Method for detecting internal defects in a folded optical waveguide

Abstract

This invention relates to a method for detecting internal defects in a composite optical waveguide, comprising: S300: a vision module focuses on the i-th longitudinal focus position along the Z-axis, detects internal defects in the i-th layer of the composite optical waveguide, and acquires an image of the internal defects in the i-th layer; S500: the vision module focuses on the (i+1)-th longitudinal focus position along the Z-axis, detects internal defects in the (i+1)-th layer of the composite optical waveguide, and acquires an image of the internal defects in the (i+1)-th layer; S600: step S500 is iteratively executed by setting the updated i=i+1 until the vision module focuses on the final position Z along the Z-axis. m The invention detects internal defects in the m-th layer of a composite optical waveguide and acquires an image of the internal defects in the m-th layer. S700: Based on the acquired images of internal defects in layers 1 to m, a comprehensive image of the internal defects in the composite optical waveguide from layers 1 to m is generated using a vertical image synthesis algorithm. This invention improves detection accuracy and efficiency.

Description

Technical Field

[0001] This invention relates to the field of optical inspection technology, and in particular to a method for detecting internal defects in composite optical waveguides. Background Technology

[0002] This background section provides the general context for the invention. To the extent described in this background section, the work of the currently named inventors and aspects of the specification that may not constitute prior art at the time of submission are neither explicitly nor implicitly considered to be prior art to the invention.

[0003] In the field of augmented reality (AR) display technology, reflective waveguides have become a mainstream optical solution due to their high brightness output, excellent outdoor visibility, and color reproduction capabilities. The technical principle of reflective waveguides is to transmit light through an array of semi-transparent and semi-reflective mirrors. The optical efficiency loss of reflective waveguide solutions is significantly lower than that of diffractive waveguides. Furthermore, the color reproduction of reflective waveguide solutions more closely resembles the visual effects of real-world environments.

[0004] The quality and function of reflective waveguides directly impact the user experience of AR devices. To meet the display requirements of wide viewing angles or high-quality color images, reflective waveguides, also known as laminated waveguides, are cut from multi-layered optical glass. During the manufacturing of laminated waveguides, even minute defects within the laminated glass can directly cause black spots, bright spots, or distortion in the user's field of view, severely degrading the user experience. In the process of stacking multiple layers of optical glass, defects such as dust, foreign objects, and excess adhesive may exist between adjacent laminated glass layers, and individual laminated glass layers may also have defects such as pitting and scratches. Therefore, high-precision 3D inspection of internal defects in laminated waveguides is a key technology for ensuring the display quality of AR devices.

[0005] However, existing manual microscopic inspection methods rely on manual visual inspection under a microscope during the semi-finished stage of the laminated optical waveguide, depending on the operator's subjective judgment of internal defects. These methods are time-consuming, labor-intensive, inefficient, highly subjective, inaccurate, and have a high false detection rate. Microscope imaging systems have a shorter working distance compared to telecentric lenses, and the longitudinal mechanical focusing method limits the focusing distance. Furthermore, existing manual microscopic inspection methods cannot quantify the three-dimensional coordinates of internal defects, lack defect labeling capabilities, and cannot meet the high-precision inspection requirements for internal defects in large-size (50 mm × 50 mm), thick (up to 50 mm), and multi-layered (30 layers) reflective laminated optical waveguides. They also cannot provide the three-dimensional coordinates of internal defects within the laminated optical waveguide, and especially cannot accurately locate which layer of the laminated glass the defect is located in.

[0006] To address the aforementioned issues, it is necessary to develop a method for detecting internal defects in composite optical waveguides that offers high detection efficiency, accurate location of internal defects, and complete information on internal defects. Summary of the Invention

[0007] One objective of this invention is to achieve efficient and accurate internal defect detection in the process of detecting internal defects in composite optical waveguides, with high detection efficiency, accurate location of internal defects, and complete information on internal defects.

[0008] To achieve the above objectives, a first aspect of the present invention provides a method for detecting internal defects in a composite optical waveguide, comprising the following steps:

[0009] S100: The reference plane of the altimeter and the imaging plane of the vision module are aligned on the same plane through optical calibration.

[0010] S200: The vision module automatically positions itself at the initial position Z1 using a height measuring instrument;

[0011] S300: The vision module focuses on the i-th longitudinal focus position at the X-axis and Y-axis positions and in the Z-axis direction, detects internal defects in the i-th layer of the stacked optical waveguide, and acquires an image of the internal defects in the i-th layer; where 1 ≤ i ≤ m; when i=1, the i-th longitudinal focus position is the initial position Z1; m is the number of steps;

[0012] S400: The vision module focuses on the (i+1)th longitudinal focus position in the Z-axis direction at the X and Y axis positions, detects internal defects in the (i+1)th layer of the stacked optical waveguide, and acquires an internal defect map of the (i+1)th layer; wherein, for the internal defect map of the (i+1)th layer, the (i+1)th longitudinal focus position is the position where the (i+1)th longitudinal focus position moves downward along the Z-axis by one Z-axis step interval ΔZ from the ith longitudinal focus position, and the step interval ΔZ is obtained based on the product of depth of field L and refractive index n;

[0013] S500: Continue iteratively executing step S400 by setting the updated i=i+1 until the vision module focuses on the final position Zm in the Z-axis direction, detects the internal defects of the m-th layer of the stacked optical waveguide, and acquires the internal defect map of the m-th layer; wherein, the final position Zm is the position accumulated from the initial position Z1 along the Z-axis by moving down along the Z-axis by m-1 Z-axis step intervals ΔZ.

[0014] S600: Based on the acquired internal defect maps of layers 1 to m, a total map of the internal defect maps of the stacked optical waveguide layers 1 to m at the X-axis and Y-axis positions is generated by using a vertical image synthesis algorithm. The vertical image synthesis algorithm analyzes the sharpness or clarity of each pixel at different vertical focus positions and selects the vertical focus position with the highest sharpness as the depth value of that pixel.

[0015] Compared with the prior art, the method of the present invention has the following beneficial technical effects:

[0016] This invention employs a large-area camera, a high-precision telecentric lens, and a customized high-collimation backlight to achieve high-precision detection of internal defects in composite optical waveguide products; and through the optical calibration method of a height gauge and a high-precision telecentric lens, the initial longitudinal position Z1 can be automatically located.

[0017] This invention uses the product of the lens's depth of field L and the sample's refractive index n, L×n, as the Z-axis step interval. It takes into account the depth of field changes caused by the refractive index during the scanning of the sample's interior, which can ensure the continuity of sharpness between two adjacent images while also taking efficiency into account.

[0018] Through optical calibration and active displacement compensation functions on the X and Y axes, the internal defect position shift of images at different longitudinal focusing positions (Z1 to Zm) at the same X and Y axis position can be controlled at the μm level.

[0019] This invention includes a vertical image synthesis algorithm that fuses multiple vertical images into a single overall image based on a sharpness algorithm, and pinpoints the precise XYZ 3D location of defects. The vertical accuracy is the product of the depth of field of a high-precision telecentric lens and the sample's refractive index n. The vertical image synthesis algorithm compares images of the same scene taken at different vertical focus positions, using a focusing method to recover the object's 3D information. Specifically, the algorithm analyzes the sharpness of each pixel at different vertical focus positions and selects the vertical focus position with the highest sharpness as the pixel's depth value. Finally, the sharpest portions from all scanned vertical focus positions are synthesized into a single overall image.

[0020] Further applicability will become apparent from the description provided herein. It should be understood that the specification and specific examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0021] The above-described features and advantages, as well as other features and advantages, of the currently disclosed systems and methods will become apparent when taken in conjunction with the accompanying drawings and the detailed description including the claims and exemplary embodiments. Attached Figure Description

[0022] The accompanying drawings used in the specific implementation or prior art description will be briefly introduced below.

[0023] Obviously, some of the accompanying drawings described below are embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0024] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, more details, features, and advantages of the present invention are disclosed in the following description of exemplary embodiments in conjunction with the accompanying drawings, in which:

[0025] Figure 1 This is a schematic diagram of the detection system for internal defects in the composite optical waveguide involved in this invention;

[0026] Figure 2 This is a schematic diagram of an embodiment of the longitudinal step scanning step of the method for detecting internal defects in a composite optical waveguide, which is involved in this invention.

[0027] Figure 3 A schematic diagram of a specific embodiment of a region-based longitudinal stepping scan sequence in the X and Y axes;

[0028] Figure 4 This is a schematic diagram of a specific embodiment of a complete internal defect distribution map of the composite optical waveguide sample under test.

[0029] Figure 5 This is a schematic diagram of a specific embodiment of a table summarizing internal defect information of a composite optical waveguide sample under test.

[0030] Figure 6 Is Figure 3 The image shows the longitudinal variation of a defect obtained from scanning region 1, and a schematic diagram of the defect location identified by the sharpness algorithm. Detailed Implementation

[0031] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0032] In the following description, many specific details will be set forth with reference to several examples of the invention illustrated in the accompanying drawings, in order to provide a full understanding of the invention. Wherever possible, the same or similar reference numerals are used in the drawings and description to denote the same or similar parts or steps.

[0033] However, the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0034] In one specific embodiment of the present invention, a method for detecting internal defects in a composite optical waveguide is provided, comprising the following steps:

[0035] S300: The vision module focuses on the i-th longitudinal focus position at the X-axis and Y-axis positions and in the Z-axis direction, detects internal defects in the i-th layer of the stacked optical waveguide, and acquires an image of the internal defects in the i-th layer; where 1 ≤ i ≤ m; when i=1, the i-th longitudinal focus position is the initial position Z1; m is the number of steps;

[0036] S400: The vision module focuses on the (i+1)th longitudinal focus position in the Z-axis direction at the X-axis and Y-axis positions, detects internal defects in the (i+1)th layer of the stacked optical waveguide, and acquires an internal defect map of the (i+1)th layer; wherein, for the internal defect map of the (i+1)th layer, the (i+1)th longitudinal focus position is the position where the (i+1)th longitudinal focus position moves downward along the Z-axis by one Z-axis step interval ΔZ.

[0037] S500: Continue iteratively executing step S400 by setting the updated i=i+1 until the vision module focuses on the final position Zm in the Z-axis direction, detects the internal defects of the m-th layer of the stacked optical waveguide, and acquires the internal defect map of the m-th layer; wherein, the final position Zm is the position accumulated from the initial position Z1 along the Z-axis by moving down along the Z-axis by m-1 Z-axis step intervals ΔZ.

[0038] S600: Based on the acquired internal defect maps of layers 1 to m, a general map of the internal defect maps of the stacked optical waveguide layers 1 to m at the X-axis and Y-axis positions is generated by using a longitudinal image synthesis algorithm.

[0039] Figure 1 This is a schematic diagram of the detection system for internal defects in a composite optical waveguide, as per the present invention. Figure 1 As shown, the detection system for internal defects in a composite optical waveguide includes a vision module, a motion control module, and an image fusion module. The composite optical waveguide sample 2 to be tested is placed on the hollowed-out carrier 1.

[0040] The vision module includes: a large-area camera 3, a high-precision telecentric lens 4, an altimeter 5, and a custom backlight 6. After optical calibration, the altimeter can automatically locate the initial longitudinal position Z1 based on the light signal reflected from the upper surface of the composite waveguide sample 2 under test. Z1 corresponds to the upper surface of the composite waveguide sample 2 under test. The custom backlight 6 comprises a point light source and a custom focusing lens, offering excellent collimation. Compared to ordinary backlights and coaxial light sources, the custom backlight with its superior collimation provides better detection results for the interior of glass materials.

[0041] The motion control module can control the X, Y, and Z axes separately, which is used to control the movement of the vision module on the X, Y, and Z axes.

[0042] The image fusion module can realize functions such as vertical image synthesis algorithm, image stitching algorithm, and defect information aggregation.

[0043] like Figure 1 As shown, the composite optical waveguide product 2 is made of multiple layers of stacked glass. The product's length and width vary from 20 mm to 50 mm, and the thickness can reach up to 50 mm. The number of layers can reach up to 30. During the stacking process, there may be defects such as dust, foreign objects, and excess glue between adjacent glass, and the glass itself may also have defects such as pitting and scratches.

[0044] Figure 2 This is a schematic diagram of an embodiment of the longitudinal step-scanning step of the method for detecting internal defects in a composite optical waveguide, which is involved in this invention.

[0045] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, such as Figure 2 As shown, the scanning proceeds downwards along the Z-axis, acquiring images at each longitudinal focus position. Each longitudinal focus position is Z1, Z2, ..., until the lowest surface of the sample is acquired, with the focus position being Zm. A total of m images of internal defects are obtained.

[0046] Then, a vertical image synthesis algorithm is used to detect the sharpness of each layer of the acquired image. The vertical image synthesis algorithm recovers the three-dimensional information of the object by comparing images taken at the same XY position at different vertical focus positions (Z1 to Zm) of the lens and using focusing methods. Specifically, the vertical image synthesis algorithm analyzes the sharpness or clarity of each pixel at different vertical focus positions and selects the vertical focus position with the highest sharpness as the depth value of that pixel.

[0047] Finally, the images (Z1 to Zm) from all the different longitudinal focus positions were scanned, and only the clear parts were combined into a single overall image.

[0048] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, step S600 includes the following steps:

[0049] S610: Analyze the sharpness of pixels in the acquired internal defect maps of each layer at each longitudinal focus position.

[0050] S630: Compare the sharpness of pixels in the internal defect map of each layer at each vertical focus position;

[0051] S650: Select the vertical focus position corresponding to the pixel of the internal defect map with the highest clarity as the depth of the internal defect of the composite optical waveguide;

[0052] S670: For the pixels of the internal defect map of each layer, select the pixels of the internal defect map with the highest clarity as the total number of pixels of the internal defect map of the stacked optical waveguide from the 1st to the mth layers.

[0053] S690: Combine all the total pixels of the internal defect map of the stacked optical waveguides from the 1st to the mth layers into a total map of the internal defect map of the stacked optical waveguides from the 1st to the mth layers.

[0054] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, after step S600, the following step is further included:

[0055] S700: The vision module moves from the position on the X-axis and Y-axis to the next position on the X-axis and Y-axis using the XY motion platform;

[0056] The vision module continues to execute steps S300-S600 at the next X-axis and Y-axis positions. After acquiring the overall image of the internal defects of the superimposed optical waveguide, it proceeds to step S700 until it obtains an atlas of overall images of the internal defects of the superimposed optical waveguide at all X-axis and Y-axis positions.

[0057] S800: By using an image stitching algorithm, the image set of the overall map of the internal defects of the superimposed optical waveguide at all X-axis and Y-axis positions is stitched together to obtain a complete defect distribution map of the internal defects of the superimposed optical waveguide.

[0058] Figure 3 This is a specific embodiment of a longitudinal step-by-step scanning sequence divided into regions along the X and Y axes.

[0059] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, such as Figure 3 As shown, the size of the composite optical waveguide samples under test is generally larger than the field of view of the vision module. Therefore, it is necessary to move the XY motion platform to acquire images and obtain an image set, and then use an image stitching algorithm to stitch the images together. Specifically, the images are hard-stitched, and a weighted fusion algorithm is used to address the issue of stitching seams.

[0060] Taking 3×4 splicing as an example, using Figure 3 The S-shaped segmented scanning sequence shown in the X and Y axes can improve scanning speed. Figure 3 In the diagram, the cross-section of the stacked optical waveguide is divided into 4 rows and 3 columns of rectangular frames. Along the X-axis, from left to right, the first row contains regions 1, 2, and 3; the second row contains regions 6, 7, 8, and 9; and the fourth row contains regions 12, 11, and 10. A total of 3 × 4 = 12 regions need to be scanned. Each scan proceeds one region at a time along the Z-axis, in the following order: Region 1 -> Region 2 -> Region 3 -> Region 4 -> Region 5 -> Region 6 -> Region 7 -> Region 8 -> Region 9 -> Region 10 -> Region 11 -> Region 12.

[0061] In a specific embodiment of the method for detecting internal defects in composite optical waveguides of the present invention, a large-area camera and a high-magnification, shallow-depth-of-field lens are used to achieve high-precision defect detection. The altimeter automatically determines the initial longitudinal position based on the light signal reflected from the upper surface of the composite optical waveguide sample under test. The specific configuration includes: a 65M camera; a 2x telecentric lens; a custom-designed high-collimation backlight; and a 15 mm × 11 mm field of view.

[0062] In a specific embodiment of the method for detecting internal defects in a composite optical waveguide according to the present invention, a height meter is used to measure the light signal reflected from the upper surface of the composite optical waveguide sample, and the height value C is read. The negative of this height value C is the initial position Z1. For example, if the reading is 5 mm, it means that the Z-axis should be moved -5 mm, and the initial position is the upper surface of the sample to be tested; wherein, Figure 4 , Figure 5 and Figure 6 It contains complete experimental data and measurement results.

[0063] like Figure 3 As shown, if the sample size is 40×40 mm and the field of view of this scheme is 15 mm×11 mm, then it needs to move 3 times in the X direction and 4 times in the Y direction, and a total of 3×4=12 regions need to be scanned. Each time, one region is scanned by stepping along the Z-axis longitudinally.

[0064] First to Figure 3 A longitudinal step-by-step scan is performed on region 1. Assuming a sample thickness of 15 mm, a refractive index of 1.5, and a 2X lens depth of field of 0.5 mm, then according to optical path theory, the equivalent depth of field is 0.5 mm × 1.5 = 0.75 mm. Each Z-axis step is 0.75 mm, requiring 15 mm / 0.75 = 20 Z-axis movements. Figure 3 During the scan of region 1, the Z-axis needs to be moved downwards 20 times.

[0065] Then on Figure 3 The optical device scans region 2, and at this time, the X-axis is moved so that the field of view of the optical device is in the... Figure 3 Region 2 was scanned from the bottom of the sample, and the same number of scans was performed 20 times.

[0066] This method involves longitudinally stepping through the entire sample to obtain a detection image set. This embodiment is only an example. When changing the lens and camera, the specific number of steps and the step interval will change, but the calculation method remains the same. The calculation method for the number of Z-axis steps is protected.

[0067] Vertical image synthesis algorithms will Figure 3 The images acquired in region 1 are subjected to sharpness detection, and defects in each layer are identified and cut out, and a total defect distribution map is synthesized; similarly, the corresponding total defect distribution maps are synthesized in other regions.

[0068] Then, the atlas of defect maps synthesized from each region is stitched together according to location to obtain, as shown below. Figure 4 The diagram shows the defect distribution of the entire product.

[0069] Ultimately obtainable Figure 4 and Figure 5 . Figure 4 This is a specific embodiment of a complete internal defect distribution map of the composite optical waveguide sample under test. Figure 5 This is a specific example of a table summarizing internal defect information of a composite optical waveguide sample under test. For example... Figure 4 The defect information summary table shown includes defect number, X coordinate, Y coordinate, Z coordinate, defect diameter, defect length, and defect width. In a specific embodiment of the defect detection method for the superimposed optical waveguide of the present invention, the defect information summary table (not shown in the figure) also includes defect type.

[0070] Figure 6 Is Figure 3 The image shows the longitudinal variation of a defect obtained from scanning region 1, and a schematic diagram of the defect location identified by the sharpness algorithm.

[0071] Based on the clarity algorithm and such Figure 4 The complete defect distribution map shown can pinpoint the accurate vertical location of the defects. Therefore, the 3D information of the defects can be determined through the 2D image, and the detection results can be output through the defect information summary function.

[0072] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, after step S400, the following step is further included:

[0073] S420: Compare the X-axis pixel offset Δx and Y-axis pixel offset Δy of the internal defects in the (i+1)th layer of the composite optical waveguide with those in the i-th layer of the composite optical waveguide.

[0074] S440: Multiply the pixel equivalent δ of the vision module of the automatic detection device by the X-axis pixel offset Δx and the Y-axis pixel offset Δy respectively to obtain the X-axis physical compensation amount Dx and the Y-axis physical compensation amount Dy.

[0075] S460: The vision module of the automatic detection device performs a reverse linear motion in the X-axis direction with a physical compensation amount of Dx and a reverse linear motion in the Y-axis direction with a physical compensation amount of Dy.

[0076] Through detailed optical calibration methods, the parallelism between the imaging plane of the high-precision telecentric lens and the stage of the superimposed optical waveguide product under test can be adjusted to no more than 0.5 degrees.

[0077] However, for high-precision telecentric lenses of 2x or higher, a parallelism of 0.5 degrees will still result in defects at the same position in images (Z1 to Zm) at different longitudinal focusing positions. This will cause a significant positional shift, affecting the performance of the longitudinal image synthesis algorithm.

[0078] The active displacement compensation function of the X-axis and Y-axis can ensure the accuracy and stability of image acquisition at different longitudinal focusing positions (Z1 to Zm).

[0079] Even with a higher precision telecentric lens (2x or more), the defect position shift in the image (Z1 to Zm) at different longitudinal focusing positions can still be controlled within the μm level.

[0080] In a specific embodiment of the method for detecting internal defects in a composite optical waveguide according to the present invention, during the detection process, a feature defect is selected from the acquired images. First, the pixel offset and offset direction of this feature defect in two adjacent images during clear imaging are determined. Then, the actual distance of the X-axis and Y-axis offset when the Z-axis moves once is calculated based on the pixel equivalent δ (i.e., the actual length corresponding to each pixel), which is generally 1-10 μm. Pixel equivalent is used to establish the relationship between pixels and objects. The proportional relationship of the dimensions is determined, and the actual physical size represented by each pixel is calibrated. Pixel equivalent δ: Determined by the lens magnification and the pixel size of the vision module. For example, the pixel equivalent δ of a 2X lens = 1.6 μm / px. The inputs are the pixel offset and direction of the feature defect, as well as the pixel equivalent δ. The actual distance of the X-axis and Y-axis offset is calculated. The output is the compensation amount used to guide the motion control module to perform linear motion compensation on the X-axis and Y-axis during Z-axis motion imaging; that is, controlling the movement in the X-axis and Y-axis directions by a corresponding distance in the opposite direction to the defect offset. The vision module performs μm-level linear motion in the X-axis and Y-axis directions during or before Z-axis motion, with the motion direction opposite to the defect offset direction.

[0081] Beneficial Technical Effects: This technology solves the problem that defects at the same location in images under different longitudinal focusing positions can shift due to the parallelism issue of high-precision telecentric lenses, affecting the performance of longitudinal image synthesis algorithms. It compensates for defect position shifts caused by lens tilt (parallelism ≥ 0.5 degrees) or high-magnification imaging, ensuring pixel alignment during longitudinal image synthesis. Through active XY-axis displacement compensation, it ensures that the XY-axis shift of defect positions at the same location in images under different longitudinal focusing positions is controlled within the micrometer level, improving the accuracy and stability of image acquisition, and thus improving the precision of defect detection. It addresses the image shift problem of high-magnification lenses (≥ 2X), resulting in defect position errors in the synthesized image controlled within 10μm, meeting the requirements for interlayer defect differentiation in 30-layer glass stacks.

[0082] Supports high-magnification lenses of 2X and above, improving detection accuracy from 32μm to 4.8μm. When customers have different detection accuracy requirements, high-precision telecentric lenses with different magnifications can be used. For example, if the defect detection accuracy requirement is 4.8μm, a 2X telecentric lens can be used with a 65M camera (3.2μm pixel size, 1.6μm single-pixel accuracy) to meet the detection needs, with a measured depth of field of 500μm. Alternatively, if the defect detection accuracy requirement is 32μm, a 0.5X telecentric lens can be used with a 65M camera (3.2μm pixel size, 6.4μm single-pixel accuracy), with a measured depth of field of 1500μm.

[0083] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, the vision module re-acquires images of various positions along the longitudinal direction of the sample to verify whether the pixel offset of the same characteristic defect in all images from Z1 to Zm is controlled at the μm level.

[0084] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, the following steps are included before step S300:

[0085] S100: The reference plane of the altimeter and the imaging plane of the vision module are aligned on the same plane through optical calibration.

[0086] S200: The vision module automatically positions itself at the initial position Z1 using a height measuring instrument.

[0087] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, such as Figure 1 As shown, in step S100, the optical calibration method for ensuring that the imaging planes of the altimeter and the high-precision telecentric lens are at the same position is as follows:

[0088] First, place the checkerboard pattern on the hollowed-out vehicle and use a high-precision telecentric lens to image the checkerboard pattern. Adjust the Z-axis to move the large target camera and the high-precision telecentric lens together. When the center of the checkerboard pattern is clearly imaged, that is, when the transition pixels at the black and white boundary of the checkerboard pattern are no more than 3, it indicates that the high-precision telecentric lens is focused on the upper surface of the checkerboard pattern. Then adjust the X and Y axes so that the exact center of the checkerboard pattern is in the exact center of the image captured by the camera.

[0089] Then adjust the camera's tilt angle so that the transition pixels at the black and white boundaries of the four sides of the checkerboard are no more than 3, indicating that the imaging surface of the camera lens is parallel to the checkerboard plane, with a parallel angle of no more than 0.5 degrees. Then move the X and Y axes while keeping the Z axis stationary, so that the light from the altimeter is in the exact center of the checkerboard. Use the altimeter to measure the height of the checkerboard, and adjust the fixing mechanism of the altimeter so that the reading of the altimeter is 0. At this point, it is ensured that the imaging surface of the altimeter is consistent with that of the high-precision telecentric lens.

[0090] Then, in S200, a method is used to automatically position the vision module at its initial position Z1 using an altimeter: The checkerboard pattern is replaced with the composite optical waveguide sample to be tested. The altimeter measures the light signal reflected from the upper surface of the sample, and the reading C is measured. Adjusting the Z-axis to move a distance C in the opposite direction makes the altimeter reading 0. At this point, the imaging plane of the high-precision telecentric lens is located on the upper surface of the composite optical waveguide sample. The initial Z-axis position Z1 is recorded at this point. This calibration method allows the altimeter to automatically position the initial longitudinal position Z1, ensuring that the imaging plane of the high-precision telecentric lens is indeed located on the upper surface of the composite optical waveguide sample.

[0091] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, step S100 includes the following steps:

[0092] S120: Place the checkerboard pattern on the hollowed-out vehicle;

[0093] S140: The vision module focuses on the upper surface of the checkerboard grid along the Z-axis; adjust the X and Y axes so that the exact center of the checkerboard grid is located at the exact center of the image acquired by the vision module;

[0094] S180: Adjust the tilt angle of the vision module so that the imaging surface of the vision module is parallel to the checkerboard plane; adjust the X-axis and Y-axis so that the light from the altimeter is in the center of the checkerboard; use the altimeter to measure the height of the checkerboard; adjust the reading of the altimeter to zero so that the reference plane of the altimeter and the imaging plane of the vision module are on the same plane.

[0095] Optical calibration is used to make the imaging plane of the high-precision telecentric lens coplanar with the altimeter's height measurement reference plane; specifically, steps S120, S140, and S180 are included.

[0096] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, in step S140, the vision module is used to image the checkerboard: the Z-axis is adjusted to move the large target camera and the vision module together so that the center of the checkerboard is clearly imaged (i.e., the transition pixels at the black and white boundary of the central area of ​​the checkerboard are ≤3) - at this time, the vision module focuses on the upper surface of the checkerboard in the Z-axis direction; then, the X-axis and Y-axis are adjusted so that the center of the checkerboard coincides with the center of the image acquired by the vision module.

[0097] In a specific embodiment of the method for detecting internal defects in the superimposed optical waveguide of the present invention, in step S180, the tilt angle of the vision module is adjusted so that the number of transition pixels at the black and white junctions of the four sides of the checkerboard is ≤3, indicating that the imaging surface of the vision module is parallel to the checkerboard plane (i.e., the parallelism error is ≤0.5°); then the X-axis and Y-axis are moved while the Z-axis remains stationary, so that the light from the altimeter is at the center of the checkerboard, and the altimeter is used to measure the height of the checkerboard. The fixing mechanism of the altimeter is adjusted so that the reading of the altimeter is 0. At this point, the coplanar calibration of the reference plane of the altimeter and the imaging surface of the high-precision telecentric lens is completed.

[0098] In a specific embodiment of the method for detecting internal defects in a composite optical waveguide of the present invention, step S200 includes the following steps:

[0099] S220: Use a height gauge to measure the optical signal reflected from the upper surface of the composite optical waveguide and obtain the reading C;

[0100] S250: Adjust the Z-axis to move C distance in the opposite direction to make the height gauge reading return to zero. At this time, the imaging plane of the vision module is located on the upper surface of the superimposed optical waveguide under test, so that the vision module automatically positions itself at the initial position Z1.

[0101] In a specific embodiment of the method for detecting internal defects in composite optical waveguides of the present invention, in step S220, the checkerboard pattern is replaced with the composite optical waveguide sample to be tested, and the light signal reflected from the upper surface of the composite optical waveguide sample to be tested is measured using a height meter to measure the height value reading C.

[0102] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, in step S250, adjusting the Z-axis to move a distance C in the opposite direction will make the height reading of the altimeter zero. At this time, the imaging plane of the high-precision telecentric lens is located on the upper surface of the composite optical waveguide sample. The Z-axis position at this time is recorded as the initial position Z1, so that the vision module automatically positions the initial position Z1 (i.e., the first longitudinal focusing position).

[0103] Beneficial technical effects: The initial position Z1 optical positioning method solves the problem of inaccurate positioning on the upper surface of transparent materials, with a positioning accuracy of ≤1μm, and establishes a reference plane for longitudinal step scanning. Zeroing with an altimeter replaces traditional focusing, converting optical plane matching into mechanical displacement and outputting the initial position Z1 coordinates. This step directly addresses the pain point of existing technologies being unable to quickly locate the upper surface of thick samples.

[0104] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, the vision module is a high-precision telecentric lens.

[0105] Beneficial technical effects: Using an altimeter to automatically locate the initial longitudinal position Z1 ensures that the imaging plane of the high-precision telecentric lens is located on the upper surface of the superimposed optical waveguide sample.

[0106] like Figure 2 As shown, focusing is achieved through Z-axis motion, with Z1 as the initial position and the product of the lens's depth of field L and the sample's refractive index n as the Z-axis step interval. When the customer's detection accuracy requirements differ, high-precision telecentric lenses with different magnifications can be used. For example, if the defect detection accuracy requirement is 4.8µm, a 2X telecentric lens can be used with a 65M camera; a pixel size of 3.2µm and a single-pixel accuracy of 1.6µm can meet the detection needs, with a measured depth of field of 500µm. For example, if the defect detection accuracy requirement is 32µm, a 0.5X telecentric lens can be used with a 65M camera; a pixel size of 3.2µm and a single-pixel accuracy of 6.4µm can meet the needs, with a measured depth of field of 1500µm. To ensure clear imaging of all defects in the Z-axis direction inside the superimposed waveguide sample during longitudinal step scanning and to maintain the continuity of the image set, according to optical principles, since the scanned area is the defect inside the superimposed waveguide, the optical path F = n × H, where n is the refractive index and H is the physical distance traveled by the light. Similarly, the equivalent depth of field when measuring the interior can be derived. The product of the lens depth of field L and the sample refractive index n, L×n, is the Z-axis step interval. This Z-axis step interval represents the equivalent depth of field. The correctness of this theory can be verified by actual machine measurements and calculations in specific embodiments. The number of Z-axis steps is h / (n×L), where h is the thickness of the composite waveguide sample under test. The lens depth of field L is generally provided by the lens supplier, but can also be measured. The sample refractive index n is provided by the customer.

[0107] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, in step S400, the step interval ΔZ is obtained based on the product of depth of field L and refractive index n.

[0108] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, in order to ensure that all internal defects in the composite optical waveguide sample are clearly imaged in the Z-axis direction during longitudinal step scanning and to ensure the continuity of the image set, according to optical principles, since the defects inside the composite optical waveguide are being scanned, the optical path F = n × H, where n is the refractive index and H is the physical distance traveled by the light.

[0109] In a specific embodiment of the method for detecting internal defects in a composite optical waveguide according to the present invention, to ensure that all internal defects of the composite optical waveguide sample are clearly imaged in the Z-axis direction during longitudinal step scanning and to ensure the continuity of the image set, the equivalent depth of field for measuring the interior is derived based on optical principles. The product of the lens depth of field L and the sample refractive index n, L×n, is the step interval ΔZ in the Z-axis direction. The step interval ΔZ in the Z-axis direction is the equivalent depth of field. The step interval ΔZ in the Z-axis direction is determined by the product of the lens depth of field L and the sample refractive index n (ΔZ = L×n), where L is the inherent depth of field parameter of the telecentric lens (provided by the supplier or measured), and n is the material refractive index of the composite optical waveguide sample to be tested (input by the user or measured). Assuming the sample thickness H is 15 mm, the refractive index n is 1.5, and the depth of field L of the 2X lens is 0.5 mm, then according to the optical path theory, the equivalent depth of field is L×n = 0.5 mm×1.5=0.75 mm, and the step interval for each Z-axis step is ΔZ=0.75 mm.

[0110] Beneficial Technical Effects: The Z-axis step interval ΔZ guides the subsequent stepping movement of the vision module in the Z-axis direction, ensuring accurate focusing on various positions inside the stacked optical waveguide during scanning and acquiring clear images. This solves the problem in existing technologies where the Z-axis step interval cannot be accurately determined, leading to inaccurate focusing and unclear image acquisition. The depth-of-field variation caused by refractive index during sample scanning is considered, ensuring both the continuity of sharpness between adjacent images and maintaining efficiency, thereby improving the accuracy and efficiency of defect detection. The physical depth of field L is converted into an equivalent depth of field through refractive index n. Input: Lens depth of field L provided by the supplier + sample refractive index n provided by the customer; Output: Z-axis step interval ΔZ. Z-axis positioning accuracy reaches 0.75 mm (example value), and longitudinal stepping scanning efficiency in the Z-axis direction is improved.

[0111] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, the number of steps m is proportional to both the thickness H of the composite optical waveguide and inversely proportional to the step interval ΔZ.

[0112] In a specific embodiment of the method for detecting internal defects in a composite optical waveguide according to the present invention, the number of steps along the Z-axis is m = H / ΔZ = H / (n×L) rounded up, where h is the thickness of the composite optical waveguide sample to be tested. Assuming the sample thickness H is 15 mm, the refractive index n is 1.5, and the depth of field L of the 2X lens is 0.5 mm, then according to optical path theory, the equivalent depth of field is L×n = 0.5 mm×1.5 = 0.75 mm. The step interval ΔZ for each step along the Z-axis is 0.75 mm. The Z-axis needs to move 15 mm / 0.75 mm = 20 times. Therefore, during the step scan, the vision module needs to move downwards 20 times along the Z-axis.

[0113] Beneficial technical effects: Calculation of the number of steps m: Automated layering is achieved through the formula H / (L×n), avoiding manual intervention and improving detection efficiency. Examples show that a 15 mm thick sample requires only 20 scans, reducing time compared to traditional methods. Full-layer scanning of a 50 mm thick sample is also possible.

[0114] In a specific embodiment of the method for detecting internal defects in the composite optical waveguide of the present invention, after step S600, the following step is further included:

[0115] Based on the collected internal defect maps of layers 1 to m, a defect information table is generated; the defect information table includes: defect number, defect location ID, defect depth, defect coordinate Z, defect coordinate X, defect coordinate Y, defect diameter, defect length, defect width, and defect type.

[0116] In a specific embodiment of the method for detecting internal defects in a composite optical waveguide of the present invention, in the above steps: based on the acquired internal defect images of layers 1 to m, a defect information table is generated; the defect information table includes: defect number, defect location ID, defect depth, defect coordinate Z, defect coordinate X, defect coordinate Y, defect diameter, defect length, defect width, and defect type. That is, the defect information table includes: the three-dimensional coordinates (X, Y, Z) of all defects, and the morphological parameters (length, width, diameter) of all defects.

[0117] Beneficial technical effects: It solves the quality traceability problem of laminated optical waveguides, allowing for the identification of internal defects at specific layers and their sizes. Defect types can also be clearly marked in the defect information table, such as whether they are pits or scratches on the glass itself, or whether they are dust, foreign matter, or excess adhesive between adjacent laminated glass layers.

[0118] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0119] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to the above embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0120] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0121] The above description is merely illustrative and is in no way intended to limit the invention, its application, or its uses. The broad teachings of this invention can be implemented in many forms. Therefore, while specific examples are included, the scope of the invention should not be limited thereto, as other modifications will become apparent upon examination of the drawings, description, and appended claims.

Claims

1. A method for detecting internal defects in a composite optical waveguide, characterized in that, Includes the following steps: S100: The reference plane of the altimeter and the imaging plane of the vision module are aligned on the same plane through optical calibration. S200: The vision module automatically positions itself at the initial position Z1 using a height measuring instrument; S300: The vision module focuses on the i-th longitudinal focus position at the X-axis and Y-axis positions and in the Z-axis direction, detects internal defects in the i-th layer of the stacked optical waveguide, and acquires an image of the internal defects in the i-th layer; where 1 ≤ i ≤ m; when i=1, the i-th longitudinal focus position is the initial position Z1; m is the number of steps; S400: The vision module focuses on the (i+1)th longitudinal focus position in the Z-axis direction at the X and Y axis positions, detects internal defects in the (i+1)th layer of the stacked optical waveguide, and acquires an internal defect map of the (i+1)th layer; wherein, for the internal defect map of the (i+1)th layer, the (i+1)th longitudinal focus position is the position where the (i+1)th longitudinal focus position moves downward along the Z-axis by one Z-axis step interval ΔZ from the ith longitudinal focus position, and the step interval ΔZ is obtained based on the product of depth of field L and refractive index n; S500: Continue iteratively executing step S400 by setting the updated i=i+1 until the vision module focuses on the final position Zm in the Z-axis direction, detects the internal defects of the m-th layer of the stacked optical waveguide, and acquires the internal defect map of the m-th layer; wherein, the final position Zm is the position accumulated from the initial position Z1 along the Z-axis by moving down along the Z-axis by m-1 Z-axis step intervals ΔZ. S600: Based on the acquired internal defect maps of layers 1 to m, a total map of the internal defect maps of the stacked optical waveguide layers 1 to m at the X-axis and Y-axis positions is generated by using a vertical image synthesis algorithm. The vertical image synthesis algorithm analyzes the sharpness or clarity of each pixel at different vertical focus positions and selects the vertical focus position with the highest sharpness as the depth value of that pixel.

2. The detection method according to claim 1, characterized in that, Step S600 includes the following steps: For the pixels of the acquired internal defect maps of each layer, analyze the sharpness at each longitudinal focus position; For the pixels of the internal defect map of each layer, the pixels of the internal defect map with the highest clarity are selected as the total number of pixels of the internal defect map of the stacked optical waveguide from the 1st to the mth layers. The total pixels of the internal defect maps of the stacked optical waveguides from the 1st to the mth layers are merged into a total map of the internal defect maps of the stacked optical waveguides from the 1st to the mth layers.

3. The detection method according to claim 1, characterized in that, Following step S600, the following steps are also included: S700: The vision module moves from the X-axis and Y-axis position to the next X-axis and Y-axis position using the XY motion platform; The vision module continues to execute steps S300-S600 at the next X-axis and Y-axis positions. After acquiring the overall image of the internal defects of the superimposed optical waveguide, it proceeds to step S700 until it obtains an atlas of overall images of the internal defects of the superimposed optical waveguide at all X-axis and Y-axis positions. S800: By using an image stitching algorithm, the image set of the overall map of the internal defects of the superimposed optical waveguide at all X-axis and Y-axis positions is stitched together to obtain a complete defect distribution map of the internal defects of the superimposed optical waveguide.

4. The detection method according to claim 1, characterized in that, Following step S400, the following steps are also included: Compare the X-axis pixel offset Δx and Y-axis pixel offset Δy of the internal defects in the (i+1)th layer of the stacked optical waveguide with those in the i-th layer of the stacked optical waveguide. The pixel equivalent δ of the vision module of the automatic detection device is multiplied by the X-axis pixel offset Δx and the Y-axis pixel offset Δy respectively to obtain the X-axis physical compensation amount Dx and the Y-axis physical compensation amount Dy. The vision module of the automatic detection device performs a reverse linear motion in the X-axis direction with a physical compensation amount of Dx, and a reverse linear motion in the Y-axis direction with a physical compensation amount of Dy.

5. The detection method according to claim 1, characterized in that, Step S100 includes the following steps: The vision module focuses on the upper surface of the checkerboard grid along the Z-axis; the X and Y axes are adjusted so that the exact center of the checkerboard grid is located at the exact center of the image acquired by the vision module. Adjust the tilt angle of the vision module so that its imaging surface is parallel to the checkerboard plane; adjust the X and Y axes so that the light from the altimeter is at the center of the checkerboard; use the altimeter to measure the height of the checkerboard; adjust the altimeter reading to zero so that the reference plane of the altimeter and the imaging plane of the vision module are on the same plane.

6. The detection method according to claim 1, characterized in that, Step S200 includes the following steps: The optical signal reflected from the upper surface of the composite optical waveguide is measured using a height gauge to obtain the reading C; Adjust the Z-axis to move a distance C in the opposite direction until the height gauge reading is zero. At this point, the imaging plane of the vision module is located on the upper surface of the superimposed optical waveguide under test, so that the vision module automatically positions itself at the initial position Z1.

7. The detection method according to claim 1, characterized in that, The number of steps m is directly proportional to the thickness H of the stacked optical waveguide and inversely proportional to the step interval ΔZ.

8. The detection method according to claim 1, characterized in that, Following step S600, the following steps are also included: Based on the collected internal defect maps of layers 1 to m, a defect information table is generated; the defect information table includes: defect number, defect location ID, defect depth, defect coordinate Z, defect coordinate X, defect coordinate Y, defect diameter, defect length, defect width, and defect type.

Images