Method and system for detecting the glossiness of a mirror-finished synthetic leather

Abstract

The present application provides a mirror synthetic leather glossiness detection method and system, and provides a three-dimensional gloss uniformity evaluation system, which upgrades the qualitative visual evaluation to quantitative index evaluation. The traditional method can only evaluate the uniformity of glossiness value from one-dimensional angle, and the present application upgrades the traditional single-point single-angle one-dimensional detection to three-dimensional uniformity detection of full-width and three parameters of each measurement point, the information richness is improved by several orders of magnitude, and the optical quality of the mirror leather surface can be fully reflected. Among them, the peak angle uniformity index UI θ The mirror reflection direction offset caused by coating process fluctuation can be captured; the reflection concentration uniformity index UI F The consistency of the coating micro-flatness can be evaluated.

Description

Technical Field

[0001] This invention relates to the field of optical property testing technology for material surfaces, specifically to a method and system for testing the gloss of mirror-finish synthetic leather. Background Technology

[0002] Mirror-finish synthetic leather is a type of polyurethane or polyvinyl chloride synthetic leather with a specially coated surface that achieves a high-gloss, mirror-like effect. It is widely used in bags, footwear, clothing accessories, and automotive interiors. Its core quality indicator is gloss unit (GU), with industry standards requiring a gloss level ≥70 GU (measured at a 60° incident angle) and a gloss difference of ≤5 GU between the same piece of leather. Current methods for testing the gloss of mirror-finish synthetic leather suffer from the following technical deficiencies: First, single-point measurements cannot reflect the uniformity of gloss over a large area. The existing standard method (GB / T 8941-2013) uses a portable gloss meter for single-point contact measurement, where the operator selects several discrete points on the synthetic leather surface and measures them one by one. The number of sampling points is limited (usually 5-9 points), which cannot cover the gloss distribution of the entire surface; it cannot detect localized dull areas; the measurement results are highly dependent on the operator's experience in selecting sampling points, resulting in poor consistency among different personnel; and for large-area mirror-finish leather (width exceeding 1.4m), the single-point measurement coverage is less than 1%.

[0003] Secondly, fixed-angle measurements cannot accurately characterize the reflective properties of mirror-finish leather. The specular reflection peak of mirror-finish synthetic leather is extremely narrow and may shift due to fluctuations in the coating process. Existing fixed-angle gloss meters (such as 20° / 60° / 85° triangulation meters) use step-by-step angle switching, which cannot capture the precise position of the reflection peak angle and is prone to measurement deviation due to angle shifts. Although known multi-angle gloss meters (such as the Linshang Technology LS197) can achieve simultaneous measurement at three angles, the number of angles is limited, and a complete reflection intensity distribution curve cannot be obtained.

[0004] Third, there is a lack of quantitative evaluation methods for gloss uniformity. Current technologies rely on visual judgment to evaluate the gloss uniformity of mirror leather, which lacks quantitative indicators. Even when using a multi-point gloss meter, only the mean and range of gloss values ​​can be calculated, which cannot reflect key information such as the uniformity of gloss spatial distribution and the location and area of ​​gloss abnormalities.

[0005] In summary, there is an urgent need for a detection method and system that can simultaneously achieve high-precision multi-angle gloss measurement and quantitative assessment of full-area gloss uniformity to meet the actual needs of quality testing of mirror-finish synthetic leather. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a method and system for detecting the gloss of mirror synthetic leather.

[0007] The technical solution adopted in this invention is as follows: The first aspect of this invention provides a method for detecting the multidimensional gloss uniformity of mirror-finish synthetic leather, comprising the following steps: S1. Divide the surface of the synthetic leather to be tested into equally spaced measurement lines along the scanning direction. Each measurement line consists of continuous scanning position points. S2. Perform continuous variable angle gloss measurement on each measurement line: acquire the original reflection image of the linear light source corresponding to different incident angles for each measurement line; S3. Extract several measurement points from the measurement line. For each measurement point, extract the original gray value of the measurement point under different incident angle linear light sources from the original reflection image according to its coordinates. This constitutes the original multi-angle gray vector of the measurement point. Correct the original multi-angle gray vector of each measurement point to obtain the multi-angle absolute gloss value of the measurement point. This constitutes the gloss-angle discrete sequence of the measurement point. S4. Perform curve fitting on the discrete sequence of glossiness-angle for each measurement point, and extract the standard glossiness value, peak reflection angle, and full width at half maximum (FWHM) of the peak reflection from the fitted curve to form a three-dimensional glossiness feature vector for each measurement point. The standard glossiness value is the standard glossiness at the standard angle, the peak reflection angle is the angle corresponding to the peak of the fitted curve, and the full width at half maximum (FWHM) of the peak reflection is the angle width at the half height of the fitted curve. S5. Summarize the three-dimensional gloss feature vectors of all measurement points into a feature matrix, calculate the gloss value uniformity index, reflection peak angle uniformity index, and reflection concentration uniformity index, and perform weighted fusion of the three to generate a comprehensive multidimensional gloss uniformity index. S6. Based on the preset uniformity grading standard, the comprehensive multidimensional gloss uniformity index is graded and a test report is output.

[0008] Preferably, in step S3, the correction specifically includes the following steps: a. Dark field correction: Acquire a dark field image in advance, extract the gray value of each measurement point under dark field conditions, subtract the dark field gray value from the original gray value at each angle, and obtain the gray value after dark field correction. b. Flat field correction: Pre-acquire flat field images of the standard white board at various angles, extract the flat field gray value of each measurement point, divide the gray value after dark field correction by the difference between the flat field gray value and the dark field gray value, and then multiply by the preset normalization constant to obtain the gray value after flat field correction. c. Gloss calibration: Acquire calibration images of the black and white standard plates at various angles in advance, extract the calibration gray value of each measurement point, establish a linear mapping relationship between gray value and absolute gloss value, and convert the gray value after flat field correction into absolute gloss value.

[0009] Preferably, in step S4, the curve fitting is performed using a Gaussian function or a Lorentz function.

[0010] Preferably, in step S5, the gloss value uniformity index is calculated based on the ratio of the statistical standard deviation to the mean of the standard gloss values ​​of all measurement points; the reflection peak angle uniformity index is calculated based on the ratio of the statistical standard deviation to the mean of the reflection peak angles of all measurement points; and the reflection concentration uniformity index is calculated based on the ratio of the statistical standard deviation to the mean of the full width at half maximum (FWHM) of the reflection peaks of all measurement points.

[0011] Preferably, in step S5, the comprehensive multidimensional gloss uniformity index is obtained by weighting and summing the three uniformity indices, each assigned a weight coefficient. The gloss value uniformity index has the largest weight coefficient, while the weight coefficients of the other two indices are equal and smaller than the weight coefficient of the gloss value uniformity index.

[0012] Preferably, step S6 further includes gloss gradient field calculation: for the standard gloss components in the feature matrix, calculate the gloss change between adjacent measurement points, generate a two-dimensional gloss gradient field, and mark areas where the gloss gradient value exceeds a preset threshold as gloss anomalous hot spots.

[0013] Preferably, in step S6, the detection report also includes visualization output: generating a gloss distribution heatmap, a peak angle distribution map, and a reflection concentration distribution map based on the feature matrix, and superimposing gloss anomalous hot spots on the gloss distribution heatmap.

[0014] A second aspect of the present invention provides a multidimensional gloss uniformity detection system for mirror-finish synthetic leather, used to implement the multidimensional gloss uniformity detection method described above, comprising: A conveyor platform is used to carry and drive the synthetic leather under test along the scanning direction; A linear light source array, mounted above the conveying platform, comprises multiple linear light sources with different incident angles. Each linear light source extends along the width direction and includes a light-emitting element and a polarization modulation element. The linear light source array is configured to sequentially illuminate the detection area in a one-by-one manner. A linear scan camera is installed directly above the detection area. Its imaging field of view covers the width direction and is used to acquire reflection images to obtain multiple frames of original reflection images corresponding to different incident angles. The motion control module is used to control the movement speed of the transmission platform and the scanning rate of the line scan camera, and to control the lighting sequence of each element of the linear light source array. The data processing module is used to extract the original multi-angle grayscale vector of each measurement point from the original reflection image, perform point-by-point correction, obtain the discrete sequence between gloss and incident angle, perform curve fitting and feature extraction, calculate the multidimensional gloss uniformity index, and generate a test report.

[0015] Preferably, the data processing module further includes: The point extraction unit is used to extract the original multi-angle grayscale vectors of each point from the original reflection image based on the preset measurement point coordinates. The correction unit is used to perform correction on the original multi-angle grayscale vector of each measurement point; The curve fitting unit is used to perform function fitting on the discrete sequence between gloss and incident angle at each measurement point; The feature extraction unit is used to extract standard gloss, reflection peak angle, and full width at half maximum (FWHM) of the reflection peak from the fitted curve. The uniformity calculation unit is used to calculate the gloss value uniformity index, the reflection peak angle uniformity index, the reflection concentration uniformity index, and the comprehensive multidimensional gloss uniformity index. The report generation unit is used to output standardized test reports.

[0016] Preferably, the correction unit is used to sequentially perform dark field correction, flat field correction, and gloss calibration on the original multi-angle grayscale vector of each measurement point. The dark field correction involves pre-acquiring a dark field image, extracting the grayscale value of each measurement point under dark field conditions, and subtracting the dark field grayscale value from the original grayscale value at each angle to obtain the dark field corrected grayscale value. The flat field correction involves pre-acquiring flat field images of a standard white board at various angles, extracting the flat field grayscale value of each measurement point, dividing the grayscale value after dark field correction by the difference between the flat field grayscale value and the dark field grayscale value, and then multiplying by a preset normalization constant to obtain the grayscale value after flat field correction. The gloss calibration involves pre-acquiring calibration images of black and white standard plates at various angles, extracting the calibration grayscale value of each measurement point, establishing a linear mapping relationship between the grayscale value and the absolute gloss value, and converting the grayscale value after flat field correction into the absolute gloss value.

[0017] The beneficial effects of this invention are as follows: 1. This invention provides a three-dimensional gloss uniformity evaluation system, upgrading qualitative visual evaluation to quantitative index evaluation. Traditional methods can only assess the uniformity of gloss values ​​from a one-dimensional perspective. This invention upgrades from traditional single-point, single-angle one-dimensional detection to full-area, three-parameter three-dimensional uniformity detection at each measurement point, increasing the information richness by several orders of magnitude and comprehensively reflecting the optical quality of mirror leather surfaces. Among them, the peak angle uniformity index UI... θ Capable of capturing the shift in specular reflection direction caused by fluctuations in coating process; UI index for reflection concentration uniformity. F It can assess the consistency of coating micro-smoothness.

[0018] 2. Different types of surface defects in mirror leather (such as orange peel texture, pinholes, runs, and localized dullness) exhibit different characteristic signatures in the three-dimensional gloss feature space. For example, the FWHM (Frequency and Width Motion) is significantly increased in orange peel texture areas (reflection peak broadening), while the GU (Gloss and Durability Motion) of locally dull areas is significantly increased. peak Significantly reduces θ in areas with thinner coatings peak Shifts may occur. Three-dimensional feature vectors have a stronger ability to distinguish defects compared to a single GU value. Attached Figure Description

[0019] 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, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0020] Figure 1 This is a schematic diagram of the detection method steps in an embodiment of the present invention; Figure 2 This is a schematic diagram of the detection system modules in an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0022] like Figure 1 As shown, this embodiment provides a method for detecting the multidimensional gloss uniformity of mirror-finish synthetic leather, including the following steps: Step S1: Scan path planning and dividing measurement lines.

[0023] S1-1. Lay the synthetic leather sample to be tested flat on the conveyor platform and establish a basic coordinate system: X-axis: horizontal, which is also the width direction of synthetic leather and the direction of pixel arrangement in a line scan camera.

[0024] Y-axis: longitudinal direction, which is also the length direction of the synthetic leather and the direction of movement of the synthetic leather.

[0025] Z-axis: Vertical direction (height), positive when pointing vertically upwards from the surface of the synthetic leather.

[0026] The surface of the synthetic leather to be tested is located in the XY plane (Z=0).

[0027] S1-2. The surface of the synthetic leather to be tested is divided into several equally spaced measurement lines along the scanning direction (Y-axis). Each measurement line is a straight line parallel to the X-axis, located at Y=Y0, Z=0, and consists of continuous scanning position points. The automatic moving platform adopts an XY two-dimensional precision slide driven by a servo motor. The sample is fixed by a vacuum adsorption fixture to ensure that the surface is flat and wrinkle-free.

[0028] Step S2: Perform continuous variable angle gloss measurement on each measurement line.

[0029] A linear light source array is provided, containing 27 independent linear LED light sources. Each linear light source extends along the X-axis, and the incident angle θ of each linear light source to the detection area is [not specified]. k The linear light sources are evenly spaced from 20° to 85°, with an angular interval of 2.5° between adjacent linear light sources. A linear polarizer is installed in front of each linear light source. To achieve the best noise reduction effect, the transmission axes of the polarizers of adjacent linear light sources are perpendicular to each other (i.e., 0° and 90° are arranged alternately).

[0030] A linear array camera is provided and mounted directly above the detection area. Its sensor is a one-dimensional pixel array with 2048 pixel columns. A rotatable polarization analyzer (linear polarizer) is mounted in front of the camera lens, with its transmission axis set at 45° to the polarization direction of most light sources to evenly receive reflected light with different polarization states.

[0031] The data collection method can be selected from either of the following two methods (A) or (B): (A) Illuminate the detection area with a linear light source, drive the synthetic leather along the Y-axis with a servo motor, and synchronize the sampling rate of the linear camera with the driving rate of the servo motor to complete the acquisition of reflection images of all measurement lines under the current incident angle linear light source. Turn off the current linear light source, drive the synthetic leather back to the original position with the servo motor, turn off the current linear light source, and let the next linear light source illuminate the detection area to acquire reflection images of each measurement line under the next linear light source. Repeat the above operation until the acquisition of reflection images of the measurement lines on the surface of the mirror synthetic leather under all linear light sources is completed. After the acquisition is completed, 27 complete original reflection patterns are obtained.

[0032] (B) Each independent linear light source is lit up one by one, illuminating the measurement lines in the detection area in sequence. The sampling rate of the line scan camera is synchronized with the switching speed of the linear light sources. The line scan camera collects the reflection images at each angle position of each measurement line. After the current measurement line has completed the collection of reflection images at 27 angle positions, the servo motor drives the next measurement line into the detection area and collects the reflection images at 27 angle positions of the next measurement line. The above operation is repeated until the reflection images of all measurement lines on the surface of the synthetic leather to be tested are collected. After the collection is completed, the images are organized by angle to obtain 27 complete original reflection patterns.

[0033] Each original reflection pattern is 2048 × P pixels in size, where the X direction represents the pixel column (position) and the Y direction represents the scan row (position). Let I be the reflection image corresponding to the k-th angle. k (x,y), where x is the pixel column index (corresponding to the position in the width direction) and y is the scan row index (corresponding to the position in the length direction).

[0034] Step S3: Extraction and preprocessing of raw data based on location.

[0035] S3-1. Based on the preset scanning resolution, each measurement point p=(x) on the surface of the synthetic leather to be tested is... m ,y n Mapped to pixel coordinates in the original image: x pixel =round( x m / Δ X ) y pixel =round( y n / Δ Y ) Where ΔX and ΔY are the pixel equivalents in the X and Y directions, respectively.

[0036] For each measurement point p=(x pixel ,y pixel From 27 original reflection images I k Extract the original grayscale value at the coordinates (x, y) to form the original multi-angle grayscale vector of that point: G raw ( p )=[ g 1( p ), g 2( p ),..., g 27 ( p )] Among them, g k (p)=I k (x pixel ,y pixel ) represents the original camera output value at this point under the k-th incident angle.

[0037] At this point, the data for each measurement point has been transformed from spatially distributed storage (organized by image) to point-based clustered storage (each point corresponds to a multi-angle grayscale vector).

[0038] S3-2. Perform the following standardized preprocessing procedure on the grayscale data at each point: a. Dark field correction Before production line startup or during routine maintenance, a dark field acquisition process is performed: Under completely dark conditions (all light sources off, camera lens cap closed), one or more frames are acquired using the exact same camera parameters (gain, exposure time, scan rate) as the actual inspection, and the average is taken to obtain the dark field image D(x,y). For each measurement point p, its dark field grayscale value d(p) = D(x) is extracted. pixel ,y pixel Point-by-point dark field correction formula: g dark (p,k)=g k (p)−d(p) This step eliminates the influence of dark current and fixed pattern noise from the image sensor of the line scan camera on the measurement point.

[0039] b. Leveling correction Flat field correction is used to compensate for three major system non-uniformity factors: ① the inherent brightness difference between the 27 linear LED light sources; ② the optical vignetting effect of the camera lens; ③ the difference in photoelectric conversion efficiency of different pixels in the image sensor of the line scan camera.

[0040] Calibration method: Before production line startup or during routine maintenance, place a standard white board with high reflectivity (≥99%) and Lambertian diffuse reflection characteristics at the testing position. Illuminate each of the 27 linear light sources sequentially, and acquire flat-field images W in sequence. k (x,y), a total of 27 images. For each measurement point pp, extract its flat-field grayscale value w at that angle. k (p)=W k (x pixel ,y pixel Point-by-point flat field correction formula: Where K is a preset target normalization constant (for example, for a 12-bit camera, K=4095).

[0041] c. Gloss calibration A two-point linear calibration method was used to establish a mapping from grayscale values ​​to gloss levels at each point. Calibration data acquisition: A black standard plate (GU) was placed. black =0), ignite 27 light sources one by one, and collect the black standard plate image B. k (x, y). For the measurement point p, extract b. k (p). Place a white standard plate (with known gloss value GU). white (e.g., 92.3), similarly acquiring image W gu,k (x,y), extract w gu,k (p). Pointwise linear mapping: After this step, each measurement point p yields a 27-dimensional gloss value vector: GU(p)=[GU1(p),GU2(p),...,GU 27 (p)] Among them, GU k (p) indicates that at the incident angle θ k The absolute gloss value at that point.

[0042] The index k of the glossiness value vector GU(p) at each measurement point directly corresponds to the incident angle θ. k This constitutes a discrete sequence of glossiness-angle at that point: GU(θ k ,p)=GU k (p), k=1,2,...,27 Step S4: Curve fitting and feature extraction.

[0043] For each measurement point p, Gaussian fitting is performed on its gloss-angle discrete data to obtain the fitted curve. The fitting formula is: Among them, GU peak For peak light intensity, θ peak σ is the peak angle, and σ is the standard deviation of the Gaussian distribution.

[0044] Extract three feature parameters from the fitted curve: Standard gloss level (GU) std (p): Read θ std =Gloss value at 60°, i.e., GU 60 (p).

[0045] Peak reflection angle θ peak (p): The angle corresponding to the peak of the fitted curve.

[0046] Full width at half maximum (FWHM) of the reflection peak (p): the angular width at half maximum of the fitted curve. FWHM ≈2.355 σ .

[0047] Therefore, the three-dimensional gloss feature vector of each location point p is: Step S5: Calculation of multidimensional uniformity index.

[0048] The three-dimensional gloss feature vectors of all P measurement points are summarized, and the uniformity index of each dimension is calculated.

[0049] (1) Gloss uniformity index UI G : Where, μ G For all measurement points GU std The mean, σ G The standard deviation is denoted as .

[0050] (2) Uniformity index of reflection peak angle UI θ : Where, μ θ For all measurement points θ peak The mean σ θ The standard deviation is denoted as .

[0051] (3) Reflection concentration uniformity index: Where, μ F σ is the mean of all measurement points FWHM. F The standard deviation is denoted as .

[0052] Step S6: Calculate the overall uniformity index, determine the grade, and output the report.

[0053] Weighted fusion of three uniformity indicators: UI multi =w G ×UI G +w θ ×UI θ +wF ×UI F .

[0054] Weighting coefficients are determined as follows: For mirror-finish synthetic leather products, the uniformity of gloss value is the most direct quality indicator and is assigned the highest weight. The uniformity of reflection peak angle and reflection concentration reflects the consistency of the coating process and serves as an auxiliary indicator. Default weight setting: w G =0.5, w θ =0.25, w F =0.25. The weighting coefficient can be adjusted according to product type and customer requirements.

[0055] According to the comprehensive uniformity index UI multi Conduct a rating assessment: The test report may also include a gloss distribution heatmap, a peak angle distribution map, a reflectance concentration distribution map, and a gloss gradient contour map. The gloss gradient field calculation steps are as follows: For the GU values ​​in the feature matrix... std The component calculates the gloss difference between adjacent measurement points, generates a two-dimensional gloss gradient field, and marks areas with gloss gradient values ​​exceeding a preset gradient threshold (such as 5GU) as gloss anomalous hotspots, which are then marked with a prominent color on the heat map.

[0056] like Figure 2 As shown, this embodiment also provides a multi-dimensional gloss uniformity detection system for mirror-finish synthetic leather, used to implement the above-mentioned multi-dimensional gloss uniformity detection method, including: A conveyor platform is used to carry and drive the synthetic leather under test along the scanning direction; A linear light source array, mounted above the conveying platform, comprises multiple linear light sources with different incident angles. Each linear light source extends along the width direction and includes a light-emitting element and a polarization modulation element. The linear light source array is configured to sequentially illuminate the detection area in a one-by-one manner. A linear scan camera is installed directly above the detection area. Its imaging field of view covers the width direction and is used to acquire reflection images to obtain multiple frames of original reflection images corresponding to different incident angles. The motion control module is used to control the movement speed of the transmission platform and the scanning rate of the line scan camera, and to control the lighting sequence of each element of the linear light source array. The data processing module is used to extract the original multi-angle grayscale vector of each measurement point from the original reflection image, perform point-by-point correction, obtain the discrete sequence between gloss and incident angle, perform curve fitting and feature extraction, calculate the multidimensional gloss uniformity index, and generate a test report.

[0057] The data processing module further includes: The point extraction unit is used to extract the original multi-angle grayscale vectors of each point from the original reflection image based on the preset measurement point coordinates. The correction unit is used to perform correction on the original multi-angle grayscale vector of each measurement point; The curve fitting unit is used to perform function fitting on the discrete sequence between gloss and incident angle at each measurement point; The feature extraction unit is used to extract standard gloss, reflection peak angle, and full width at half maximum (FWHM) of the reflection peak from the fitted curve. The uniformity calculation unit is used to calculate the gloss value uniformity index, the reflection peak angle uniformity index, the reflection concentration uniformity index, and the comprehensive multidimensional gloss uniformity index. The report generation unit is used to output standardized test reports.

[0058] The correction unit is used to sequentially perform dark field correction, flat field correction, and gloss calibration on the original multi-angle grayscale vector of each measurement point. The dark field correction involves pre-acquiring a dark field image, extracting the grayscale value of each measurement point under dark field conditions, and subtracting the dark field grayscale value from the original grayscale value at each angle to obtain the dark field corrected grayscale value. The flat field correction involves pre-acquiring flat field images of a standard white board at various angles, extracting the flat field grayscale value of each measurement point, dividing the grayscale value after dark field correction by the difference between the flat field grayscale value and the dark field grayscale value, and then multiplying by a preset normalization constant to obtain the grayscale value after flat field correction. The gloss calibration involves pre-acquiring calibration images of black and white standard plates at various angles, extracting the calibration grayscale value of each measurement point, establishing a linear mapping relationship between the grayscale value and the absolute gloss value, and converting the grayscale value after flat field correction into the absolute gloss value.

[0059] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for detecting the multidimensional gloss uniformity of mirror-finish synthetic leather, characterized in that, Includes the following steps: S1. Divide the surface of the synthetic leather to be tested into equally spaced measurement lines along the scanning direction. Each measurement line consists of continuous scanning position points. S2. Perform continuous variable angle gloss measurement on each measurement line: Apply a continuous variable angle linear light source to each measurement line within a preset angle range, and acquire the original reflection image of the linear light source corresponding to different incident angles for each measurement line; S3. Extract several measurement points from the measurement line. For each measurement point, extract the original gray value of the measurement point under different incident angle linear light sources from the original reflection image according to its coordinates. This constitutes the original multi-angle gray vector of the measurement point. Correct the original multi-angle gray vector of each measurement point to obtain the multi-angle absolute gloss value of the measurement point. This constitutes the gloss-angle discrete sequence of the measurement point. S4. Perform curve fitting on the discrete sequence of glossiness-angle for each measurement point, and extract the standard glossiness value, peak reflection angle, and full width at half maximum (FWHM) of the peak reflection from the fitted curve to form a three-dimensional glossiness feature vector for each measurement point. The standard glossiness value is the standard glossiness at the standard angle, the peak reflection angle is the angle corresponding to the peak of the fitted curve, and the full width at half maximum (FWHM) of the peak reflection is the angle width at the half height of the fitted curve. S5. Summarize the three-dimensional gloss feature vectors of all measurement points into a feature matrix, calculate the gloss value uniformity index, reflection peak angle uniformity index, and reflection concentration uniformity index, and perform weighted fusion of the three to generate a comprehensive multidimensional gloss uniformity index. S6. Based on the preset uniformity grading standard, the comprehensive multidimensional gloss uniformity index is graded and a test report is output.

2. The method for detecting the multidimensional gloss uniformity of mirror-finish synthetic leather according to claim 1, characterized in that, In step S3, the correction specifically includes the following steps: a. Dark field correction: Acquire a dark field image in advance, extract the gray value of each measurement point under dark field conditions, subtract the dark field gray value from the original gray value at each angle, and obtain the gray value after dark field correction. b. Flat field correction: Pre-acquire flat field images of the standard white board at various angles, extract the flat field gray value of each measurement point, divide the gray value after dark field correction by the difference between the flat field gray value and the dark field gray value, and then multiply by the preset normalization constant to obtain the gray value after flat field correction. c. Gloss calibration: Acquire calibration images of the black and white standard plates at various angles in advance, extract the calibration gray value of each measurement point, establish a linear mapping relationship between gray value and absolute gloss value, and convert the gray value after flat field correction into absolute gloss value.

3. The method for detecting the multidimensional gloss uniformity of mirror-finish synthetic leather according to claim 1, characterized in that, In step S4, the curve fitting is performed using a Gaussian function or a Lorentz function.

4. The method for detecting the multidimensional gloss uniformity of mirror-finish synthetic leather according to claim 1, characterized in that, In step S5, the gloss uniformity index is calculated based on the ratio of the statistical standard deviation to the mean of the standard gloss values ​​of all measurement points; the reflection peak angle uniformity index is calculated based on the ratio of the statistical standard deviation to the mean of the reflection peak angles of all measurement points. The uniformity index of reflection concentration is calculated based on the ratio of the statistical standard deviation to the mean of the full width at half maximum (FWHM) of the reflection peaks at all measurement points.

5. The method for detecting the multidimensional gloss uniformity of mirror-finish synthetic leather according to claim 1, characterized in that, In step S5, the comprehensive multidimensional gloss uniformity index is obtained by weighting and summing the three uniformity indices, each assigned a weight coefficient. The gloss value uniformity index has the largest weight coefficient, while the weight coefficients of the other two indices are equal and smaller than the weight coefficient of the gloss value uniformity index.

6. The method for detecting the multidimensional gloss uniformity of mirror-finish synthetic leather according to claim 1, characterized in that, Step S6 also includes gloss gradient field calculation: for the standard gloss components in the feature matrix, calculate the gloss change between adjacent measurement points, generate a two-dimensional gloss gradient field, and mark the areas where the gloss gradient value exceeds a preset threshold as gloss abnormal hot spots.

7. The method for detecting the multidimensional gloss uniformity of mirror-finish synthetic leather according to claim 6, characterized in that, In step S6, the detection report also includes visualization output: generating a gloss distribution heatmap, a peak angle distribution map, and a reflection concentration distribution map based on the feature matrix, and superimposing gloss anomalous hot spots on the gloss distribution heatmap.

8. A multidimensional gloss uniformity detection system for mirror-finish synthetic leather, used to implement the multidimensional gloss uniformity detection method according to any one of claims 1-7, characterized in that, include: A conveyor platform is used to carry and drive the synthetic leather under test along the scanning direction; A linear light source array, mounted above the conveying platform, comprises multiple linear light sources with different incident angles. Each linear light source extends along the width direction and includes a light-emitting element and a polarization modulation element. The linear light source array is configured to sequentially illuminate the detection area in a one-by-one manner. A linear scan camera is installed directly above the detection area. Its imaging field of view covers the width direction and is used to acquire reflection images to obtain multiple frames of original reflection images corresponding to different incident angles. The motion control module is used to control the movement speed of the transmission platform and the scanning rate of the line scan camera, and to control the lighting sequence of each element of the linear light source array. The data processing module is used to extract the original multi-angle grayscale vector of each measurement point from the original reflection image, perform point-by-point correction, obtain the discrete sequence between gloss and incident angle, perform curve fitting and feature extraction, calculate the multidimensional gloss uniformity index, and generate a test report.

9. A multidimensional gloss uniformity detection system for mirror-finish synthetic leather according to claim 8, characterized in that, The data processing module further includes: The point extraction unit is used to extract the original multi-angle grayscale vectors of each point from the original reflection image based on the preset measurement point coordinates. The correction unit is used to perform correction on the original multi-angle grayscale vector of each measurement point; The curve fitting unit is used to perform function fitting on the discrete sequence between gloss and incident angle at each measurement point; The feature extraction unit is used to extract standard gloss, reflection peak angle, and full width at half maximum (FWHM) of the reflection peak from the fitted curve. The uniformity calculation unit is used to calculate the gloss value uniformity index, the reflection peak angle uniformity index, the reflection concentration uniformity index, and the comprehensive multidimensional gloss uniformity index. The report generation unit is used to output standardized test reports.

10. The multidimensional gloss uniformity detection system for mirror-finish synthetic leather according to claim 9, characterized in that, The correction unit is used to sequentially perform dark field correction, flat field correction, and gloss calibration on the original multi-angle grayscale vector of each measurement point. The dark field correction involves pre-acquiring a dark field image, extracting the grayscale value of each measurement point under dark field conditions, and subtracting the dark field grayscale value from the original grayscale value at each angle to obtain the dark field corrected grayscale value. The flat field correction involves pre-acquiring flat field images of a standard white board at various angles, extracting the flat field grayscale value of each measurement point, dividing the grayscale value after dark field correction by the difference between the flat field grayscale value and the dark field grayscale value, and then multiplying by a preset normalization constant to obtain the grayscale value after flat field correction. The gloss calibration involves pre-acquiring calibration images of black and white standard plates at various angles, extracting the calibration grayscale value of each measurement point, establishing a linear mapping relationship between the grayscale value and the absolute gloss value, and converting the grayscale value after flat field correction into the absolute gloss value.

Images