A transparent plastic plate internal defect detection method, system and device based on polarized light and transmittance analysis and a storage medium

Abstract

This invention discloses a method, system, device, and storage medium for detecting internal defects in transparent plastic sheets based on polarization and transmittance analysis. It relates to the field of optical measurement technology, and includes acquiring multi-angle polarization response and multi-band transmittance data of the same region to generate optical measurement data; calculating polarization phase perturbation values ​​and transmittance residuals based on the optical measurement data to generate polarization-transmission coupling state quantities; and extracting internal defect perturbation regions based on the polarization-transmission coupling state quantities to generate defect types and defect levels. The method described in this invention improves the anti-interference capability, repeatability, and classification stability of measuring weak internal defects in transparent plastic sheets.

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, specifically to a method, system, device, and storage medium for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis. Background Technology

[0002] Transparent plastic sheets are widely used in display windows, protective covers, optical isolation plates, transparent structural components, and precision instrument housings. Microcracks, bubbles, inclusions, delamination, and residual stress inside the sheet can alter the intensity of transmitted light, polarization response, and spatial uniformity.

[0003] As transparent plastic sheets develop towards larger sizes, thinner walls, and higher light transmittance, the testing process is no longer satisfied with observing surface scratches or black spots. Instead, it needs to convert invisible internal disturbances into stable measurement quantities, so that the test results have the attributes of location traceability, numerical comparison, and grade determination.

[0004] Current methods for detecting internal defects in transparent plastic sheets typically employ manual light transmission observation, conventional machine vision, single transmittance measurement, or polarization stress observation. Manual light transmission observation relies on the inspector's experience; conventional machine vision easily identifies surface reflections, dust, and thickness variations as internal defects; single transmittance measurement struggles to distinguish between overall transparency fluctuations and localized absorption and scattering anomalies; and single polarization stress observation can only reflect localized birefringence or stress texture changes, making it difficult to simultaneously quantify transparency attenuation and spatial continuity anomalies.

[0005] Even when the above methods are used in combination, they usually remain at the level of parallel detection or back-end image judgment, lacking a unified measurement expression of polarization response, transmission residual and spatial gradient for the same transparent plastic plate detection area, resulting in insufficient stability in the location, classification and grade determination of internal weak defects. Summary of the Invention

[0006] In view of the above-mentioned problems, the present invention is proposed.

[0007] Existing methods for measuring internal defects in transparent plastic sheets suffer from unstable weak defect responses, difficulty in distinguishing true internal defects from thickness, reflection, and light source fluctuations, lack of unified measurement state quantities in the test results, and problems in how to convert internal defects into calculable, comparable, and classifiable optical measurement results.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for detecting internal defects in transparent plastic sheets based on polarization light and transmittance analysis, comprising collecting multi-angle polarization response and multi-band transmittance data in the same area to generate optical measurement data.

[0009] The polarization phase perturbation value and transmittance residual are calculated based on optical measurement data to generate polarization transmission coupling state quantities.

[0010] The internal defect disturbance region is extracted based on the polarization transmission coupling state quantity, and the defect type and defect level are generated.

[0011] As a preferred embodiment of the method for detecting internal defects in transparent plastic sheets based on polarization and transmittance analysis described in this invention, the step of acquiring multi-angle polarization responses in the same area includes fixing the transparent plastic sheet to a support platform in a transmission polarization measurement optical path.

[0012] A two-dimensional detection coordinate system is established on the upper surface of the transparent plastic sheet, dividing the transparent plastic sheet into detection zones that are continuously arranged along the scanning direction and whose adjacent boundaries overlap.

[0013] In each detection zone, the incident optical axis, the imaging optical axis and the normal of the transparent plastic plate are kept coincident, and polarization transmission response images are acquired at four polarization angles of 0°, 45°, 90° and 135° respectively.

[0014] Exposure uniformity, angle calibration, and subpixel registration are performed on the polarization transmission response images acquired at four polarization angles to ensure that the same pixel in the four polarization transmission response images corresponds to the same volume position inside the transparent plastic sheet.

[0015] A polarization response sequence is generated based on the detection zone number, polarization angle, pixel coordinates, and acquisition time.

[0016] As a preferred embodiment of the method for detecting internal defects in transparent plastic sheets based on polarization light and transmittance analysis according to the present invention, the multi-band transmittance data includes: after completing the acquisition of the polarization response sequence in each detection zone, keeping the detection zone position unchanged, and outputting measurement beams sequentially in the visible light band and near-infrared band through a stable transmission light source.

[0017] The incident light intensity corresponding to each wavelength band is recorded synchronously by the incident light monitoring unit, and the outgoing light intensity after passing through the transparent plastic plate is recorded by the outgoing light receiving unit.

[0018] Based on the baseline transmission records of the standard thickness sample, the average transmission values ​​of the initial screening normal zones after edge exclusion, and the adjacent detection zones, a reference transmittance is established for each detection zone.

[0019] Incident light intensity, outgoing light intensity, reference transmittance, detection zone number, and band number are bound together to form multi-band transmittance data, which, together with the polarization response sequence, constitutes the optical measurement data.

[0020] As a preferred embodiment of the method for detecting internal defects in transparent plastic sheets based on polarization and transmittance analysis described in this invention, the polarization phase perturbation value includes reading the registration grayscale response of four polarization angles under the same detection zone in the optical measurement data, first removing saturated pixels and edge reflective pixels, and then calculating the grayscale difference between mutually orthogonal polarization angles and the grayscale difference between diagonal polarization angles.

[0021] The two types of grayscale differences are normalized according to the average grayscale of the detection zone to obtain the initial polarization disturbance amount that reflects the birefringence disturbance inside the transparent plastic sheet.

[0022] The polarization phase disturbance value is obtained by differentiating the initial polarization disturbance value with the polarization disturbance reference value of the normal zone surrounding the same detection zone.

[0023] When the polarization phase disturbance value of the detection zone is continuously higher than the upper limit of the polarization disturbance reference obtained by the standard template calibration, the detection zone is marked as a polarization anomaly candidate zone.

[0024] As a preferred embodiment of the method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis according to the present invention, the transmittance residual and the polarized transmission coupling state include: calculating the measured transmittance of each detection zone based on the multi-band transmittance data, and correcting the reference transmittance using the standard thickness of the transparent plastic sheets in the same batch, the monitored value of the light source intensity, and the average transmittance of the adjacent normal zones.

[0025] The difference between the measured transmittance and the reference transmittance is normalized according to the reference transmittance to obtain the transmittance residual.

[0026] The transmittance residual, the polarization phase perturbation value, and the spatial gradient difference between the test and adjacent detection zones are respectively dimensionless and weighted and summed according to the weighting coefficients determined by the calibration template to generate the polarization transmission coupling state quantity.

[0027] When the same detection zone simultaneously satisfies at least two of the following conditions: increased transmittance residual, increased polarization phase perturbation value, or increased spatial gradient difference, the polarization transmission coupling state of the detection zone is written into the spatial state diagram.

[0028] As a preferred embodiment of the method for detecting internal defects in transparent plastic sheets based on polarization and transmittance analysis described in this invention, the method for extracting the internal defect disturbance region includes establishing a four-neighborhood connectivity relationship in the spatial state diagram according to the physical adjacency relationship of the detection partitions, and using the detection partitions whose polarization transmission coupling state quantity is higher than the upper limit of the coupling anomaly reference as seed partitions. Starting with the seed partition, adjacent detection partitions with consistent polarization transmission coupling state variables and continuous boundary gradients are merged into candidate perturbation regions. The candidate perturbation region is filled with holes, isolated points are removed, and edge artifacts are eliminated, retaining regions whose area, continuous length, and coupling state peak all meet the calibration conditions. The retained candidate disturbance regions are mapped back to the two-dimensional detection coordinates of the transparent plastic sheet to obtain the internal defect disturbance regions.

[0029] As a preferred embodiment of the method for detecting internal defects in transparent plastic sheets based on polarization and transmittance analysis described in this invention, the generated defect type and defect level include: statistically analyzing the mean value of polarization phase disturbance, the mean value of transmittance residual, the peak value of polarization-transmission coupling state quantity, the area of ​​the region, the aspect ratio, the roundness, the continuous length, and the sheet expansion rate in each internal defect disturbance region.

[0030] When the average value of polarization phase perturbation is higher than the polarization perturbation classification benchmark and the average value of transmittance residual is lower than the transmittance residual classification benchmark, residual stress type defects are generated.

[0031] When the mean value of the transmittance residual is higher than the transmittance residual classification benchmark and the roundness of the region meets the bubble morphology benchmark, a bubble-type defect is generated.

[0032] When the mean value of the transmittance residual is higher than the transmittance residual classification benchmark and the roundness of the region does not meet the bubble morphology benchmark, an inclusion-type defect is generated.

[0033] When the mean value of polarization phase perturbation and the mean value of transmittance residual are both higher than the corresponding parting datum, and the aspect ratio and continuous length of the region satisfy the linear continuous datum, microcrack-type defects are generated.

[0034] When the regional sheet expansion rate meets the stratified morphology benchmark, a stratified defect is generated.

[0035] The severity metric is calculated based on the peak value of the polarization transmission coupling state quantity, the area of ​​the region, and the continuous length. The defect level is then generated according to the severity metric interval.

[0036] Another objective of this invention is to provide a transparent plastic sheet internal defect detection system based on polarization and transmittance analysis. This system, through a detection and processing scheme consisting of an optical data acquisition module, a coupling state calculation module, and a defect result determination module, can acquire multi-angle polarization response and multi-band transmittance data in the same area, generate polarization-transmission coupling state quantities, and output defect types and defect levels accordingly. This solves the problems of current transparent plastic sheet internal defect detection technologies, such as the difficulty in characterizing internal defects with a single optical parameter, the lack of correlation between different detection data within the same area, and the reliance on manual experience for defect classification and grading.

[0037] As a preferred embodiment of the transparent plastic sheet internal defect detection system based on polarized light and transmittance analysis described in this invention, it includes an optical data acquisition module, a coupling state calculation module, and a defect result determination module.

[0038] The optical data acquisition module is used to acquire multi-angle polarization response and multi-band transmittance data in the same area to generate optical measurement data.

[0039] The coupling state calculation module is used to calculate the polarization phase perturbation value and transmittance residual based on the optical measurement data, and generate polarization transmission coupling state quantity.

[0040] The defect result determination module is used to extract the internal defect disturbance region based on the polarization transmission coupling state quantity, and generate the defect type and defect level.

[0041] Another object of the present invention is to provide a device for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of a method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis.

[0042] Another object of the present invention is to provide a storage medium for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis, wherein a computer program is stored thereon, and when the computer program is executed by a processor, it implements the steps of a method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis.

[0043] The beneficial effects of this invention are as follows: The method for detecting internal defects in transparent plastic sheets based on polarization and transmittance analysis provided by this invention transforms the detection of internal defects in transparent plastic sheets from single-image observation to multi-source optical measurement by establishing multi-angle polarization response and multi-band transmittance data for the same region. By constructing a polarization-transmission coupling state quantity involving polarization phase perturbation, transmittance residual, and spatial gradient difference, internal defects have a calculable and comparable unified expression. Through spatial extraction, classification, and grading of the coupling state quantity, the detection results simultaneously output the defect location, defect type, and defect level. This invention improves the anti-interference, repeatability, and classification stability of weak internal defect measurements in transparent plastic sheets. Attached Figure Description

[0044] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. 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.

[0045] Figure 1 This is a measurement data acquisition diagram of a method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis, provided in Embodiment 1 of the present invention.

[0046] Figure 2 This is a calculation diagram of the coupling state quantity of a method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis, provided in Embodiment 2 of the present invention.

[0047] Figure 3 This is a defect domain classification and grading diagram for a method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis, provided in Embodiment 3 of the present invention. Detailed Implementation

[0048] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0049] Example 1: Refer to Figure 1 This is an embodiment of the present invention, which provides a specific implementation of a method for detecting internal defects in transparent plastic sheets based on polarization light and transmittance analysis, in which multi-angle polarization response and multi-band transmittance data of the same area are collected to generate optical measurement data.

[0050] A transparent plastic plate is fixed on a support platform in the transmission polarization measurement optical path. Two-dimensional detection coordinates are established on the upper surface of the transparent plastic plate, and the transparent plastic plate is divided into detection zones that are continuously arranged along the scanning direction and whose adjacent boundaries overlap.

[0051] In each detection zone, the incident optical axis, the imaging optical axis and the normal of the transparent plastic plate are kept coincident, and polarization transmission response images are acquired at four polarization angles of 0°, 45°, 90° and 135° respectively.

[0052] Exposure uniformity, angle calibration, and subpixel registration are performed on the polarization transmission response images acquired at four polarization angles to ensure that the same pixel in the four polarization transmission response images corresponds to the same volume position inside the transparent plastic sheet.

[0053] A polarization response sequence is generated based on the detection zone number, polarization angle, pixel coordinates, and acquisition time.

[0054] Furthermore, the support platform adopts a negative pressure adsorption platform or an edge clamping platform, and the tilt angle between the detection surface of the transparent plastic plate and the reference surface of the support platform is controlled within 0.05°. The incident optical axis and the imaging optical axis are adjusted to the same normal direction through a coaxial collimation component.

[0055] The two-dimensional detection coordinates take the lower left corner of the transparent plastic plate as the origin, the detection partition size is set to 2mm×2mm, and the overlap width of adjacent detection partitions is set to 0.2mm, so that the boundary defects between adjacent detection partitions will not be cut off by the scanning segmentation.

[0056] Furthermore, multi-angle polarization response is achieved through a four-polarization camera, a rotating polarizer, or a liquid crystal adjustable polarizer; when using a four-polarization camera, polarization transmission response images at four polarization angles of 0°, 45°, 90°, and 135° are acquired simultaneously within the same exposure cycle.

[0057] When using a rotating polarizer or a liquid crystal adjustable polarizer, samples are collected sequentially in the same detection zone at 0°, 45°, 90°, and 135°. Angle calibration is performed using an angle encoder or a standard polarizer before collection, and the angle error is controlled within 0.5°.

[0058] Furthermore, exposure uniformity includes subtracting camera dark current from dark field images, calculating illumination flat field coefficients from transmission images without substrate, and converting polarization transmission response images at each polarization angle into flat-field corrected grayscale responses; subpixel registration includes extracting edge positioning points of the transparent plastic sheet and calibration points of the support platform, and using affine transformation to map the image coordinates of the four polarization angles to the same detection coordinates, so that the difference in polarization response within the same detection zone originates from optical disturbances inside the transparent plastic sheet.

[0059] After completing the acquisition of the polarization response sequence in each detection zone, the detection zone position remains unchanged, and the measurement beam is output sequentially in the visible light band and near-infrared band through a stable transmission light source.

[0060] The incident light intensity corresponding to each wavelength band is recorded synchronously by the incident light monitoring unit, and the outgoing light intensity after passing through the transparent plastic plate is recorded by the outgoing light receiving unit.

[0061] Based on the baseline transmission records of the standard thickness sample, the average transmission values ​​of the initial screening normal zones after edge exclusion, and the adjacent detection zones, a reference transmittance is established for each detection zone.

[0062] Incident light intensity, outgoing light intensity, reference transmittance, detection zone number, and band number are bound together to form multi-band transmittance data, which, together with the polarization response sequence, constitutes the optical measurement data.

[0063] Furthermore, the stable transmission light source adopts a constant current driven narrowband LED array or a tunable transmission light source, with output wavelengths including four center wavelengths of 450nm, 530nm, 630nm and 850nm, and the allowable error of the center wavelength is ±10nm.

[0064] Before each acquisition, the incident reference light intensity without a substrate is acquired first, and then the output reference light intensity of a standard thickness, defect-free sample is acquired. If the relative fluctuation of the incident reference light intensity in the same wavelength band exceeds 0.5% for three consecutive times, the acquisition is stopped and the light source is re-stabilized.

[0065] Furthermore, the initial screening of normal partitions is determined using three rules: The detection zone is located 5mm inward from the edge of the transparent plastic sheet. No saturated pixels appeared in the grayscale response at the four polarization angles. The measured transmittance of the detection zone falls within the range of ±5% of the median transmittance of the entire sheet. The average transmission value of adjacent detection zones is calculated using zones within a 3×3 neighborhood that meet the three rules. If there are fewer than five zones that meet the conditions in the neighborhood, the range is expanded to 5×5.

[0066] Furthermore, the reference transmittance is determined by the standard thickness sample reference transmittance record, the average transmittance of normal zones of transparent plastic sheets in the same batch, and the real-time incident light intensity correction term.

[0067] When the difference between the thickness of the transparent plastic sheet and the thickness of the standard thickness sample exceeds 0.05mm, the reference transmittance is linearly corrected according to the overall transmission change caused by the thickness difference, so as to avoid writing the overall light intensity change caused by the thickness tolerance into the internal defect measurement data.

[0068] Furthermore, the optical measurement data is stored with the detection partition number as the primary key. Each detection partition records the grayscale response of four polarization angles, the incident light intensity of four bands, the outgoing light intensity of four bands, the reference transmittance, the acquisition timestamp, and the registration transformation parameters.

[0069] The polarization response sequence and multi-band transmittance data are merged under the same detection partition number to form a unified input for subsequent calculation of polarization phase perturbation value and transmittance residual.

[0070] It should be noted that the design concept is to limit the detection of internal defects in transparent plastic sheets to multi-source optical measurements under the same area, coordinates, and optical path. First, the systematic influence of angle, exposure, light source, and sheet thickness on the measurement data is eliminated, and then structured optical measurement data is output, thereby providing a repeatable data basis for non-dedicated variable measurements in the sense of G01D.

[0071] The beneficial effects are that by synchronously binding multi-angle polarization response and multi-band transmittance data in the same area, the information on internal stress disturbance and transmission attenuation of transparent plastic sheets can be collected from the same source; by establishing reference transmittance and light source stabilization rules, the interference of thickness tolerance, illumination fluctuation and surface reflection on subsequent measurements can be reduced, so that subsequent defect extraction can be based on calibrable and traceable optical measurement data.

[0072] Example 2: Refer to Figure 2 This is an embodiment of the present invention, which provides a specific implementation of a method for detecting internal defects in transparent plastic sheets based on polarization light and transmittance analysis, wherein the polarization phase perturbation value and transmittance residual are calculated based on optical measurement data to generate polarization transmission coupling state quantities.

[0073] In the optical measurement data, the registration grayscale response of four polarization angles under the same detection zone is read. Saturated pixels and edge reflective pixels are first removed, and then the grayscale difference between mutually orthogonal polarization angles and the grayscale difference between diagonal polarization angles are calculated.

[0074] The two types of grayscale differences are normalized according to the average grayscale of the detection zone to obtain the initial polarization disturbance amount that reflects the birefringence disturbance inside the transparent plastic sheet.

[0075] The polarization phase disturbance value is obtained by differentiating the initial polarization disturbance value with the polarization disturbance reference value of the normal zone surrounding the same detection zone.

[0076] When the polarization phase disturbance value of the detection zone is continuously higher than the upper limit of the polarization disturbance reference obtained by the standard template calibration, the detection zone is marked as a polarization anomaly candidate zone.

[0077] Furthermore, saturated pixels refer to pixels whose grayscale value reaches 98% or higher of the camera's quantization limit, and edge reflective pixels refer to pixels located within 0.5mm inward from the geometric boundary of the transparent plastic sheet and whose grayscale gradient exceeds the 95th percentile of the overall grayscale gradient. After removing the above pixels, the effective grayscale average value of the detection zone is calculated at four polarization angles: 0°, 45°, 90°, and 135°. If the number of effective pixels is less than 80% of the total number of pixels in the detection zone, the detection zone is recorded as an invalid zone and rescanned.

[0078] Furthermore, the polarization phase perturbation value is calculated jointly based on the orthogonal polarization difference and the diagonal polarization difference, specifically expressed as follows: It should be noted that D a Depend on minus get, Indicates the first The difference in grayscale value at the diagonal polarization angle of each detection zone Depend on minus get.

[0079] in, Indicates the first The polarization phase perturbation value of each detection zone, Indicates the first The grayscale difference of the orthogonal polarization angle of each detection zone Indicates the first The difference in grayscale value at the diagonal polarization angle of each detection zone Indicates the first Each detection zone is in Effective grayscale mean value under polarization angle Indicates the first Each detection zone is in Effective grayscale mean value under polarization angle Indicates the first Each detection zone is in Effective grayscale mean value under polarization angle Indicates the first Each detection zone is in Effective grayscale mean value under polarization angle Indicates the first The arithmetic mean of the effective grayscale values ​​at four polarization angles in each detection zone. This represents the stability constant to prevent the denominator from being zero. Take 0.001.

[0080] Furthermore, the polarization disturbance reference value is determined by the mean and standard deviation of the polarization phase disturbance values ​​of the detection zone of the standard defect-free sample, and the upper limit of the polarization disturbance reference is set as the mean plus three times the standard deviation.

[0081] When sufficient standard sample data is not available, the upper limit of the polarization perturbation reference is set to 0.18. The condition for continuously exceeding the upper limit of the polarization perturbation reference is that at least three adjacent detection zones are all above the upper limit of the polarization perturbation reference.

[0082] The measured transmittance of each detection zone is calculated based on the multi-band transmittance data, and the reference transmittance is corrected using the standard thickness of the transparent plastic sheet of the same batch, the monitored value of the light source intensity, and the average transmittance of the adjacent normal zones.

[0083] The difference between the measured transmittance and the reference transmittance is normalized according to the reference transmittance to obtain the transmittance residual.

[0084] The transmittance residual, the polarization phase perturbation value, and the spatial gradient difference between the test and adjacent detection zones are respectively dimensionless and weighted and summed according to the weighting coefficients determined by the calibration template to generate the polarization transmission coupling state quantity.

[0085] When the same detection zone simultaneously satisfies at least two of the following conditions: increased transmittance residual, increased polarization phase perturbation value, or increased spatial gradient difference, the polarization transmission coupling state of the detection zone is written into the spatial state diagram.

[0086] Furthermore, the transmittance residual is calculated based on the normalized squared difference between the measured transmittance and the reference transmittance, specifically expressed as follows: in, Indicates the first The transmittance residual of each detection zone Indicates the first The transmission difference between each detection zone It is obtained by subtracting the product of the incident light intensity and the reference transmittance from the emitted light intensity. Indicates the first Transmission normalization reference for each detection zone It is obtained by multiplying the incident light intensity by the sum of the reference transmittance and the stability constant.

[0087] Furthermore, the multi-band transmittance residuals are first calculated independently for each band, and then a weighted average is obtained by using the reciprocal of the band noise as the weight.

[0088] The 450nm and 530nm bands are used to enhance the scattering response caused by small inclusions and bubbles, while the 630nm and 850nm bands are used to reduce the influence of slight surface contamination on short-wavelength transmission measurements. The transmittance residuals calculated from the four bands are uniformly mapped to the a-th detection zone.

[0089] Furthermore, the polarization transmission coupling state variables are generated as a weighted combination of polarization phase perturbation values, transmittance residuals, and spatial gradient differences, specifically expressed as follows: in, Indicates the first Polarization transmission coupling state quantity of each detection zone Indicates the first The polarization phase perturbation value of each detection zone Indicates the first The transmittance residual of each detection zone Indicates the first Spatial gradient difference between the detection partition and its four neighboring detection partitions.

[0090] The weighting coefficients represent the polarization phase perturbation values. Take 0.40.

[0091] The weighting coefficient represents the transmittance residual. Take 0.40.

[0092] Weighting coefficients representing spatial gradient differences. Take 0.20.

[0093] Furthermore, the spatial gradient difference is determined by the first... The differences in polarization phase perturbation values ​​and transmittance residuals between each detection zone and its four adjacent detection zones (upper, lower, left, and right) are used to determine the overall detection outcome.

[0094] When the detection zone is located at the edge of the transparent plastic sheet and there are fewer than four adjacent detection zones, only the actual adjacent detection zones are used to calculate the spatial gradient difference, and the edge confidence level is marked in the spatial state diagram.

[0095] Furthermore, the upper limit of the coupling anomaly benchmark for polarization transmission coupling state quantity is set as the mean of polarization transmission coupling state quantity in the standard defect-free sample plus three times the standard deviation.

[0096] When sufficient standard template data is not available, the upper limit of the coupling anomaly baseline is set to 0.30.

[0097] Only when the detection zone meets the condition that at least two of the three types of quantities—polarization phase perturbation, transmittance residual, and spatial gradient difference—exceed the corresponding upper limit of the reference, will the detection zone be written into the spatial state diagram to avoid false triggering caused by a single noise source.

[0098] It should be noted that the design concept of this embodiment is to integrate polarization response, transmission attenuation and spatial abrupt change from parallel observations into the same polarization transmission coupling state quantity.

[0099] The polarization phase perturbation value reflects the birefringence and stress concentration inside the transparent plastic sheet, the transmittance residual reflects absorption, scattering or shading anomalies, and the spatial gradient difference reflects the continuity of the defect boundary.

[0100] With all three factors combined, the detection results no longer depend on a single image for judgment, which can solve the problem that single polarization detection or single transmittance detection cannot reliably identify internal weak defects.

[0101] The beneficial effect is that by constructing polarization transmission coupling state quantities through polarization phase perturbation values, transmittance residuals, and spatial gradient differences, the internal defects of transparent plastic sheets can be transformed from invisible optical anomalies into calculable and measurable quantities.

[0102] By using standard template calibration and triggering rules for at least two types of anomalies, the influence of light source fluctuations, plate thickness variations, and local reflections on measurement judgment is reduced, resulting in more stable numerical characterization of internal microcracks, inclusions, and residual stress concentrations.

[0103] Example 3: Refer to Figure 3This is an embodiment of the present invention, which provides a method for detecting internal defects in transparent plastic sheets based on polarization and transmittance analysis. The specific embodiment of the method extracts the internal defect disturbance region based on the polarization and transmission coupling state quantity and generates the defect type and defect level.

[0104] In the spatial state diagram, a four-neighbor connectivity relationship is established according to the physical adjacency relationship of the detection partitions, and the detection partitions with polarization transmission coupling state quantities higher than the upper limit of the coupling anomaly reference are used as seed partitions.

[0105] Starting with the seed partition, adjacent detection partitions with consistent polarization transmission coupling state variables and continuous boundary gradients are merged into candidate perturbation regions.

[0106] The candidate perturbation region is filled with holes, isolated points are removed, and edge artifacts are eliminated, retaining regions whose area, continuous length, and coupling state peak all meet the calibration conditions.

[0107] The retained candidate disturbance regions are mapped back to the two-dimensional detection coordinates of the transparent plastic sheet to obtain the internal defect disturbance regions.

[0108] Furthermore, the four-neighbor connectivity relationship is established based on the top, bottom, left, and right adjacency relationships of the detection partitions, and the physical distance between adjacent detection partitions is calculated from the detection partition size and overlap width.

[0109] The seed partitions are expanded sequentially starting from the detection partition with the highest polarization transmission coupling state value. The expansion conditions are that the polarization transmission coupling state value of the adjacent detection partitions is higher than 0.24, and the decrease in coupling state value between adjacent detection partitions does not exceed 40% of the coupling state value of the seed partition.

[0110] Furthermore, hole filling of candidate perturbation regions is only performed on blank detection partitions that are completely surrounded by the same candidate perturbation region and whose area is less than 10% of the area of ​​the candidate perturbation region.

[0111] Isolated point deletion is used to remove noise points with an area smaller than three detection zones and not connected to any other abnormal detection zones.

[0112] Edge artifact removal is used to remove candidate perturbation regions that overlap with the outer contour boundary of the transparent plastic sheet by more than 50% of the region's perimeter and whose transmittance residual does not exceed 0.12.

[0113] Furthermore, the conditions for retaining the internal defect disturbance region include a region area of ​​not less than 0.5 mm², a continuous length of not less than 1.5 mm, or a peak value of polarization transmission coupling state quantity of not less than 0.40.

[0114] Candidate perturbation regions only need to satisfy one of the continuous length condition or the peak coupling condition, and if they also satisfy the region area condition, they are retained as internal defect perturbation regions.

[0115] The retained internal defect disturbance region records the centroid coordinates, circumscribed rectangle, area, perimeter, aspect ratio, and region boundary points.

[0116] In each internal defect disturbance region, the mean value of polarization phase disturbance, the mean value of transmittance residual, the peak value of polarization transmission coupling state quantity, the region area, aspect ratio, roundness, continuous length and sheet expansion rate are statistically analyzed.

[0117] When the average value of polarization phase perturbation is higher than the polarization perturbation classification benchmark and the average value of transmittance residual is lower than the transmittance residual classification benchmark, residual stress type defects are generated.

[0118] When the mean value of the transmittance residual is higher than the transmittance residual classification benchmark and the roundness of the region meets the bubble morphology benchmark, a bubble-type defect is generated.

[0119] When the mean value of the transmittance residual is higher than the transmittance residual classification benchmark and the roundness of the region does not meet the bubble morphology benchmark, an inclusion-type defect is generated.

[0120] When the mean value of polarization phase perturbation and the mean value of transmittance residual are both higher than the corresponding parting datum, and the aspect ratio and continuous length of the region satisfy the linear continuous datum, microcrack-type defects are generated.

[0121] When the regional sheet expansion rate meets the stratified morphology benchmark, a stratified defect is generated.

[0122] The severity metric is calculated based on the peak value of the polarization transmission coupling state quantity, the area of ​​the region, and the continuous length. The defect level is then generated according to the severity metric interval.

[0123] Furthermore, the polarization perturbation classification benchmark is set to 0.18, the transmission residual classification benchmark is set to 0.12, the bubble morphology benchmark is set to a region roundness of not less than 0.70, the linear continuity benchmark is set to a region aspect ratio of not less than 5 and a continuous length of not less than 3 mm, and the layered morphology benchmark is set to a sheet expansion rate of not less than 0.65.

[0124] The roundness of a region is calculated by combining the region area and perimeter. The sheet-like expansion rate is calculated by the ratio of the region area to the area of ​​the circumscribed rectangle. The continuous length is obtained by converting the length of the skeleton line of the internal defect disturbance region.

[0125] Furthermore, the severity metric is calculated based on the peak value of the polarization transmission coupling state quantity, the area of ​​the region, and the continuous length, specifically expressed as follows: in, Indicates the first The severity metric for each internal defect disturbance region Indicates the first Normalized peak value of polarization transmission coupling state quantity within the internal defect disturbance region. Indicates the first Normalized area of ​​each internal defect disturbance region Indicates the first Normalized continuous length of each internal defect disturbance region The level weights represent the peak values ​​of polarization transmission coupling state quantities. Take 0.50, The ranking weights representing the area of ​​a region. Take 0.25, The ranking weights represent the length of consecutive ranks. Take 0.25.

[0126] Furthermore, the defect severity is divided into three levels based on the severity metric: When the severity metric is less than 0.35, a first-level defect level is generated.

[0127] A level 2 defect is generated when the severity metric is greater than or equal to 0.35 and less than 0.60.

[0128] A level 3 defect is generated when the severity metric is greater than or equal to 0.60.

[0129] For microcrack-type defects, if the continuous length is greater than or equal to 8 mm, the defect level shall be at least a level 2 defect.

[0130] Furthermore, after the defect type and defect level are generated, the two-dimensional detection coordinates of the internal defect disturbance area, defect type, defect level, average polarization phase disturbance value, average transmittance residual value, and peak value of polarization transmission coupling state quantity are written into the detection result table.

[0131] Each row in the test results table corresponds to an internal defect disturbance area, and the original test zone number is retained to facilitate verification and positioning on the actual transparent plastic sheet.

[0132] It should be noted that the design concept of this embodiment is to first extract the internal defect disturbance region by utilizing the spatial continuity of polarization transmission coupling state quantities, and then use the combination rules of polarization disturbance, transmission residual and morphological index to perform classification and grading.

[0133] Simple image classification methods are difficult to explain the source of defect levels, and simple thresholding methods are easily affected by local noise. This step incorporates the peak value of the measurement, the range of the region, and the continuous morphology into the judgment, so that the detection results can correspond to the actual location and severity of disturbance inside the transparent plastic sheet.

[0134] The beneficial effect is that, through four-neighbor connectivity, spatial gradient continuity, and morphology preservation rules, discrete anomaly detection partitions are transformed into internal defect perturbation regions with physical boundaries.

[0135] By using classification criteria and severity measurements, residual stress, bubbles, inclusions, microcracks, and delamination defects can be differentiated by measurement criteria, and defect levels that can be used for quality grading and process traceability can be output.

[0136] Example 4: As an embodiment of the present invention, a system for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis is provided, including an optical data acquisition module, a coupling state calculation module, and a defect result determination module.

[0137] The optical data acquisition module is used to collect multi-angle polarization response and multi-band transmittance data in the same area to generate optical measurement data.

[0138] The coupling state calculation module is used to calculate the polarization phase perturbation value and transmittance residual based on the optical measurement data, and generate polarization transmission coupling state quantities.

[0139] The defect result determination module is used to extract the internal defect disturbance region based on the polarization transmission coupling state quantity, and generate the defect type and defect level.

[0140] This embodiment also provides a computer device, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis as proposed in the above embodiment.

[0141] This embodiment also provides a computer-readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements the method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis as proposed in the above embodiment.

[0142] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0143] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-including system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device.

[0144] More specific examples of computer-readable media (a non-exhaustive list) include: electrical connections (electronic devices) having one or more wires, portable computer disk drives (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Furthermore, computer-readable media can even be paper or other suitable media on which the program can be printed, because the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in computer memory.

[0145] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0146] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis, characterized in that, include: Collect multi-angle polarization response and multi-band transmittance data in the same area to generate optical measurement data; The polarization phase perturbation value and transmittance residual are calculated based on optical measurement data to generate polarization transmission coupling state quantities. The internal defect disturbance region is extracted based on the polarization transmission coupling state quantity, and the defect type and defect level are generated.

2. The method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis as described in claim 1, characterized in that: The acquisition of multi-angle polarization response in the same area includes fixing a transparent plastic plate to a support platform in the transmission polarization measurement optical path; Two-dimensional detection coordinates are established on the upper surface of the transparent plastic sheet, and the transparent plastic sheet is divided into detection zones that are continuously arranged along the scanning direction and whose adjacent boundaries overlap. In each detection zone, the incident optical axis, the imaging optical axis and the normal of the transparent plastic plate are kept coincident, and polarization transmission response images are acquired at four polarization angles of 0°, 45°, 90° and 135° respectively. Exposure uniformity, angle calibration, and sub-pixel registration are performed on the polarization transmission response images acquired at four polarization angles to ensure that the same pixel in the four polarization transmission response images corresponds to the same volume position inside the transparent plastic sheet. A polarization response sequence is generated based on the detection zone number, polarization angle, pixel coordinates, and acquisition time.

3. The method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis as described in claim 1 or 2, characterized in that: The multi-band transmittance data includes, after completing the acquisition of the polarization response sequence in each detection zone, keeping the detection zone position unchanged, and outputting measurement beams sequentially in the visible light band and near-infrared band through a stable transmission light source; The incident light intensity corresponding to each wavelength band is recorded synchronously by the incident light monitoring unit, and the outgoing light intensity after passing through the transparent plastic plate is recorded by the outgoing light receiving unit. Based on the baseline transmission record of the standard thickness sample, the average transmission values ​​of the initial screening normal zone after edge exclusion and the adjacent detection zones, a reference transmittance is established for each detection zone. Incident light intensity, outgoing light intensity, reference transmittance, detection zone number, and band number are bound together to form multi-band transmittance data, which together with the polarization response sequence constitutes the optical measurement data.

4. The method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis as described in claim 3, characterized in that: The polarization phase perturbation value includes reading the registration grayscale response of four polarization angles under the same detection partition in the optical measurement data, first removing saturated pixels and edge reflective pixels, and then calculating the grayscale difference between mutually orthogonal polarization angles and the grayscale difference between diagonal polarization angles. The two types of grayscale differences are normalized according to the average grayscale of the detection zone to obtain the initial polarization perturbation amount that reflects the birefringence perturbation inside the transparent plastic sheet. The polarization phase disturbance value is obtained by differentiating the initial polarization disturbance value with the polarization disturbance reference value of the normal zone surrounding the same detection zone. When the polarization phase disturbance value of the detection zone is continuously higher than the upper limit of the polarization disturbance reference obtained by the standard template calibration, the detection zone is marked as a polarization anomaly candidate zone.

5. The method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis as described in claim 1, 2, or 4, characterized in that: The transmittance residual and the polarization transmission coupling state include calculating the measured transmittance of each detection zone based on the multi-band transmittance data, and correcting the reference transmittance using the standard thickness of the transparent plastic sheet in the same batch, the monitored value of the light source intensity, and the average transmittance of the adjacent normal zones. The difference between the measured transmittance and the reference transmittance is normalized according to the reference transmittance to obtain the transmittance residual. The transmittance residual, the polarization phase perturbation value, and the spatial gradient difference with adjacent detection zones are respectively processed into dimensionless values, and then weighted and summed according to the weighting coefficients determined by the calibration template to generate the polarization transmission coupling state quantity. When the same detection zone simultaneously satisfies at least two of the following conditions: increased transmittance residual, increased polarization phase perturbation value, or increased spatial gradient difference, the polarization transmission coupling state of the detection zone is written into the spatial state diagram.

6. The method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis as described in claim 5, characterized in that: The extraction of the internal defect disturbance region includes establishing a four-neighbor connectivity relationship in the spatial state diagram according to the physical adjacency relationship of the detection partitions, and using the detection partitions whose polarization transmission coupling state quantity is higher than the upper limit of the coupling anomaly reference as seed partitions. Starting with the seed partition, adjacent detection partitions with consistent polarization transmission coupling state variables and continuous boundary gradients are merged into candidate perturbation regions. The candidate perturbation region is filled with holes, isolated points are removed, and edge artifacts are eliminated, retaining regions whose area, continuous length, and coupling state peak all meet the calibration conditions. The retained candidate disturbance regions are mapped back to the two-dimensional detection coordinates of the transparent plastic sheet to obtain the internal defect disturbance regions.

7. The method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis as described in claim 1, 2, 4, or 6, characterized in that: The generated defect types and defect levels include the average polarization phase perturbation value, average transmittance residual, peak value of polarization transmission coupling state quantity, area, aspect ratio, roundness, continuous length and sheet expansion rate in each internal defect perturbation region. When the average polarization phase perturbation value is higher than the polarization perturbation classification benchmark and the average transmittance residual is lower than the transmittance residual classification benchmark, a residual stress type defect is generated. When the mean value of the transmittance residual is higher than the transmittance residual classification benchmark and the roundness of the region meets the bubble morphology benchmark, a bubble-type defect is generated. When the mean value of the transmittance residual is higher than the transmittance residual classification benchmark and the roundness of the region does not meet the bubble morphology benchmark, an inclusion-type defect is generated. When the mean value of polarization phase perturbation and the mean value of transmittance residual are both higher than the corresponding classification benchmark and the aspect ratio and continuous length of the region satisfy the linear continuous benchmark, microcrack-type defects are generated. When the regional sheet expansion rate meets the layered morphology benchmark, a layered defect is generated; The severity metric is calculated based on the peak value of the polarization transmission coupling state quantity, the area of ​​the region, and the continuous length. The defect level is then generated according to the severity metric interval.

8. A system for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis, employing the method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis as described in any one of claims 1 to 7, characterized in that: It includes an optical data acquisition module, a coupling state calculation module, and a defect result determination module; The optical data acquisition module is used to acquire multi-angle polarization response and multi-band transmittance data in the same area to generate optical measurement data. The coupling state calculation module is used to calculate the polarization phase perturbation value and transmittance residual based on the optical measurement data, and generate polarization transmission coupling state quantity. The defect result determination module is used to extract the internal defect disturbance region based on the polarization transmission coupling state quantity, and generate the defect type and defect level.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for detecting internal defects in transparent plastic sheets based on polarized light and transmittance analysis as described in any one of claims 1 to 7.

Images