A grating defect detection device and a detection method

Abstract

The present invention discloses a grating defect detection device and a detection method. Among them, the defect detection device includes a monochromatic light source module, an image acquisition module, an XZ two-dimensional displacement platform, a grating fixture module and a protective shell. The image acquisition module uses a CMOS camera and also includes high and low resolution optical lenses that can be replaced according to requirements; the XZ two-dimensional moving platform moves and scans the grating under control in the X-axis and Z-axis directions to achieve XZ plane scanning; the image acquisition module is electrically connected to the image processing module, and the size and defects of the obtained grating surface image are detected through image processing algorithms; the grating fixture module vertically fixes a large-size grating. Among them, the grating detection device adopts the principle of dark field imaging and a monochromatic light source, avoiding mirror imaging of the grating and the generation of colored light spots due to diffraction, and the mechanical structure is simple and compact, and can be modularly set according to the width of the workpiece to be measured. The present invention improves the accuracy and efficiency of detecting surface defects of large-size gratings.

Description

Technical Field

[0001] The present invention relates to the technical field of optical element detection, and particularly relates to a grating defect detection device and a detection method. Background Art

[0002] As an important device in modern optics, the detection of defects on the surface of large-size gratings has received more attention. At present, there are many studies on the defect detection of large-aperture optical elements, but there is almost no research on grating defect detection. The defects of large-size gratings generally come from the manufacturing process. First, due to uneven grinding of the substrate, scratches and pits will be left on the surface of the grating substrate. Secondly, in the subsequent processes of spin coating, exposure, development, coating, and etching, random distributed point defects will also be caused by factors such as the standardization of personnel operation, the use of operation media such as photoresist and developer, and the stability of the environment. The traditional method for detecting defects on large-size gratings is that an experienced master observes the surface of the large-size grating with the naked eye, finds the defects on the grating, and marks the positions and shapes of the found defects on paper according to a certain proportion. This method requires a long time for large-size gratings and it is difficult to move large-size gratings. Prolonged observation of the grating will cause eye fatigue, resulting in inaccurate marked positions and shapes, and the actual size of the defects cannot be marked. This method not only wastes manpower but also the drawn defect graphics may not be accurate. Summary of the Invention

[0003] The purpose of the present invention is to solve the above-mentioned defects in the prior art, and provide a grating defect detection device and a detection method to realize the detection of defects on the grating surface.

[0004] The first object of the present invention can be achieved by adopting the following technical solutions:

[0005] A grating defect detection device, the grating defect detection device includes a monochromatic light source module 10, an image acquisition module 20, an XZ two-dimensional displacement platform 30, a grating fixture module 40 and a protective shell 50. Among them, the monochromatic light source module 10 and the image acquisition module 20 are installed at the same height on the XZ two-dimensional displacement platform 30 at a certain interval; the XZ two-dimensional displacement platform drives the monochromatic light source module 10 and the image acquisition module 20 to scan the XZ plane; the grating fixture module 40 is placed parallel to the XZ two-dimensional displacement platform 30 at a certain interval directly opposite; the protective shell 50 wraps the monochromatic light source module 10, the image acquisition module 20, the XZ two-dimensional displacement platform 30 and the grating fixture module 40 in the cavity.

[0006] Further, the XZ two-dimensional displacement platform 30 includes a stage 31, an X moving axis 32, and a Z moving axis 33. The Z moving axis is vertically fixed on the X moving axis, the X moving axis is placed on a horizontal plane, and the stage 31 is mounted on the Z moving axis. The XZ two-dimensional displacement stage realizes the relative movement of the large-size grating and the image acquisition module, thereby scanning the entire surface of the grating.

[0007] Further, the monochromatic light source module 10 and the image acquisition module 20 are installed in parallel on the stage 31 of the XZ two-dimensional displacement platform 30 at a certain interval, and the monochromatic light source module 10 and the image acquisition module 20 are at the same horizontal height. The relative positions of the monochromatic light source module and the image acquisition module are maintained, which can ensure that each captured image is at the same position and illuminated by the same light source.

[0008] Further, the image acquisition module 20 includes a CMOS area array camera 21, an optical adapter backplane 22, a high-low resolution optical lens 23, and a two-degree-of-freedom pitching stage 24. Among them, the high-low resolution optical lens 23, the CMOS area array camera 21, the optical adapter backplane 22, and the two-degree-of-freedom pitching stage 24 are combined in sequence front and back. The image acquisition module can achieve focusing by rotating the high- and low-resolution optical lenses and adjusting the two-degree-of-freedom pitching stage to obtain a clear image of the grating surface.

[0009] Further, the monochromatic light source module 10 includes a light source fixing bracket 11, an LED monochromatic light source 12, and a collimating and beam-expanding lens 13. Among them, the collimating and beam-expanding lens 13, the LED monochromatic light source 12, and the light source fixing bracket 11 are combined in sequence front and back. The monochromatic light source module provides a monochromatic light spot with a certain area, which is incident on the grating surface at an angle of 45 degrees, so that the defective part can undergo diffuse reflection and enter the image acquisition module. At the same time, the provided monochromatic light spot can avoid diffraction on the grating to generate colored light spots, ensuring that an effective defective image can be captured.

[0010] Further, the grating fixture module 40 includes a base 41 and a top block 42. The grating fixture module 40 is placed in parallel at a certain interval directly opposite to the two-dimensional displacement platform 30. The grating fixture module can enable the large-size grating with weight to stand vertically and stably on the horizontal plane. And the distance from the XZ two-dimensional displacement platform can be adjusted so that the grating surface is within the clear acquisition range of the image acquisition module.

[0011] Further, the protective shell 60 is a rectangular parallelepiped metal shell lacking one face. The protective shell can effectively prevent external stray light from entering the device and provide a stable dark environment required for dark-field imaging, thereby ensuring the consistency of each captured image.

[0012] Another object of the present invention can be achieved by adopting the following technical solutions:

[0013] A detection method based on a grating defect detection device, the detection method comprising the following steps:

[0014] S1. First, fix the large-size grating to be measured on the grating fixture module 40 by adjusting the top block 42;

[0015] S2. By adjusting the starting point position of the stage 31 of the XZ two-dimensional displacement platform 30, make the center of the field of view area of the CMOS area array camera 21 fall on any corner of the large-size grating, and at the same time make the monochromatic light source module 10 obliquely incident on the center of the CMOS field of view area at a certain angle;

[0016] S3. Adjust the detection light intensity and spot size of the monochromatic light source module 10 to make the CMOS area array camera 21 receive a bright image, and at the same time adjust the high and low resolution optical lens 23 and the two-degree-of-freedom pitching platform 24 of the image acquisition module 20 to make the CMOS area array camera 21 capture a clear image;

[0017] S4. Perform an S-shaped scan of the large-size grating. After the CMOS area array camera 21 moves a certain distance and stops, capture an image, pause after completing one row, move the XZ two-dimensional displacement platform 30 a certain distance along the Z axis, and perform the scan of the next row. Repeat this process until the images of the entire grating are captured;

[0018] S5. Preprocess and feature splice the images of the large-size grating collected in step S4, and obtain the defect map on the surface of the large-size grating by performing defect detection algorithm operations on the spliced images.

[0019] The present invention has the following advantages and effects compared with the prior art:

[0020] The grating defect detection device disclosed by the present invention adopts the principle of dark field imaging and a monochromatic light source, avoids mirror imaging of the grating and the occurrence of colored light spots due to grating diffraction, and can clearly capture the defects on the surface of the grating. At the same time, the XZ two-dimensional displacement platform adopted drives the monochromatic light source module and the image acquisition module to scan the surface of the large-size grating in the XZ plane, which can avoid moving the large-weight grating. And the structure of the present invention is simple and compact, and can be modularly set according to the size of the grating to be measured. Compared with the traditional manual detection method, it saves manpower, realizes automation, can obtain a complete and clear grating surface defect map and defect calibration map, and improves the detection efficiency and accuracy at the same time. Description of the Drawings

[0021] The drawings described herein are used to provide a further understanding of the present invention, form a part of this application, and the schematic embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation to the present invention. In the drawings:

[0022] Figure 1It is a schematic structural diagram of the grating defect detection device disclosed by the present invention;

[0023] Figure 2 It is a schematic diagram of the grating defect detection disclosed by the present invention;

[0024] Figure 3 It is a schematic diagram of the image stitching effect diagram disclosed by the present invention;

[0025] Figure 4 It is the schematic principle diagram of the grating defect detection disclosed by the present invention;

[0026] Figure 5 It is a flowchart of the large-size grating defect detection method disclosed by the present invention;

[0027] Figure 6 It is a schematic diagram of the single-image effect during image acquisition in Embodiment 4 of the present invention;

[0028] Figure 7 It is the defect detection effect diagram of a single image in Embodiment 4 of the present invention;

[0029] Figure 8 It is a statistical chart of the number of grating defects in Embodiment 4 of the present invention;

[0030] Figure 9 It is a schematic diagram of feature defects less than 50μm in Embodiment 4 of the present invention;

[0031] Figure 10 It is a schematic diagram of feature defects of 50 - 100μm in Embodiment 4 of the present invention;

[0032] Figure 11 It is a schematic diagram of feature defects of 100 - 200μm in Embodiment 4 of the present invention;

[0033] Figure 12 It is a schematic diagram of feature defects of 200 - 500μm in Embodiment 4 of the present invention;

[0034] Figure 13 It is a schematic diagram of feature defects greater than 500μm in Embodiment 4 of the present invention. Detailed implementation manners

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] Embodiment 1

[0037] This embodiment discloses a specific grating defect detection device. Refer to Figure 1 , the grating defect detection device includes a monochromatic light source module 10, an image acquisition module 20, an XZ two-dimensional displacement platform 30, a grating fixture module 40, and a protective shell 50. The monochromatic light source module 10 and the image acquisition module 20 are fixed on the carrier stage of the two-dimensional displacement platform 30 through an adapter plate. By controlling the motor of the XZ two-dimensional displacement platform 30, the monochromatic light source module 10 and the image acquisition module 20 are driven to scan a large-size grating simultaneously, and defects on the surface of the grating are found and marked from the acquired images.

[0038] The connection relationships of the above components are as follows: The light source irradiation module 10 and the image acquisition module 20 are fixed on the same height of the carrier stage of the XZ two-dimensional displacement platform 30 through an adapter plate at a certain interval, and the grating fixture module 40 is placed directly opposite the XZ two-dimensional displacement platform 30.

[0039] Among them, the image acquisition module 20 includes a CMOS area array camera 21, an optical adapter backplane 22, a high and low resolution optical lens 23, and a two-degree-of-freedom pitching platform 24. The optical adapter backplane 22, the two-degree-of-freedom pitching platform 24, the CMOS camera 21, and the high and low resolution optical lens 23 are combined in sequence from front to back.

[0040] Among them, the CMOS area array camera 21 can slightly adjust the inclination angle of the CMOS area array camera 21 through the two-degree-of-freedom pitching platform 24, and adjust the focal length by rotating the high and low resolution optical lens 23, so that the CMOS area array camera can clearly collect the surface of the grating.

[0041] Among them, the monochromatic light source module 10 includes a light source fixing frame 11, a monochromatic light source 12, and a collimating and expanding lens 13. Among them, the collimating and expanding lens 13, the monochromatic light source 12, and the light source fixing frame 11 are combined in sequence from front to back. The monochromatic light source 12 can adjust the angle of the monochromatic light source incident on the grating and the size of the light spot incident on the surface of the grating through the light source fixing frame 11.

[0042] Among them, the protective shell 50 wraps the monochromatic light source module 10, the image acquisition module 20, the XZ two-dimensional displacement platform 30, and the grating fixture module 40 therein, providing the required dark environment for image acquisition. Figure 1 Only half of the protective shell 50 is shown.

[0043] Embodiment 2

[0044] Based on the grating defect detection device disclosed in the above Embodiment 1, this embodiment further discloses a detection method for the grating defect detection device. The detection method includes the following steps:

[0045] S1. First, fix the large-size grating to be measured on the grating fixture module by adjusting the top block;

[0046] S2. By adjusting the starting point position of the stage of the XZ two-dimensional displacement platform, the center of the field of view area of the CMOS area array camera is made to fall on any corner of the large-size grating, and at the same time, the monochromatic light source module is obliquely incident on the center of the CMOS field of view area at a certain angle;

[0047] S3. Adjust the detection light intensity and spot size of the monochromatic light source module 10 to make the CMOS area array camera 21 receive a bright image. At the same time, adjust the high- and low-resolution optical lenses and the two-degree-of-freedom pitching platform of the image acquisition module to make the CMOS area array camera capture a clear image;

[0048] S4. Perform an S-shaped scan of the large-size grating. After the CMOS area array camera moves a certain distance and stops, it captures an image. After pausing for one line, the XZ two-dimensional displacement platform moves a certain distance along the Z-axis to perform the scan of the next line. Repeat this process until the images of the entire grating are captured;

[0049] S5. Preprocess and perform feature stitching on the images of the large-size grating collected in step S4, and obtain the defect map on the surface of the large-size grating by operating the defect detection algorithm on the stitched images.

[0050] Embodiment 3

[0051] Based on the grating defect detection device and detection method disclosed in the above Embodiment 1 and 2, in this embodiment, a 170 mm × 170 mm large-size grating is first vertically placed on the grating fixture module, and the large-size grating is fixed on the grating fixture module by the adjustable screws on both sides of the grating fixture module. By controlling the XZ two-dimensional displacement platform, the movement of the stage of the XZ two-dimensional displacement platform is aligned to the upper left corner of the large-size grating, and the field of view size of the CMOS camera is adjusted to 20 mm × 20 mm, and at the same time, the CMOS camera is focused on the upper left corner of the grating. If the image is not in focus, adjust the high- and low-resolution optical lenses and the two-degree-of-freedom pitching platform to focus the CMOS camera.

[0052] Then set the movement parameters of the two-dimensional displacement platform and the acquisition parameters of the CMOS camera, so that after the stage of the two-dimensional displacement platform moves 15 mm horizontally to the right, the CMOS camera captures the first image. Next, in the same way as the first image acquisition, the two-dimensional displacement platform drives the CMOS camera to scan the entire large-size grating in an S shape while capturing a total of 81 images.

[0053] Finally, perform noise reduction and filtering processing on the 81 images captured, and then perform feature stitching of the images.

[0054] Embodiment 4

[0055] Based on the grating defect marking method and grating defect feature classification disclosed in the above-mentioned Embodiment 3, in this embodiment, defect detection is performed on a picture collected in Embodiment 3. Figure 5 It is a single image collected by a CMOS area array camera, with a field of view size of 20mm×20mm. It can be seen from the figure that there are no light spots due to light source problems, and the defects on the grating surface can be clearly seen. Figure 6 For Figure 5 The defect detection effect diagram of a single image of

[0056] Continuing to count the number of defects on the surfaces of two large-sized gratings, numbered 3 and 6 respectively, and classifying defects with different sizes and characteristics. First, the sizes of the defects are divided into 5 levels: <50um, 50 - 100um, 100 - 200um, 200 - 500um, and >500um. The number of defects gradually decreases according to different levels. The grating defects with a size less than 50um are mainly white circular defects and black circular defects; the grating defects with a size between 50um and 100um are mainly white circular defects and black circular defects; the grating defects with a size between 100um and 200um are mainly white circular defects, black circular defects, white irregular defects, and black linear defects; the defects between 200um and 500um are mainly black linear defects, white linear defects, white irregular defects, and black irregular defects. The defects with a size greater than 500um are black irregular defects and white linear defects.

[0057] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A grating defect detection device, characterized in that, The grating defect detection device includes a monochromatic light source module (10), an image acquisition module (20), an XZ two-dimensional displacement platform (30), a grating fixture module (40), and a protective housing (50). Among them, the monochromatic light source module (10) and the image acquisition module (20) are installed at the same height on the XZ two-dimensional displacement platform (30) at a certain interval; the XZ two-dimensional displacement platform drives the monochromatic light source module (10) and the image acquisition module (20) to scan the XZ plane; the grating fixture module (40) is placed in parallel at a certain interval directly opposite the XZ two-dimensional displacement platform (30); the protective housing (50) encloses the monochromatic light source module (10), the image acquisition module (20), the XZ two-dimensional displacement platform (30), and the grating fixture module (40) in a cavity; The monochromatic light source module (10) and the image acquisition module (20) are installed in parallel on the stage (31) of the XZ two-dimensional displacement platform (30) at a certain interval, and the monochromatic light source module (10) and the image acquisition module (20) are at the same horizontal height; The image acquisition module (20) includes a CMOS area array camera (21), an optical adapter backplane (22), a high-low resolution optical lens (23), and a two-degree-of-freedom pitching platform (24). Among them, the high-low resolution optical lens (23), the CMOS area array camera (21), the optical adapter backplane (22), and the two-degree-of-freedom pitching platform (24) are combined in sequence from front to back.

2. The grating defect detection device according to claim 1, characterized in that, The XZ two-dimensional displacement platform (30) includes a stage (31), an X moving axis (32), and a Z moving axis (33). The Z moving axis is vertically fixed on the X moving axis, the X moving axis is placed on a horizontal plane, and the stage (31) is installed on the Z moving axis.

3. The grating defect detection device according to claim 1, characterized in that, The monochromatic light source module (10) includes a light source fixing bracket (11), an LED monochromatic light source (12), and a collimating and beam expanding lens (13). Among them, the collimating and beam expanding lens (13), the LED monochromatic light source (12), and the light source fixing bracket (11) are combined in sequence from front to back.

4. The grating defect detection device according to claim 1 of the claims, characterized in that, The grating fixture module (40) includes a base (41) and a top block (42). The grating fixture module (40) is placed in parallel at a certain interval directly opposite the two-dimensional displacement platform (30).

5. A detection method for a grating defect detection device according to any one of claims 1 to 4, characterized in that, The detection method includes the following steps: S1. First, fix the large-size grating to be measured on the grating fixture module (40) by adjusting the top block (42); S2. By adjusting the starting point position of the stage (31) of the XZ two-dimensional displacement platform (30), make the center of the field of view area of the CMOS area array camera (21) fall on any corner of the large-size grating, and at the same time make the monochromatic light source module (10) obliquely incident on the center of the CMOS field of view area at a certain angle; S3. Adjust the detection light intensity and spot size of the monochromatic light source module (10) to make the CMOS area array camera (21) receive a bright image. At the same time, adjust the high-low resolution optical lens (23) and the two-degree-of-freedom pitching platform (24) of the image acquisition module (20) to make the CMOS area array camera (21) acquire a clear image; S4. Perform S-shaped scanning on a large-size grating. After the CMOS area array camera (21) moves a certain distance and stops, capture an image, pause after completing one row, move the XZ two-dimensional displacement platform (30) a certain distance along the Z-axis, and perform scanning for the next row. Repeat this process until the images of the entire grating are captured; S5. Preprocess and perform feature stitching on the images of the large-size grating collected in step S4, and obtain a defect map of the surface of the large-size grating by performing defect detection algorithm operations on the stitched images.

Images