal interference image respectively; G y and G y0 are the ordinate distance of each pixel coordinate of the reference interference image and the crystal interference image and the gray value of the pixel Multiply; g and g0 represent the gray value of each pixel in the reference interference image and the crystal interference image, respectively.
  • Step S300 calculating the pixel points of the first average width of dark fringes and the second average width of pixels of bright fringes in the reference interference image, and obtaining the obtained pixel points of the first average width and the second average width of pixels The fringe width of the reference interference image mentioned above.
  • step S300 wherein the calculation of the number of pixels of the first average width of the dark stripes and the number of pixels of the second average width of the bright stripes in the reference interference image includes but is not limited to the following steps:
  • the detection threshold of the dark stripes can be set according to historical experience. If so, calculate the gray value of the row The number of pixels of the width of the dark stripe, if not, calculate the gray value of the desired pixel of the next row of stripes and judge the gray value. Judging whether a bright stripe area is encountered, if so, add one to the number of dark stripes, if not, calculate the gray value of the desired pixel of the next row of stripes and judge the gray value. Judging whether it exceeds the image area, if so, end, if not, calculate the gray value of the desired pixel of the next line of stripes and perform gray value judgment.
  • the detection threshold of the bright stripes can be set according to historical experience, and if so, calculate the The number of pixels of the width of the bright stripe, if not, calculate the gray value of the desired pixel of the next row of stripes and judge the gray value. Judging whether a bright stripe area is encountered, if so, add one to the number of bright stripes, if not, calculate the gray value of the desired pixel of the next row of stripes and judge the gray value. Judging whether it exceeds the image area, if so, end, if not, calculate the gray value of the desired pixel of the next line of stripes and perform gray value judgment.
  • the total width pixels of all the bright stripes and the number of the bright stripes are calculated according to the above method.
  • obtaining the fringe width of the reference interference image according to the number of pixels of the first average width and the number of pixels of the second average width includes but is not limited to the following steps:
  • 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.
  • nD ⁇ k ⁇
  • the refractive index of the crystal is expressed by the following formula: In the formula, n is the refractive index of the crystal, s(r) is the variation of the fringe, l is the fringe width of the reference interference image, ⁇ is the wavelength of the source beam, and D is the thickness of the crystal .
  • Fig. 4 is a binarized image of a reference interference image
  • Fig. 5 is a binarized image of a crystal interference image.
  • the wavelength of the helium-neon laser is 632.8nm, and the measured thickness of the crystal is 3.9mm.
  • Figure 4 and Figure 5 are processed by using the above crystal refractive index measurement method.
  • the measured refractive index of the crystal is 2.0964, while the actual crystal refractive index is 2.0974.
  • the measured The refractive index error is 0.046%, which is basically similar.
  • the refractive index can be directly measured without processing the crystal to change the crystal shape, and the measurement accuracy is high, and the measurement rate is high, which greatly improves the efficiency and accuracy of the crystal refractive index measurement.
  • an embodiment of the second aspect of the present invention provides a crystal refraction index measurement device based on fringe images.
  • the crystal refractive index measuring device adopts the crystal refractive index measuring method of the embodiment of the first aspect of the present invention.
  • the crystal refractive index measurement device includes an interferometer 100 , an interference image acquisition module 200 , a center of gravity calculation module 300 , a fringe width calculation module 400 and a refractive index calculation module 500 .
  • the interference image acquisition module 200 is used to acquire a reference interference image and a crystal interference image, the reference interference image is generated by the source beam passing through the interferometer without placing a crystal, and the crystal interference image is generated by the source beam passing through the interferometer. produced by the interferometer with the crystal.
  • the interference image acquisition module 200 is a CCD camera.
  • the center of gravity point calculation module 300 is used to calculate the center of gravity point of the reference interference image and the crystal interference image to obtain the first center of gravity point coordinates of the reference interference image and the second center of gravity point coordinates of the crystal interference image respectively, And calculating the difference between the coordinates of the first center of gravity point and the coordinates of the second center of gravity point to obtain the variation amount of the stripes.
  • the fringe width calculation module 400 is used to calculate the pixel points of the first average width of dark fringes and the second average width of pixels of bright fringes in the reference interference image, according to the number of pixels of the first average width and the second average width The number of pixels obtains the fringe width of the reference interference image.
  • the refractive index calculation module 500 is used to obtain the refractive index of the crystal according to the variation of the fringe, the width of the fringe, the thickness of the crystal and the wavelength of the source light beam.
  • the crystal refractive index measurement device used in the embodiment of the second aspect of the present invention adopts the crystal refractive index measurement method of the embodiment of the first aspect of the present invention, has the same technical solution, and solves the same problem Technical problems, to achieve the same technical effect, will not be described in detail here.
  • An embodiment of the third aspect of the present invention provides a crystal refraction index measurement device based on a fringe image.
  • the crystal refractive index measurement device includes a memory, a processor, and a computer program stored on the memory and operable on the processor, wherein the processor implements the computer program as described in the first aspect of the present invention when executing the computer program. method for measuring the refractive index of crystals.
  • An embodiment of a fourth aspect of the present invention provides a storage medium. Executable instructions are stored in the storage medium, and when the executable instructions are executed by the processor, the crystal refractive index measurement method according to the first aspect of the present invention is implemented.
  • Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disk (DVD) or other optical disk storage, magnetic cartridges, tape, magnetic disk storage or other magnetic storage devices, or can Any other medium used to store desired information and which can be accessed by a computer.
  • 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 may include any information delivery media .

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Abstract

本发明公开了基于条纹图像的晶体折射率测量方法、装置及存储介质，其中方法包括获取参考干涉图像和晶体干涉图像；对参考干涉图像和晶体干涉图像进行重心点计算进而得到条纹变化量；计算参考干涉图像中暗条纹的第一平均宽度像素点数和亮条纹的第二平均宽度像素点数进而得到所述参考干涉图像的条纹宽度；根据条纹变化量、条纹宽度、晶体的厚度和源光束的波长得到折射率；无需对晶体进行加工改变晶体形状即可直接进行折射率测量，且测量精度高，测量速率高，大大提升了晶体折射率测量的效率和准确率。

Description

基于条纹图像的晶体折射率测量方法、装置及存储介质 技术领域
本发明涉及折射率测量领域，特别是基于条纹图像的晶体折射率测量方法、装置及存储介质。
背景技术
折射率是晶体的一个重要参数，能反映晶体的光学性质及物理性质。目前测量折射率的代表性方法主要有精密测角仪法、显微观察法、油浸法和全反射定律测量法等。精密测角仪法测量精度高，但存在操作复杂耗时的问题，需要对晶体特殊加工为棱镜，加工精度要求高、难度大，破坏了原材料的形状，对样品的重复利用造成限制。显微观察法主要是使用偏光显微镜观察薄片中晶体主要用于测量薄膜折射率,对于测量过程的要求比较高并且比较费时。油浸法所使用的溶液配制繁杂，且油浸时会使晶体透明度降低，测量精度变差。全反射定律测量法是光从光密介质入射到光疏介质时,折射角等于90°时的入射角称为全反射临界角,据临界角和折射率的物理关系计算得出，对测量环境要求较高。
发明内容
本发明的目的在于至少解决现有技术中存在的技术问题之一，提供基于条纹图像的晶体折射率测量方法、装置及存储介质。
本发明解决其问题所采用的技术方案是：
本发明的第一方面，基于条纹图像的晶体折射率测量方法，包括：
获取参考干涉图像和晶体干涉图像，所述参考干涉图像是源光束经过无放置晶体的干涉仪产生的，所述晶体干涉图像是所述源光束经过放置有所述晶体的干涉仪产生的；
对所述参考干涉图像和所述晶体干涉图像进行重心点计算，分别得到所述参考干涉图像的第一重心点坐标和所述晶体干涉图像的第二重心点坐标，并对所述第一重心点坐标和所述第二重心点坐标求差得到条纹变化量；
计算所述参考干涉图像中暗条纹的第一平均宽度像素点数和亮条纹的第二平均宽度像素点数，根据所述第一平均宽度像素点数和所述第二平均宽度像素点数得到所述参考干涉图像的条纹宽度；
根据所述条纹变化量、所述条纹宽度、所述晶体的厚度和所述源光束的波长得到所述晶 体的折射率。
根据本发明的第一方面，在对所述参考干涉图像和所述晶体干涉图像进行重心点计算之前，还包括：
对所述参考干涉图像和所述晶体干涉图像进行图像二值化处理。
根据本发明的第一方面，所述重心点计算包括处理图像得到像素点的灰度值和以像素点的灰度值作为像素点的质量计算图像的重心点坐标。
根据本发明的第一方面，所述所述条纹变化量通过以下式子表示：
Figure PCTCN2022092452-appb-000001
式中，s(r)为所述条纹变化量，m为图像的像素点数量，y ij表示所述参考干涉图像的第i行第j列的像素点的纵坐标，g ij表示所述参考干涉图像的第i行第j列的像素点的灰度值,y0 ij表示所述晶体干涉图像的第i行第j列的像素点的纵坐标，g0 ij表示所述晶体干涉图像的第i行第j列的像素点的灰度值。
根据本发明的第一方面，所述计算所述参考干涉图像中暗条纹的第一平均宽度像素点数和亮条纹的第二平均宽度像素点数，包括：
计算所有所述暗条纹的总宽度像素点数和所述暗条纹的数量，将所有所述暗条纹的总宽度像素点数和所述暗条纹的数量相除得到所述第一平均宽度像素点数；
计算所有所述亮条纹的总宽度像素点数和所述亮条纹的数量，将所有所述亮条纹的总宽度像素点数和所述亮条纹的数量相除得到所述第二平均宽度像素点数。
根据本发明的第一方面，所述根据所述第一平均宽度像素点数和所述第二平均宽度像素点数得到所述参考干涉图像的条纹宽度，包括：
对所述第一平均宽度像素点数和所述第二平均宽度像素点数进行平均计算得到条纹宽度像素数；
将所述条纹宽度像素数与相机像素相乘，得到所述参考干涉图像的条纹宽度。
根据本发明的第一方面，所述晶体的折射率通过以下式子表示：
Figure PCTCN2022092452-appb-000002
式中，n为所述晶体的折射率，s(r)为所述条纹变化量，l为所述参考干涉图像的条纹宽度，λ为所述源光束的波长，D为所述晶体的厚度。
本发明的第二方面，基于条纹图像的晶体折射率测量装置，应用如本发明的第一方面所述的晶体折射率测量方法；所述装置包括：
干涉仪；
干涉图像获取模块，用于获取参考干涉图像和晶体干涉图像，所述参考干涉图像是源光束经过无放置晶体的所述干涉仪产生的，所述晶体干涉图像是所述源光束经过放置有所述晶体的所述干涉仪产生的；
重心点计算模块，用于对所述参考干涉图像和所述晶体干涉图像进行重心点计算，分别得到所述参考干涉图像的第一重心点坐标和所述晶体干涉图像的第二重心点坐标，并对所述第一重心点坐标和所述第二重心点坐标求差得到条纹变化量；
条纹宽度计算模块，用于计算所述参考干涉图像中暗条纹的第一平均宽度像素点数和亮条纹的第二平均宽度像素点数，根据所述第一平均宽度像素点数和所述第二平均宽度像素点数得到所述参考干涉图像的条纹宽度；
折射率计算模块，用于根据所述条纹变化量、所述条纹宽度、所述晶体的厚度和所述源光束的波长得到所述晶体的折射率。
本发明的第三方面，基于条纹图像的晶体折射率测量装置，包括存储器、处理器及存储在存储器上并可在处理器上运行的计算机程序，其特征在于，所述处理器执行所述计算机程序时实现如本发明的第一方面所述的晶体折射率测量方法。
本发明的第四方面，一种存储介质，存储有可执行指令，所述可执行指令被处理器执行时实现如本发明的第一方面所述的晶体折射率测量方法。
上述方案至少具有以下的有益效果：无需对晶体进行加工改变晶体形状即可直接进行折射率测量，且测量精度高，测量速率高，大大提升了晶体折射率测量的效率和准确率。
本发明的附加方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本发明的实践了解到。
附图说明
下面结合附图和实例对本发明作进一步说明。
图1是本发明实施例基于条纹图像的晶体折射率测量方法的流程图；
图2是本发明实施例一种晶体折射率测量装置的结构图；
图3是干涉仪和干涉图像获取模块的结构示意图；
图4是参考干涉图像的二值化图像；
图5是晶体干涉图像的二值化图像。
具体实施方式
本部分将详细描述本发明的具体实施例，本发明之较佳实施例在附图中示出，附图的作 用在于用图形补充说明书文字部分的描述，使人能够直观地、形象地理解本发明的每个技术特征和整体技术方案，但其不能理解为对本发明保护范围的限制。
在本发明的描述中，需要理解的是，涉及到方位描述，例如上、下、前、后、左、右等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本发明和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本发明的限制。
在本发明的描述中，若干的含义是一个或者多个，多个的含义是两个以上，大于、小于、超过等理解为不包括本数，以上、以下、以内等理解为包括本数。如果有描述到第一、第二只是用于区分技术特征为目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量或者隐含指明所指示的技术特征的先后关系。
本发明的描述中，除非另有明确的限定，设置、安装、连接等词语应做广义理解，所属技术领域技术人员可以结合技术方案的具体内容合理确定上述词语在本发明中的具体含义。
参照图1，本发明的第一方面的实施例，提供了基于条纹图像的晶体折射率测量方法。
晶体折射率测量方法包括：
步骤S100、获取参考干涉图像和晶体干涉图像，参考干涉图像是源光束经过无放置晶体的干涉仪100产生的，晶体干涉图像是源光束经过放置有晶体的干涉仪100产生的。
在步骤S100中，干涉仪100通过分振幅法产生双光束以实现干涉，干涉仪100具体为马赫曾德干涉仪100。
参照图3，干涉仪100包括源光束产生器10、第一透镜21、第二透镜22、第一分束镜31、第二分束镜32、衰减片40和晶体放置台50；源光束产生器10产生的源光束依次经过第一透镜21、第二透镜22和第一分束镜31，第一分束镜31分束得到的其中一个光束经过衰减片40和第二分束镜32，第一分束镜31分束得到的另一个光束经过晶体放置台50和第二分束镜32。干涉仪100还可以设置反射镜60，以调整光束的传播方向。
具体地，源光束产生器10为氦氖激光器；源光束为氦氖激光器发出的激光。氦氖激光器是以中性原子气体氦和氖作为工作物质的气体激光器；以连续激励方式输出连续激光。气体原子具有确定的能级结构，由外界电子激发发生能级跃迁，产生受激辐射发出激光，因此氦氖激光波长是纯净的单色光，线宽极窄，波长误差只有几纳米，具有极大的相干长度。原子能级结构是确定的，因此激光不受温度波动影响。加上谐振腔的作用保障了激光输出具有良好的准直性，发散角小，只有几个毫弧度。
当晶体放置台50不放置晶体，则通过干涉仪100产生的光束能得到参考干涉图像。当晶 体放置台50放置晶体，其中一个光束经过晶体，则通过干涉仪100产生的光束能得到晶体干涉图像。
干涉仪100产生的光束进入CCD相机，进而能得到参考干涉图像和晶体干涉图像。
在步骤S200之前还需要对所述参考干涉图像和所述晶体干涉图像进行图像二值化处理。
需要说明的是，图像二值化是将图像上的像素点的灰度值设置为0或255，使整个图像呈现出明显的黑白效果。在数字图像处理中，图像二值化使图像的数据量大为减少，从而能凸显出目标的轮廓。将灰度大于或等于设定阈值的像素的灰度值用255表示，将灰度小于设定阈值的像素的灰度值用0表示。
步骤S200、对所述参考干涉图像和所述晶体干涉图像进行重心点计算，分别得到所述参考干涉图像的第一重心点坐标和所述晶体干涉图像的第二重心点坐标，并对所述第一重心点坐标和所述第二重心点坐标求差得到条纹变化量。
对于步骤S200，由于光束经过晶体后，光程差发生了变化，干涉图像有明显的干涉条纹移动和条纹宽度的变化。在图像处理过程中，将图像的单个像素点看成一个区域，该像素点的灰度值作为该像素点的质量，这样能够求出干涉图像的重心点。
对参考干涉图像和晶体干涉图像均进行重心点计算，图像的重心点坐标的纵坐标通过以下式子表示：
Figure PCTCN2022092452-appb-000003
式中，Y为所述重心点的纵坐标，m为所述图像的像素点数量，y ij表示所述图像的第i行第j列的像素点的纵坐标，g ij表示所述图像的第i行第j列的像素点的灰度值。
按照上述式子对所述参考干涉图像和所述晶体干涉图像进行重心点计算，能得到对应参考干涉图像的第一重心点坐标和对应晶体干涉图像的第二重心点坐标。对所述第一重心点坐标和所述第二重心点坐标求差即可得到条纹变化量s(r)，即
Figure PCTCN2022092452-appb-000004
G和G0分别为参考干涉图像和晶体干涉图像的总灰度值；G y和G y0分别为参考干涉图像和晶体干涉图像的每个像素点坐标的纵坐标距离与该像素点的灰度值相乘；g和g0分别表示为参考干涉图像和晶体干涉图像的每个像素点的 灰度值。
步骤S300，计算所述参考干涉图像中暗条纹的第一平均宽度像素点数和亮条纹的第二平均宽度像素点数，根据所述第一平均宽度像素点数和所述第二平均宽度像素点数得到所述参考干涉图像的条纹宽度。
对于步骤S300，其中，计算所述参考干涉图像中暗条纹的第一平均宽度像素点数和亮条纹的第二平均宽度像素点数，包括但不限于以下步骤：
计算第一行暗条纹的所有像素点的灰度值，判断该灰度值是否大于或等于设定的暗条纹的检测阈值，该暗条纹的检测阈值可以根据历史经验设置，若是则计算该行暗条纹的宽度像素点数，若否则计算下一行条纹的所欲像素点的灰度值并进行灰度值判断。判断是否遇到亮条纹区域，若是则暗条纹数量加一，若否则计算下一行条纹的所欲像素点的灰度值并进行灰度值判断。判断是否超过图像区域，若是则结束，若否则计算下一行条纹的所欲像素点的灰度值并进行灰度值判断。
按照上述方法计算所有所述暗条纹的总宽度像素点数和所述暗条纹的数量。
将所有所述暗条纹的总宽度像素点数和所述暗条纹的数量相除得到所述第一平均宽度像素点数。
计算第一行亮条纹的所有像素点的灰度值，判断该灰度值是否大于或等于设定的亮条纹的检测阈值，该亮条纹的检测阈值可以根据历史经验设置，若是则计算该行亮条纹的宽度像素点数，若否则计算下一行条纹的所欲像素点的灰度值并进行灰度值判断。判断是否遇到亮条纹区域，若是则亮条纹数量加一，若否则计算下一行条纹的所欲像素点的灰度值并进行灰度值判断。判断是否超过图像区域，若是则结束，若否则计算下一行条纹的所欲像素点的灰度值并进行灰度值判断。
按照上述方法计算所有所述亮条纹的总宽度像素点数和所述亮条纹的数量。
将所有所述亮条纹的总宽度像素点数和所述亮条纹的数量相除得到所述第二平均宽度像素点数。
其中，根据所述第一平均宽度像素点数和所述第二平均宽度像素点数得到所述参考干涉图像的条纹宽度，包括但不限于以下步骤：
对所述第一平均宽度像素点数和所述第二平均宽度像素点数进行平均计算得到条纹宽度像素数；将所述条纹宽度像素数与相机像素相乘，得到所述参考干涉图像的条纹宽度。
步骤S400，根据所述条纹变化量、所述条纹宽度、所述晶体的厚度和所述源光束的波长得到所述晶体的折射率。
对于步骤S400，根据晶体产生的光程差和条纹移动量的关系有nD＝Δkλ，所述晶体的折射率通过以下式子表示：
Figure PCTCN2022092452-appb-000005
式中，n为所述晶体的折射率，s(r)为所述条纹变化量，l为所述参考干涉图像的条纹宽度，λ为所述源光束的波长，D为所述晶体的厚度。
参照图4和图5，图4是参考干涉图像的二值化图像；图5是晶体干涉图像的二值化图像。氦氖激光器波长为632.8nm，晶体测量厚度为3.9mm，利用上述晶体折射率测量方法对图4和图5进行处理，测量得到的晶体折射率为2.0964，而实际晶体折射率为2.0974，测量的折射率误差为0.046％，两者基本相近。
通过上述晶体折射率测量方法，无需对晶体进行加工改变晶体形状即可直接进行折射率测量，且测量精度高，测量速率高，大大提升了晶体折射率测量的效率和准确率。
参照图2，本发明的第二方面的实施例，提供了基于条纹图像的晶体折射率测量装置。晶体折射率测量装置采用如本发明的第一方面的实施例的晶体折射率测量方法。
晶体折射率测量装置包括干涉仪100、干涉图像获取模块200、重心点计算模块300、条纹宽度计算模块400和折射率计算模块500。
其中，干涉图像获取模块200用于获取参考干涉图像和晶体干涉图像，所述参考干涉图像是源光束经过无放置晶体的所述干涉仪产生的，所述晶体干涉图像是所述源光束经过放置有所述晶体的所述干涉仪产生的。具体地，干涉图像获取模块200为CCD相机。
重心点计算模块300用于对所述参考干涉图像和所述晶体干涉图像进行重心点计算，分别得到所述参考干涉图像的第一重心点坐标和所述晶体干涉图像的第二重心点坐标，并对所述第一重心点坐标和所述第二重心点坐标求差得到条纹变化量。
条纹宽度计算模块400用于计算所述参考干涉图像中暗条纹的第一平均宽度像素点数和亮条纹的第二平均宽度像素点数，根据所述第一平均宽度像素点数和所述第二平均宽度像素点数得到所述参考干涉图像的条纹宽度。
折射率计算模块500用于根据所述条纹变化量、所述条纹宽度、所述晶体的厚度和所述源光束的波长得到所述晶体的折射率。
需要说明的是，本发明的第二方面的实施例所采用的晶体折射率测量装置采用如本发明的第一方面的实施例的晶体折射率测量方法，具有相同的技术方案，解决了相同的技术问题，达到相同的技术效果，在此不再详述。
本发明的第三方面的实施例，提供了基于条纹图像的晶体折射率测量装置。晶体折射率测量装置包括存储器、处理器及存储在存储器上并可在处理器上运行的计算机程序，其特征在于，所述处理器执行所述计算机程序时实现如本发明的第一方面所述的晶体折射率测量方 法。
本发明的第四方面的实施例，提供了一种存储介质。存储介质中存储有可执行指令，所述可执行指令被处理器执行时实现如本发明的第一方面所述的晶体折射率测量方法。
本领域普通技术人员可以理解，上文中所公开方法中的全部或某些步骤、系统可以被实施为软件、固件、硬件及其适当的组合。某些物理组件或所有物理组件可以被实施为由处理器，如中央处理器、数字信号处理器或微处理器执行的软件，或者被实施为硬件，或者被实施为集成电路，如专用集成电路。这样的软件可以分布在计算机可读介质上，计算机可读介质可以包括计算机存储介质(或非暂时性介质)和通信介质(或暂时性介质)。如本领域普通技术人员公知的，术语计算机存储介质包括在用于存储信息(诸如计算机可读指令、数据结构、程序模块或其他数据)的任何方法或技术中实施的易失性和非易失性、可移除和不可移除介质。计算机存储介质包括但不限于RAM、ROM、EEPROM、闪存或其他存储器技术、CD-ROM、数字多功能盘(DVD)或其他光盘存储、磁盒、磁带、磁盘存储或其他磁存储装置、或者可以用于存储期望的信息并且可以被计算机访问的任何其他的介质。此外，本领域普通技术人员公知的是，通信介质通常包含计算机可读指令、数据结构、程序模块或者诸如载波或其他传输机制之类的调制数据信号中的其他数据，并且可包括任何信息递送介质。
以上所述，只是本发明的较佳实施例而已，本发明并不局限于上述实施方式，只要其以相同的手段达到本发明的技术效果，都应属于本发明的保护范围。

Claims (10)

  1. 基于条纹图像的晶体折射率测量方法，其特征在于，包括：
    获取参考干涉图像和晶体干涉图像，所述参考干涉图像是源光束经过无放置晶体的干涉仪产生的，所述晶体干涉图像是所述源光束经过放置有所述晶体的干涉仪产生的；
    对所述参考干涉图像和所述晶体干涉图像进行重心点计算，分别得到所述参考干涉图像的第一重心点坐标和所述晶体干涉图像的第二重心点坐标，并对所述第一重心点坐标和所述第二重心点坐标求差得到条纹变化量；
    计算所述参考干涉图像中暗条纹的第一平均宽度像素点数和亮条纹的第二平均宽度像素点数，根据所述第一平均宽度像素点数和所述第二平均宽度像素点数得到所述参考干涉图像的条纹宽度；
    根据所述条纹变化量、所述条纹宽度、所述晶体的厚度和所述源光束的波长得到所述晶体的折射率。
  2. 根据权利要求1所述的基于条纹图像的晶体折射率测量方法，其特征在于，在对所述参考干涉图像和所述晶体干涉图像进行重心点计算之前，还包括：
    对所述参考干涉图像和所述晶体干涉图像进行图像二值化处理。
  3. 根据权利要求1所述的基于条纹图像的晶体折射率测量方法，其特征在于，所述重心点计算包括处理图像得到像素点的灰度值和以像素点的灰度值作为像素点的质量计算图像的重心点坐标。
  4. 根据权利要求3所述的基于条纹图像的晶体折射率测量方法，其特征在于，所述条纹变化量通过以下式子表示：
    Figure PCTCN2022092452-appb-100001
    式中，s(r)为所述条纹变化量，m为图像的像素点数量，y ij表示所述参考干涉图像的第i行第j列的像素点的纵坐标，g ij表示所述参考干涉图像的第i行第j列的像素点的灰度值,y0 ij表示所述晶体干涉图像的第i行第j列的像素点的纵坐标，g0 ij表示所述晶体干涉图像的第i行第j列的像素点的灰度值。
  5. 根据权利要求1所述的基于条纹图像的晶体折射率测量方法，其特征在于，所述计算所述参考干涉图像中暗条纹的第一平均宽度像素点数和亮条纹的第二平均宽度像素点数，包括：
    计算所有所述暗条纹的总宽度像素点数和所述暗条纹的数量，将所有所述暗条纹的总宽度像素点数和所述暗条纹的数量相除得到所述第一平均宽度像素点数；
    计算所有所述亮条纹的总宽度像素点数和所述亮条纹的数量，将所有所述亮条纹的总宽度像素点数和所述亮条纹的数量相除得到所述第二平均宽度像素点数。
  6. 根据权利要求1或5所述的基于条纹图像的晶体折射率测量方法，其特征在于，所述根据所述第一平均宽度像素点数和所述第二平均宽度像素点数得到所述参考干涉图像的条纹宽度，包括：
    对所述第一平均宽度像素点数和所述第二平均宽度像素点数进行平均计算得到条纹宽度像素数；
    将所述条纹宽度像素数与相机像素相乘，得到所述参考干涉图像的条纹宽度。
  7. 根据权利要求1所述的基于条纹图像的晶体折射率测量方法，其特征在于，所述晶体的折射率通过以下式子表示：
    Figure PCTCN2022092452-appb-100002
    式中，n为所述晶体的折射率，s(r)为所述条纹变化量，l为所述参考干涉图像的条纹宽度，λ为所述源光束的波长，D为所述晶体的厚度。
  8. 基于条纹图像的晶体折射率测量装置，其特征在于，应用如权利要求1至7任一项所述的晶体折射率测量方法；所述装置包括：
    干涉仪；
    干涉图像获取模块，用于获取参考干涉图像和晶体干涉图像，所述参考干涉图像是源光束经过无放置晶体的所述干涉仪产生的，所述晶体干涉图像是所述源光束经过放置有所述晶体的所述干涉仪产生的；
    重心点计算模块，用于对所述参考干涉图像和所述晶体干涉图像进行重心点计算，分别得到所述参考干涉图像的第一重心点坐标和所述晶体干涉图像的第二重心点坐标，并对所述第一重心点坐标和所述第二重心点坐标求差得到条纹变化量；
    条纹宽度计算模块，用于计算所述参考干涉图像中暗条纹的第一平均宽度像素点数和亮条纹的第二平均宽度像素点数，根据所述第一平均宽度像素点数和所述第二平均宽度像素点数得到所述参考干涉图像的条纹宽度；
    折射率计算模块，用于根据所述条纹变化量、所述条纹宽度、所述晶体的厚度和所述源光束的波长得到所述晶体的折射率。
  9. 基于条纹图像的晶体折射率测量装置，包括存储器、处理器及存储在存储器上并可在处理器上运行的计算机程序，其特征在于，所述处理器执行所述计算机程序时实现如权利要求1至7任一项所述的晶体折射率测量方法。
  10. 一种存储介质，其特征在于，所述存储介质中存储有可执行指令，所述可执行指令被处理器执行时实现如权利要求1至7任一项所述的晶体折射率测量方法。
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