WO2020191545A1 - 曲面检材的应力分析系统 - Google Patents

曲面检材的应力分析系统 Download PDF

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WO2020191545A1
WO2020191545A1 PCT/CN2019/079333 CN2019079333W WO2020191545A1 WO 2020191545 A1 WO2020191545 A1 WO 2020191545A1 CN 2019079333 W CN2019079333 W CN 2019079333W WO 2020191545 A1 WO2020191545 A1 WO 2020191545A1
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curved
interference
wavefront
stress
phase
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PCT/CN2019/079333
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English (en)
French (fr)
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王星泽
何良雨
闫静
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合刃科技（深圳）有限公司
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Priority to PCT/CN2019/079333 priority Critical patent/WO2020191545A1/zh
Priority to CN201980005547.1A priority patent/CN111386449B/zh
Publication of WO2020191545A1 publication Critical patent/WO2020191545A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet

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  • the invention relates to the technical field of industrial inspection, in particular to a stress analysis system for surface inspection materials.
  • the current glass stress detection methods are mostly aimed at flat glass.
  • the accuracy is often not high.
  • the method of detecting coherent light plane glass stress is used to detect 3D curved glass, since the optical elements such as lenses cannot be attached to the optical surface of the 3D curved glass, it is difficult for the illumination beam to propagate as required in the part that cannot be attached.
  • the stress distribution of 3D curved glass detected by interference imaging is not accurate.
  • a stress analysis system for surface inspection materials including:
  • Light source used to emit illumination beam
  • a polarizer a first wavefront modulating lens, a curved surface inspection material, a second wavefront modulating lens, an analyzer, and an image sensor sequentially arranged on the light path of the illumination beam;
  • the polarizer is used to polarize the illumination beam to a preset target polarization direction
  • the thickness distribution of the first wavefront modulating lens and the distance to the curved specimen satisfy a condition: the wavefront of the illumination beam reaching the incident surface of the curved specimen is consistent with the incident surface of the curved specimen;
  • the thickness distribution of the second wavefront modulating lens and the distance to the curved sample satisfy a condition: the second wavefront modulating lens and the first wavefront modulating lens form a conjugate system;
  • the analyzer is used to combine the components of the illumination beam with different polarization directions to produce interference
  • the image sensor is used to collect interference imaging of the illumination beam
  • the device also includes a processor for acquiring the interference imaging collected by the image sensor, and detecting the stress distribution of the curved surface inspection material according to the interference imaging.
  • the light source is a monochromatic coherent light source
  • the illumination light beam is a monochromatic coherent light beam
  • the processor is used to detect the interference position and interference fringe interval of the interference imaging, determine the stress point of the curved surface inspection material according to the interference position, and determine the stress according to the interference fringe interval Point stress distribution.
  • the thickness distribution of the first wavefront modulating lens and the distance from the curved surface inspection material satisfy:
  • N is the refractive index of the first wavefront modulating lens
  • two beams i and j of the illuminating beam are incident on the incident surface of the first wavefront modulating lens through positions Ai and Aj respectively, and are modulated by the first wavefront
  • the lens exits at positions Bi and Bj on the exit surface, and then enters via the positions Ci and Cj on the entrance surface of the curved sample.
  • system further includes:
  • phase adjuster arranged on the optical path of the illumination light beam, the phase adjuster is located between the light source and the polarizer, and is used to adjust the phase of the illumination light beam;
  • the image sensor is also used to collect interference imaging in multiple phases adjusted by the phase adjuster.
  • the adjacent phase difference of the multiple phases adjusted by the phase adjuster is ⁇ /2.
  • the processor is further configured to obtain at least 4 interference imaging images collected by the image sensor, and the phase differences of the illumination beams corresponding to the 4 interference images are ⁇ /2, ⁇ , and 3 respectively. ⁇ /2;
  • the processor is also used to obtain the light intensity information of the same position in the four interference imaging, calculate the phase of the interference fringe at this position according to the light intensity information, and then obtain the phase distribution of the interference fringe through unwrapping processing, according to The phase distribution is combined with the photoelastic coefficient of the curved surface inspection material to obtain the stress distribution of the curved surface inspection material.
  • the processor is further configured to:
  • the I 1 (x, y), I 2 (x, y), I 3 (x, y), I 4 (x, y) are the light intensities of 4 interference images at the same (x, y) position ,
  • the A(x, y) is the background intensity, and the B(x, y) is the intensity of the illumination beam.
  • the processor is further configured to obtain a defect recognition model based on machine learning.
  • the defect recognition model includes at least cracks, bubbles, stones, and non-defect output categories, and the output categories pass through corresponding categories.
  • the stress distribution of the sample has a corresponding confidence after machine learning training;
  • the processor is further configured to input the stress distribution into the defect recognition model, and determine the defect corresponding to the curved surface inspection material according to the obtained confidence level of the output category.
  • a wavefront modulation lens is added before and after the curved inspection materials.
  • the wavefront modulation lens makes the interference imaging detection stress distribution
  • the illuminating beam reaches the curved specimen since the optical path difference of each beam propagating to the outer surface of the curved specimen is the same, the wavefront of the illuminating beam reaching the curved specimen coincides with the outer surface of the curved specimen, thereby causing interference Imaging is only an objective reflection of the stress distribution in the surface sample, and will not be affected by the interference phenomenon caused by the inconsistent wavefront at the same time, thereby improving the accuracy of stress analysis.
  • Fig. 1 is a schematic diagram of a stress analysis system for surface inspection materials in an embodiment
  • Figure 2 is a schematic diagram of wavefront modulation in an embodiment
  • FIG. 3 is a schematic diagram of a process of calculating a phase diagram by phase shifting in an embodiment
  • FIG. 4 is a flowchart of a process of calculating a stress distribution map according to interference imaging in an embodiment
  • FIG. 5 is a schematic diagram of defect recognition for stress distribution based on machine learning in an embodiment.
  • Figure 1 shows the optical device and light path diagram, where the stress analysis system includes:
  • the light source 10 is used to emit an illumination beam.
  • Light emitting diodes, laser diodes, etc. can be used as the light source 10.
  • the light source 10 is a monochromatic coherent light source, and the emitted illuminating beam is a monochromatic coherent light.
  • it can be a blue laser or a blue laser diode.
  • the stress analysis system further includes a polarizer 20, a first wavefront modulating lens 30, a second wavefront modulating lens 40, an analyzer 50, and an image sensor 60 sequentially arranged on the optical path of the illumination beam. .
  • a polarizer 20 When analyzing the stress distribution of the curved sample, it is necessary to place the curved sample between the first wavefront modulation lens 30 and the second wavefront modulation lens 40, and the outer curve of the curved sample faces the first wavefront modulation lens 30,
  • the inner curved surface faces the second wavefront modulating lens 40, and the distance and relative position of the curved sample from the first wavefront modulating lens 30 and the first wavefront modulating lens 40 need to meet certain conditions, specifically:
  • the polarizer 20 is used to polarize the illumination beam to a preset target polarization direction.
  • the thickness distribution of the first wavefront modulating lens 30 and the distance to the curved sample meet the condition: the wavefront of the illumination beam reaching the incident surface of the curved sample is consistent with the incident surface of the curved sample.
  • the design of the wavefront modulation lens 30 is the key to the optical system.
  • the wavefront is used to calculate the lattice of the lens surface, and then through fitting The spline curve finally generates a smooth and continuous lens surface shape.
  • the thickness distribution of the first wavefront modulating lens and the distance to the curved inspection material satisfy:
  • N is the refractive index of the first wavefront modulating lens
  • two beams i and j of the illuminating beam are incident on the incident surface of the first wavefront modulating lens through positions Ai and Aj respectively, and are modulated by the first wavefront
  • the lens exits at positions Bi and Bj on the exit surface, and then enters via the positions Ci and Cj on the entrance surface of the curved sample.
  • A1 and A2 are two points on the incident surface of the first wavefront modulating lens.
  • the beam 1 enters the first wavefront modulating lens from A1, and exits the first wavefront modulating lens from B1. That is, the thickness L1 of the first wavefront modulation lens at the A1 position.
  • C1 is the position where the beam 1 is emitted from B1 and enters the curved specimen. That is, the optical path of beam 1 from A1 to C1 through B1, That is, the optical path of beam 2 from A2 to C2 through B2. Keeping beam 1 and beam 2 reaching the same optical path at different positions of the incident surface of the curved sample can ensure that the wavefront of the illumination beam reaching the incident surface of the curved sample is consistent with the incident surface of the curved sample.
  • the first wavefront modulation lens is a free-form surface mirror, and the process of customizing the surface of the free-form surface mirror is based on the outer surface of the curved surface.
  • the optical length from wavefront A to wavefront C it can be determined as N ⁇ L1+B1C1. Since the wavefront C has been determined (the incident surface of the curved sample), C2 is determined.
  • the A2 on the wavefront A is also determined, and because the light path of the corresponding point during the evolution of the wavefront A to the wavefront C is the same, the thickness of A2B2 can be calculated as L2.
  • the lens thickness of the first wavefront modulating lens at different positions can be calculated and fitted, that is, the curved shape of the first wavefront modulating lens, which corresponds to the incident surface of the curved sample and can be adapted to any
  • the incident surface of the curved sample is a free-form surface, thus completing the design of the free-form surface wavefront modulation lens.
  • the thickness distribution of the second wavefront modulation lens and the distance to the curved sample also satisfy the condition that the second wavefront modulation lens and the first wavefront modulation lens form a conjugate system.
  • the wavefront of the illumination light beam emitted from the exit surface of the second wavefront modulation lens is consistent with the exit surface of the second wavefront modulation lens.
  • the matching second wavefront modulation lens can also be customized by calculating the optical path, and this process will not be repeated.
  • the interference method when using the interference method to analyze the stress distribution of flat glass, it is based on the principle that the light at the same wavefront position interferes due to the phase change caused by the uneven stress distribution.
  • the phase change can be analyzed by analyzing the interference fringe. Get the stress distribution.
  • the illuminating beam is parallel light.
  • the wavefront is naturally attached to the surface of the flat glass.
  • the curved surface is directly irradiated without modulation, the wavefront and curved surface cannot be guaranteed. Fit, so that the interference fringes not only depend on the phase change caused by the uneven stress distribution, but also affected by the phase change caused by the inconsistent wavefront.
  • the influence of the phase change caused by the wavefront inconsistency on the interference fringes is eliminated, so that the phase change detected by the interference fringe depends only on the stress. Distribution, so the stress distribution analysis can be performed more accurately.
  • the analyzer 50 is used to combine the components of the illumination beam with different polarization directions to produce interference.
  • the image sensor 60 is used to collect interference imaging of the illumination beam.
  • the light emitted by the monochromatic light source becomes linearly polarized light that is consistent with the vibration direction after passing through the polarizer, and then passes through the first wavefront modulation lens (customized according to the surface of the curved sample) to make the wave of the emitted light
  • the front can be consistent with the surface of the curved material.
  • After the light passes through the curved glass it is decomposed into different polarized light according to the main stress direction of the force point, and then passes through the second wavefront modulating lens and the analyzer.
  • the analyzer combines the two light components with different polarization directions before and after the light passes to generate an interference fringe pattern, which is collected by the image sensor 60.
  • the above is the light path part of the stress analysis system for the curved surface inspection material.
  • the stress analysis system also includes a processor 70 for acquiring the interference imaging collected by the image sensor, and detecting the stress of the curved surface inspection material according to the interference imaging. distributed.
  • the processor 70 is configured to detect the interference position and the interference fringe interval of the interference imaging, determine the stress point of the curved surface inspection material according to the interference position, and determine the stress distribution of the stress point according to the interference fringe interval .
  • the method of the processor 70 to analyze the stress distribution can refer to the detection method of the plane glass based on the interference principle in the traditional technology. This is because due to the action of the first wavefront modulation lens and the second wavefront modulation lens, the image sensor The interferometric imaging collected by 60 is not interfered by the phase error caused by the non-fitting of the curved sample and the wavefront, so that the stress distribution of the curved sample is analyzed with the same accuracy as the stress distribution of the plane sample.
  • the first wavefront modulation lens and the second wavefront modulation lens are optical devices customized according to the curved surface inspection material. That is to say, when replacing curved samples with different shapes or different outer surface curvatures for testing, the first wavefront modulating lens and the second wavefront modulating lens that match them need to be re-customized according to the aforementioned method.
  • a customizable refraction element in order to adapt to a variety of curved surfaces, can also be used as the first wavefront modulation lens and the second wavefront modulation lens.
  • the customizable refractive element includes a transparent elastic cavity and a filling liquid with a fixed refractive index.
  • the processor 70 is connected to it. After the curved sample is replaced, the outer surface shape of the curved sample is photographed by the camera, and then the processor 70 controls the filling or withdrawal of the filling liquid in the transparent elastic cavity according to the outer surface shape, thereby passing the filling And the method of extracting the filling liquid increases or decreases the thickness of the refractive element to achieve the effect of modulating the wavefront.
  • the stress analysis system for curved material inspection further includes a phase adjuster 80 arranged on the optical path of the illuminating beam.
  • the phase adjuster is located between the light source and the polarizer. To adjust the phase of the illumination beam.
  • the image sensor 60 is also used to collect interference imaging in multiple phases adjusted by the phase adjuster 80.
  • the adjacent phase difference of the multiple phases adjusted by the phase adjuster is ⁇ /2
  • the processor 70 is further configured to obtain at least four interference imaging images collected by the image sensor, and the illumination corresponding to the four interference images
  • the phase difference of the light beam is ⁇ /2, ⁇ , and 3 ⁇ /2, respectively.
  • the processor 70 needs to control the image sensor 60 to collect at least 4 images. First take a picture (equivalent to a phase shift of 0 ⁇ ), and then use the phase adjuster 80 to shift the illumination beam relative to the initial phase by ⁇ /2 on the light path of the illuminating beam, and then take another picture. On the optical path of the illuminating beam, the illuminating beam is phase-shifted relative to the initial phase by ⁇ and then another shot is taken. The phase adjuster 80 shifts the illuminating beam relative to the initial phase by 3 ⁇ /2 on the optical path of the illuminating beam and then takes another shot. A total of 4 interference images were collected.
  • the phase adjuster 80 can be connected to the processor 70, and under the control of the control instruction of the processor 70, the phase adjustment is performed sequentially.
  • the phase adjuster 70 can also be adjusted manually, every phase shift by ⁇ /2, that is, the processor 70 is manually controlled to obtain the interference image corresponding to the phase from the image sensor 60.
  • the processor 70 is also used to obtain the light intensity information of the same position in the four interference imaging, calculate the phase of the interference fringe at that position according to the light intensity information, and then obtain the phase distribution of the interference fringe through the unwrapping process.
  • the phase distribution is combined with the photoelastic coefficient of the curved surface inspection material to obtain the stress distribution of the curved surface inspection material.
  • the processor is used to calculate the interference fringe phase at the same position in the four interference imaging images according to the light intensity information at the same position, according to the following formula:
  • the I 1 (x, y), I 2 (x, y), I 3 (x, y), I 4 (x, y) are the light intensities of 4 interference images at the same (x, y) position ,
  • the A(x, y) is the background intensity, and the B(x, y) is the intensity of the illumination beam. That is to say, when the interference method in the traditional technology detects the stress distribution, the interference imaging detected by the image sensor will be affected by the ambient light and the background light, and because the light intensity of the ambient light or the background light cannot be effectively measured, the Cosine value reverse calculation phase When the calculation result is not accurate, the wrong phase data is obtained.
  • phase shift method it can be seen that four interference imaging images with phase differences of 0, ⁇ /2, ⁇ , 3 ⁇ /2 are taken, and the ambient light A(x, y) can be eliminated through corresponding calculations. And then by calculating the arctangent, the phase of any point on the interference imaging can be obtained The phase diagram of the entire interferometric imaging is finally obtained (refer to Figure 3).
  • the processor can execute the following methods by running a computer program:
  • Step S102 Obtain the interference imaging image collected by the image sensor.
  • Step S104 Calculate the arctangent of the phase of the point position according to the light intensity information of any point in the interference imaging image, thereby calculating the phase of the point position.
  • Step S106 Obtain a phase map (full-field phase distribution map) corresponding to the interference imaging through filtering and denoising combined with a dewrapping algorithm.
  • Step S108 Combining the phase diagram and the photoelastic coefficient of the curved surface material to calculate the corresponding stress distribution diagram.
  • the collected stress diagrams can be analyzed category by category to provide reference for the improvement of glass production process.
  • machine learning can also be used for large sample training and learning based on the glass stress distribution map.
  • the processor is also used to obtain a defect recognition model based on machine learning.
  • the defect recognition model includes at least output categories of cracks, bubbles, stones, and non-defects, and the output categories pass through corresponding categories.
  • the stress distribution of the sample has a corresponding confidence after machine learning training;
  • the processor is further configured to input the stress distribution into the defect recognition model, and determine the defect corresponding to the curved surface inspection material according to the obtained confidence level of the output category.
  • the stress distribution diagram generated by cracks, the stress distribution diagram generated by bubbles, and the stress distribution diagram generated by stones can be input as sample data into the defect recognition model for training.
  • the stress distribution The probability decision tree corresponding to the features in the figure is gradually improved and accurate.
  • the defect recognition model will output the probability of each defect category (crack, bubble, stone and no defect) corresponding to the stress distribution map Degree is the degree of confidence.
  • the processor can select the defect category with the highest confidence as the defect identification of the curved surface inspection material corresponding to the stress distribution map.
  • a wavefront modulation lens is added before and after the curved inspection materials.
  • the wavefront modulation lens makes the interference imaging detection stress distribution
  • the illuminating beam reaches the curved specimen since the optical path difference of each beam propagating to the outer surface of the curved specimen is the same, the wavefront of the illuminating beam reaching the curved specimen coincides with the outer surface of the curved specimen, thereby causing interference Imaging is only an objective reflection of the stress distribution in the surface sample, and will not be affected by the interference phenomenon caused by the inconsistent wavefront at the same time, thereby improving the accuracy of stress analysis.

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Abstract

一种曲面检材的应力分析系统，包括：光源（10），用于发出照明光束；以及在该照明光束的光路上依次设置的起偏器（20）、第一波前调制透镜（30）、曲面检材、第二波前调制透镜（40）、检偏器（50）和图像传感器（60）；第一波前调制透镜（30）的厚度分布与到曲面检材的距离满足条件：照明光束抵达曲面检材的入射面的波前与该曲面检材的入射面一致；图像传感器（60）用于采集照明光束的干涉成像；该装置还包括处理器（70），用于获取图像传感器（60）采集的干涉成像，根据该干涉成像检测该曲面检材的应力分布。该曲面检材的应力分析系统更加准确。

Description

曲面检材的应力分析系统 技术领域
本发明涉及工业检测技术领域，特别涉及一种曲面检材的应力分析系统。
背景技术
随着移动互联网行业的迅猛发展，智能移动终端的厂商和产品层出不穷，智能移动终端的外观壳体的材质也在不断的改进。目前，主流的手机厂商纷纷推出了基于3D曲面玻璃的终端产品，因其透明洁净、抗指纹、防眩光、易与柔性OLED屏配合、更符合人体工程学等优点而得到众多手机厂商和消费者的青睐。
但在3D曲面玻璃的加工制程需要经过玻璃的“热弯”工艺。该工艺产出的玻璃会不同程度的存在残余应力，影响玻璃的使用性。另外，由于玻璃质量不良或成分不均匀(例如玻璃中存在裂缝、结石、气泡等缺陷)，各组分的热膨胀系数不同，冷却至室温时会产生应力突变，该突变点为应力奇异点，严重时会造成玻璃的炸裂。因此，在3D曲面玻璃的生产工艺中，需要对玻璃应力进行测量，从而保证3D曲面玻璃的良率和安全性能。
然而，目前的玻璃应力检测方法多针对平面玻璃。在采用检测平面玻璃应力分布的方法去检测3D曲面玻璃的应力分布时，往往准确度不高。例如，采用检测相干光平面玻璃应力的方法去检测3D曲面玻璃时，由于透镜等光学元件和3D曲面玻璃的光学表面不能贴合，使得照明光束难以在不能贴合的部分按要求传播，从而使得通过干涉成像检测到的3D曲面玻璃的应力分布不准确。
发明内容
基于此，为解决现有技术中通过干涉成像检测到的3D曲面玻璃的应力分布不准确的技术问题，特提出了一种曲面检材的应力分析系统。
一种曲面检材的应力分析系统，包括：
光源，用于发出照明光束；
以及在所述照明光束的光路上依次设置的起偏器、第一波前调制透镜、曲 面检材、第二波前调制透镜、检偏器和图像传感器；
所述起偏器用于将所述照明光束偏振预设的目标偏振方向；
所述第一波前调制透镜的厚度分布与到所述曲面检材的距离满足条件：所述照明光束抵达所述曲面检材的入射面的波前与所述曲面检材的入射面一致；
所述第二波前调制透镜的厚度分布与到所述曲面检材的距离满足条件：所述第二波前调制透镜与第一波前调制透镜形成共轭系统；
所述检偏器用于结合不同偏振方向的照明光束的分量产生干涉；
所述图像传感器用于采集所述照明光束的干涉成像；
所述装置还包括处理器，用于获取所述图像传感器采集的干涉成像，根据所述干涉成像检测所述曲面检材的应力分布。
在其中一个实施例中，所述光源为单色相干光源，所述照明光束为单色相干光束。
在其中一个实施例中，所述处理器用于检测所述干涉成像的干涉位置和干涉条纹间隔，根据所述干涉位置确定所述曲面检材的应力点，根据所述干涉条纹间隔确定所述应力点的应力分布。
在其中一个实施例中，所述第一波前调制透镜的厚度分布、到所述曲面检材的距离满足：
Figure PCTCN2019079333-appb-000001
N为所述第一波前调制透镜的折射率，照明光束中的两束i和j分别经位置Ai和Aj入射所述第一波前调制透镜的入射表面，经所述第一波前调制透镜的出射表面上的位置Bi和Bj出射，再分别经所述曲面检材的入射表面上的位置Ci和Cj入射。
在其中一个实施例中，所述系统还包括：
设置在所述照明光束的光路上的相位调节器，所述相位调节器位于所述光源和起偏器之间，用于调节所述照明光束的相位；
所述图像传感器还用于采集经所述相位调节器调节的多个相位下的干涉成像。
在其中一个实施例中，相位调节器调节的多个相位的相邻相位差为π/2。
在其中一个实施例中，所述处理器还用于获取所述图像传感器采集的至少4幅干涉成像，且所述4幅干涉图像对应的照明光束的相位差分别为π/2、π、3 π/2；
所述处理器还用于获取所述4幅干涉成像中同一位置的光强信息，根据所述光强信息计算该位置的干涉条纹相位，再通过去包裹处理，得到干涉条纹的相位分布，根据所述相位分布结合所述曲面检材的光弹性系数得到所述曲面检材的应力分布。
在其中一个实施例中，所述处理器还用于根据：
Figure PCTCN2019079333-appb-000002
Figure PCTCN2019079333-appb-000003
Figure PCTCN2019079333-appb-000004
Figure PCTCN2019079333-appb-000005
Figure PCTCN2019079333-appb-000006
计算干涉图像上(x，y)位置处对应的照明光束的相位
Figure PCTCN2019079333-appb-000007
所述I 1(x，y)、I 2(x，y)、I 3(x，y)、I 4(x，y)为4幅干涉图像分别在相同(x，y)位置的光强，所述A(x，y)为背景强度，所述B(x，y)为照明光束的强度。
在其中一个实施例中，所述处理器还用于获取基于机器学习的缺陷识别模型，所述缺陷识别模型至少包括裂纹、气泡、结石和无缺陷的输出类别，且所述输出类别经过对应类别的样本应力分布的机器学习训练后具有相应的置信度；
所述处理器还用于将所述应力分布输入到所述缺陷识别模型中，根据得到的输出类别的置信度的高低确定所述曲面检材对应的缺陷。
实施本发明实施例，将具有如下有益效果：
采用了上述曲面检材的应力分析系统之后，在经过曲面检材的光路中，在曲面检材的前后添加了波前调制透镜，该波前调制透镜使得，用于进行干涉成像检测应力分布的照明光束在抵达曲面检材时，由于各光束传播到曲面检材的外表面的光程差相同，使得照明光束抵达曲面检材的波前与曲面检材的外表面 吻合，从而使得形成的干涉成像仅仅为曲面检材中应力分布的客观反映，而不会同时受到波前不一致而产生的干涉现象的影响，从而提高了应力分析的准确度。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
其中：
图1为一个实施例中一种曲面检材的应力分析系统的示意图；
图2为一个实施例中波前调制的原理图；
图3为一个实施例中通过相移计算位相图的过程的示意图；
图4为一个实施例中根据干涉成像计算应力分布图的过程的流程图；
图5为一个实施例中基于机器学习针对应力分布进行缺陷识别的原理图。
具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
为解决采用传统技术中的基于干涉原理的应力分析系统在分析3D曲面玻璃等曲面检材时准确度较低的技术问题，本发明特提出了一种曲面检材的应力分析系统，可参考图1所示，图1展示了该的光学器件和光路图，其中，该应力分析系统包括：
光源10，用于发出照明光束。可采用发光二极管、激光二极管等作为光源10。在本实施例中，为提高准确度，该光源10为单色相干光源，发出的照明光束为单色相干光。例如，可以是蓝光激光器或蓝光激光二极管等。
如图1所示，该应力分析系统还包括在照明光束的光路上依次设置的起偏器20、第一波前调制透镜30、第二波前调制透镜40、检偏器50和图像传感器60。在分析曲面检材的应力分布时，需要将曲面检材置于第一波前调制透镜30和第二波前调制透镜40之间，曲面检材的外曲面朝向第一波前调制透镜30，内曲面朝向第二波前调制透镜40，且曲面检材与第一波前调制透镜30和第一波前调制透镜40的距离和相对位置需要满足一定的条件，具体的：
起偏器20用于将照明光束偏振预设的目标偏振方向。
第一波前调制透镜30的厚度分布与到曲面检材的距离满足条件：照明光束抵达曲面检材的入射面的波前与曲面检材的入射面一致。
在本实施例中，波前调制透镜30的设计为光学系统的关键。而实施例中，基于惠更斯原理，结合光线和波前同时进行设计，在已知曲面检材的表面的几何形状的情况下，利用波前计算出透镜表面的点阵，再通过拟合样条曲线，最终生成光滑连续的透镜表面形状。
第一波前调制透镜的厚度分布、到所述曲面检材的距离满足：
Figure PCTCN2019079333-appb-000008
N为所述第一波前调制透镜的折射率，照明光束中的两束i和j分别经位置Ai和Aj入射所述第一波前调制透镜的入射表面，经所述第一波前调制透镜的出射表面上的位置Bi和Bj出射，再分别经所述曲面检材的入射表面上的位置Ci和Cj入射。
参考图2所示，A1和A2为第一波前调制透镜的入射表面上两点，光束1从A1入射入第一波前调制透镜，由B1出射第一波前调制透镜，线段
Figure PCTCN2019079333-appb-000009
即为在A1位置处第一波前调制透镜的厚度L1。C1为光束1由B1出射后，入射曲面检材的位置。
Figure PCTCN2019079333-appb-000010
即为光束1由A1入射经B1抵达C1的光程，
Figure PCTCN2019079333-appb-000011
即为光束2由A2入射经B2抵达C2的光程。保持光束1和光束2抵达曲面检材的入射表面不同位置的光程一致，即可保证照明光束抵达曲面检材的入射面的波前与曲面检材的入射面一致。
在一个实施例中，第一波前调制透镜为自由曲面镜，而根据曲面检材的外表面即为定制自由曲面镜表面的过程。根据波前A到波前C的光程便可确定为N×L1+B1C1。由于波前C已经确定(曲面检材的入射表面)，因此C2便被确定。 波前A上的A2也是确定的，又因为波前A演变为波前C过程中所对应的点经过的光程是一样的，由此便可计算出A2B2的厚度为L2。以此类推可计算拟合出第一波前调制透镜在不同位置处的透镜厚度，也即第一波前调制透镜的曲面形状，该形状与曲面检材的入射表面对应，可适配任一曲面检材的入射表面，为自由曲面，从而完成自由曲面的波前调制透镜的设计。
相应的，在本实施例中，第二波前调制透镜的厚度分布与到曲面检材的距离也满足条件：所述第二波前调制透镜与第一波前调制透镜形成共轭系统。
也就是说，照明光束由第二波前调制透镜的出射面出射的波前与所述第二波前调制透镜的出射面一致。基于前述相同的理由，也可通过计算光程来定制相配套的第二波前调制透镜，此过程不再赘述。
在传统技术中，采用干涉法分析平面玻璃的应力分布时，其基于的原理为同一波前位置的光线由于应力分布的不均匀导致相位变化而产生干涉，通过干涉条纹分析相位变化，即可分析得到应力分布。而在分析平面玻璃时，照明光束为平行光，垂直照射在平面玻璃上时，波前自然与平面玻璃的表面贴合，但若不经调制直接照射曲面检材，则无法保证波前与曲面贴合，从而使得干涉条纹不光取决于应力分布不均匀所导致的相位变化，还受到波前不一致产生的相位变化的影响。
而采用了上述第一波前调整透镜30和第二波前调制透镜40后，排除了波前不一致产生的相位变化对干涉条纹的影响，从而使得通过干涉条纹检测到的相位变化仅仅取决于应力分布情况，因此可更加准确地进行应力分布分析。
在本实施例中，检偏器50则用于结合不同偏振方向的照明光束的分量产生干涉。
图像传感器60用于采集所述照明光束的干涉成像。
也就是说，单色光源发出的光，通过起偏器后变为与振动方向一致的线偏振光，然后经过第一波前调制透镜(根据曲面检材的表面定制)，使出射光的波前能够和曲面检材的表面一致。光线通过曲面玻璃后，根据受力点的主应力方向被分解成不同的偏振光，之后再通过第二波前调制透镜和检偏器。检偏器在光线通过前后将两个偏振方向不同的光线分量结合起来，从而生成干涉条纹图案，并由图像传感器60采集。
以上即为本曲面检材的应力分析系统的光路部分，该应力分析系统还包括 处理器70，用于获取所述图像传感器采集的干涉成像，根据所述干涉成像检测所述曲面检材的应力分布。
具体的，处理器70用于检测所述干涉成像的干涉位置和干涉条纹间隔，根据所述干涉位置确定所述曲面检材的应力点，根据所述干涉条纹间隔确定所述应力点的应力分布。
也就是说，处理器70分析应力分布的方法可参考传统技术中基于干涉原理而针对平面玻璃的检测方法，这是因为由于第一波前调制透镜和第二波前调制透镜的作用，图像传感器60采集的干涉成像不受曲面检材与波前不贴合所造成相位误差干扰，使得此时采用干涉法分析曲面检材的应力分布和分析平面检材的应力分布有着相同的准确性。
需要说明的是，在本实施例中，第一波前调制透镜和第二波前调制透镜为根据曲面检材进行定制的光学器件。也就是说，当更换不同形状或不同外表面曲率的曲面检材进行检测时，需要按照前述的方法重新定制与之匹配的第一波前调制透镜和第二波前调制透镜。
而在另一个实施例中，为了适应多种曲面检材，还可采用可定制的折射元件作为第一波前调制透镜和第二波前调制透镜。该可定制的折射元件包括透明弹性腔体和具有固定折射率的填充液。处理器70与其连接，在更换了曲面检材后，先通过相机拍摄曲面检材的外表面形状，然后处理器70根据外表面形状控制透明弹性腔体内填充液的充入或抽出，从而通过填充和抽出填充液的方法增减折射元件的厚度，以达到对波前调制的作用。
在一个实施例中，如图1所示，该曲面检材的应力分析系统还包括设置在照明光束的光路上的相位调节器80，相位调节器位于所述光源和起偏器之间，用于调节照明光束的相位。
图像传感器60还用于采集经相位调节器80调节的多个相位下的干涉成像。
具体的，相位调节器调节的多个相位的相邻相位差为π/2，处理器70还用于获取所述图像传感器采集的至少4幅干涉成像，且所述4幅干涉图像对应的照明光束的相位差分别为π/2、π、3π/2。
也就是说，参考图3所示，处理器70需要控制图像传感器60采集至少4幅图像。初始先拍摄一张(相当于相移了0π)，然后通过相位调节器80在照明光束的光路上将照明光束相对于初始相位相移π/2后再拍摄一张，通过相位调 节器80在照明光束的光路上将照明光束相对于初始相位相移π后再拍摄一张，通过相位调节器80在照明光束的光路上将照明光束相对于初始相位相移3π/2后再拍摄一张，共计采集4幅干涉图像。在本实施例中，相位调节器80可与处理器70连接，在处理器70的控制指令的控制下，依序进行相位调节。在其他实施例中，也可手动对相位调节器70进行调节，每相移π/2，即手动控制处理器70由所述图像传感器60获取该相位对应的干涉图像。
处理器70还用于获取所述4幅干涉成像中同一位置的光强信息，根据所述光强信息计算该位置的干涉条纹相位，再通过去包裹处理，得到干涉条纹的相位分布，根据所述相位分布结合所述曲面检材的光弹性系数得到所述曲面检材的应力分布。
具体的，所述处理器用于根据4幅干涉成像的图像中同一位置的光强信息计算该位置的干涉条纹相位，是根据如下公式：
Figure PCTCN2019079333-appb-000012
Figure PCTCN2019079333-appb-000013
Figure PCTCN2019079333-appb-000014
Figure PCTCN2019079333-appb-000015
Figure PCTCN2019079333-appb-000016
计算干涉图像上(x，y)位置处对应的照明光束的相位
Figure PCTCN2019079333-appb-000017
所述I 1(x，y)、I 2(x，y)、I 3(x，y)、I 4(x，y)为4幅干涉图像分别在相同(x，y)位置的光强，所述A(x，y)为背景强度，所述B(x，y)为照明光束的强度。也就是说，传统技术中的干涉法检测应力分布的时候，图像传感器检测的干涉成像会受到环境光和背景光的影响，且由于环境光或背景光的光强无法有效测量，使得在通过计算余弦值反向计算相位
Figure PCTCN2019079333-appb-000018
时，计算结果不准确，从而得到错误的相位数据。
而通过上述相移的方法可看出，拍摄4张相位差依次为0、π/2、π、3π/2的干涉成像图像，通过相应的运算，可排除掉环境光A(x，y)的影响，然后通过计算反正切，即可得到干涉成像上任意一点的相位
Figure PCTCN2019079333-appb-000019
最终得到整个干涉成像的位相图(参考图3)。
在得到干涉成像的位相图之后，即可去包裹处理，得到干涉条纹的相位分布，根据所述相位分布结合所述曲面检材的光弹性系数得到所述曲面检材的应力分布。具体的，参考图4所示，处理器可通过运行计算机程序执行如下方法：
步骤S102：获取图像传感器采集的干涉成像图像。
步骤S104：根据干涉成像图像中任一点的光强信息计算该点位置的相位的反正切，从而计算该点位置的相位。
步骤S106：通过滤波去噪结合去包裹算法，得到与干涉成像对应的位相图(全场相位分布图)。
步骤S108：结合位相图和曲面检材的光弹性系数计算得到相应的应力分布图。
玻璃产生应力的原因多种多样，包括热处理后未释放的残留应力，异物(裂纹，气泡，结石等)缺陷带来的结构应力等。不同的原因对应着各不相同的应力图，因此，可以对采集到的应力图进行逐类分析，为玻璃生产工艺的改良提供参考。在本实施例中，还可根据玻璃应力分布图，利用机器学习进行大样本训练和学习。具体的，参考图5所示，处理器还用于获取基于机器学习的缺陷识别模型，所述缺陷识别模型至少包括裂纹、气泡、结石和无缺陷的输出类别，且所述输出类别经过对应类别的样本应力分布的机器学习训练后具有相应的置信度；
处理器还用于将所述应力分布输入到所述缺陷识别模型中，根据得到的输出类别的置信度的高低确定所述曲面检材对应的缺陷。
也就是说，可预先将裂纹产生的应力分布图、气泡产生的应力分布图、结石产生的应力分布图作为样本数据输入到缺陷识别模型中进行训练，通过训练的加深和样本的递增，应力分布图中的特征对应的概率决策树逐渐完善和准确。当处理器将分析得到的应力分布图输入到该已训练的缺陷识别模型中后，该缺陷识别模型则会输出该应力分布图对应的各个缺陷类别(裂纹、气泡、结石和无缺陷)的概率度，即置信度。处理器可选择置信度最高的缺陷类别作为对该应力分布图对应的曲面检材的缺陷认定。
本发明实施例，将具有如下有益效果：
采用了上述曲面检材的应力分析系统之后，在经过曲面检材的光路中，在 曲面检材的前后添加了波前调制透镜，该波前调制透镜使得，用于进行干涉成像检测应力分布的照明光束在抵达曲面检材时，由于各光束传播到曲面检材的外表面的光程差相同，使得照明光束抵达曲面检材的波前与曲面检材的外表面吻合，从而使得形成的干涉成像仅仅为曲面检材中应力分布的客观反映，而不会同时受到波前不一致而产生的干涉现象的影响，从而提高了应力分析的准确度。
以上所揭露的仅为本发明较佳实施例而已，当然不能以此来限定本发明之权利范围，因此依本发明权利要求所作的等同变化，仍属本发明所涵盖的范围。

Claims (9)

  1. 一种曲面检材的应力分析系统，其特征在于，包括：
    光源，用于发出照明光束；
    以及在所述照明光束的光路上依次设置的起偏器、第一波前调制透镜、曲面检材、第二波前调制透镜、检偏器和图像传感器；
    所述起偏器用于将所述照明光束偏振预设的目标偏振方向；
    所述第一波前调制透镜的厚度分布与到所述曲面检材的距离满足条件：所述照明光束抵达所述曲面检材的入射面的波前与所述曲面检材的入射面一致；
    所述第二波前调制透镜的厚度分布与到所述曲面检材的距离满足条件：所述第二波前调制透镜与第一波前调制透镜形成共轭系统；
    所述检偏器用于结合不同偏振方向的照明光束的分量产生干涉；
    所述图像传感器用于采集所述照明光束的干涉成像；
    所述装置还包括处理器，用于获取所述图像传感器采集的干涉成像，根据所述干涉成像检测所述曲面检材的应力分布。
  2. 根据权利要求1所述的曲面检材的应力分析系统，其特征在于，所述光源为单色相干光源，所述照明光束为单色相干光束。
  3. 根据权利要求1所述的曲面检材的应力分析系统，其特征在于，所述处理器用于检测所述干涉成像的干涉位置和干涉条纹间隔，根据所述干涉位置确定所述曲面检材的应力点，根据所述干涉条纹间隔确定所述应力点的应力分布。
  4. 根据权利要求1所述的曲面检材的应力分析系统，其特征在于，所述第一波前调制透镜的厚度分布、到所述曲面检材的距离满足：
    Figure PCTCN2019079333-appb-100001
    N为所述第一波前调制透镜的折射率，照明光束中的两束i和j分别经位置Ai和Aj入射所述第一波前调制透镜的入射表面，经所述第一波前调制透镜的出射表面上的位置Bi和Bj出射，再分别经所述曲面检材的入射表面上的位置Ci和Cj入射。
  5. 根据权利要求1所述的曲面检材的应力分析系统，其特征在于，所述系统还包括：
    设置在所述照明光束的光路上的相位调节器，所述相位调节器位于所述光 源和起偏器之间，用于调节所述照明光束的相位；
    所述图像传感器还用于采集经所述相位调节器调节的多个相位下的干涉成像。
  6. 根据权利要求5所述的曲面检材的应力分析系统，其特征在于，所述相位调节器调节的多个相位的相邻相位差为π/2。
  7. 根据权利要求6所述的曲面检材的应力分析系统，其特征在于，所述处理器还用于获取所述图像传感器采集的至少4幅干涉成像，且所述4幅干涉图像对应的照明光束的相位差分别为π/2、π、3π/2；
    所述处理器还用于获取所述4幅干涉成像中同一位置的光强信息，根据所述光强信息计算该位置的干涉条纹相位，再通过去包裹处理，得到干涉条纹的相位分布，根据所述相位分布结合所述曲面检材的光弹性系数得到所述曲面检材的应力分布。
  8. 根据权利要求7所述的曲面检材的应力分析系统，其特征在于，所述处理器还用于根据：
    Figure PCTCN2019079333-appb-100002
    Figure PCTCN2019079333-appb-100003
    Figure PCTCN2019079333-appb-100004
    Figure PCTCN2019079333-appb-100005
    Figure PCTCN2019079333-appb-100006
    计算干涉图像上(x，y)位置处对应的照明光束的相位
    Figure PCTCN2019079333-appb-100007
    所述I 1(x，y)、I 2(x，y)、I 3(x，y)、I 4(x，y)为4幅干涉图像分别在相同(x，y)位置的光强，所述A(x，y)为背景强度，所述B(x，y)为照明光束的强度。
  9. 根据权利要求1至8任一项所述的曲面检材的应力分析系统，其特征在于，所述处理器还用于获取基于机器学习的缺陷识别模型，所述缺陷识别模型至少包括裂纹、气泡、结石和无缺陷的输出类别，且所述输出类别经过对应类别的样本应力分布的机器学习训练后具有相应的置信度；
    所述处理器还用于将所述应力分布输入到所述缺陷识别模型中，根据得到 的输出类别的置信度的高低确定所述曲面检材对应的缺陷。
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