A method for distinguishing dust and real defects with high similarity

Abstract

The invention discloses a method for distinguishing dust and real defects with high similarity. A first positive image, a first negative image and a second image are obtained respectively by a positive vertical camera, a negative vertical camera and an oblique camera. When the grayscale gradients of the first positive image and the first negative image are different, it is determined to be a dust defect. When the grayscale gradients of the first positive image and the first negative image are the same, the second image is introduced. According to the first positive image and the second image, an affine transformation matrix is ​​determined. At the same time, a scaling operation is performed on the oblique camera to obtain a second scaled image. According to the affine transformation matrix, an affine transformation is performed on the second scaled image to obtain a registration image. A distance measurement data collection is formed by a positive infrared distance determination device and an oblique infrared distance determination device, and compared with the registration image. When the distance measurement data collection is consistent with the registration image, the location is a real defect, otherwise it is a dust defect. The invention has the advantages of realizing secondary judgment and distance determination judgment, and higher efficiency.

Description

Technical Field

[0001] The invention relates to the field of liquid crystal screen detection, in particular to a method for distinguishing dust and real defects with high similarity. Background Art

[0002] Liquid crystal display, abbreviated as LCD in English, is a type of flat panel display used for screen display of televisions and computers. LCD screens have the advantages of low power consumption, small size and low radiation, and are deeply loved by users. From top to bottom, the LCD screen is composed of TP glass, upper polarizer, first glass substrate, liquid crystal layer, second glass substrate, lower polarizer and backlight module. However, defects often occur in the liquid crystal layer of the LCD screen, causing users to see bad pixels in the playback picture when using the LCD screen, affecting the picture quality and resulting in poor viewing experience for users.

[0003] Visual inspection of LCD screen defects is an automatic inspection technology that uses a high-resolution industrial camera to collect images of the LCD screen, analyze the collected images, and determine whether the LCD screen has defects. During the visual inspection of LCD screen defects, it is necessary to be in a cleanroom with a cleanliness level of 10,000 to prevent dust from falling on the surface of the LCD screen. However, during the installation and movement of the LCD screen, a lot of dust may still fall on the surface. This dust is likely to be imaged in the collected images, and the dust may be easily judged as a defect in the subsequent image analysis, resulting in misjudgment.

[0004] In the prior art, the inspection method for LCD screens is to use an industrial camera. Under the premise of clear focus, the industrial camera is used to shoot the display status of the LCD screen when it is lit, and the display status is converted into an image. The image is then processed by a visual processing system to finally obtain a result of whether the LCD screen is good or bad. However, due to interference from the external environment, dust and other impurities are inevitably introduced into the LCD screen. Under conventional direct-view shooting conditions of industrial cameras, the imaging of dust and defects on the camera target surface is consistent and cannot be accurately distinguished, which interferes with the results of defect detection, such as causing over-detection and attributing dust to defects in the liquid crystal layer.

[0005] In order to reduce the possibility of dust on the surface of the LCD screen being misjudged as a defect during visual inspection, the conventional technical means is to use an auxiliary light source to pre-calibrate the dust position before inspection, and then filter the collected image according to the position of the dust, for example, removing abnormal points at the corresponding position of the dust in the image. However, during the assembly process of the LCD screen, the cover glass (CG glass) needs to be bonded to the upper polarizer or the screen. Dust is easily sandwiched between the CG glass and the upper polarizer, causing a bonding foreign body defect between the CG glass and the upper polarizer. This bonding foreign body defect will result in defective LCD screens, so visual inspection of the bonding foreign body defect is also required. Summary of the invention

[0006] Purpose of the invention: The purpose of the present invention is to address the deficiencies in the prior art and provide a method for distinguishing dust and real defects with high similarity.

[0007] Technical solution: The present invention discloses a method for distinguishing dust and real defects with high similarity, comprising the following steps: obtaining a first positive image of a liquid crystal screen to be tested by a positive vertical camera, and obtaining a second image of the liquid crystal screen to be tested by a tilted camera; setting up a negative vertical camera with the same height as the positive vertical camera and coaxial with the positive vertical camera on a side of the liquid crystal screen to be tested opposite to the positive vertical camera, and obtaining a first negative image by the negative vertical camera;

[0008] Firstly, the grayscale gradients of the first positive image and the first negative image are compared, and when the grayscale gradients are different, it is determined that the defect is a dust defect;

[0009] When the grayscale gradient of the first positive image is the same as that of the first negative image, introducing the second image;

[0010] Determine an affine transformation matrix according to the first positive image and the second image, perform a scaling operation on the tilted camera at the same time to obtain a second scaled image, and perform an affine transformation on the second scaled image according to the affine transformation matrix to obtain a registered image;

[0011] Record the height parameters of the forward vertical camera and the angle and height parameters of the oblique camera, move the forward vertical camera and the oblique camera away, introduce the forward infrared distance-determining device and the oblique infrared distance-determining device according to the height parameters of the forward vertical camera and the angle and height parameters of the oblique camera, then take the defect point position as the center point, keep the shooting point of the oblique infrared distance-determining device coincident with the center point, keep the incident radius unchanged, linearly change the incident angle of the oblique infrared distance-determining device, and obtain continuously changing distance measurement data;

[0012] The distance data of the forward infrared distance measuring device and the inclined infrared distance measuring device are integrated to form a distance measuring data collection, which is compared with the registration image. When the distance measuring data collection is consistent with the registration image, the location is a real defect, otherwise it is a dust defect.

[0013] Preferably, there are multiple tilted cameras.

[0014] Preferably, there are four tilted cameras, and the four tilted cameras are arranged to be equidistant from the center point and equidistant from the circumference.

[0015] Preferably, a movable closed shading plate is provided between the positive vertical camera and the negative vertical camera and the LCD screen to be tested.

[0016] Compared with the prior art, the present invention has the following beneficial effects: by introducing a negative vertical camera, a grayscale gradient comparison between the first positive image and the first negative image is realized, and when the dust defect is more obvious, a one-step judgment can be achieved, which simplifies the subsequent steps. At the same time, a distance measurement data collection consisting of the distance data of the positive infrared distance-fixing device and the inclined infrared distance-fixing device is introduced, and a more intuitive distance judgment is used to replace the point-by-point comparison judgment, which effectively improves the measurement efficiency, realizes secondary judgment and distance judgment, and is more efficient. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0019] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0020] The technical solution of the present invention is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0021] Embodiment 1: A method for distinguishing dust and real defects with high similarity, comprising the following steps: obtaining a first positive image of a liquid crystal screen to be tested by a positive vertical camera, and obtaining a second image of the liquid crystal screen to be tested by a tilted camera; setting up a negative vertical camera with a height equal to that of the positive vertical camera and coaxial with the positive vertical camera on a side of the liquid crystal screen to be tested opposite to the positive vertical camera, and obtaining a first negative image by the negative vertical camera;

[0022] Firstly, the grayscale gradients of the first positive image and the first negative image are compared, and when the grayscale gradients are different, it is determined that the defect is a dust defect;

[0023] When the grayscale gradient of the first positive image is the same as that of the first negative image, introducing the second image;

[0024] Determine an affine transformation matrix according to the first positive image and the second image, perform a scaling operation on the tilted camera at the same time to obtain a second scaled image, and perform an affine transformation on the second scaled image according to the affine transformation matrix to obtain a registered image;

[0025] Record the height parameters of the forward vertical camera and the angle and height parameters of the oblique camera, move the forward vertical camera and the oblique camera away, introduce the forward infrared distance-determining device and the oblique infrared distance-determining device according to the height parameters of the forward vertical camera and the angle and height parameters of the oblique camera, then take the defect point position as the center point, keep the shooting point of the oblique infrared distance-determining device coincident with the center point, keep the incident radius unchanged, linearly change the incident angle of the oblique infrared distance-determining device, and obtain continuously changing distance measurement data;

[0026] The distance data of the forward infrared distance measuring device and the inclined infrared distance measuring device are integrated to form a distance measuring data collection, which is compared with the registration image. When the distance measuring data collection is consistent with the registration image, the location is a real defect, otherwise it is a dust defect.

[0027] The advantage of this technical solution is that by introducing a negative vertical camera, a grayscale gradient comparison between the first positive image and the first negative image is achieved. When dust defects are more obvious, a one-step judgment can be achieved, which simplifies the subsequent steps. At the same time, a distance measurement data collection consisting of the distance data of the positive infrared distance device and the inclined infrared distance device is introduced, and a more intuitive distance judgment replaces the point-by-point comparison judgment, which effectively improves the measurement efficiency, realizes secondary judgment and distance judgment, and is more efficient.

[0028] In a specific implementation, a plurality of tilt cameras are provided, specifically, four tilt cameras are provided, and the four tilt cameras are arranged to be equidistant from the center point and evenly spaced from the circumference. The four tilt cameras can obtain four registration images, and there are four reference marking points when comparing the subsequent ranging data collection with the registration image, which further reduces the comparison time and improves the comparison efficiency.

[0029] A movable closed shading plate is provided between the positive vertical camera, the negative vertical camera and the LCD screen to be tested. The movable closed shading plate is provided to avoid mutual interference between the positive vertical camera and the negative vertical camera when sampling the first positive image and the first negative image.

[0030] In the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first feature is in direct contact with the second feature, or the first feature and the second feature are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature. In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example.

[0031] Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples without contradicting each other.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for distinguishing dust and real defects with high similarity, characterized by: The following steps are involved: A first positive image of the LCD screen to be tested is obtained by a positive vertical camera, and a second image of the LCD screen to be tested is obtained by a tilted camera; a negative vertical camera with a height equal to that of the positive vertical camera and coaxial with the positive vertical camera is set up on a side of the LCD screen to be tested opposite to the positive vertical camera, and a first negative image is obtained by the negative vertical camera; Firstly, the grayscale gradients of the first positive image and the first negative image are compared, and when the grayscale gradients are different, it is determined that the defect is a dust defect; When the grayscale gradient of the first positive image is the same as that of the first negative image, introducing the second image; Determine an affine transformation matrix according to the first positive image and the second image, perform a scaling operation on the tilted camera at the same time to obtain a second scaled image, and perform an affine transformation on the second scaled image according to the affine transformation matrix to obtain a registered image; Record the height parameters of the forward vertical camera and the angle and height parameters of the oblique camera, move the forward vertical camera and the oblique camera away, introduce the forward infrared distance-determining device and the oblique infrared distance-determining device according to the height parameters of the forward vertical camera and the angle and height parameters of the oblique camera, then take the defect point position as the center point, keep the shooting point of the oblique infrared distance-determining device coincident with the center point, keep the incident radius unchanged, linearly change the incident angle of the oblique infrared distance-determining device, and obtain continuously changing distance measurement data; The distance data of the forward infrared distance measuring device and the inclined infrared distance measuring device are integrated to form a distance measuring data collection, which is compared with the registration image. When the distance measuring data collection is consistent with the registration image, the location is a real defect, otherwise it is a dust defect.

2. A method for distinguishing dust and real defects with high similarity according to claim 1, characterized in that: The tilted camera is provided in plurality.

3. A method for distinguishing dust and real defects with high similarity according to claim 2, characterized in that: There are four tilted cameras, and the four tilted cameras are arranged to be equidistant from the center point and equidistant from the circumference.

4. The method for distinguishing dust and real defects with high similarity according to claim 1, characterized in that: A movable closed shading plate is provided between the positive vertical camera, the negative vertical camera and the liquid crystal screen to be tested.