Internal defect detection method for folded light path lens

Abstract

The invention discloses a method for detecting internal defects of a folded optical path lens. The method comprises the following steps: driving a telecentric lens to move step by step in the vertical direction based on a Z-axis motion mode so as to focus the telecentric lens; step size is set, positions of a plurality of telecentric lenses are obtained, images of different positions of the folded optical path lens are collected based on the focused telecentric lenses, and a detection image set is obtained; obtaining a gray value of the detection image set to obtain gray value distribution information of different positions; performing definition detection on the detection image set, and analyzing the definition of the images at different positions; defect information is obtained based on gray value distribution information and definition of images at different positions, image acquisition of different layers of the lens by different depths of field is sequentially realized through a large-target-surface camera according to a stepping mode, defect positions and defect depths are analyzed according to image gray values, and defect types are accurately analyzed.

Description

Technical Field

[0001] The present invention relates to the field of defect detection technology, and more specifically, to a method for detecting internal defects of a folded light path lens. Background Art

[0002] Pancake Lens (folded optical path lens) is made up of multiple layers of products stacked together. The product diameter ranges from 20mm to 50mm, the thickest thickness can reach about 20mm, and the number of layers can reach up to 3. The film layer includes linear polarizer (LP), quarter phase retarder (QWP), half-reflective mirror (BS) and reflective polarizer, etc. During the stacking process, there may be defects such as dust, foreign matter, wrinkles, dents, etc. between adjacent lenses. The lens injection molded parts themselves may also have defects such as bubbles, white spots, black spots, etc.

[0003] Pancake Lens (folded optical path lens) is a key technology for making VR devices lighter and thinner. Due to its complex optical design, high-precision manufacturing process and high sensitivity of user experience, defect detection is necessary. Defect detection is also a core link to ensure optical performance, user experience and mass production economy.

[0004] Existing defect detection methods are difficult to accurately detect defects such as white spots, scratches, wrinkles, indentations, and pits. The defect location positioning is biased and the detection accuracy is low. Summary of the Invention

[0005] In order to solve at least one of the above technical problems, the present invention proposes a method for detecting internal defects of a folded light path lens.

[0006] A first aspect of the present invention provides a method for detecting internal defects of a folded light path lens, comprising the following steps:

[0007] S1, based on the Z-axis movement mode, drives the telecentric lens to move step by step in the vertical direction to focus the telecentric lens;

[0008] S2, setting the step size to obtain the positions of several telecentric lenses, collecting images of different positions of the folded optical path lens based on the focused telecentric lens to obtain a detection atlas;

[0009] S3, obtain the grayscale value of the detection atlas and obtain the grayscale value distribution information at different positions;

[0010] S4, performing clarity detection on the detection atlas and analyzing the clarity of images at different positions;

[0011] S5, obtaining defect information based on the grayscale value distribution information and the clarity of the image at different positions, wherein the defect information includes the defect position and the defect type.

[0012] In a preferred embodiment of the present invention, step S2 specifically includes:

[0013] The optical components for collecting images include a large-area camera, a telecentric lens, an auxiliary lens, and a collimated backlight source;

[0014] The collimated backlight emits collimated light, which is focused by the auxiliary lens and then diverged. The divergent conical light enters from the bottom of the folded optical path lens, penetrates the interior, and enters the telecentric lens and large-target camera from the top. The image containing defect information is obtained based on the large-target camera to obtain a detection atlas.

[0015] It should be noted that the auxiliary lens modulates the collimated light source into a conical divergent light source. This not only allows the detection of defects with depth information, such as wrinkles, indentations, and pits, which conventional backlight sources cannot detect with a pancake lens, but also provides a uniform image for the camera, facilitating defect detection. Using a conventional backlight directly would create a large bright spot in the center of the image, resulting in uneven illumination due to the pancake lens's converging effect. Defects with depth information would also be unable to be detected.

[0016] In a preferred embodiment of the present invention, step S2 specifically includes:

[0017] Set the step size, and set n acquisition positions along the vertical direction based on the step size, which are recorded as Z1, Z2, Z3...Zn;

[0018] Taking the Z1 position as the initial acquisition position, the large target area camera is controlled to move downward step by step, and the lens is imaged layer by layer to generate images at different positions and obtain a detection atlas.

[0019] It should be noted that the focus is adjusted by Z-axis movement, with Z1 as the initial position and the focus at the top of the Pancake Lens product. The depth of field of the lens is the Z-axis stepping interval, such as Figure 3 As shown, it moves downward step by step, collecting images at various positions, and finally collecting the bottom surface of the sample to obtain the Znth image; then the Z-direction image synthesis algorithm is used to detect the clarity of the images of each layer collected, detect the defects of the Pancake Lens product, and provide information such as the size, location, and type of the defects.

[0020] In a preferred embodiment of the present invention, the clarity detection method in step S4 is as follows:

[0021] Collect n pictures based on a large-area camera and calculate the grayscale value of each picture;

[0022] Compare the grayscale values of different images to obtain grayscale difference information;

[0023] Determine the location of the defect based on the grayscale difference information, use the Laplace variance method to traverse all images, calculate the edge strength of the detected defects, and obtain the variance value;

[0024] Analyze the depth information of defects based on the variance value.

[0025] In a preferred embodiment of the present invention, the defect type analysis method is as follows:

[0026] Get the roundness size of the defect and determine whether the defect is a point defect.

[0027] If it is a point defect, it is determined to be a point type defect, and the defect is analyzed to see if there are bubbles;

[0028] If bubbles exist, the grayscale difference information in the point defects is detected;

[0029] The regional dot features are analyzed based on the grayscale difference information, and the defects are analyzed as white spots or bubble defects according to the dot features.

[0030] In a preferred embodiment of the present invention, the defect type analysis further comprises: obtaining the aspect ratio of the defects for screening and classification, and comparing the aspect ratio of the detected defects with a set ratio;

[0031] If the aspect ratio of the detected defect is greater than the set ratio, it is determined to be a linear defect;

[0032] Analyze the location of linear defects and classify them into edge line defects and internal defects.

[0033] In a preferred embodiment of the present invention, the defect location analysis method is as follows:

[0034] The lens is photographed using a large-area camera to obtain a lens image. The center of the lens is used as the coordinate origin, the length of the lens is used as the X-axis, and the thickness of the lens is used as the Y-axis to establish a product coordinate system.

[0035] Convert the detected defect information into a coordinate system and unify it into the product coordinate system to obtain the defect location coordinates;

[0036] The position and number of defective pixels are analyzed based on the defect position coordinates to obtain the defect position and defect area.

[0037] The above technical solution of the present invention has the following advantages over the prior art:

[0038] This application uses a large-scale camera to capture images of different layers of the lens at different depths of field in a step-by-step manner, analyzes the defect position and depth based on the image grayscale value, and accurately analyzes the defect type. It can accurately analyze defect types such as white spots, scratches, wrinkles, indentations, pits, etc., and accurately locate the defect position. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific embodiments or the description of the prior art. Obviously, some of the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0040] Figure 1 2. This is a schematic diagram of the structure of a folded optical path lens according to an embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the positions of the camera and light source according to an embodiment of the present invention;

[0042] Figure 3 1 is a schematic diagram of step-by-step image acquisition according to an embodiment of the present invention;

[0043] Figure 4 It is a schematic diagram of constructing a product coordinate system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below in conjunction with specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0045] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may 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.

[0046] Example 1

[0047] See also Figure 1-Figure 4 As shown, the present invention proposes a method for detecting internal defects of a folded light path lens, comprising the following steps:

[0048] S1, based on the Z-axis movement mode, drives the telecentric lens to move step by step in the vertical direction to focus the telecentric lens;

[0049] S2, setting the step size to obtain the positions of several telecentric lenses, collecting images of different positions of the folded optical path lens based on the focused telecentric lens to obtain a detection atlas;

[0050] S3, obtain the grayscale value of the detection atlas and obtain the grayscale value distribution information at different positions;

[0051] S4, performing clarity detection on the detection atlas and analyzing the clarity of images at different positions;

[0052] S5, obtaining defect information based on the grayscale value distribution information and the clarity of the image at different positions, where the defect information includes the defect position and the defect type.

[0053] According to an embodiment of the present invention, step S2 specifically includes:

[0054] The optical components for collecting images include a large-area camera, a telecentric lens, an auxiliary lens, and a collimated backlight source;

[0055] The collimated backlight emits collimated light, which is focused by the auxiliary lens and then diverged. The divergent conical light enters from the bottom of the folded optical path lens, penetrates the interior, and enters the telecentric lens and large-target camera from the top. The image containing defect information is obtained based on the large-target camera to obtain a detection atlas.

[0056] According to an embodiment of the present invention, step S2 specifically includes:

[0057] Set the step size, and set n acquisition positions along the vertical direction based on the step size, which are recorded as Z1, Z2, Z3...Zn;

[0058] Taking the Z1 position as the initial acquisition position, the large target area camera is controlled to move downward step by step, and the lens is imaged layer by layer to generate images at different positions and obtain a detection atlas.

[0059] According to an embodiment of the present invention, the clarity detection method in step S4 is as follows:

[0060] Collect n pictures based on a large-area camera and calculate the grayscale value of each picture;

[0061] Compare the grayscale values of different images to obtain grayscale difference information;

[0062] Determine the location of the defect based on the grayscale difference information, use the Laplace variance method to traverse all images, calculate the edge strength of the detected defects, and obtain the variance value;

[0063] Analyze the depth information of defects based on the variance value.

[0064] According to an embodiment of the present invention, the defect type analysis method is as follows:

[0065] Get the roundness size of the defect and determine whether the defect is a point defect.

[0066] If it is a point defect, it is determined to be a point type defect, and the defect is analyzed to see if there are bubbles;

[0067] If bubbles exist, the grayscale difference information in the point defects is detected;

[0068] The regional dot features are analyzed based on the grayscale difference information, and the defects are analyzed as white spots or bubble defects according to the dot features.

[0069] According to an embodiment of the present invention, defect type analysis further includes: obtaining aspect ratios of defects for screening and classification, and comparing the aspect ratios of the detected defects with a set ratio;

[0070] If the aspect ratio of the detected defect is greater than the set ratio, it is determined to be a linear defect;

[0071] Analyze the location of linear defects and classify them into edge line defects and internal defects.

[0072] According to an embodiment of the present invention, the defect location analysis method is as follows:

[0073] The lens is photographed using a large-area camera to obtain a lens image. The center of the lens is used as the coordinate origin, the length of the lens is used as the X-axis, and the thickness of the lens is used as the Y-axis to establish a product coordinate system.

[0074] Convert the detected defect information into a coordinate system and unify it into the product coordinate system to obtain the defect location coordinates;

[0075] The position and number of defective pixels are analyzed based on the defect position coordinates to obtain the defect position and defect area.

[0076] To summarize, the present application uses a large-surface camera to capture images of different layers of the lens at different depths of field in a step-by-step manner, analyzes the defect position and depth based on the image grayscale value, and accurately analyzes the defect type. It can accurately analyze defect types such as white spots, scratches, wrinkles, indentations, pits, etc., and accurately locate the defect position.

[0077] Specifically, the present invention uses an auxiliary lens to modulate the light of the collimated light source into a conical divergent light source. This not only can detect defects with depth information such as wrinkles, indentations, and pits that conventional backlight sources cannot detect with pancake lenses, but also the image obtained by the camera is uniform, which is conducive to defect detection.

[0078] When the Pancake Lens samples to be tested have different sizes, the distance between the auxiliary lens and the lens is changed to change the size of the light diffused by the auxiliary lens to accommodate different sizes;

[0079] The embodiment of the present invention uses a large-area camera and a low-magnification, large-depth-of-field lens, and does not require XY axes or image stitching for Pancake Lens detection.

[0080] The Z-direction image synthesis algorithm included in the present invention can fuse multiple Z-direction images into an overall image according to a clarity algorithm, and mark defects in the overall image.

[0081] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, 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.

[0082] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present 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 present invention. Therefore, the present invention is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

[0083] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person 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 based on the scope of protection of the claims.

Claims

1. A method for detecting internal defects of a folded light path lens, characterized in that: The steps include: S1, based on the Z-axis movement mode, drives the telecentric lens to move step by step in the vertical direction to focus the telecentric lens; S2, setting the step size to obtain the positions of several telecentric lenses, collecting images of different positions of the folded optical path lens based on the focused telecentric lens to obtain a detection atlas; S3, obtain the grayscale value of the detection atlas and obtain the grayscale value distribution information at different positions; S4, performing clarity detection on the detection atlas and analyzing the clarity of images at different positions; S5, obtaining defect information based on the grayscale value distribution information and the clarity of the image at different positions, wherein the defect information includes the defect position and the defect type.

2. The method for detecting internal defects of a folded light path lens according to claim 1, wherein: Step S2 specifically includes: The optical components for collecting images include a large-area camera, a telecentric lens, an auxiliary lens, and a collimated backlight source; The collimated backlight emits collimated light, which is focused by the auxiliary lens and then diverged. The divergent conical light enters from the bottom of the folded optical path lens, penetrates the interior, and enters the telecentric lens and large-target camera from the top. The image containing defect information is obtained based on the large-target camera to obtain a detection atlas.

3. The method for detecting internal defects of a folded light path lens according to claim 2, wherein: Step S2 specifically includes: Set the step size, and set n acquisition positions along the vertical direction based on the step size, which are recorded as Z1, Z2, Z3...Zn; Taking the Z1 position as the initial acquisition position, the large target area camera is controlled to move downward step by step, and the lens is imaged layer by layer to generate images at different positions and obtain a detection atlas.

4. The method for detecting internal defects of a folded light path lens according to claim 1, wherein: The clarity detection method in step S4 is as follows: Collect n pictures based on a large-area camera and calculate the grayscale value of each picture; Compare the grayscale values of different images to obtain grayscale difference information; Determine the location of the defect based on the grayscale difference information, use the Laplace variance method to traverse all images, calculate the edge strength of the detected defects, and obtain the variance value; Analyze the depth information of defects based on the variance value.

5. The method for detecting internal defects of a folded light path lens according to claim 1, wherein: The defect type analysis method is as follows: Get the roundness size of the defect and determine whether the defect is a point defect. If it is a point defect, it is determined to be a point type defect, and the defect is analyzed to see if there are bubbles; If bubbles exist, the grayscale difference information in the point defects is detected; The regional dot features are analyzed based on the grayscale difference information, and the defects are analyzed as white spots or bubble defects according to the dot features.

6. The method for detecting internal defects of a folded light path lens according to claim 5, wherein: Defect type analysis also includes: obtaining the aspect ratio of defects for screening and classification, and comparing the aspect ratio of the detected defects with the set ratio; If the aspect ratio of the detected defect is greater than the set ratio, it is determined to be a linear defect; Analyze the location of linear defects and classify them into edge line defects and internal defects.

7. The method for detecting internal defects of a folded light path lens according to claim 6, wherein: The defect location analysis method is as follows: The lens is photographed using a large-area camera to obtain a lens image. The center of the lens is used as the coordinate origin, the length of the lens is used as the X-axis, and the thickness of the lens is used as the Y-axis to establish a product coordinate system. Convert the detected defect information into a coordinate system and unify it into the product coordinate system to obtain the defect location coordinates; The position and number of defective pixels are analyzed based on the defect position coordinates to obtain the defect position and defect area.

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