CN110782456A - Light guide plate mesh point detection method based on digital image processing - Google Patents
Light guide plate mesh point detection method based on digital image processing Download PDFInfo
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- CN110782456A CN110782456A CN201911174177.2A CN201911174177A CN110782456A CN 110782456 A CN110782456 A CN 110782456A CN 201911174177 A CN201911174177 A CN 201911174177A CN 110782456 A CN110782456 A CN 110782456A
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- 238000012545 processing Methods 0.000 title claims abstract description 35
- 238000001514 detection method Methods 0.000 title claims abstract description 18
- 238000009826 distribution Methods 0.000 claims abstract description 16
- 230000005484 gravity Effects 0.000 claims abstract description 12
- 238000012937 correction Methods 0.000 claims abstract description 8
- 239000003960 organic solvent Substances 0.000 claims abstract description 7
- 239000011248 coating agent Substances 0.000 claims abstract description 6
- 238000000576 coating method Methods 0.000 claims abstract description 6
- 238000005260 corrosion Methods 0.000 claims abstract description 6
- 230000007797 corrosion Effects 0.000 claims abstract description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 13
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 12
- 238000005530 etching Methods 0.000 claims description 4
- 230000003628 erosive effect Effects 0.000 claims description 3
- 239000011259 mixed solution Substances 0.000 claims description 3
- 238000011426 transformation method Methods 0.000 claims description 2
- 238000010586 diagram Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000012780 transparent material Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000023077 detection of light stimulus Effects 0.000 description 1
- 238000005538 encapsulation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 231100000289 photo-effect Toxicity 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
Images
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/0002—Inspection of images, e.g. flaw detection
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- G06T5/80—
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/10—Segmentation; Edge detection
- G06T7/13—Edge detection
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/10—Segmentation; Edge detection
- G06T7/155—Segmentation; Edge detection involving morphological operators
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
- G06T2207/30108—Industrial image inspection
- G06T2207/30121—CRT, LCD or plasma display
Abstract
The invention discloses a light guide plate mesh point detection method based on digital image processing, which comprises the following steps: 1, coating ink or ink on the surface of the light guide plate with the screen dots, and removing the ink or ink at the non-screen dot positions on the surface of the light guide plate by using an organic solvent; 2, using a camera to collect an image of the surface of the light guide plate with the screen dots; 3, respectively and sequentially carrying out binarization processing and gray inversion on the image; 4, performing edge corrosion on light guide dots in the image; 5, perspective correction is carried out on the image; taking each light guide dot as a connected domain, and counting the pixel coordinates of the gravity center of each light guide dot; 7, converting the pixel coordinate of the gravity center of each light guide dot into an actual coordinate according to the actual size of the light guide plate and the pixel number occupied by the light guide plate in the perspective corrected picture; and 8, outputting the actual coordinate and the density distribution information. The invention realizes the rapid and accurate detection of the distribution of the light guide dots, and obtains the position information and the density distribution information of the dots.
Description
Technical Field
The invention relates to the technical field of light guide plate detection, in particular to a light guide plate mesh point detection method based on digital image processing.
Background
The light guide plate is an important component in the side-in type liquid crystal backlight, and converts the LED point light source into a surface light source by utilizing the function of destroying total reflection of light guide dots. The main performance indexes of the light guide plate include surface uniformity of light emission and conversion efficiency of light energy. Because the onboard display requires high brightness (>1000Nit), and works in an environment with strong vibration and a wide temperature range, the thickness of the light guide plate is limited by the encapsulation of high-light-efficiency and high-brightness LEDs and the position offset of the LEDs and the light guide plate caused by vibration and temperature, and the thickness of the light guide plate of the onboard display can be 3mm and 4 mm. The light guide plate mesh points are usually manufactured in the following three ways: ink printing, nanoimprint, and laser dotting. The dots of the light guide plate printed by the ink are easily abraded and shed off in the strong vibration process; the nanoimprint method requires the preparation of an imprint template in advance, but the imprint template is expensive, so the nanoimprint method is only suitable for mass production; therefore, under the condition that lots of airborne displays used in special environments are required and the quantity of the required displays in each lot is small, laser dotting is generally adopted, the mode is flexible in dot production, customized designs can be made for products with different sizes, and the diameter of the light guide dot is 0.2mm to 0.8 mm.
For the light guide dots prepared by laser dotting, because the size of the light guide dots is relatively large, the detection mode is to manually and visually detect whether the problems of missing dotting, excessive dotting and the like exist under strong light generally, and the distance and the appearance of the light guide dots can be measured by using a microscope or a 3D microscope with a scale. Because the light guide plate needs to output a uniform surface light source, and the uniformity of the surface brightness is closely related to the distribution of the mesh points of the light guide plate, the specific position information of the mesh points of the light guide plate cannot be obtained by manual detection. The microscope can be used to obtain the position information of the light guide plate such as the size of the mesh points, the spacing of the mesh points and the like, but because the mesh point density of different areas of the light guide plate is different, if the distribution information of all the areas is to be obtained, the microscope is required to be used for measuring the area by area, and the workload of testing and subsequent data processing is huge.
Disclosure of Invention
The embodiment of the invention aims to provide a light guide plate mesh point detection method based on digital image processing, which realizes the rapid and accurate detection of the distribution of light guide mesh points and obtains the position information and the density distribution information of the mesh points.
In order to achieve the above object, an embodiment of the present invention provides a light guide plate mesh point detection method based on digital image processing, where the light guide plate mesh point detection method based on digital image processing includes: step 1, coating ink or ink on the surface of a light guide plate with screen dots, and removing the ink or ink on the non-screen dots on the surface of the light guide plate by using an organic solvent so as to form gray contrast at the screen dots and the non-screen dots of the light guide plate; step 2, collecting the image of the surface of the light guide plate with the screen dots by using a camera, and transmitting the image to a computer; step 3, respectively and sequentially carrying out binarization processing and gray inversion on the acquired images in the computer; step 4, conducting edge corrosion on light guide dots in the image after gray inversion; step 5, performing perspective correction on the image with corroded edge; step 6, taking each light guide dot as a connected domain, and counting the pixel coordinates of the gravity center of each light guide dot; step 7, converting the pixel coordinate of the gravity center of each light guide dot into an actual coordinate according to the actual size of the light guide plate and the pixel number occupied by the light guide plate in the perspective corrected picture; and 8, outputting the actual coordinate and density distribution information of each light guide dot.
Preferably, the diameter of the detected light guide dot is 0.2mm to 0.8mm, and the morphology of the light guide dot is in a three-dimensional pit shape.
Preferably, the ink or the color of the ink is black or blue; the organic solvent is at least one of the following: ethanol, acetone, a mixed solution of ethanol and acetone.
Preferably, the camera is a CCD camera or a CMOS camera including a lens, wherein the resolution of the CCD camera or the CMOS camera is greater than 1280 × 1024.
Preferably, the binarization processing and the gradation inversion include: converting an image acquired by the camera into a black and white picture with only 0 and 1, wherein the image acquired by the camera is a color picture or a gray picture; and changing the pixel with the gray scale of 0 of the black-and-white picture into 1 and changing the pixel with the gray scale of 1 into 0.
Preferably, the edge etching is to perform gray inversion on edge pixels of light guide dots in the image after gray inversion.
Preferably, the perspective correction is performed by correcting a perspective distortion part of the image after the edge erosion, which is caused by the non-parallel object plane and image plane during the image acquisition, by a perspective transformation method.
Through the technical scheme, the light guide plate image of the end face where the light guide plate mesh points are located can be acquired, and through binarization processing, gray inversion, edge corrosion and perspective correction processing of the light guide plate image, compared with manual visual detection or detection by using a microscope, rapid and accurate detection of light guide mesh point distribution is realized, and position information and density distribution information of the mesh points are obtained.
Additional features and advantages of embodiments of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings:
FIG. 1 is a photograph of a light guide plate without ink;
FIG. 2 is a drawing of a light guide plate after ink coating, ink outside the dots, or ink removal;
FIG. 3 is a picture of a light guide plate with a dot surface captured by a camera and transmitted to a computer;
FIG. 4 is an image after binarization processing and gray scale inversion;
FIG. 5 is an image after edge erosion processing;
FIG. 6 is an image output based on the resulting dot center of gravity pixel coordinates;
FIG. 7 is a dot distribution diagram in real coordinates;
FIG. 8a is a txt format of the actual coordinates of each mesh point;
FIG. 8b is a diagram of the display effect of the dot density image;
fig. 9 is a flow chart illustrating a method for detecting dots of a light guide plate based on digital image processing according to the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating embodiments of the invention, are given by way of illustration and explanation only, not limitation.
The method for detecting the dots of the light guide plate will be described in detail below by taking an 8-inch light guide plate with a thickness of 4mm as an example. Fig. 9 is a flowchart of a light guide plate mesh point detection method based on digital image processing according to an embodiment.
As shown in fig. 9, the method for detecting dots of a light guide plate based on digital image processing includes:
s101, coating ink or ink on the surface of the light guide plate with the screen dots, and removing the ink or ink on the non-screen dots on the surface of the light guide plate by using an organic solvent so as to enable the screen dots and the non-screen dots of the light guide plate to form gray contrast.
The surface of the light guide plate with the screen dots is one side of the light guide plate, the surface comprises the screen dots and non-screen dots, the base material of the light guide plate is made of transparent materials, the image of the side face where the screen dots are located of the light guide plate is particularly shot through a photo for the convenience of viewing, and as shown in fig. 1, the screen dots and the non-screen dots are low in contrast and difficult to distinguish through the image clearly shown in fig. 1. Wherein the organic solvent may be ethanol (alcohol), acetone, or a mixed solution of ethanol and acetone. By applying ink or ink and removing the ink or ink on the non-dot positions, gray scale contrast can be formed between the dot positions and the non-dot positions of the light guide plate, as shown in fig. 2, so that subsequent processing is facilitated.
The ink or the ink is black or blue, and the substrate of the light guide plate is a transparent material, so that the dark color can be used for further distinguishing the mesh points and the non-mesh points of the light guide plate, in other words, the color of the end face where the preset color and the mesh points of the light guide plate are located is different from the color of the end face where the preset color and the mesh points of the light guide plate are located, and the chroma is preset so as to facilitate subsequent distinguishing.
And S102, acquiring an image of the surface of the light guide plate with the screen dots by using a camera, and transmitting the image to a computer.
The camera collects an image of the surface of the light guide plate with the screen dots as shown in fig. 3, the camera may be a CCD camera or a CMOS camera including a lens, and the resolution of the CCD camera or the CMOS camera is greater than 1280 × 1024, wherein the resolution may be used to improve the subsequent image processing capability. The image of the surface of the light guide plate with the dots acquired by the camera can be regarded as a picture obtained by performing graying processing and cutting on the image shown in fig. 2, wherein the cutting is to substantially remove the portion of the surface of the light guide plate with the dots, except for the light guide dot region.
And S103, respectively and sequentially carrying out binarization processing and gray inversion on the acquired images in the computer.
Fig. 4 is an effect diagram of an image photograph after binarization processing and gray scale inversion processing, where the binarization processing is specifically to convert the color image or gray scale image of the light guide plate into a black-and-white picture. In other words, a color picture or a grayscale picture of the light guide plate image is converted into a black-and-white picture having only "0" and "1". The gray inversion process is actually to perform gray inversion on each pixel of the black-and-white picture to obtain an inverted halftone dot image and an inverted non-halftone dot image. In other words, "0" of each pixel of the black-and-white picture is changed to "1", and "1" of each pixel is changed to "0".
And S104, performing edge corrosion on the light guide dots in the image after the gray inversion.
Fig. 5 is a photograph effect display diagram obtained by performing edge etching on the inverted dot images, where the edge etching is used to eliminate the possible interconnection between dots.
And S105, performing perspective correction on the image subjected to edge corrosion.
The perspective correction is configured to correct a perspective distortion region showing that an object plane and an image plane are not parallel in the gray-reversed dot image, so that perspective distortion caused by the fact that the object plane and the image plane are not parallel in image acquisition is eliminated.
And S106, taking each light guide dot as a connected domain, and counting the pixel coordinates of the gravity center of each light guide dot.
Taking each dot as a connected domain, and counting the pixel coordinates of the gravity center of each light guide plate dot, fig. 6 is an image display photo effect diagram of the pixel coordinates of the gravity center of each light guide plate dot. The number of pixels is used for subsequent determination.
And S107, converting the pixel coordinate of the gravity center of each light guide dot into an actual coordinate according to the actual size of the light guide plate and the number of pixels occupied by the light guide plate in the perspective-corrected picture.
In this embodiment, according to the actual size of the light guide plate and the number of pixels occupied by each dot, the corresponding relationship between each pixel and the actual size can be obtained, and since the actual size is known, the actual coordinate of each pixel point including the actual coordinate of the center-of-gravity pixel of each dot can be obtained based on the known actual size. The dot distribution plot in real coordinates is shown in fig. 7. The pixel number occupied by the light guide plate in the perspective corrected picture is actually the pixel number occupied by the whole area of the light guide plate in the perspective corrected picture.
And S108, outputting the actual coordinate and density distribution information of each light guide dot.
The actual coordinates of each dot are shown in fig. 8a, which shows the actual coordinates of the central pixel of each dot. The display effect of the dot density image is shown in fig. 8b, wherein the dots of the light guide plate are divided into 12 × 16 regions according to the requirement, the dot density of each region is obtained, and the image is formed. In fig. 8b, x is an abscissa for indicating a coordinate position in the lateral direction of the light guide plate, and y is an ordinate for indicating a coordinate position in the longitudinal direction of the light guide plate.
Through the embodiment of the invention, the contrast ratio of the dot region and the non-dot region can be increased by coating the paint with the preset color on the end face where the dots of the light guide plate are positioned, so that the subsequent image comparison can be more convenient, in addition, the actual coordinate of each gravity pixel coordinate can be conveniently determined according to the actual size and the number of pixels of the light guide plate through a series of subsequent image processing, and the dot density image is generated based on the actual coordinate, so that the invention can be applied to the rapid and accurate detection of the dot distribution of the light guide plate prepared by laser dotting.
The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (7)
1. A light guide plate mesh point detection method based on digital image processing is characterized by comprising the following steps:
step 1, coating ink or ink on the surface of a light guide plate with screen dots, and removing the ink or ink on the non-screen dots on the surface of the light guide plate by using an organic solvent so as to form gray contrast at the screen dots and the non-screen dots of the light guide plate;
step 2, collecting the image of the surface of the light guide plate with the screen dots by using a camera, and transmitting the image to a computer;
step 3, respectively and sequentially carrying out binarization processing and gray inversion on the acquired images in the computer;
step 4, conducting edge corrosion on light guide dots in the image after gray inversion;
step 5, performing perspective correction on the image with corroded edge;
step 6, taking each light guide dot as a connected domain, and counting the pixel coordinates of the gravity center of each light guide dot;
step 7, converting the pixel coordinate of the gravity center of each light guide dot into an actual coordinate according to the actual size of the light guide plate and the pixel number occupied by the light guide plate in the perspective corrected picture;
and 8, outputting the actual coordinate and density distribution information of each light guide dot.
2. The method for detecting the distribution of the dots of the light guide plate based on the digital image processing as claimed in claim 1, wherein the diameter of the detected light guide dots is 0.2mm to 0.8mm, and the morphology of the light guide dots is three-dimensional pit-shaped.
3. The method for detecting the dots of the light guide plate based on the digital image processing as claimed in claim 1, wherein the ink or the color of the ink is black or blue; the organic solvent is at least one of the following: ethanol, acetone, a mixed solution of ethanol and acetone.
4. The light guide plate mesh point detection method based on digital image processing according to claim 1, wherein the camera is a CCD camera or a CMOS camera including a lens, wherein the resolution of the CCD camera or the CMOS camera is greater than 1280 x 1024.
5. The method for detecting the halftone dots of the light guide plate based on the digital image processing as claimed in claim 1, wherein the binarization processing and the gray inversion comprise:
converting an image acquired by the camera into a black and white picture with only 0 and 1, wherein the image acquired by the camera is a color picture or a gray picture; and
and changing the pixel with the gray scale of 0 of the black-and-white picture into 1, and changing the pixel with the gray scale of 1 into 0.
6. The method for detecting the dots of the light guide plate based on the digital image processing as claimed in claim 1, wherein the edge etching is to perform gray inversion on the edge pixels of the light guide dots in the image after the gray inversion.
7. The method for detecting the halftone dots of the light guide plate based on the digital image processing as claimed in claim 1, wherein the perspective correction is performed by a perspective transformation method on a perspective distortion part of the image after the edge erosion, which is caused by the non-parallel object plane and image plane during the image acquisition.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112268663A (en) * | 2020-09-10 | 2021-01-26 | 杭州电子科技大学 | Machine vision soap bubble method air tightness inspection method |
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| US20050073543A1 (en) * | 2003-10-01 | 2005-04-07 | Canon Kabushiki Kaisha | Ink jet printing method, ink jet printing system, ink jet printing apparatus and control program |
| CN102878958A (en) * | 2012-09-28 | 2013-01-16 | 杭州电子科技大学 | Measuring method for printing dot area of lithographic printing |
| CN107527340A (en) * | 2017-08-25 | 2017-12-29 | 江南大学 | A kind of method of quick judge and optimization light guide plate luminous mass based on image processing techniques |
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- 2019-11-26 CN CN201911174177.2A patent/CN110782456B/en active Active
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|---|---|---|---|---|
| US20050073543A1 (en) * | 2003-10-01 | 2005-04-07 | Canon Kabushiki Kaisha | Ink jet printing method, ink jet printing system, ink jet printing apparatus and control program |
| CN102878958A (en) * | 2012-09-28 | 2013-01-16 | 杭州电子科技大学 | Measuring method for printing dot area of lithographic printing |
| CN107527340A (en) * | 2017-08-25 | 2017-12-29 | 江南大学 | A kind of method of quick judge and optimization light guide plate luminous mass based on image processing techniques |
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