Method and device for detecting thickness uniformity of optical element

Abstract

The invention discloses an optical element thickness uniformity detection method and device, and relates to the field of optical measurement. A single-axis point-type spectrum confocal measurement system based on a color sensor is used, a return signal color superposition model of each surface of a to-be-measured piece is established, and the thickness difference existing at different positions of the element is determined by using the superposition chromaticity difference returned at different positions of the to-be-measured piece so as to realize efficient detection of the thickness uniformity of the to-be-measured piece. According to the invention, the detection efficiency is obviously improved, the coaxial single-probe spectrum confocal light path enhances the stability in the aspect of detecting the thickness uniformity of the element, and a new solution thought is provided for the spectrum confocal detection of the thickness uniformity of the element.

Description

Technical Field

[0001] This invention relates to the field of optical measurement, and more specifically to a method and apparatus for detecting the thickness uniformity of optical elements. Background Technology

[0002] With the rapid development of optical manufacturing and precision measurement, the thickness uniformity of products has become one of the important parameters. Glass substrates are widely used in various industries, and their thickness uniformity is particularly important. Accurately obtaining the thickness and surface uniformity of these glass substrates has become one of the important research topics in the field of measurement instruments.

[0003] Currently, the thickness uniformity of optical components is measured by detecting the specific positional information of the upper and lower surfaces of the optical component. The thickness information is then determined based on this positional information, and finally, the thickness uniformity is assessed. This method significantly increases the detection time and lacks a direct way to determine thickness uniformity, thus drastically reducing the efficiency of optical component thickness measurement. Summary of the Invention

[0004] This invention provides a method and apparatus for detecting the thickness uniformity of optical components, which solves the problems of long detection time and low detection efficiency in existing methods for detecting the thickness uniformity of optical components.

[0005] This invention provides a method for detecting the thickness uniformity of optical components, comprising:

[0006] A wedge-shaped optical element with the same refractive index as the optical element under test is placed in a spectral confocal system. The reference plane of the wedge-shaped optical element is determined and aligned with the set color position in the spectral confocal system. The wedge-shaped optical element is then scanned laterally by an electronically controlled displacement stage to obtain the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element, as well as the formula for calculating the thickness difference-chromaticity difference.

[0007] The optical element under test is placed in a spectral confocal system. The reference plane of the optical element under test is determined and aligned with the set color position in the spectral confocal system. The optical element under test is then scanned laterally by an electronically controlled displacement stage according to a set step, and the color superposition chromaticity value of the detection signal of the optical element under test at each scanning position is obtained.

[0008] The absolute value of the color superposition chromaticity difference between the color superposition chromaticity value of the detection signal at each scanning position and the color superposition chromaticity value of the reference signal at the scanning start point is determined. Based on the calculation formula of the thickness difference-chromaticity difference and the absolute value of the color superposition chromaticity difference, the thickness difference of each scanning position of the optical element under test relative to the scanning start point is determined.

[0009] Preferably, the step of scanning the wedge-shaped optical element horizontally using an electrically controlled displacement stage to obtain the superimposed chromatic difference of the spectral signals within the thickness range of the wedge-shaped optical element specifically includes:

[0010] The wedge-shaped optical element is transversely scanned at a set scanning interval using an electric displacement stage. At each position, the color superposition information returned from the upper and lower surfaces of the wedge-shaped optical element is repeatedly collected. The color superposition information is then processed by difference to obtain the color superposition chromaticity difference at different positions of the wedge-shaped optical element.

[0011] Preferably, the formula for calculating the chromatic difference between the superimposed spectral signal and the thickness difference of the wedge optical element is as follows:

[0012] |Δd|=|k·ΔH|

[0013] Where Δd represents the thickness difference, ΔH represents the color difference of the superimposed spectral signals at different locations, and k represents the calibration coefficient.

[0014] Preferably, the spectral confocal system includes a broadband light source, a converging lens, a first pinhole, a beam splitter, a dispersive mirror group, a second pinhole, and a color sensor;

[0015] The broadband light source is used to emit stable continuous band polychromatic light. The polychromatic light passes through a converging lens and a first pinhole in sequence and then enters a dispersive lens group where it undergoes axial dispersion. The dispersed light is projected onto the surface of the test piece, and the reflected light generates color superposition information. The color superposition information is collected by a color sensor after passing through a beam splitter and a second pinhole.

[0016] The wide spectral operating band of the spectral confocal system is 460 nm to 660 nm, and the axial dispersion is 1.58 nm.

[0017] Preferably, the step of laterally scanning the wedge-shaped optical element using an electrically controlled displacement stage to obtain the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element specifically includes:

[0018] The wedge-shaped optical element is scanned laterally by an electronically controlled displacement stage, and multiple acquisitions are performed at each scanning position to obtain the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element.

[0019] The process of scanning the optical element under test laterally at set intervals using an electronically controlled displacement stage to obtain the color superposition chromaticity values ​​of the detection signals of the optical element under test at each scanning position specifically includes:

[0020] The optical element under test is scanned laterally at set intervals using an electronically controlled displacement stage. Multiple data acquisitions are performed at each scanning position to obtain the color superposition chromaticity value of the detection signal of the optical element under test at each scanning position.

[0021] Preferably, before obtaining the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element, the method further includes:

[0022] The color overlay signal at any scan position is determined using the following formula:

[0023]

[0024] x up =(R up G up B up )

[0025] x down =(R down G down B down )

[0026] Where X represents the color superposition signal acquired by the color sensor at the color position corresponding to the wedge optical element, x up This represents the RGB array of the upper surface of the wedge-shaped optical element, acquired at the corresponding color position. down This represents the RGB array of the lower surface of the wedge-shaped optical element, acquired at the corresponding color position. n is the refractive index of the wedge-shaped optical element, n0 is the air refractive index, and x... up R represents the RGB array corresponding to the color positions on the upper surface of the wedge-shaped optical element. up G up B up These represent the red, green, and blue values ​​included in the RGB array on the upper surface, respectively. down G down B down These represent the red, green, and blue values ​​included in the RGB array on the lower surface, respectively.

[0027] This invention provides a detection system for implementing a method for detecting the thickness uniformity of optical components, comprising:

[0028] Spectral confocal module: It consists of a broadband light source, a focusing lens unit, a pinhole unit, a beam splitting unit, a dispersion unit, and a signal acquisition sensing unit. It is used to generate polychromatic light, realize light dispersion, and acquire color superposition feature information.

[0029] Displacement module: includes a displacement device for calibration operation and a displacement mechanism for scanning the test piece, wherein the displacement device for calibration can scan the wedge-shaped optical element, and the displacement mechanism for scanning can scan the optical element under test.

[0030] Data processing module: Connected to the signal acquisition sensing unit and displacement module, it is used to receive the acquired color superposition information and displacement position information, calculate the absolute value of the thickness difference according to the thickness difference-chromaticity difference calculation formula obtained from calibration, and determine the thickness uniformity of the optical element under test.

[0031] This invention provides an optical element thickness uniformity detection device, comprising:

[0032] The calibration unit is used to set a wedge-shaped optical element with the same refractive index as the optical element under test in the spectral confocal system, determine the reference plane of the wedge-shaped optical element, align the reference plane with the set color position in the spectral confocal system, and perform a transverse scan of the wedge-shaped optical element by an electronically controlled displacement stage to obtain the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element, as well as the thickness difference-chromaticity difference calculation formula.

[0033] The unit is used to set the optical element under test in the spectral confocal system, determine the reference plane of the optical element under test, align the reference plane with the set color position in the spectral confocal system, and perform a transverse scan of the optical element under test by an electronically controlled displacement stage according to a set step, so as to obtain the color superposition chromaticity value of the detection signal of the optical element under test at each scanning position.

[0034] The determining unit is used to determine the absolute value of the color superposition chromaticity difference between the color superposition chromaticity value of the detection signal at each scanning position and the color superposition chromaticity value of the reference signal at the scanning start point, and to determine the thickness difference of each scanning position of the optical element under test relative to the scanning start point according to the calculation formula of the thickness difference-chromaticity difference and the absolute value of the color superposition chromaticity difference.

[0035] This invention provides a computer device, characterized in that the computer device includes a memory and a processor, the memory stores a computer program, and when the computer program is executed by the processor, the processor performs any of the above-described optical element thickness uniformity detection methods.

[0036] This invention provides a computer-readable storage medium, characterized in that it stores a computer program, which, when executed by a processor, causes the processor to perform any of the above-described optical element thickness uniformity detection methods.

[0037] This invention achieves efficient and rapid detection of the thickness uniformity of optical components by establishing a quantitative mapping model between the color difference of the spectral confocal superposition signal and the thickness change. Compared with existing technologies, the advantages of this invention are: compared with existing methods for detecting the thickness uniformity of optical components, this detection method significantly reduces the amount of data in a single detection, thus improving detection efficiency; it has the advantage of real-time and efficient detection, is not easily affected by the external environment, and has strong stability. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic flowchart of the optical element thickness uniformity detection method provided in an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of the spectral confocal system structure provided in an embodiment of the present invention;

[0041] Figure 3 This is a schematic diagram of the actual optical element under test and its thickness cross-section provided in an embodiment of the present invention;

[0042] Figure 4 This is a schematic diagram of the color value results of the superimposed spectral signal at various positions in the X direction of the optical element under test provided in an embodiment of the present invention;

[0043] Figure 5 This is a schematic diagram showing the absolute value results of the thickness difference between each position of the optical element under test in the X direction and the AC position, provided in an embodiment of the present invention.

[0044] Figure 6 This is a schematic diagram of the optical element thickness uniformity detection device provided in an embodiment of the present invention. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] The optical element thickness uniformity detection method provided in this embodiment of the invention, such as... Figure 1 As shown, the method includes the following steps:

[0047] Step 101: Place a wedge-shaped optical element with the same refractive index as the optical element under test in the spectral confocal system, determine the reference plane of the wedge-shaped optical element, align the reference plane with the set color position in the spectral confocal system, and perform a lateral scan on the wedge-shaped optical element using an electronically controlled displacement stage to obtain the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element, as well as the thickness difference-chromaticity difference calculation formula.

[0048] Step 102: Set the optical element under test in the spectral confocal system, determine the reference plane of the optical element under test, and align the reference plane with the set color position in the spectral confocal system. Use an electronically controlled displacement stage to perform a lateral scan on the optical element under test according to the set step, and obtain the color superposition chromaticity value of the detection signal of the optical element under test at each scanning position.

[0049] Step 103: Determine the absolute value of the color superposition chromaticity difference between the color superposition chromaticity value of the detection signal at each scanning position and the color superposition chromaticity value of the reference signal at the scanning start point. Based on the calculation formula of thickness difference - chromaticity difference and the absolute value of color superposition chromaticity difference, determine the thickness difference of each scanning position of the optical element under test relative to the scanning start point.

[0050] In practical applications, the number of reflections and transmissions of light of different wavelengths to the surfaces of optical elements varies, and the color information of each surface of the optical element is also affected by the surface reflectivity. The final color superposition of the signals at each position of the optical element collected by the color sensor is the result of the combined influence of these two factors, which can be clearly expressed by the following logic:

[0051] (I) The mechanism of the difference between the number of reflections and transmissions of light of different wavelengths

[0052] After the polychromatic light is axially dispersed by the dispersive lens group, light of different wavelengths is focused at different positions of the optical element along the optical axis: short wavelength light (such as 460nm blue light) is focused near the upper surface of the optical element, and only one reflection occurs on the upper surface, with zero transmission times; long wavelength light (such as 660nm red light) is focused near the lower surface, and needs to pass through the upper surface once, be reflected once on the lower surface, and then pass through the upper surface once again, for a total of 2 transmission times and 1 reflection time.

[0053] (II) Quantitative Influence of Surface Reflectivity on Spectral Color Information

[0054] 1. Mathematical expression of Fresnel reflectance: According to the Fresnel principle of reflection, the reflectance of light at the interface between air (refractive index n0) and an optical element (refractive index n) is:

[0055] The single reflectivity of the upper surface determines the proportion of energy of the light reflected from the upper surface:

[0056]

[0057] The reflectivity of light reflected from the lower surface includes the multiple reflection effects of light passing through the upper surface, being reflected from the lower surface, and then passing through the upper surface again.

[0058]

[0059] Where C1 is the reflectivity of the upper surface of the optical element after one reflection, n is the refractive index of the optical element, n0 is the air refractive index, and C2 is the reflectivity of the light beam reflected from the lower surface of the optical element.

[0060] 2. The implicit relationship between reflectivity and wavelength

[0061] The refractive index (n) of optical element materials for different wavelengths of light λ Slight differences in refractive index (material dispersion) cause the reflectivity C1(λ) and C2(λ) to vary with wavelength, thus affecting the reflected energy weights for each wavelength. For example, glass materials have a slightly higher refractive index for short-wavelength light, and their reflectivity C1(λ) increases accordingly.

[0062] (III) Spectral Signal Superposition Model under Combined Influence

[0063] The difference in the number of reflections / transmissions of light of different wavelengths, together with reflectivity modulation, determines the light intensity distribution received by the color sensor.

[0064] RGB signal of light reflected from the upper surface:

[0065] X up =C1·x up (3)

[0066] RGB signal of light reflected from the lower surface:

[0067] X down =C2·x down (4)

[0068] The total signal after superposition:

[0069]

[0070] Where, x up The RGB array returned for the upper surface of the optical element, x up =(R up G up B up );x down The RGB array returned for the lower surface of the optical element, x down =(R down G down B down).

[0071] This process utilizes the Fresnel reflection principle and optical path reversibility to convert geometric quantities (thickness) into quantifiable optical signals (color difference), providing theoretical support for thickness uniformity detection based on spectral confocal color superposition.

[0072] In step 101, a wedge-shaped optical element with the same refractive index as the optical element under test is selected as the calibration element, and the wedge-shaped optical element is set as follows: Figure 2 In the spectral confocal system shown, the wedge-shaped optical element is scanned laterally by an electrically controlled displacement stage and a full-Euro OTS-200 thickness gauge according to a set step, so as to obtain the color superposition chromaticity value and the true thickness value of the calibration signal within the thickness range of the wedge-shaped optical element, as well as the thickness difference-chromaticity difference calculation formula.

[0073] like Figure 2 As shown, the spectral confocal system provided in this embodiment of the invention is a single-axis spectral confocal structure. Specifically, a broadband light source 1 emits stable, continuous-wavelength polychromatic light. The polychromatic light passes through a converging lens 2 and a first pinhole 3 before entering a dispersive lens group 5. The dispersive lens group 5 uses a combination of lenses made of different materials to cause the polychromatic light to undergo axial dispersion to a wedge-shaped optical element 6. When the surface of the wedge-shaped optical element 6 is at the visible light focal plane, the surface of the wedge-shaped optical element 6 reflects color signals back to the upper and lower surfaces of the wedge-shaped optical element 6. These color signals generate color superposition information during the return process. According to the principle of optical path reversibility, the color superposition information returns to the dispersive lens group 5, is reflected by a beam splitter 4, and after being filtered again by a second pinhole 8 to remove stray light, it successfully reaches the color sensor 9.

[0074] The wide spectral operating band of this confocal system is 460 nm to 660 nm, and the axial dispersion is 1.58 nm.

[0075] In this spectral confocal detection scenario, "color signal" refers to the RGB information carried by the single wavelength (or narrow band) light reflected back after the polychromatic light is axially dispersed by the dispersive lens group and focused at different positions along the axis. When the light is incident on the surface of the wedge-shaped optical element, the light of a specific wavelength will be reflected on the corresponding surface (upper or lower surface).

[0076] Breaking it down from a principle perspective: Polychromatic light (containing multiple wavelengths, such as the visible light band (460nm-660nm)) will be dispersed along the axial direction (direction of light propagation) after passing through a dispersive lens group due to the difference in refractive index of different wavelengths. Different wavelengths correspond to different focusing positions.

[0077] When the surface of a wedge-shaped optical element is at the focal plane of a visible light wavelength, light of that wavelength will be reflected from the surface (upper or lower) of the wedge-shaped optical element. The reflected light will carry only information about that specific wavelength (or a very narrow band), i.e., the "color signal". For example, if light of 550nm wavelength is focused on the upper surface of the wedge-shaped optical element, the light reflected back from the upper surface will mainly be the 550nm wavelength signal, which is the color signal of the upper surface; similarly, if light of other wavelengths is focused on the lower surface and reflected, it will be the color signal of the lower surface.

[0078] Furthermore, in this system, "color superposition information" refers to the comprehensive spectral color characteristic information formed by the superposition of different wavelength color information reflected back from the upper and lower surfaces of the wedge optical element in the common return optical path.

[0079] The upper and lower surfaces of the wedge-shaped optical element reflect back their respective monochromatic signals (different wavelengths), and these signals return in space along the same optical path (based on the principle of optical reversibility).

[0080] The mixing and superposition of monochromatic light of different wavelengths, much like the mixing of multiple colors of light to create a new color, results in a comprehensive spectral color representation. Color sensors collect this comprehensive color information, which includes the wavelengths and intensities of the light reflected from the upper and lower surfaces—this is called "color superposition information." For example, if the monochromatic light reflected from the upper surface is bluish (short wavelength) and the monochromatic light reflected from the lower surface is reddish (long wavelength), their superposition may produce a purplish hue. The color sensor collects this mixed color data for subsequent analysis of thickness uniformity.

[0081] In step 101, the refractive index of the wedge optical element (n = 1.52), the length of the wedge optical element is 15.0 mm, its reference surface corresponding color position is fixed at 9.5 mm, and the thickness ranges from 0.1 to 1.0 mm. The wedge optical element is scanned laterally by an electrically controlled displacement stage, selecting a position every 0.5 mm. At each scanning position, the upper and lower surfaces of the wedge optical element need to be repeatedly sampled, that is, the color superposition value of the signals returned from the upper and lower surfaces is obtained respectively. Then, the color superposition value of the signal is averaged to obtain the color superposition color of the calibration signal of the upper and lower surfaces of each measured point. Furthermore, the color superposition chromaticity value of the calibration signal of the upper and lower surfaces of each measured point is obtained.

[0082] It should be noted that the color superposition color of the calibration signal here refers to information represented in the RGB color model, while the color superposition chromaticity value of the calibration signal represents the conversion of information represented in the RGB color model to information represented in the HSI model. This ultimately yields the color superposition chromaticity values ​​of the calibration signals for different thicknesses of the wedge optical element.

[0083] Furthermore, combining the actual thickness of the wedge-shaped optical element determined by the thickness gauge (where the selected measurement point is consistent with the measurement point determined by the spectral confocal system), the thickness-chromaticity calculation formula for the wedge-shaped optical element can be obtained based on the actual thickness of the wedge-shaped optical element determined by the actual measurement and the color superposition chromaticity value of the calibration signal, as shown below:

[0084] d=k·H+h0 (1)

[0085] Wherein, H value represents the color superposition chromaticity value of the calibration signal returned by the reference surface and dynamic surface of the wedge element, h0 represents the color information corresponding to the starting position of the spectrum, k represents the calibration coefficient, and d represents the actual thickness of the wedge element.

[0086] Furthermore, based on the thickness-chromaticity calculation formula of the wedge-shaped optical element described above, the thickness difference-chromaticity difference formula of the wedge-shaped optical element can be obtained as follows:

[0087] |Δd|=|k·ΔH| (2)

[0088] Where Δd represents the thickness difference, ΔH represents the color difference of color superposition at different positions, and k represents the calibration coefficient.

[0089] In practical applications, the OTS-200 thickness gauge from the European Union can be selected.

[0090] In step 102, since the wedge-shaped optical element used in step 101 has a thickness range of 0.1-1.0 mm, its refractive index and length are known. The fixed color position (9.5 mm) and scanning movement interval of the wedge-shaped optical element are also determined. In step 102, the optical element to be tested, with a thickness range of 0.1-0.5 mm, is determined, and its specially designed inclined optical surface... Figure 3 As shown, the optical element under test is placed within the measurement range of the spectral confocal system. The lower surface CD of the optical element under test is used as the reference plane. The CD surface of the optical element under test is placed at the 9.5mm position of the spectral confocal system. The CD direction is set as the X direction. An electronically controlled displacement stage is used to perform a transverse scan of the optical element under test in the X direction. The scanning interval is set to 1mm. The spectral confocal system scans each scanning position of the optical element under test in the X direction and obtains the color superposition chromaticity value of the detection signal corresponding to each scanning position.

[0091] It should be noted that the scanning path of the optical element under test starts from point C and proceeds along the direction of point C to point D. At each scanning position, it is necessary to repeatedly collect data on the upper and lower surfaces of the optical element under test, that is, to obtain the color superposition value of the signals returned from the upper and lower surfaces respectively. Then, the color superposition value of the signals is averaged to obtain the color superposition color of the calibration signal of the upper and lower surfaces of each test point. Furthermore, the color superposition chromaticity value of the detection signal of the upper and lower surfaces of each test point is obtained.

[0092] Furthermore, the color superposition chromaticity values ​​of the detection signals at each position of the optical element under test in the X direction are as follows: Figure 4 As shown in the figure, the horizontal axis represents the distance of each detection point from point A, and the vertical axis represents the color superposition chromaticity value of the detection signal corresponding to each detection point. It can be clearly seen from the figure that from point A to point B, as the number of detection points increases, the color superposition chromaticity value of the detection signal shows a significant decreasing trend. This indicates that in the X direction, the color superposition chromaticity value of the detection signal at different locations of the optical element under test decreases with the increase of the thickness of each detection point.

[0093] In step 103, the color superposition chromaticity value of the reference signal at the scanning start point of the optical element under test is determined, and then the absolute value of the color superposition chromaticity difference between the color superposition chromaticity value of the detection signal at each scanning position and the color superposition chromaticity value of the reference signal at the scanning start point is determined.

[0094] For example, the absolute value information of the color superposition chromaticity difference corresponding to the thickness difference between each position of the component under test in the X direction and the component at AC is as follows: Figure 5 As shown in the figure, the horizontal axis represents the sequence number of the difference between the color superimposed chromaticity value of the detection signal at each detection point other than the detection start point A and the color superimposed chromaticity value of the reference signal at detection start point A. The vertical axis represents the absolute value of the color superimposed chromaticity difference between the color superimposed chromaticity value of the detection signal at each detection point other than the detection start point A and the color superimposed chromaticity value of the reference signal at detection start point A. It can be clearly seen from the figure that from point A to point B, the absolute value of the color superimposed chromaticity difference shows a significant upward trend as the number of detection points increases. This indicates that in the X direction, the absolute value of the color superimposed chromaticity difference between different detection positions of the optical element under test and the detection start point A increases with the increase of the thickness at each detection point.

[0095] Furthermore, based on the thickness difference-chromaticity difference calculation formula obtained in step 101 and the absolute value of the color difference obtained from color superposition, the thickness difference of each scanning position of the optical element under test is determined. Taking the thickness difference between the optical element under test and its AC position detected by the spectral confocal system at 9.00 mm and 22.00 mm as examples, the results of the spectral confocal system are 161.00 μm and 395.70 μm, respectively. Compared with the thickness difference data of the OTS-200 thickness gauge, the relative error of the thickness difference data measured by the spectral confocal system in this experiment is controlled within the range of 1.2% to 2.3%. The spectral confocal system realizes the thickness difference detection of optical elements with continuously varying thickness, and has the advantages of real-time and efficient detection.

[0096] In this embodiment of the invention, the thickness of the wedge-shaped optical element ranges from 0.1 to 1.0 mm, while the thickness of the optical element under test ranges from 0.1 to 0.5 mm. The applicable range of the wedge-shaped optical element completely covers the thickness variation range of the optical element under test, and a redundancy is provided to avoid calculation errors caused by the thickness of the optical element under test approaching the boundary value of the wedge-shaped optical element. In this embodiment, the maximum thickness of the optical element under test is 0.5 mm, and the maximum thickness of the wedge-shaped optical element is 1.0 mm, which can verify the linearity of the spectral confocal system under larger thickness differences and enhance robustness.

[0097] Furthermore, the axial dispersion of the spectral confocal system is 1.58 nm, meaning that the maximum difference in the focusing position of different wavelengths of light along the axis is 1.58 nm. The thickness of the wedge-shaped optical element ranges from 0.1 to 1.0 mm, and its maximum thickness is less than the axial dispersion, thus preventing light from failing to focus on the lower surface and resulting in the returned signal only containing the color signal from the upper surface.

[0098] Based on the same inventive concept, embodiments of the present invention provide a detection system for an optical element thickness uniformity detection method, wherein the system can perform the above-mentioned optical element thickness uniformity detection method, and includes a spectral confocal module, a displacement module and a data processing module;

[0099] Spectral confocal module: It consists of a broadband light source, a focusing lens unit, a pinhole unit, a beam splitting unit, a dispersion unit, and a signal acquisition sensing unit. It is used to generate polychromatic light, realize light dispersion, and acquire color superposition feature information.

[0100] Displacement module: includes a displacement device for calibration operation and a displacement mechanism for scanning the test piece, wherein the displacement device for calibration can scan the wedge-shaped optical element, and the displacement mechanism for scanning can scan the optical element under test.

[0101] Data processing module: Connected to the signal acquisition sensing unit and displacement module, it is used to receive the acquired color superposition feature information and displacement position information, calculate the absolute value of the thickness difference according to the thickness difference-chromaticity difference calculation formula obtained from calibration, and determine the thickness uniformity of the optical element under test.

[0102] Based on the same inventive concept, this invention provides an optical element thickness uniformity detection device. Since the principle of this device in solving the technical problem is similar to that of the optical element thickness uniformity detection method, the implementation of this device can refer to the implementation of the method, and the repeated parts will not be described again.

[0103] like Figure 6 As shown, the device includes a calibration unit 601, a obtaining unit 602, and an obtaining unit 603.

[0104] The calibration unit 601 is used to set a wedge-shaped optical element with the same refractive index as the optical element under test in the spectral confocal system, determine the reference plane of the wedge-shaped optical element, align the reference plane with the set color position in the spectral confocal system, and perform a transverse scan of the wedge-shaped optical element by an electronically controlled displacement stage to obtain the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element, as well as the thickness difference-chromaticity difference calculation formula.

[0105] Unit 602 is used to set the optical element under test in the spectral confocal system, determine the reference plane of the optical element under test, align the reference plane with the set color position in the spectral confocal system, and perform a lateral scan of the optical element under test by an electronically controlled displacement stage according to a set step, so as to obtain the color superposition chromaticity value of the detection signal of the optical element under test at each scanning position.

[0106] The determining unit 603 is used to determine the absolute value of the color superposition chromaticity difference between the color superposition chromaticity value of the detection signal at each scanning position and the color superposition chromaticity value of the reference signal at the scanning start point, and to determine the thickness difference of each scanning position of the optical element under test relative to the scanning start point according to the calculation formula of the thickness difference-chromaticity difference and the absolute value of the color superposition chromaticity difference.

[0107] It should be understood that the units included in the above optical element thickness uniformity detection device are only logically divided according to the functions implemented by the device. In practical applications, the above units can be superimposed or separated. Furthermore, the functions implemented by the optical element thickness uniformity detection device provided in this embodiment correspond one-to-one with the optical element thickness uniformity detection method provided in the above embodiments. The more detailed processing flow implemented by the device has been described in detail in the first embodiment of the above method, and will not be described in detail here.

[0108] Another embodiment of the present invention provides a computer device, the computer device including: a processor and a memory; the memory is used to store computer program code, the computer program code including computer instructions; when the processor executes the computer instructions, the electronic device performs each step of the optical element thickness uniformity detection method shown in the above method embodiment.

[0109] Another embodiment of the present invention provides a computer-readable storage medium storing computer instructions that, when executed on a computer device, cause the computer device to perform the various steps of the optical element thickness uniformity detection method shown in the above-described method embodiment.

[0110] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for detecting the thickness uniformity of an optical element, characterized in that, include: A wedge-shaped optical element with the same refractive index as the optical element under test is placed in a spectral confocal system. The reference plane of the wedge-shaped optical element is determined and aligned with the set color position in the spectral confocal system. The wedge-shaped optical element is then scanned laterally by an electronically controlled displacement stage to obtain the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element, as well as the formula for calculating the thickness difference-chromaticity difference. The optical element under test is placed in a spectral confocal system. The reference plane of the optical element under test is determined and aligned with the set color position in the spectral confocal system. The optical element under test is then scanned laterally by an electronically controlled displacement stage according to a set step, and the color superposition chromaticity value of the detection signal of the optical element under test at each scanning position is obtained. The absolute value of the color superposition chromaticity difference between the color superposition chromaticity value of the detection signal at each scanning position and the color superposition chromaticity value of the reference signal at the scanning start point is determined. Based on the calculation formula of the thickness difference-chromaticity difference and the absolute value of the color superposition chromaticity difference, the thickness difference of each scanning position of the optical element under test relative to the scanning start point is determined.

2. The method as described in claim 1, characterized in that, The step of scanning the wedge-shaped optical element horizontally using an electrically controlled displacement stage to obtain the superimposed chromatic difference of the spectral signals within the thickness range of the wedge-shaped optical element specifically includes: The wedge-shaped optical element is transversely scanned at a set scanning interval using an electric displacement stage. At each position, the color superposition information returned from the upper and lower surfaces of the wedge-shaped optical element is repeatedly collected. The color superposition information is then processed by difference to obtain the color superposition chromaticity difference at different positions of the wedge-shaped optical element.

3. The method as described in claim 1, characterized in that, The formula for calculating the chromatic difference between the superimposed spectral signal and the thickness difference of the wedge optical element is as follows: |Δd|=|k·ΔH| Where Δd represents the thickness difference, ΔH represents the color difference of the superimposed spectral signals at different locations, and k represents the calibration coefficient.

4. The method as described in claim 1, characterized in that, The spectral confocal system includes a broadband light source, a converging lens, a first pinhole, a beam splitter, a dispersive mirror group, a second pinhole, and a color sensor; The broadband light source is used to emit stable continuous band polychromatic light. The polychromatic light passes through a converging lens and a first pinhole in sequence and then enters a dispersive lens group where it undergoes axial dispersion. The dispersed light is projected onto the surface of the test piece, and the reflected light generates color superposition information. The color superposition information is collected by a color sensor after passing through a beam splitter and a second pinhole. The wide spectral operating band of the spectral confocal system is 460 nm to 660 nm, and the axial dispersion is 1.58 nm.

5. The method as described in claim 1, characterized in that, The step of laterally scanning the wedge-shaped optical element using an electrically controlled displacement stage to obtain the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element specifically includes: The wedge-shaped optical element is scanned laterally by an electronically controlled displacement stage, and multiple acquisitions are performed at each scanning position to obtain the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element. The process of scanning the optical element under test laterally at set intervals using an electronically controlled displacement stage to obtain the color superposition chromaticity values ​​of the detection signals of the optical element under test at each scanning position specifically includes: The optical element under test is scanned laterally at set intervals using an electronically controlled displacement stage. Multiple data acquisitions are performed at each scanning position to obtain the color superposition chromaticity value of the detection signal of the optical element under test at each scanning position.

6. The method as described in claim 1, characterized in that, Before obtaining the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element, the method further includes: The color overlay signal at any scan position is determined using the following formula: x up =(R up ,G up ,B up ) x down =(R down ,G down ,B down ) Where X represents the color superposition signal acquired by the color sensor at the color position corresponding to the wedge optical element, x up This represents the RGB array of the upper surface of the wedge-shaped optical element, acquired at the corresponding color position. down This represents the RGB array of the lower surface of the wedge-shaped optical element, acquired at the corresponding color position. n is the refractive index of the wedge-shaped optical element, n0 is the air refractive index, and x... up R represents the RGB array corresponding to the color positions on the upper surface of the wedge-shaped optical element. up G up B up These represent the red, green, and blue values ​​included in the RGB array on the upper surface, respectively. down G down B down These represent the red, green, and blue values ​​included in the RGB array on the lower surface, respectively.

7. A detection system for implementing the optical element thickness uniformity detection method according to any one of claims 1-6, characterized in that, include: Spectral confocal module: It consists of a broadband light source, a focusing lens unit, a pinhole unit, a beam splitting unit, a dispersion unit, and a signal acquisition sensing unit. It is used to generate polychromatic light, realize light dispersion, and acquire color superposition feature information. Displacement module: includes a displacement device for calibration operation and a displacement mechanism for scanning the test piece, wherein the displacement device for calibration can scan the wedge-shaped optical element, and the displacement mechanism for scanning can scan the optical element under test. Data processing module: Connected to the signal acquisition sensing unit and displacement module, it is used to receive the acquired color superposition information and displacement position information, calculate the absolute value of the thickness difference according to the thickness difference-chromaticity difference calculation formula obtained from calibration, and determine the thickness uniformity of the optical element under test.

8. A device for detecting the thickness uniformity of optical elements, characterized in that, include: The calibration unit is used to set a wedge-shaped optical element with the same refractive index as the optical element under test in the spectral confocal system, determine the reference plane of the wedge-shaped optical element, align the reference plane with the set color position in the spectral confocal system, and perform a transverse scan of the wedge-shaped optical element by an electronically controlled displacement stage to obtain the color superposition chromaticity value of the calibration signal within the thickness range of the wedge-shaped optical element, as well as the thickness difference-chromaticity difference calculation formula. The unit is used to set the optical element under test in the spectral confocal system, determine the reference plane of the optical element under test, align the reference plane with the set color position in the spectral confocal system, and perform a transverse scan of the optical element under test by an electronically controlled displacement stage according to a set step, so as to obtain the color superposition chromaticity value of the detection signal of the optical element under test at each scanning position. The determining unit is used to determine the absolute value of the color superposition chromaticity difference between the color superposition chromaticity value of the detection signal at each scanning position and the color superposition chromaticity value of the reference signal at the scanning start point, and to determine the thickness difference of each scanning position of the optical element under test relative to the scanning start point according to the calculation formula of the thickness difference-chromaticity difference and the absolute value of the color superposition chromaticity difference.

9. A computer device, characterized in that, The computer device includes a memory and a processor. The memory stores a computer program, which, when executed by the processor, causes the processor to perform the optical element thickness uniformity detection method as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The device contains a computer program that, when executed by a processor, causes the processor to perform the optical element thickness uniformity detection method as described in any one of claims 1-7.

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