JPH08254499A - Displaying/appearance inspection device - Google Patents

Abstract

PURPOSE: To provide a displaying/appearance inspection device which is to make parallel processing using a plurality of cameras and ensures a high reliability in the inspection accuracy to enable image processing in the condition that continuity is given in adjoining images by relieving the influence of the difference in the sensitivity between cameras and also individuality of the applicable illuminating system. CONSTITUTION: The standard image having a uniform reflectance is photographed by a plurality of cameras 10, and a low-period unevenness in the density of two images from adjoining cameras is corrected into a uniform lightness by a shading correction part 20. The overlapped parts of adjoining images are given the same density an offset adjusting part 30, and a coupling correction part 40 performs a weighting process to the densities of the adjoining images in their overlapped parts, and they are coupled together in a continuous image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display / appearance inspection apparatus for inspecting a display state of a liquid crystal display, and an appearance (copy quality) of a wafer pattern or copied paper.

[0002]

2. Description of the Related Art Conventionally, in a system for inspecting a display pattern of an object to be inspected or inspecting for scratches or stains on the appearance, the object to be inspected is magnified by an optical system in order to obtain a certain resolution. In general, a mechanism is provided to continuously capture local images of the object to be inspected and inspect each input inspection image.

However, with this method, it has been pointed out that the number of images to be inspected increases, and accordingly, the number of times of movement of the visual field by the feed mechanism increases, resulting in a longer inspection time. More specifically, it is as follows.

In the conventional display / appearance inspection, C
Due to the resolution of a CD camera, it has been common practice to use an image memory of 512 × 512 pixels. Therefore, 1
If you try to obtain a resolution of 1 μm pixel, the field of view is 512 μm
m, for example, when inspecting a 2 mm × 2 mm inspected object, image input / processing is required 16 times. Along with this, mechanical movement is required 16 times to move the field of view of the object to be inspected to the imaging position of the camera. In such a case, the image processing itself is completed in 0.1 to 0.5 seconds, while the feed mechanism system moves / moves once.
Vibration control / stopping takes about 1 second, which is a major obstacle to shortening the inspection time. Further, since the positioning with extremely high accuracy is required, the price of the feeding mechanism system is usually 2 to 4 times as large as the price of the image processing system.

[0005]

In order to solve the above problems, a method of parallel processing using a plurality of cameras is also conceivable. In this case, the movement of the mechanical system is omitted, so 1 /
It is possible to shorten the time by 10 to 1/2. Also, the price of the feeding mechanism system can be kept low.

However, since there is a difference in sensitivity of cameras used in parallel and a difference in optical system / illumination system, it is difficult to detect continuous display and pattern defects between cameras, and the processing becomes complicated. there were. Specifically, it is as follows.

6A and 6B show two cameras A,
The shading state of the grayscale image input by B is shown. Generally, an image input by a CCD camera is affected by individual differences in lens systems, differences due to illumination, and variations in sensitivity of CCD elements. Among these, the influence of the individual difference of the lens system and the difference due to the illumination results in a low-period density unevenness, and there is a tendency that the center is bright and the periphery is dark due to the characteristics of the lens system and general illumination. The result is as shown by the dotted line. On the other hand, since variations in the sensitivity of the CCD elements have a high period, the final shading of the input image has the form shown by the solid line in FIG.

By using a correction value ε obtained from the density value of the overlapping portion C of the visual field, the input image having different shading characteristics depending on the individual cameras is set to the shading state so that the average density value of the overlapping portion C becomes equal. to correct. This is the state of FIGS. 7 (a) and 7 (b). The correction value ε is represented by ε = average density value of overlapping portion of camera A / average density value of overlapping portion of camera B, and shading correction is performed so that ε = 1. And both cameras A and B
Images are actually combined at their overlapping portions C to obtain continuous images as shown in FIG. However, even if the average densities of both images in the combined portion are approximately the same, the low-frequency density change indicated by the broken line and the high-cycle density change indicated by the solid line both do not match, and a continuous image with good image quality is obtained. I can't.

The present invention was devised in view of such circumstances, and on the premise that parallel processing is performed by using a plurality of cameras, the influence of the difference between the cameras is mitigated and adjacent images are displayed. It is an object of the present invention to provide a display / appearance inspection device having a high inspection accuracy and capable of performing image processing in a continuous state.

[0010]

SUMMARY OF THE INVENTION A display / appearance inspection apparatus according to the present invention has a plurality of cameras and a low-cycle density unevenness of a standard image having a uniform reflectance taken by each camera and a uniform brightness. Shading correction unit, an offset adjustment unit that equalizes the density values in the overlapping portions of the images of the adjacent cameras that have been subjected to the shading correction, and the overlapping portion by weighting the density values of the adjacent images in the overlapping portion. And a combination correction unit that obtains continuous images.

Further, in the display / appearance inspection apparatus according to the present invention, a correction value obtained by integrating shading correction, offset adjustment, and connection correction is stored in a lookup table, and the table is referred to each camera input. It is characterized by that.

[0012]

In the above construction, since the images of the object to be inspected are simultaneously processed in parallel using a plurality of cameras,
The processing speed can be improved and the cost can be reduced as compared with the conventional example in which one camera is moved by the feed mechanism system. Then, even if there is a difference in sensitivity or a difference in illumination system among a plurality of cameras, the adjacent images can be correctly handled as overlapping images in the overlapping portion by the shading correction, the offset adjustment, and the joint correction.

If the total correction value is converted by referring to the table, the processing time can be further shortened.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a display / appearance inspection apparatus according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the schematic arrangement of the display / appearance inspection apparatus of the embodiment. In FIG. 1, 10 is a plurality of CCD cameras prepared according to the purpose, 20 is a shading correction unit that performs low-period shading correction on an image captured and sent by each camera 10, and 30 is each An offset adjustment unit that performs offset adjustment based on the data of the image overlapping portion in the camera 10, 40
Is a combination correction unit that performs combination correction to maintain the continuity of the combined portions of adjacent images, 50 is a combined image storage unit that combines and stores the images from each combination correction unit 40, and 60 is according to the purpose of the system. An image processing unit that performs a required process on the image data read from the composite image storage unit 50, and 70 is an overall control unit that integrally controls a series of processes of each unit.

An object having a uniform reflectance is prepared in advance, and the object is imaged by a plurality of cameras 10 arranged in a grid, and the image data for each camera 10 is sent to the shading correction section 20. . Each shading correction unit 20 performs shading correction for each camera in units of CCD pixels. Here, an image captured by camera A and an image captured by camera B that are adjacent to each other in the horizontal direction will be described. As shown in (a) and (b) of FIG. 2, in the grayscale data of the image by the camera A and the grayscale data of the image by the camera B, the low cycle indicated by the dotted line due to the influence of the individual difference of the lens system and the difference due to the illumination. The density unevenness occurs, and the center is bright and the periphery is dark. The levels of both grayscale data are different from each other. Therefore, shading correction is performed for cameras A and B based on equations (1) and (2), respectively.

[0017]

[Equation 1]

[0018]

[Equation 2]

This shading correction corrects the tendency of shading in which the center is bright and the periphery is dark as shown in FIGS. 3A and 3B, and both images have uniform low-cycle shading indicated by a dotted line. It becomes bright.
That is, both the density values AI _xy ′ and BI _xy ′ are constant over the entire width in the x direction.

Next, the shading-corrected image data is sent to the offset adjusting section 30.

The offset adjusting unit 30 has density values AI _xy ′ and BI _xy ′ of both cameras A and B in the overlapping portion C of the visual fields.
Are adjusted so that they become equal to each other as shown in (a) and (b) of FIG. In this offset adjustment, a correction value ε represented by ε = average density value of overlapping portion of camera A / average density value of overlapping portion of camera B is used to perform adjustment so that ε = 1.

By the shading correction shown in FIG. 3 and the offset adjustment shown in FIG. 4, the difference between the individual lens systems and the difference due to illumination are absorbed. However, variations in the sensitivity of CCD elements have not been completely absorbed. This is because unstable noise components due to power supply fluctuations are included in the sensitivity variations of the CCD elements. Therefore,
Strictly speaking, dark and light discontinuous lines appear on the boundary between the two images.

Therefore, the image data after the offset adjustment is sent to the combination correction unit 40. The combining correction unit 40 performs weighting processing based on the equation (3) on the overlapping portion C of the visual fields of the cameras A and B, and then combines the images of both cameras A and B at the overlapping portion C. A continuous image is obtained as shown in FIG.

[0024]

(Equation 3)

From this expression, for example, when the x-direction CCD pixel is at the left end of the overlapping portion C and x = x _C1 , the second term becomes 0, and from x _CN −x _C1 = N, the left end thereof becomes C
The density value at the CD pixel is I _xy = AI _xy ′. Also,
For example, if the x-direction CCD pixel is at the right end of the overlapping portion C,
When x = x _CN , the first term becomes 0, and x _CN −
From x _C1 = N, the density value at the CCD pixel at the right end is I
_xy = BI _xy '.

That is, the portion C where the CCD pixel positions overlap
The density value AI _xy ′ by the camera A is emphasized toward the left side of the image, and the density value B by the camera B is increased toward the right side.
I _xy ′ is emphasized.

By the above weighting processing, smooth continuous image combination is performed in a state where no discontinuous component is generated between the cameras A and B as shown in FIG.

Although the above description has been made with respect to the images of two arbitrary cameras A and B that are adjacent in the horizontal direction (x direction), this description is for any image that is adjacent in the vertical direction (y direction). The same applies to images from two cameras.

As described above, it is possible to input a wide-field image by a relatively simple process, and it is expected that the speed will be improved by 2 to 10 times compared with the conventional system. Further, since the expensive feeding mechanism system can be omitted by simply increasing the number of cameras, the cost can be reduced to about 1/2 to 1/4.

The above equations (1), (2), (3)
The correction is performed by capturing an image of a subject with a uniform reflectance prepared in advance, and the correction value is uniquely determined for each CCD element. The correction value for each element may be stored in the memory in the form of a look-up table, and an accurate density value may be obtained by referring to the table without performing actual calculation. In this case, since the time required for calculation can be shortened, real-time processing with camera input is also possible.

[0031]

According to the display / appearance inspection apparatus according to the present invention, the processing speed can be improved and the cost can be reduced as compared with the conventional example which requires the mechanism system for moving the camera, and the plurality of cameras can be used. Even if there is a difference in sensitivity or a difference in the illumination system, it is possible to process adjacent images as continuous images in the overlapping part by shading correction, offset adjustment, and joint correction, and increase the reliability of the inspection accuracy. can do.

Further, the processing time can be further shortened by converting the camera input from the total correction value by referring to the table.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a display / appearance inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a shading state of an image input by two cameras according to the embodiment.

FIG. 3 is a diagram showing a state in which low-period shading is corrected to uniform brightness in the embodiment.

FIG. 4 is a diagram showing a state in which offset adjustment is performed in the embodiment.

FIG. 5 is a diagram showing a state in which the density values of overlapping portions of both images are weighted in the embodiment to provide continuity.

FIG. 6 is a diagram showing a shading state of an image input by two cameras in a conventional example.

FIG. 7 is a diagram of an image in which shading correction is performed so that an average density value of an overlapping portion is the same in both images in a conventional example.

FIG. 8 is a diagram of an image in which images after shading correction of two cameras are combined in an overlapping portion in a conventional example.

[Explanation of symbols]

 10 ... Camera (CCD camera) 20 ... Shading correction unit 30 ... Offset adjustment unit 40 ... Combination correction unit 50 ... Composite image storage unit 60 ... Image processing unit 70 ... Overall control unit

Claims (3)

[Claims] 1. A plurality of cameras, a shading correction unit that corrects low-cycle density unevenness of a standard image captured by each camera to have uniform brightness, and the shading-corrected adjacent camera. An offset adjustment unit that equalizes the density values in the overlapping portions of the image, and a combining correction unit that weights the density values of the adjacent images in the overlapping portion to obtain continuous images in the overlapping portion. Characteristic display / appearance inspection device. 2. The display / appearance inspection apparatus according to claim 1, wherein shading correction by the shading correction unit and weighting processing by the combination correction unit are performed for each pixel unit of each camera. 3. A look-up table stores a correction value that is a combination of shading correction, offset adjustment, and combined correction, and the table is referred to each camera input. Display / appearance inspection device described in 2.