A Visually Assisted Method and System for Quality Inspection of Laser Engraving on Mobile Phone Buttons

Abstract

This application relates to the field of image recognition technology, specifically to a visually assisted method and system for quality inspection of laser engraving on mobile phone buttons, solving the technical problem that the accuracy of laser engraving quality inspection of mobile phone buttons in the prior art cannot meet the requirements. The method includes: acquiring image sequences of the laser engraved area of ​​the mobile phone button under multiple different lighting directions, and design trajectory information; determining the microscopic gradient vector field and texture contrast value of the laser engraved area based on the image sequences; constructing a light transmission resistance field based on the geometric deviation between the macroscopic light transmission direction and the microscopic gradient vector field, characterized by the design trajectory information, and the texture contrast value; calculating the light transmission attenuation index, which characterizes the overall light transmittance performance of the laser engraved area to be inspected, based on the light transmission attenuation field; and determining the light transmittance quality of the laser engraved area to be inspected based on the light transmission attenuation index.

Description

Technical Field

[0001] This application relates to the field of image recognition technology, and specifically relates to a method and system for laser engraving quality inspection of mobile phone keys assisted by vision. Background Art

[0002] In the manufacturing process of mobile phone keys, a structural design of a translucent substrate + an opaque coating is often adopted, and the coating in a specific area is removed through a laser engraving process to form a light-transmitting character or pattern. In an automated production line, the workpiece is usually placed on an opaque tray, making it impossible for the vision inspection station to directly measure the light transmittance with the help of a backlight source, and only relying on the method of imaging with front reflected light for quality inspection.

[0003] In the prior art, usually through front coaxial light or annular light illumination, after obtaining the image of the laser engraving area, it is judged whether the coating is effectively removed according to the image gray value. When the gray value of the laser engraving area reaches the preset threshold, it is determined as a qualified product. However, in the actual production scenario, even if the surface coating is removed and the gray value meets the requirements, there may still be a situation where when the laser energy is unstable or the focal length drifts, the surface coating is removed (the gray display is white), but the microscopic etching texture on the substrate surface is in a disorderly state, or the etching depth is too shallow resulting in insufficient diffuse reflection. This leads to the accuracy of the current laser engraving quality inspection of mobile phone keys not meeting the requirements. Summary of the Invention

[0004] In order to solve the technical problem that the accuracy of laser engraving quality inspection of mobile phone keys in the prior art cannot meet the requirements, the purpose of this application is to provide a method for laser engraving quality inspection of mobile phone keys assisted by vision, and the specific technical solution adopted is as follows:

[0005] Obtain an image sequence of the laser engraving area of the mobile phone key in multiple different illumination directions, as well as the design trajectory information.

[0006] According to the image sequence, determine the microscopic gradient vector field and texture contrast difference of the laser engraving area. The microscopic gradient vector field is used to characterize the direction of microscopic surface undulation. The texture contrast difference is used to characterize the etching depth.

[0007] Based on the geometric deviation degree between the macroscopic light transmission direction characterized by the design trajectory information and the microscopic gradient vector field, as well as the texture contrast difference, construct a light transmission resistance field. The light transmission resistance field is used to quantify the degree of obstruction of the microscopic surface to light transmission.

[0008] According to the light transmission resistance field, calculate the light transmission attenuation index characterizing the overall light transmission performance of the laser engraving area.

[0009] According to the light transmission attenuation index, determine the light transmission quality of the laser engraving area.

[0010] In one possible implementation, the micro-gradient vector field and texture contrast value of the laser-engraved region are determined based on the image sequence, including: obtaining the original gradient vector of each pixel in the laser-engraved region based on the brightness difference between each image in the image sequence; determining the texture contrast value of each pixel based on the magnitude of the original gradient vector; and normalizing the original gradient vector to obtain the micro-gradient vector field.

[0011] In one possible implementation, the original gradient vector of each pixel in the laser-engraved region is obtained based on the brightness difference between images in the image sequence, including: calculating the first gradient component of each pixel based on the first image pair in the image sequence; the illumination directions of the two sets of images in the first image pair are relatively distributed along the first direction; calculating the second gradient component of each pixel based on the second image pair in the image sequence; the illumination directions of the two sets of images in the second image pair are relatively distributed along the second direction; the first direction and the second direction are orthogonal in space; and combining the first gradient component and the second gradient component of each pixel into the original gradient vector of each pixel.

[0012] In one possible implementation, an optical transmission resistance field is constructed based on the geometric deviation between the macroscopic optical transmission direction and the microscopic gradient vector field, characterized by the design trajectory information, and the texture contrast value. This includes: generating a tangential vector field corresponding to the laser-engraved area based on the design trajectory information; using the tangential vector field to characterize the ideal macroscopic optical transmission direction; calculating the absolute value of the dot product between the unit gradient vector of the pixel in the microscopic gradient vector field and the tangential vector of the pixel in the design trajectory tangential vector field for each pixel in the laser-engraved area to obtain the geometric deviation; determining the optical transmission resistance value of the pixel based on the geometric deviation and the texture contrast value; and constructing the optical transmission resistance field based on the optical transmission resistance values ​​of each pixel.

[0013] In one possible implementation, determining the light transmission resistance value of a pixel based on geometric deviation and texture contrast includes: determining a first resistance component characterizing the influence of etching depth based on the texture contrast and a first preset parameter; wherein the first resistance component is negatively correlated with the texture contrast; determining a second resistance component characterizing the influence of directional deviation based on the geometric deviation and a second preset parameter; wherein the second resistance component is positively correlated with the geometric deviation; and determining the light transmission resistance value based on the fusion result of the first resistance component and the second resistance component.

[0014] In one possible implementation, the light transmission attenuation index, which characterizes the overall light transmittance of the laser-engraved area, is calculated based on the light transmission resistance field. This includes: searching for the path with the minimum cumulative resistance within the path range defined by the design trajectory information in the light transmission resistance field as the dominant light path; and calculating the light transmission attenuation index based on the light transmission resistance values ​​at each position on the dominant light path.

[0015] In one possible implementation, the optical transmission attenuation index is calculated based on the optical transmission resistance values ​​at each position on the dominant optical path, including: determining the effective light guide channel width at multiple positions on the dominant optical path; and performing a weighted integral calculation based on the optical transmission resistance value and the effective light guide channel width at each position on the dominant optical path to obtain the optical transmission attenuation index.

[0016] In one possible implementation, determining the effective light guide channel width at multiple locations along the dominant light path includes: for each location along the dominant light path, determining a detection direction perpendicular to the macroscopic light transmission direction at that location; probing both sides along the detection direction in the light transmission resistance field; and determining the channel width at the location as the effective light guide channel width based on the change in the light transmission resistance value during the detection process or a preset path boundary.

[0017] In one possible implementation, the light transmission quality of the laser-engraved area is determined based on the light transmission attenuation index, including: comparing the light transmission attenuation index with a preset attenuation threshold; if the light transmission attenuation index is less than the attenuation threshold, the light transmission quality of the laser-engraved area is deemed acceptable; if the light transmission attenuation index is greater than or equal to the attenuation threshold, the light transmission quality of the laser-engraved area is deemed unacceptable.

[0018] This application also provides a vision-assisted mobile phone button laser engraving quality inspection system, the system comprising:

[0019] The acquisition unit is used to acquire image sequences and design trajectory information of the laser-engraved area of ​​the mobile phone buttons under multiple different lighting directions.

[0020] The feature parsing unit is used to determine the microscopic gradient vector field and texture contrast value of the laser-etched region based on the image sequence. The microscopic gradient vector field is used to characterize the direction of microscopic surface undulations. The texture contrast value is used to characterize the etching depth.

[0021] The model building unit is used to construct an optical transmission resistance field based on the geometric deviation between the macroscopic optical transmission direction and the microscopic gradient vector field, as well as the texture contrast value, represented by the design trajectory information. The optical transmission resistance field is used to quantify the degree to which microscopic surfaces impede optical transmission.

[0022] The index calculation unit is used to calculate the light transmission attenuation index, which characterizes the overall light transmittance of the laser-engraved area, based on the light transmission resistance field.

[0023] The quality control unit is used to determine the light transmission quality of the laser-engraved area based on the light transmission attenuation index.

[0024] This application offers the following advantages: By acquiring image sequences under multi-angle illumination, it can resolve the gradient vector field characterizing the undulation direction of the microscopic surface of the laser-engraved region and the texture contrast value characterizing the etching depth, providing richer surface features compared to relying solely on macroscopic grayscale information. Furthermore, by calculating the geometric deviation between the design trajectory information characterizing the macroscopic light transmission direction and the microscopic gradient vector field, and combining this with the texture contrast value, this application constructs a light transmission resistance field that quantifies the degree to which the microscopic surface hinders light transmission. This resistance field comprehensively reflects the actual impact of the directionality of the microscopic texture and the etching depth on light transmission performance. Finally, based on this resistance field, the light transmission attenuation index can more comprehensively and accurately evaluate the overall light transmission performance of the laser-engraved region, thereby achieving precise judgment of light transmission quality, effectively improving the accuracy and reliability of detection, and solving the problem of unsatisfactory detection results in existing technologies. Attached Figure Description

[0025] To more clearly illustrate the technical solutions and advantages in the embodiments of this application 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a flowchart illustrating a vision-assisted laser engraving quality inspection method for mobile phone buttons, provided in one embodiment of this application.

[0027] Figure 2 This is a schematic diagram of the system architecture of a vision-assisted laser engraving quality inspection system for mobile phone buttons, provided as an embodiment of this application. Detailed Implementation

[0028] To further illustrate the technical means and effects adopted by this application to achieve the intended purpose of the invention, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a vision-assisted laser engraving quality inspection method for mobile phone buttons proposed in this application. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0030] Unless otherwise specified, the normalization function Norm() mentioned in this application uses maximum and minimum value normalization. The maximum and minimum values ​​are preset empirical extreme values ​​derived from a large amount of historical experimental data. If the calculation result exceeds the [0,1] interval, a truncation function is used to limit it to the [0,1] range (i.e., if the result is less than 0, it is taken as 0; if it is greater than 1, it is taken as 1) to eliminate the influence of outliers on the evaluation index.

[0031] The following description, in conjunction with the accompanying drawings, details the specific scheme of a visually assisted laser engraving quality inspection method for mobile phone buttons provided in this application.

[0032] Please see Figure 1 It illustrates a flowchart of a vision-assisted laser engraving quality inspection method for mobile phone buttons according to an embodiment of this application, such as... Figure 1 As shown, the method includes the following steps:

[0033] Step 101: Obtain image sequences and design trajectory information of the laser-engraved area of ​​the mobile phone button under multiple different lighting directions.

[0034] The laser-engraved area of ​​the mobile phone button refers to a specific area where the coating is removed using a laser engraving process to form translucent characters or patterns. This area is located on the translucent substrate of the mobile phone button. Different lighting directions refer to multiple discrete lighting angles set around the laser-engraved area. For example, lighting directions of east, south, west, and north can be set. Each lighting direction forms a low angle of incidence of 15-30 degrees with the workpiece plane to enhance the shadow contrast generated by micro-undulations, which facilitates subsequent analysis of micro-surface features.

[0035] Image sequence refers to grayscale images of the laser-engraved area acquired in a time-division manner under different lighting directions. During the acquisition process, the workpiece must be kept stationary, and camera parameters such as exposure time and gain must be kept constant to ensure that the pixel resolution of each image is consistent and the pixel coordinates are strictly aligned. Design trajectory information refers to the design drawing data corresponding to the laser engraving process, usually a vector file in DXF or PLT format, containing information such as the centerline trajectory of character strokes and theoretical line width, used to characterize the ideal transmission direction of light in the laser-engraved area.

[0036] As one possible implementation, this application can achieve image sequence acquisition by using an industrial camera in conjunction with a ring-shaped segmented light source. The resolution of the industrial camera needs to meet the requirements of micro-texture recognition. For example, a camera with more than 12 million pixels can be selected. The design trajectory information can be loaded and stored by the industrial control system for subsequent registration with the image sequence.

[0037] In one specific implementation, the image sequence acquisition process includes: first, illuminating only the north (N) sector light source, waiting for the light source brightness to stabilize (e.g., 5ms), then triggering the industrial camera to expose and acquiring the first grayscale image. Immediately after acquisition, turn off the light source. Then, only illuminate the south (S) sector light source and repeat the triggering and acquisition process to obtain the second grayscale image. Then, only the east-facing (E) sector light source is illuminated to acquire a third grayscale image. Finally, only the west-facing (W) sector light source was illuminated to obtain the fourth grayscale image. .

[0038] Throughout the acquisition process, the workpiece remained stationary, and the camera's exposure time, gain, and other parameters remained constant, resulting in four images with identical pixel resolution. And the corresponding pixel coordinates Strict alignment.

[0039] For subsequent geometric registration, this application further calculates the arithmetic mean of the above four images to generate an average illumination macroscopic image. ,satisfy:

[0040]

[0041] This average illumination macroscopic image eliminates unidirectional shadows and reveals the macroscopic contour features of the workpiece.

[0042] Step 102: Determine the micro-gradient vector field and texture contrast value of the laser-engraved area based on the image sequence.

[0043] The micro-gradient vector field is used to characterize the direction of micro-surface undulations. The texture contrast value is used to characterize the etching depth. Optionally, the micro-gradient vector field is a set of vectors characterizing the direction of micro-surface undulations in the laser-etched area, with each vector corresponding to a pixel in the image, and its direction pointing in the direction of the fastest decrease in surface height at that pixel; the texture contrast value is a scalar parameter characterizing the micro-etching depth of the laser-etched area, with a larger value indicating a deeper etching depth and higher surface roughness.

[0044] This step infers the undulation features of the microscopic surface based on the brightness differences of images under different illumination directions. Since the undulations of the microscopic surface will cause different reflected light intensities under different illumination directions, by analyzing the brightness changes between images, the invisible microscopic texture features can be transformed into calculable vector and scalar parameters, laying the foundation for subsequent optical transmission performance evaluation.

[0045] In some embodiments, this application can determine the microscopic gradient vector field and texture contrast value of the laser-engraved area through the principle of photometric stereo vision. In other words, this application can calculate the surface normal vector and gradient information based on multiple images illuminated from different directions. This method can effectively remove the influence of surface albedo and accurately extract microscopic geometric features.

[0046] Step 103: Construct the light transmission resistance field based on the geometric deviation between the macroscopic light transmission direction and the microscopic gradient vector field, as well as the texture contrast value, represented by the design trajectory information.

[0047] The light transmission resistance field is used to quantify the degree to which microscopic surfaces impede light transmission. In other words, the macroscopic light transmission direction refers to the ideal light transmission direction defined by the design trajectory information, i.e., the direction of movement of the laser head during laser engraving, under which light transmission is minimally hindered in a semi-transparent substrate; the geometric deviation is a parameter used to quantify the degree of deviation between the microscopic gradient vector and the macroscopic light transmission direction, the greater the deviation, the more significant the obstruction of light transmission by the microscopic texture; the light transmission resistance field is a two-dimensional field distribution that integrates the effects of directional deviation and etching depth, where the value of each pixel represents the degree of obstruction to light transmission at that location, the larger the value, the stronger the obstruction.

[0048] It is understandable that the ideal micro-texture of the laser-etched area should align with the macroscopic light transmission direction, meaning the micro-gradient direction and the macroscopic light transmission direction should have a specific geometric relationship, minimizing light transmission obstruction. Conversely, when the micro-texture direction is chaotic or the etching depth is insufficient, additional resistance to light transmission will be created. Therefore, this step, by fusing geometric deviation and texture contrast values, can comprehensively quantify the obstruction effect of the microscopic surface on light transmission, achieving a shift from macroscopic grayscale detection to microscopic light-guiding performance evaluation.

[0049] Step 104: Calculate the light transmission attenuation index, which characterizes the overall light transmittance of the laser-engraved area, based on the light transmission resistance field.

[0050] Among them, the light transmission attenuation index is a quantitative indicator that comprehensively reflects the overall light transmission performance of the laser-engraved area. This index is calculated based on the global characteristics of the light transmission resistance field and can reflect the degree of energy loss of light during the transmission process of the laser-engraved area. The smaller the index, the better the light transmission performance, and vice versa.

[0051] As one implementation method, this application simulates the transmission process of light in the laser-engraved area. By analyzing the resistance distribution in the light transmission resistance field, the dominant path of light transmission is found, and the overall attenuation is calculated based on the resistance characteristics of this path. This global quantization method can avoid the one-sidedness of local feature detection, comprehensively reflect the light transmission quality of the laser-engraved area, and in particular, can identify the impact of local microscopic defects on the overall light transmission performance.

[0052] Step 105: Determine the light transmission quality of the laser-engraved area based on the light transmission attenuation index.

[0053] In one possible implementation, this step determines the light transmission quality by comparing the optical transmission attenuation index with a preset attenuation threshold. The attenuation threshold is a critical value obtained based on a large number of qualified and unqualified samples. For example, this application can determine the attenuation threshold by selecting a set of critically defective samples and calculating the statistical value of their optical transmission attenuation index, ensuring the accuracy and reliability of the determination result.

[0054] Optionally, when the light transmission attenuation index is less than the attenuation threshold, it indicates that the micro-texture of the laser-engraved area conforms to the macro-light transmission direction, the etching depth is sufficient, and the light transmission is less obstructed, thus the light transmission quality is deemed acceptable; when the light transmission attenuation index is greater than or equal to the attenuation threshold, it indicates that there are obvious abnormalities in the micro-texture or insufficient etching depth, and the light transmission is severely obstructed, thus the light transmission quality is deemed unacceptable.

[0055] Based on the above technical solution, this application, by acquiring image sequences under multi-angle illumination, can resolve the gradient vector field characterizing the undulation direction of the microscopic surface of the laser-engraved area and the texture contrast value characterizing the etching depth, providing richer surface features compared to relying solely on macroscopic grayscale information. Furthermore, this application constructs a light transmission resistance field that quantifies the degree of obstruction to light transmission by combining the design trajectory information characterizing the macroscopic light transmission direction with the microscopic gradient vector field and the texture contrast value. This resistance field comprehensively reflects the actual impact of the directionality of the microscopic texture and the etching depth on light transmission performance. Finally, the light transmission attenuation index calculated based on this resistance field can more comprehensively and accurately evaluate the overall light transmission performance of the laser-engraved area, thereby achieving precise judgment of light transmission quality, effectively improving the accuracy and reliability of detection, and solving the problem of unsatisfactory detection results in existing technologies.

[0056] In one possible implementation, the above steps—determining the microscopic gradient vector field and texture contrast value of the laser-engraved region based on the image sequence—specifically include:

[0057] Step 201: Based on the brightness differences between images in the image sequence, obtain the original gradient vector of each pixel in the laser-engraved area.

[0058] Optionally, this step can be implemented as follows: based on the first image pair in the image sequence, calculate the first gradient component of each pixel; the illumination directions of the two sets of images in the first image pair are relatively distributed along the first direction; based on the second image pair in the image sequence, calculate the second gradient component of each pixel; the illumination directions of the two sets of images in the second image pair are relatively distributed along the second direction; the first direction and the second direction are orthogonal in space; and combine the first gradient component and the second gradient component of each pixel into the original gradient vector of each pixel.

[0059] As an example, the first direction is east-west, and the second direction is north-south; the first gradient component is also called the horizontal gradient component, and the second gradient component is also called the vertical gradient component. The first image pair includes a third grayscale image obtained by illuminating the east-facing (E) sector light source and a fourth grayscale image obtained by illuminating the west-facing (W) sector light source. The second image pair includes a first grayscale image obtained by illuminating the north-facing (N) sector light source and a second grayscale image obtained by illuminating the south-facing (S) sector light source.

[0060] For example, the first gradient component Satisfying the formula: ;in, The third grayscale image was acquired to illuminate the east-facing (E) sector light source. To illuminate the west-facing (W) sector light source, a fourth grayscale image was acquired.

[0061] Second gradient component Satisfying the formula: .in, Light up the north (N) sector light source to obtain the first grayscale image; Illuminate the south-facing (S) sector light source to acquire the second grayscale image.

[0062] Correspondingly, the original gradient vector Satisfying the formula: , where T represents transpose.

[0063] Step 202: Determine the texture contrast value of each pixel based on the magnitude of the original gradient vector.

[0064] As an example, the magnitude of the original gradient vector represents the contrast intensity of the micro-texture at that point (i.e., a combination of etching depth and roughness), denoted as the texture contrast value. It satisfies the formula:

[0065]

[0066] in, Let L be the L2 norm of a vector, and let L be the magnitude of the vector in space.

[0067] Step 203: Normalize the original gradient vector to obtain the micro-gradient vector field.

[0068] It should be noted that, in order to perform geometric verification solely based on directional features, it is necessary to eliminate the interference of texture intensity on direction determination. Therefore, this application normalizes the original gradient vector. Simultaneously, to avoid interference in unetched smooth areas (… Because noise causes random jumps in the calculated direction, a noise threshold is introduced. (For example, the value can be 5 gray levels).

[0069] As an example, the normalized unit gradient vector is denoted as the microscopic gradient vector field. Satisfy the following formula:

[0070]

[0071] It should be noted that the above calculations yielded... Physically, the gradient direction characterizes the microscopic surface, i.e., the direction in which the surface height decreases most rapidly. In an ideal linear etched trench structure, this gradient direction is geometrically perpendicular to the extension direction of the trench ridge. Through the above processing, two key feature maps can be output: one characterizing the microscopic orientation field. Figure and characterization of etching intensity picture.

[0072] Based on the above technical solution, this application estimates the surface gradient (original gradient vector) by calculating the brightness difference between images, with the physical basis being photometric stereo vision. Then, the magnitude of the original gradient vector is used to quantify the etching intensity or depth, defined as the texture contrast value. Finally, by normalizing the original gradient vector and stripping away the intensity information, a pure unit vector field representing only the direction of microscopic surface undulations is obtained, i.e., the microscopic gradient vector field. This application can transform multiple two-dimensional grayscale images into a feature field containing three-dimensional surface orientation and etching depth information, laying a data foundation for subsequent quality assessment based on geometric relationships. Through normalization processing, it ensures that the subsequent evaluation of texture direction is not affected by varying etching depths, improving the robustness of the evaluation.

[0073] In one possible implementation, the above steps—constructing the optical transmission resistance field based on the geometric deviation between the macroscopic optical transmission direction and the microscopic gradient vector field, as well as the texture contrast value, characterized by the design trajectory information—specifically include:

[0074] Step 301: Based on the design trajectory information, generate the tangential vector field of the design trajectory corresponding to the laser engraving area.

[0075] The design trajectory tangential vector field is used to characterize the ideal macroscopic light transmission direction. In other words, the design trajectory tangential vector field is a two-dimensional field distribution composed of the tangential vectors of each point on the design trajectory. The tangential vector of each pixel in the field represents the ideal macroscopic light transmission direction corresponding to that position, that is, the direction in which the light transmission is least obstructed at that position.

[0076] The specific process of generating this vector field is as follows: map the design trajectory information to the image coordinate system, and achieve accurate registration between the design trajectory and the laser-engraved area image through template matching and other methods to ensure the correspondence of the direction information; for each pixel in the laser-engraved area, find its nearest projection point on the center line of the design trajectory, calculate the unit tangential vector of the design trajectory at the projection point, and this vector is the tangential vector of the design trajectory of the pixel.

[0077] For example, if the design trajectory is a straight line, its tangential vector is the direction vector of the straight line; if the design trajectory is a curve, the tangential vector is the tangential direction vector of each point on the curve.

[0078] Step 302: For each pixel in the laser-engraved area, calculate the absolute value of the dot product between the unit gradient vector of the pixel in the micro gradient vector field and the tangential vector of the pixel in the design trajectory tangential vector field to obtain the geometric deviation.

[0079] The unit gradient vector is a normalized version of the microscopic gradient vector field, with a magnitude of 1, retaining only directional information. The absolute value of the dot product is a mathematical index used to quantify the degree of deviation between the directions of two vectors, and its calculation result ranges from [0,1]. When the two vector directions are completely aligned, the absolute value of the dot product is 1, and the geometric deviation is at its maximum; when the two vector directions are completely perpendicular, the absolute value of the dot product is 0, and the geometric deviation is at its minimum.

[0080] As an example, geometric deviation Satisfy the following formula:

[0081]

[0082] in, The unit gradient vector, To design the tangential vector of the trajectory, "." represents the dot product operation.

[0083] It should be noted that, ideally, the direction of the micro-gradient should be perpendicular to the direction of macroscopic light transmission (i.e., the direction of the micro-texture should be consistent with the direction of light transmission). At this point, the geometric deviation is zero, and the light transmission resistance is minimized. However, when the direction of the micro-texture is disordered, the geometric deviation increases, and the light transmission resistance increases. By calculating the absolute value of the dot product, this degree of directional deviation can be accurately quantified, providing a directional dimension as a basis for resistance modeling.

[0084] Step 303: Determine the light transmission resistance value of the pixel based on the geometric deviation and texture contrast value.

[0085] The light transmission resistance value is a single-value parameter that comprehensively considers the effects of directional deviation and etching depth, used to characterize the degree to which a single pixel hinders light transmission. The greater the geometric deviation, the more obvious the directional obstruction to light transmission, and the greater the resistance value; the smaller the texture contrast value, the shallower the etching depth, the weaker the diffuse reflection effect of light transmission, and the greater the resistance value.

[0086] Optionally, this step can be implemented as follows: determining a first resistance component characterizing the influence of etching depth based on the texture contrast value and a first preset parameter; wherein the first resistance component is negatively correlated with the texture contrast value; determining a second resistance component characterizing the influence of directional deviation based on the geometric deviation degree and a second preset parameter; wherein the second resistance component is positively correlated with the geometric deviation degree; and determining the optical transmission resistance value based on the fusion result of the first resistance component and the second resistance component.

[0087] Specifically, the first preset parameter is a calibration parameter used to adjust the weight of the influence of texture contrast value on resistance. Its value is determined based on a large amount of experimental data to ensure that the influence of etching depth on resistance is reasonable. The first resistance component is a parameter specifically characterizing the effect of etching depth on light transmission obstruction. It is negatively correlated with texture contrast value. That is, the larger the texture contrast value (the deeper the etching), the smaller the first resistance component, and the weaker the light transmission obstruction. Conversely, the smaller the texture contrast value (the shallower the etching), the larger the first resistance component, and the stronger the light transmission obstruction.

[0088] The second preset parameter is a calibration parameter used to adjust the weight of the influence of geometric deviation on the resistance. Its value is also determined based on experimental data. The second resistance component is a parameter specifically characterizing the effect of directional deviation on light transmission. It is positively correlated with the geometric deviation. That is, the greater the geometric deviation (the more serious the directional deviation), the greater the second resistance component, and the stronger the light transmission is blocked. Conversely, the smaller the geometric deviation (the closer the direction), the smaller the second resistance component, and the weaker the light transmission is blocked.

[0089] For example, the formula for calculating the first resistance component is: ,in, The first preset parameter, α is the texture contrast value, and ε is a parameter tuning coefficient with a very small positive value (e.g., 0.01) to avoid a denominator of 0. This formula achieves a negative correlation between the first resistance component and the texture contrast value through reciprocal transformation, which conforms to the physical logic that the deeper the etching, the lower the resistance. The value of α can be calibrated using a standard sample; for example, α can be 1.0.

[0090] The formula for calculating the second resistance component is: ,in, This is the second preset parameter. Here, γ represents the geometric deviation, and γ is the nonlinear exponent. This formula enhances the drag penalty for large directional deviations through power function transformation, significantly increasing the drag value in areas of severe directional deviation, which better reflects the actual obstruction of light transmission. The recommended value for γ is ≥2.0; for example, γ is 2.0. The value of β can be calibrated using standard samples to ensure that the impact of directional deviation on drag matches the impact of etching depth; for example, β can be 10.0.

[0091] Light transmission resistance value .in, It is the result of fusing the first and second resistance components, and the fusing method uses addition, that is... Based on this formula, the first resistance component and the second resistance component characterize the light transmission resistance from two independent dimensions: etching depth and directional deviation. The two components have a superimposed effect on light transmission, and the addition operation can intuitively reflect this superimposed effect. For a pre-set maximum resistance threshold, (exemplary, (Take 100.0). When the fusion result exceeds this threshold, the threshold is taken as the final resistance value, i.e. .

[0092] Step 304: Construct an optical transmission resistance field based on the optical transmission resistance values ​​of each pixel.

[0093] Optionally, the optical transmission resistance field is a two-dimensional data matrix formed by arranging the optical transmission resistance values ​​of all pixels according to their pixel coordinates. This matrix can intuitively reflect the distribution of obstruction to light transmission at different locations in the laser-engraved area. By constructing the optical transmission resistance field, the scattered pixel resistance information is integrated into global field information, providing global data support for subsequent search of the dominant optical path and calculation of the optical transmission attenuation index.

[0094] Based on this, this application maps the design intent (trajectory tangency) to the image space through geometric registration, generating an ideal light path guide. By calculating the absolute value of the dot product between the micro-gradient direction and the macro-optical path direction, it creatively transforms whether the micro-texture orientation meets the light guiding requirements into a calculable geometric deviation scalar, which establishes a mathematical model between the micro-physical structure and the macro-optical function. This geometric deviation is fused with the texture contrast value characterizing the adequacy of etching to calculate the comprehensive resistance value of light transmission for each pixel, thus forming a light transmission resistance field. This resistance field intuitively identifies which locations within the laser-etched area may have poor light transmission due to incorrect texture orientation or insufficient etching, achieving a quantitative characterization of latent defects.

[0095] In one possible implementation, the specific process of calculating the light transmission attenuation index, which characterizes the overall light transmittance of the laser-engraved region, based on the light transmission resistance field includes:

[0096] Step 401: In the optical transmission resistance field, based on the path range defined by the design trajectory information, search for the path with the minimum cumulative resistance as the dominant optical path.

[0097] Among them, the path range defined by the design trajectory information refers to the effective range of laser etching in the laser engraving area, that is, the trench mask area. This range is determined by the center line of the design trajectory and the theoretical line width. The cumulative resistance refers to the sum of the light transmission resistance values ​​of all pixels on the path. The dominant light path refers to the path with the least cumulative resistance of light transmission within the path range. This path is the optimal path for light transmission in the laser engraving area and can most intuitively reflect the overall light transmission performance.

[0098] Optionally, this application may employ Dijkstra's algorithm or A... Algorithm search for dominant light paths, Dijkstra's algorithm or A... The algorithm can efficiently find the shortest path (i.e., the path with the minimum cumulative resistance) between two points in a weighted graph. The specific search process is as follows: First, determine the start and end boundaries of the path. The start point is the set of pixels in the neighborhood of the starting end of the designed trajectory, and the end point is the set of pixels in the neighborhood of the ending end of the designed trajectory. Then, within the trench mask area, using the light transmission resistance value as the weight, search for the path with the minimum cumulative resistance from the start point to the end point. This path is the dominant light path.

[0099] During the search process, a mask constraint must be applied, allowing path expansion only within the trench mask area to prevent the path from overflowing into unetched areas. If no valid path connecting the start and end points can be found during the search (e.g., there is a completely unetched breakpoint), the light transmission quality of the laser-engraved area is directly determined to be unqualified.

[0100] Step 402: Calculate the optical transmission attenuation index based on the optical transmission resistance values ​​at each position on the dominant optical path.

[0101] Optionally, this step can be implemented as follows: determining the effective light guide channel width at multiple locations on the dominant light path; and performing a weighted integral calculation based on the light transmission resistance value and the effective light guide channel width at each location on the dominant light path to obtain the light transmission attenuation index.

[0102] The calculation process of the effective light guide channel width includes: for each position on the dominant light path, determining the detection direction perpendicular to the macroscopic light transmission direction at that position; probing both sides along the detection direction in the light transmission resistance field, and determining the channel width at that position as the effective light guide channel width based on the change in the light transmission resistance value or the preset path boundary during the detection process.

[0103] Specifically, the process of determining the effective light guide channel width is as follows: for each position on the main light path... First, determine the macroscopic light transmission direction at that location (i.e., the tangential vector direction of the design trajectory), and then calculate the normal direction perpendicular to that direction. Perform a ray scan along the normal direction to both sides, with the scanning range limited to the trench mask area. When the light transmission resistance value of the scanned pixel exceeds the preset edge resistance threshold (for example, the edge resistance threshold is 5α, where α is the first preset parameter mentioned above) or exceeds the trench mask area, stop the scan. Count the number of effective pixels scanned on both sides, which is the original width at that location. To avoid division by zero errors, perform minimum truncation on the original width at each location on the dominant light path. Effective light guide channel width Satisfy the following formula: ,in To ensure the effective width of the light guide channel, The original width is described below for its specific determination process. The introduction of the effective light guide channel width can reflect the bottleneck effect on the path. That is, even if the resistance value at a certain position on the path is not large, if the channel width is too narrow, it will limit the light flux and lead to a decrease in light transmission performance.

[0104] The purpose of the weighted integral calculation of the optical transmission attenuation index is to use the effective light guide channel width as a weighting factor to weight the normalized optical transmission resistance value. The narrower the channel width, the greater the weight of the corresponding resistance value, and the more significant the impact on the attenuation index, thereby highlighting the restrictive effect of the bottleneck area on the overall light transmission performance.

[0105] As an example, the optical transmission attenuation index satisfies the following formula:

[0106]

[0107] Where N is the number of pixels in the dominant light path. For the k-th pixel on the path, Σ represents the light transmission resistance value of this pixel, and Σ indicates the summation operation. To design the theoretical width of the trajectory, The effective light guide channel width is at the k-th position. The width penalty factor is greater than 1 when the effective light guide channel width is less than the theoretical linewidth. This will amplify the resistance value weight at that location, which is consistent with the physical logic that the narrower the channel, the greater the light transmission limitation. The setting of the square term can enhance the penalty of narrow channels and make the attenuation index more sensitive to channel necking defects.

[0108] Optionally, the above-mentioned detection direction refers to the ray direction used to scan the width of the effective light guide channel. This direction is perpendicular to the macroscopic light transmission direction (i.e., the tangential vector direction of the design trajectory) and includes two opposite ray directions (i.e., positive and negative directions along the normal direction).

[0109] The specific process for determining the detection direction is as follows: obtain a certain position on the dominant optical path. Design trajectory tangential vector Calculate its normal direction (That is, the direction perpendicular to the path), the normal direction of this vector is the detection direction. During the detection process, from point... Depart, along respectively and Direction in the light transmission resistance diagram The determination of the X-ray scanning detection direction ensures that the scanning direction is perpendicular to the light transmission direction, which can accurately measure the actual light transmission width of the channel and avoid width measurement errors caused by scanning direction deviation.

[0110] The specific process of performing a ray scan along two detection directions is as follows: from position Depart, along The light transmission resistance value of each scanned pixel is recorded in a directional scan until the scanned pixel meets any of the following conditions:

[0111] 1. The optical transmission resistance value is greater than the preset edge resistance threshold. : To characterize the critical resistance value of the non-light-guiding region, for example, =5α (α is the first preset parameter). When the resistance value exceeds this threshold, it indicates that a high-resistance non-light-guiding area has been reached, and the channel terminates at the boundary.

[0112] 2. Scanning pixels extend beyond the trench mask area. The trench mask area is the effective range for laser etching; exceeding this range indicates the termination of the channel boundary.

[0113] Similarly, along Perform the same scanning process in both directions, and record the termination boundaries of the scans on both sides. Statistical position. The original channel width is obtained by summing the number of pixels at both termination boundaries. .

[0114] During the scanning process, the scanning step size must be 1 pixel to ensure the accuracy of the width measurement; at the same time, the scanning range is limited to the light transmission resistance field and the trench mask area to avoid interference from irrelevant areas on the measurement results.

[0115] Based on the above technical solution, this application searches for the dominant light path, a natural phenomenon where light seeks the easiest path through complex channels. This path represents the main transmission channel for light flux under the current microtexture state. Calculating the average or cumulative resistance along this path effectively assesses the channel's accessibility. This method is more sensitive to localized severe defects (i.e., the weakest link effect) than averaging across all pixels in the entire region; because if there is a point with extremely high resistance, it will inevitably be included in the path of least resistance (otherwise, the path would not be the least), thus being reflected in the final index. This path-based integration strategy makes the evaluation index more reflective of the physical essence of light transmission performance.

[0116] In one possible implementation, the specific process of determining the light transmission quality of the laser-engraved area based on the light transmission attenuation index includes:

[0117] The optical transmission attenuation index is compared with a preset attenuation threshold. If the optical transmission attenuation index is less than the attenuation threshold, the light transmission quality of the laser-engraved area is deemed acceptable. If the optical transmission attenuation index is greater than or equal to the attenuation threshold, the light transmission quality of the laser-engraved area is deemed unacceptable.

[0118] Among them, attenuation threshold This is the critical value used to distinguish between acceptable and unacceptable light transmittance quality. The calibration of this threshold needs to be based on a large amount of sample data to ensure the accuracy and reliability of the judgment results. Optionally, the calibration process for the attenuation threshold is as follows:

[0119] Sample preparation: Select a group of samples that are on the verge of being defective, confirmed by manual or backlight testing. The macroscopic grayscale of these samples meets the existing standards, but their actual light transmittance is on the borderline between qualified and unqualified.

[0120] Data acquisition: The samples were tested using the quality control method of this application to obtain the optical transmission attenuation index of each sample.

[0121] Statistical constant: Calculate the average value of the optical transmission attenuation index for this group of samples. and standard deviation .set up ( This is a stringency coefficient, typically set to 1.0~2.0, to ensure that all workpieces exceeding this value are rejected. For example, k is set to 1.5. The threshold determined by this statistical method ensures that the vast majority of critically defective products are rejected, while avoiding misjudgment of qualified products.

[0122] In practical applications, the attenuation threshold can be adjusted according to different mobile phone button models, materials, or manufacturing processes to meet the quality inspection needs of different scenarios.

[0123] When the optical transmission attenuation index When the laser engraving is successful, it indicates that the overall resistance of the dominant light path is small, the micro-texture direction matches the macro-light transmission direction, the etching depth is sufficient, the light transmission in the laser-engraved area is less obstructed, and the light transmission performance is good, which can meet the display requirements in actual use. Therefore, the light transmission quality is judged to be qualified. In actual use (when the backlight is on), the qualified laser-engraved area will have uniform and sufficient brightness of characters, and there will be no dim or uneven illumination.

[0124] When the optical transmission attenuation index If the light transmission is obstructed, it indicates that the overall resistance of the dominant light path is high, which may be due to defects such as disordered micro-texture direction, insufficient etching depth, or channel necking. Light transmission in the laser-engraved area is severely impeded, resulting in poor light transmission performance and failing to meet actual usage requirements. Therefore, the light transmission quality is deemed unqualified. In actual use, unqualified laser-engraved areas will exhibit problems such as uneven character illumination and dim brightness, affecting the user experience. Products deemed unqualified can be removed from the production line by a rejection mechanism to prevent them from entering subsequent processes.

[0125] It should be noted that, in order to combat the gradual decline in processing capability caused by laser aging, thermal effects of optical lenses, or dust contamination, this application implements time-series-based trend monitoring, specifically including:

[0126] Trend analysis logic: Maintain a length of (For example A first-in-first-out (FIFO) queue that stores the most recently entered items. A good product Data. Calculate the moving average of the queue data in real time. and its slope over time .like A continuously positive value (i.e., the attenuation exponent slowly increases) directly reflects that the laser energy density is decreasing or the focus is slightly defocused, resulting in the etched micro-texture gradually becoming shallower or less directional.

[0127] Closed-loop compensation strategy: When detected Exceeding the preset warning slope, and Approaching When the power level reaches 80% (i.e., no defective products have been generated, but the trend is worsening), the feedforward compensation mechanism is triggered. At this point, a correction instruction is generated: the system calculates the power correction increment. This increment is a preset, fixed, tiny step (e.g., 0.5% of rated power) designed to offset energy loss in a smooth manner.

[0128] Through industrial communication protocols (such as Modbus / TCP) The laser controller of the laser engraving machine is sent to increase the laser output power. After each compensation, an observation period begins (e.g., for the next 100 workpieces), during which no new compensation is triggered, awaiting feedback for effect. If this process is repeated continuously... After one (e.g., 3) compensations, If the value continues to rise instead of decreasing, it indicates a possible non-power-related fault in the system (such as severe lens contamination or a complete focus deviation). In this case, automatic compensation should be stopped, triggering a shutdown alarm and prompting manual intervention for maintenance.

[0129] Please see Figure 2 This diagram illustrates a system architecture of a vision-assisted mobile phone button laser engraving quality inspection system according to an embodiment of the present invention. The system includes: an acquisition unit 201, a feature parsing unit 202, a model building unit 203, an index calculation unit 204, and a quality inspection unit 205. The units communicate bidirectionally via a communication link to ensure real-time interaction of collected data and analysis results. The communication link can employ wired or wireless transmission methods to meet the communication needs of different monitoring scenarios.

[0130] The acquisition unit 201 is used to acquire image sequences and design trajectory information of the laser-engraved area of ​​the mobile phone button under multiple different lighting directions.

[0131] The feature parsing unit 202 is used to determine the microscopic gradient vector field and texture contrast value of the laser-engraved region based on the image sequence. The microscopic gradient vector field is used to characterize the direction of microscopic surface undulations. The texture contrast value is used to characterize the etching depth.

[0132] Model building unit 203 is used to construct an optical transmission resistance field based on the geometric deviation between the macroscopic optical transmission direction and the microscopic gradient vector field, as well as the texture contrast value, characterized by the design trajectory information. The optical transmission resistance field is used to quantify the degree to which microscopic surfaces impede optical transmission.

[0133] The index calculation unit 204 is used to calculate the light transmission attenuation index, which characterizes the overall light transmittance performance of the laser-engraved area, based on the light transmission resistance field.

[0134] Quality inspection unit 205 is used to determine the light transmission quality of the laser-engraved area based on the light transmission attenuation index.

[0135] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0136] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for quality inspection of laser engraving on mobile phone buttons under visual assistance, characterized in that, The method includes: Acquire image sequences and design trajectory information of the laser-engraved area of ​​mobile phone buttons under multiple different lighting directions; Based on the image sequence, the micro-gradient vector field and texture contrast value of the laser-engraved area are determined; the micro-gradient vector field is used to characterize the direction of micro-surface undulations; the texture contrast value is used to characterize the etching depth. Based on the design trajectory information, a tangential vector field corresponding to the laser-engraved area is generated; the tangential vector field is used to characterize the ideal macroscopic light transmission direction. For each pixel in the laser-engraved area, the absolute value of the dot product between the unit gradient vector of the pixel in the micro-gradient vector field and the tangential vector of the pixel in the design trajectory tangential vector field is calculated to obtain the geometric deviation. The light transmission resistance value of the pixel is determined based on the geometric deviation and the texture contrast value. The light transmission resistance field is constructed based on the light transmission resistance value of each pixel. Based on the light transmission resistance field, calculate the light transmission attenuation index, which characterizes the overall light transmittance of the laser-engraved region; The light transmission quality of the laser-engraved area is determined based on the light transmission attenuation index. Specifically, determining the microscopic gradient vector field and texture contrast value of the laser-engraved region based on the image sequence includes: Based on the brightness differences between the images in the image sequence, the original gradient vector of each pixel in the laser-engraved region is obtained; The texture contrast value of each pixel is determined based on the magnitude of the original gradient vector. The original gradient vector is normalized to obtain the microscopic gradient vector field; Specifically, based on the brightness differences between images in the image sequence, the original gradient vector of each pixel in the laser-engraved region is obtained, including: Based on the first image pair in the image sequence, the first gradient component of each pixel is calculated; the illumination directions of the two sets of images in the first image pair are relatively distributed along the first direction; Based on the second image pair in the image sequence, the second gradient component of each pixel is calculated; the illumination directions of the two sets of images in the second image pair are relatively distributed along the second direction; the first direction and the second direction are orthogonal in space; The first gradient component and the second gradient component of each pixel are combined to form the original gradient vector of each pixel; The determination of the light transmission resistance value of the pixel based on the geometric deviation and the texture contrast value includes: Based on the texture contrast value and the first preset parameter, a first resistance component characterizing the influence of etching depth is determined; wherein, the first resistance component is negatively correlated with the texture contrast value; Based on the geometric deviation degree and the second preset parameter, a second drag component characterizing the influence of directional deviation is determined; wherein, the second drag component is positively correlated with the geometric deviation degree; The optical transmission resistance value is determined based on the fusion result of the first resistance component and the second resistance component. The calculation of the light transmission attenuation index, which characterizes the overall light transmittance of the laser-engraved region, based on the light transmission resistance field includes: In the optical transmission resistance field, based on the path range defined by the design trajectory information, the path with the minimum cumulative resistance is searched as the dominant optical path; Determine the effective light guide channel width at multiple locations along the dominant light path; The optical transmission attenuation index is obtained by performing a weighted integral calculation based on the optical transmission resistance value and the effective light guide channel width at each position on the dominant optical path.

2. The method for quality inspection of laser engraving of mobile phone buttons under vision assistance according to claim 1, characterized in that, Determining the effective light guide channel width at multiple locations along the dominant light path includes: For each position on the dominant optical path, determine the detection direction perpendicular to the macroscopic optical transmission direction at that position; The light transmission resistance field is probed in both directions along the probe direction. Based on the change in the light transmission resistance value or the preset path boundary during the probe process, the channel width at the location is determined as the effective light guiding channel width.

3. The method for quality inspection of laser engraving of mobile phone buttons under visual assistance according to claim 1, characterized in that, The light transmission quality of the laser-engraved area is determined based on the light transmission attenuation index, including: The optical transmission attenuation index is compared with a preset attenuation threshold; If the optical transmission attenuation index is less than the attenuation threshold, then the light transmission quality of the laser-engraved area is deemed to be qualified. If the optical transmission attenuation index is greater than or equal to the attenuation threshold, then the light transmission quality of the laser-engraved area is deemed unqualified.

4. A vision-assisted mobile phone button laser engraving quality inspection system, characterized in that, The system includes: The acquisition unit is used to acquire image sequences and design trajectory information of the laser-engraved area of ​​the mobile phone buttons under multiple different lighting directions; The feature parsing unit is used to determine the micro-gradient vector field and texture contrast value of the laser-engraved region based on the image sequence; the micro-gradient vector field is used to characterize the direction of micro-surface undulations; the texture contrast value is used to characterize the etching depth. The model building unit is used to generate a tangential vector field of the design trajectory corresponding to the laser-engraved area based on the design trajectory information; the tangential vector field of the design trajectory is used to characterize the ideal macroscopic light transmission direction; for each pixel in the laser-engraved area, the absolute value of the dot product between the unit gradient vector of the pixel in the microscopic gradient vector field and the tangential vector of the pixel in the design trajectory tangential vector field is calculated to obtain the geometric deviation; the light transmission resistance value of the pixel is determined based on the geometric deviation and the texture contrast value; and a light transmission resistance field is constructed based on the light transmission resistance values ​​of each pixel. An index calculation unit is used to calculate the light transmission attenuation index, which characterizes the overall light transmittance of the laser-engraved region, based on the light transmission resistance field. The quality inspection unit is used to determine the light transmission quality of the laser-engraved area based on the light transmission attenuation index. Specifically, determining the microscopic gradient vector field and texture contrast value of the laser-engraved region based on the image sequence includes: Based on the brightness differences between the images in the image sequence, the original gradient vector of each pixel in the laser-engraved region is obtained; The texture contrast value of each pixel is determined based on the magnitude of the original gradient vector. The original gradient vector is normalized to obtain the microscopic gradient vector field; Specifically, based on the brightness differences between images in the image sequence, the original gradient vector of each pixel in the laser-engraved region is obtained, including: Based on the first image pair in the image sequence, the first gradient component of each pixel is calculated; the illumination directions of the two sets of images in the first image pair are relatively distributed along the first direction; Based on the second image pair in the image sequence, the second gradient component of each pixel is calculated; the illumination directions of the two sets of images in the second image pair are relatively distributed along the second direction; the first direction and the second direction are orthogonal in space; The first gradient component and the second gradient component of each pixel are combined to form the original gradient vector of each pixel; The determination of the light transmission resistance value of the pixel based on the geometric deviation and the texture contrast value includes: Based on the texture contrast value and the first preset parameter, a first resistance component characterizing the influence of etching depth is determined; wherein, the first resistance component is negatively correlated with the texture contrast value; Based on the geometric deviation degree and the second preset parameter, a second drag component characterizing the influence of directional deviation is determined; wherein, the second drag component is positively correlated with the geometric deviation degree; The optical transmission resistance value is determined based on the fusion result of the first resistance component and the second resistance component. The calculation of the light transmission attenuation index, which characterizes the overall light transmittance of the laser-engraved region, based on the light transmission resistance field includes: In the optical transmission resistance field, based on the path range defined by the design trajectory information, the path with the minimum cumulative resistance is searched as the dominant optical path; The optical transmission attenuation index is calculated based on the optical transmission resistance values ​​at each position along the dominant optical path. The optical transmission attenuation index is calculated based on the optical transmission resistance values ​​at various locations along the dominant optical path, including: Determine the effective light guide channel width at multiple locations along the dominant light path; The optical transmission attenuation index is obtained by performing a weighted integral calculation based on the optical transmission resistance value and the effective light guide channel width at each position on the dominant optical path.

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