Large-aperture plate glass stress birefringent surface imaging measurement method

Abstract

The invention discloses a large-aperture plate glass stress birefringence surface imaging measurement method, belongs to the technical field of optical measurement, and aims to solve the technical problem of low glass stress birefringence measurement efficiency in the prior art. Comprising the following steps: moving a sample to be measured and a 1 / 4 wave plate out of a measuring light path, rotating a polarizer to find an extinction position, and rotating the polarizer by N angles nearby to obtain an angle # imgabs0 #; keeping the polarizer and the analyzer unchanged, moving the 1 / 4 wave plate into a measurement light path, rotating the 1 / 4 wave plate, and finding an extinction position; rotating the polarizer by N angles near the extinction position to obtain an angle # imgabs 1 #; the positions and the directions of the 1 / 4 wave plate and the polarization analyzer are kept unchanged, and the sample to be measured is moved into a measuring light path between the polarizer and the 1 / 4 wave plate; the polarizer is rotated through the polarization rotating mechanism, when the included angles between the polarizer and the x axis of the reference coordinate system are 0 degree, 60 degrees and 120 degrees respectively, the light intensities of the three images are obtained through the CCD camera, and the stress birefringence of the sample to be measured is obtained according to the three light intensities.

Description

Technical Field

[0001] The invention belongs to the technical field of optical measurement, and relates to the measurement of large-diameter flat glass, and in particular to a stress birefringence surface imaging measurement method of large-diameter flat glass. Background Art

[0002] During the annealing cooling process, there is a temperature gradient in the thickness direction of the flat glass, which will generate central stress. Along the thickness direction, the central stress at different positions of the flat glass is different, but the direction is parallel to the glass surface, and it appears as compressive stress on the glass surface and tensile stress inside the glass. Due to the existence of stress, the internal structure of the glass changes and becomes anisotropic, and birefringence occurs when light passes through the glass. Therefore, the stress condition of the glass can be measured by measuring the stress birefringence of the glass.

[0003] The invention patent application with application number 202410028352.1 discloses a high-precision birefringence phase difference measurement device with a wide spectrum and a large range, which includes: an LED light source with adjustable output wavelength, a converging lens, a polarizer, an achromatic 1 / 4 wave plate, an imaging lens, a detector, an electric rotating stage and a control unit; by using an LED light source with adjustable output wavelength in conjunction with an achromatic 1 / 4 wave plate, measurements can be performed within a wide spectrum; by adjusting the relative angles of the fast and slow axes of the achromatic 1 / 4 wave plate and the polarization direction of the linear polarizer, the fast and slow axes of the measured sample, and the rotation angle of each polarization device around the transmission axis, the working mode can be switched between circular polarization mode, dark field / bright field mode and compensation mode, and the corresponding algorithms for the three measurement modes are given. By switching the three modes, a large range and high-precision measurement can be achieved.

[0004] The invention patent application with application number 202411081547.9 also discloses an optical glass stress testing device and a digital testing method. The testing device includes a light source, a diffuse filter, a polarizer, a quantitative wave plate, an analyzer, a circular grating, a CCD imaging capturer, a glass strip to be tested and a host computer. The light source, the diffuse filter, the polarizer, the quantitative wave plate, the analyzer, the circular grating and the CCD imaging capturer are arranged in sequence in the horizontal direction; the circular grating and the analyzer are configured to perform synchronous axial rotation, and the minimum rotation angle of the circular grating is smaller than the minimum rotation angle of the analyzer; the glass strip to be tested is arranged between the polarizer and the quantitative wave plate, and the host computer is used to calculate the stress of the glass strip to be tested based on the rotation angle of the circular grating and the image obtained by the CCD imaging capturer. The measuring method comprises: arranging the glass strip to be tested between the polarizer and the quantitative wave plate, and using the CCD imaging capture device to obtain the image of the glass strip to be tested; based on the light transmission width and light transmission thickness of the glass strip to be tested, using computer testing software to generate a virtual straight bar mark on the image of the glass strip to be tested; using the light source to emit light to the light transmission surface of the glass strip to be tested to form a test light path, forming polarized light through the diffusion filter and the polarizer, using the CCD imaging capture device to obtain the image information of the light transmission dark band on the glass strip to be tested, and feeding back the light transmission dark band generation to the image of the glass strip to be tested; synchronously rotating the analyzer and the circular grating, and performing synchronous sampling through the CCD imaging capture device until the light transmission dark band coincides with the virtual straight bar mark, and using the host computer to calculate the stress data of the glass strip to be tested based on the rotation angle of the circular grating.

[0005] As in the above-mentioned invention patent application, the prior art requires not only rotating the polarizer but also rotating the 1 / 4 wave plate and / or the analyzer when performing stress birefringence measurement. The rotation mechanism has high requirements and also needs to be accompanied by a term shifting step, which greatly reduces the measurement efficiency. Summary of the invention

[0006] The purpose of the present invention is to provide a method for imaging and measuring the stress birefringence of large-diameter flat glass in order to solve the technical problem of low efficiency in measuring glass stress birefringence in the prior art.

[0007] In order to achieve the above-mentioned purpose, the present invention specifically adopts the following technical solutions: A method for measuring the stress birefringence surface imaging of large-caliber flat glass, wherein the measuring optical path comprises a parallel light source, a polarizer, a quarter wave plate, an analyzer, an imaging lens and a CCD camera arranged in sequence; the polarizer is mounted on a polarizing rotation mechanism, the quarter wave plate is mounted on a wave plate rotation and displacement mechanism, and the sample to be measured is mounted between the polarizer and the quarter wave plate through a horizontal displacement mechanism; the measuring steps are specifically as follows: Step 1, move the sample to be tested and the 1 / 4 wave plate out of the measuring light path, keep the direction of the polarizer unchanged, and rotate the polarizer counterclockwise through the polarization rotation mechanism to find the extinction position; The polarizer is rotated by N angles near the extinction position through the polarization rotation mechanism, and the angle is obtained through the least squares fitting function. ; Step 2, keeping the polarizer and the analyzer in an orthogonal state and in an unchanged direction, move the 1 / 4 wave plate into the measuring optical path between the polarizer and the analyzer, and rotate the 1 / 4 wave plate counterclockwise through the wave plate rotation and displacement mechanism to find the extinction position; The polarizer is rotated N angles by the polarization rotation mechanism near the extinction position, and the angle is obtained by the least squares fitting function. ; Step 3, keeping the position and direction of the 1 / 4 wave plate and the analyzer unchanged, move the sample to be measured into the measurement light path between the polarizer and the 1 / 4 wave plate; The polarizer is rotated by the polarizing rotating mechanism. When the angles between the polarizer and the x-axis of the reference coordinate system are 0°, 60°, and 120° respectively, the light intensity of three images is obtained by the CCD camera. , , , and according to the light intensity , , Obtaining the stress birefringence of the sample to be tested; Step 4, move the sample to be tested, repeat step 3, and measure the stress birefringence distribution at different positions of the sample to be tested.

[0008] Furthermore, in step 1, the angle is obtained by the least squares fitting function. When , the calculation formula is: ; in, Represents the light intensity signal measured by the CCD camera, represents the initial light intensity of the light source, Indicates the rotation angle of the polarizer.

[0009] Furthermore, in step 2, the angle is obtained by the least squares fitting function. When , the calculation formula is: ; in, Represents the light intensity signal measured by the CCD camera, represents the initial light intensity of the light source, Indicates the angle of rotation of the quarter wave plate.

[0010] Further, in step 3, according to the light intensity , , Get the stress birefringence of the sample to be tested The specific algorithm is: ; ; in, represents the wavelength, , , It represents the light intensity signal incident on the CCD camera at 0°, 60°, and 120° when the polarizer is rotated. Represents the birefringence phase difference.

[0011] Furthermore, it also includes a gantry dual-drive platform, which includes a base, and a left vertical guide rail and a right vertical guide rail are respectively provided on the left and right sides of the base, and a left mounting seat and a right mounting seat are respectively provided on the left vertical guide rail and the right vertical guide rail, a parallel light source and a polarizer are installed on the left mounting seat, and a 1 / 4 wave plate, an analyzer, an imaging lens and a CCD camera are installed on the right mounting seat; the sample to be tested is set between the left mounting seat and the right mounting seat through a horizontal displacement mechanism.

[0012] The beneficial effects of the present invention are as follows: 1. In the present invention, a stress measurement method of three-step rotation phase shift of the polarizer is innovatively adopted. While ensuring the phase shift accuracy, it is only necessary to rotate the polarizer, without the need to rotate the 1 / 4 wave plate and the analyzer at the same time. This greatly reduces the configuration and control requirements for the rotation mechanism, reduces the phase shift steps, and effectively improves the measurement efficiency of glass stress birefringence.

[0013] 2. In the present invention, in order to realize the positioning of the polarization direction of the polarizer and the fast axis direction of the 1 / 4 wave plate, a least square fitting method is proposed, which improves the positioning accuracy of the polarization direction of the polarizer and the fast axis direction of the 1 / 4 wave plate, realizes rapid positioning, and improves measurement efficiency.

[0014] 3. In the present invention, a gantry dual-drive structure is proposed for the detection of large-diameter component splicing, which realizes the vertical movement of the detection system and the horizontal movement of the components to be tested. This scheme ensures the stability of the structure while greatly improving the load-bearing capacity of the system, and can realize stress birefringence testing of large-scale and heavy-weight samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of the measurement system of the present invention; Figure 2 Schematic diagram of the measuring principle of the present invention; wherein x and y in the coordinate diagram below each component represent the horizontal and vertical coordinates; Figure 3It is a schematic diagram of the structure of the gantry dual-drive platform driving the measurement system to move up and down in the present invention; Figure 4 It is a schematic diagram of achieving full coverage measurement of the sample to be tested by moving the measurement system and the sample to be tested in the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0017] Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0018] Example 1 This embodiment provides a large-diameter flat glass stress birefringence surface imaging measurement system. Figure 3 As shown, it includes a gantry dual-drive platform, which includes a base, and a left vertical rail and a right vertical rail are respectively arranged on the left and right sides of the base, and a left mounting seat and a right mounting seat are respectively arranged on the left vertical rail and the right vertical rail, and the left mounting seat and the right mounting seat can move up and down along the height direction of the left vertical rail and the right vertical rail respectively on the left vertical rail and the right vertical rail. The parallel light source and the polarizer are installed on the left mounting seat, and the 1 / 4 wave plate, the analyzer, the imaging lens and the CCD camera are installed on the right mounting seat; the sample to be tested is set between the left mounting seat and the right mounting seat through a horizontal displacement mechanism.

[0019] Furthermore, the polarizer is mounted on the left mounting seat through a polarizing rotation mechanism, and the polarizer can be driven to rotate through the polarizing rotation mechanism. The 1 / 4 wave plate is mounted on the right mounting seat through a wave plate rotation and displacement mechanism, and the 1 / 4 wave plate can be driven to rotate and move through the wave plate rotation and displacement mechanism. The sample to be tested is mounted on the base through a horizontal displacement mechanism, and the sample to be tested is driven to move through the horizontal displacement mechanism. Under the combined action of the up and down movement of the mounting seat and the horizontal movement of the sample to be tested, full coverage measurement of the sample to be tested is achieved, such as Figure 4 shown.

[0020] like Figure 1 As shown in the figure, the measurement optical path of the measurement system is: The parallel light source emits a parallel light beam, which passes through the polarizer, the sample to be tested, the 1 / 4 wave plate, the analyzer, and the imaging lens in sequence and then is imaged onto the CCD camera. Example 2 This embodiment provides a method for measuring the stress birefringence surface imaging of large-diameter flat glass. The method adopts Figure 1 The measurement optical path of the measurement system is shown.

[0021] When using this measurement system for measurement, the measurement steps are as follows: Step 1, move the sample to be tested and the 1 / 4 wave plate out of the measuring light path, keep the direction of the polarizer unchanged, and rotate the polarizer counterclockwise through the polarization rotation mechanism to find the extinction position; The polarizer is rotated by N angles near the extinction position through the polarization rotation mechanism, and the angle is obtained through the least squares fitting function. ;angle The calculation formula is: (1); in, Represents the light intensity signal measured by the CCD camera, represents the initial light intensity of the light source, Indicates the rotation angle of the polarizer.

[0022] Step 2, keeping the polarizer and the analyzer in an orthogonal state and in an unchanged direction, move the 1 / 4 wave plate into the measuring optical path between the polarizer and the analyzer, and rotate the 1 / 4 wave plate counterclockwise through the wave plate rotation and displacement mechanism to find the extinction position; The polarizer is rotated N angles by the polarization rotation mechanism near the extinction position, and the angle is obtained by the least squares fitting function. ;angle The calculation formula is: (2); in, Represents the light intensity signal measured by the CCD camera, represents the initial light intensity of the light source, Indicates the angle of rotation of the quarter wave plate.

[0023] Step 3, keeping the position and direction of the 1 / 4 wave plate and the analyzer unchanged, move the sample to be measured into the measurement light path between the polarizer and the 1 / 4 wave plate; The polarizer is rotated by the polarizing rotating mechanism. When the angles between the polarizer and the x-axis of the reference coordinate system are 0°, 60°, and 120° respectively, the light intensity of three images is obtained by the CCD camera. , , , and according to the light intensity , , Get the stress birefringence of the sample to be tested ; Stress birefringence The specific algorithm is: (3); (4); in, represents the wavelength, , , It represents the light intensity signal incident on the CCD camera at 0°, 60°, and 120° when the polarizer is rotated. Represents the birefringence phase difference.

[0024] Step 4, move the sample to be tested, repeat step 3, and measure the stress birefringence distribution at different positions of the sample to be tested.

[0025] like Figure 2 As shown, the measurement principle of this method is: Based on the polarization measurement principle of the Senarmont method (also known as the single quarter wave plate method), the linearly polarized light passes through the sample to be measured, the quarter wave plate, and the analyzer, and then is imaged and observed by a CCD camera. The measurement light path is as follows: Figure 2 As shown. Figure 2 In the optical path shown, the angle between the polarizer P and the x-axis of the reference coordinate system is , the angle between the analyzer A and the x-axis of the reference coordinate system is , the angle between the fast axis F of the 1 / 4 wave plate and the x-axis of the reference coordinate system is , the birefringence phase difference introduced by the sample to be tested is δ, and the principal stress direction of the sample to be tested forms an angle θ with the x-axis of the reference coordinate system. When the fast axis F of the 1 / 4 wave plate and the direction of the analyzer are kept at 45°, the polarizer is rotated so that the angles between the polarizer direction and the x-axis of the reference coordinate system are 0°, 60° and 120° respectively, and the detector obtains three light intensity signals respectively. , , Finally, the stress birefringence of the sample to be tested is calculated by formula (3) and formula (4).

Claims

1. A method for measuring the stress birefringence surface imaging of large-diameter flat glass, characterized in that: The measuring optical path includes a parallel light source, a polarizer, a quarter wave plate, an analyzer, an imaging lens and a CCD camera arranged in sequence; the polarizer is installed on the polarization rotation mechanism, the quarter wave plate is installed on the wave plate rotation and displacement mechanism, and the sample to be measured is installed between the polarizer and the quarter wave plate through the horizontal displacement mechanism; the measuring steps are as follows: Step 1, move the sample to be tested and the 1 / 4 wave plate out of the measuring light path, keep the direction of the polarizer unchanged, and rotate the polarizer counterclockwise through the polarization rotation mechanism to find the extinction position; The polarizer is rotated by N angles near the extinction position through the polarization rotation mechanism, and the angle is obtained through the least squares fitting function. ; Step 2, keeping the polarizer and the analyzer in an orthogonal state and in an unchanged direction, move the 1 / 4 wave plate into the measuring optical path between the polarizer and the analyzer, and rotate the 1 / 4 wave plate counterclockwise through the wave plate rotation and displacement mechanism to find the extinction position; The polarizer is rotated N angles by the polarization rotation mechanism near the extinction position, and the angle is obtained by the least squares fitting function. ; Step 3, keeping the position and direction of the 1 / 4 wave plate and the analyzer unchanged, move the sample to be measured into the measurement light path between the polarizer and the 1 / 4 wave plate; The polarizer is rotated by the polarizing rotating mechanism. When the angles between the polarizer and the x-axis of the reference coordinate system are 0°, 60°, and 120° respectively, the light intensity of three images is obtained by the CCD camera. , , , and according to the light intensity , , Obtaining the stress birefringence of the sample to be tested; Step 4, move the sample to be tested, repeat step 3, and measure the stress birefringence distribution at different positions of the sample to be tested.

2. A method for measuring stress birefringence surface imaging of large-diameter flat glass according to claim 1, characterized in that: In step 1, the angle is obtained by the least squares fitting function When , the calculation formula is: ； in, Represents the light intensity signal measured by the CCD camera, represents the initial light intensity of the light source, Indicates the rotation angle of the polarizer.

3. A method for measuring stress birefringence surface imaging of large-diameter flat glass as claimed in claim 1, characterized in that: In step 2, the angle is obtained by the least squares fitting function. When , the calculation formula is: ； in, Represents the light intensity signal measured by the CCD camera, represents the initial light intensity of the light source, Indicates the angle of rotation of the quarter wave plate.

4. A method for measuring stress birefringence surface imaging of large-diameter flat glass as claimed in claim 1, characterized in that: In step 3, according to the light intensity , , Get the stress birefringence of the sample to be tested The specific algorithm is: ； ； in, represents the wavelength, , , It represents the light intensity signal incident on the CCD camera at 0°, 60°, and 120° when the polarizer is rotated. Represents the birefringence phase difference.

5. A method for measuring stress birefringence surface imaging of large-diameter flat glass as claimed in claim 1, characterized in that: It also includes a gantry dual-drive platform, which includes a base, and a left vertical guide rail and a right vertical guide rail are respectively arranged on the left and right sides of the base, and a left mounting seat and a right mounting seat are respectively arranged on the left vertical guide rail and the right vertical guide rail, a parallel light source and a polarizer are installed on the left mounting seat, and a 1 / 4 wave plate, an analyzer, an imaging lens and a CCD camera are installed on the right mounting seat; the sample to be tested is set between the left mounting seat and the right mounting seat through a horizontal displacement mechanism.

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