KR100249597B1 - Apparatus for inspecting optical uniformity and method therefor - Google Patents

Abstract

The present invention provides an optical nonuniformity inspection device and an optical nonuniformity inspection method capable of automatically inspecting an optical nonuniformity of an object without variation.

The inspection object 100 is photographed by the CCD camera 17, and image data corresponding to the image of the inspection object 100 is output. By normalizing the image data, normalized image data is obtained. On the basis of the average value of the pixel values of the standardized image data, one or more sets of the first threshold value lower than the average value and the second threshold value higher than the average value are set. Pixels having a value lower than the first threshold of each pair and pixels having a value higher than the second threshold are extracted for each pair. The number of extracted pixels is counted for each group. The presence or absence of optical nonuniformity is determined based on the count value obtained for each pair.

Description

Optical nonuniformity inspection device and optical nonuniformity inspection method

The present invention relates to an optical nonuniformity inspection device and an optical nonuniformity inspection method for inspecting the presence or absence of optical nonuniformity such as nonuniformity of object concentration and nonuniformity of light transmittance.

Sheet-like objects such as shadow masks, display panels, films, and paper for color CRTs are manufactured to have a uniform or almost uniform concentration or transmittance. In the inspection step of such a sheet-like article, it is necessary to determine whether or not the produced sheet-like article has a non-uniformity of concentration or light transmittance.

For example, a shadow mask is manufactured by forming a large number of transmission holes almost periodically in a metal thin plate using the photo etching method. If there is a local dimension abnormality in the plurality of transmission holes, non-uniformity of light transmittance occurs in the shadow mask. The presence or absence of the nonuniformity of the light transmittance of such a shadow mask is normally judged by the inspection by the eye of an inspector.

In this case, even if it is a good quality shadow mask, the optical nonuniformity of the allowable range exists. The inspector determines whether the shadow mask is to be inspected by comparing the shadow mask to be inspected with the non-uniformity of the shadow mask of a good product that empirically recognizes the unevenness of the shadow mask while visually inspecting the shadow mask to be inspected.

Such determination of good faith requires a high degree of skill and considerable experience. In addition, even if the degree of skill and experience are almost the same, the judgment result of the couple may vary depending on the individual difference or the state of health of the inspector.

On the other hand, Japanese Patent Laid-Open No. 3-61805 discloses a two-dimensional nonuniform inspection device. In this inspection apparatus, the sample surface is photographed two-dimensionally, and the photographed data is converted into an intermediate level having a certain width, a level exceeding the intermediate level upward, and a level exceeding the intermediate level downward. 3 images are displayed.

According to the conventional inspection apparatus, it is easy to see the two-dimensional nonuniformity, but the final judgment as to whether or not the inspection object is good is left to the inspector, and the nonuniformity cannot be detected automatically. For this reason, even when the inspection apparatus is used, the determination of the acceptance is required to have a high level of skill and considerable experience, and the determination result of the acceptance may vary depending on the individual differences or the health conditions of the inspectors.

An object of the present invention is to provide an optical non-uniformity inspection apparatus and an optical non-uniformity inspection method that can automatically inspect the optical nonuniformity of an object without variation.

1 is a front view of an optical non-uniformity inspection device in one embodiment of the present invention,

2 is a block diagram showing the electrical configuration of the optical non-uniformity inspection device of FIG.

3 is a waveform diagram showing an example of normalization processing of image data;

4 is a flow chart showing a determination process of optical nonuniformity in the optical nonuniformity inspection apparatus of FIG. 1;

5 is a waveform diagram showing data processing in an optical nonuniformity determination process.

<Description of the reference numerals for the main parts of the drawings>

10 optical measuring device, 12 diffuser plate,

13 light source, 17 CCD camera,

20 data processing units, 22 image processing units,

100 Inspection Object.

(1) First invention

An optical nonuniformity inspecting apparatus according to the first invention is an optical nonuniformity inspecting apparatus for inspecting an optical nonuniformity of an object, and includes standardizing means, setting means, extraction means, counting means, and determining means.

The normalization means obtains normalized image data by standardizing image data corresponding to the image of the object. The setting means sets one set or more of the first threshold value lower than the average value and the second threshold value higher than the average value on the basis of the average value of the pixel values of the standardized image data obtained by the standardizing means. The extracting means extracts, for each group, pixels having a value lower than the first threshold value of each set and each pixel having a value higher than the second threshold value from the standardized image data obtained by the standardizing means. The counting means counts the number of pixels extracted by the extracting means for each pair. The judging means judges the presence or absence of optical nonuniformity on the basis of the count value obtained for each group by the counting means.

In the optical non-uniformity inspection apparatus according to the first invention, in the normalized image data, a pixel having a value lower than the first threshold and a pixel having a value higher than the second threshold are extracted for each pair, and The number is counted for each pair, and the presence or absence of optical nonuniformity is determined based on the count value. In this case, the count value represents an area of nonuniformity having a larger variation than the difference between the first threshold value and the second threshold value.

In this way, the presence or absence of the optical nonuniformity is determined based on the area of the nonuniformity having a variation width larger than the width determined by the first and second threshold values. In this case, by setting the first and second threshold values to arbitrary values, it is possible to detect nonuniformity having an arbitrary variation range. Therefore, it becomes possible to determine whether there exists an optical nonuniformity exceeding a predetermined standard automatically and without change with a high degree of freedom.

(2) second invention

In the optical non-uniformity inspection apparatus according to the second invention, in the configuration of the optical non-uniformity inspection apparatus according to the first invention, the setting means sets a plurality of sets of the first and second thresholds, and the determination means sets each set by the counting means. The weighted sum of the coefficient values obtained for each calculation is calculated, and the presence or absence of optical nonuniformity is determined by comparing the weighted sum with a determination reference value.

In this case, in calculating the weighted sum, by setting the weighting coefficient and the determination reference value given to the count value of each group to arbitrary values, it becomes possible to selectively detect the optical nonuniformity having an arbitrary variation width and an arbitrary magnitude.

(3) Third invention

The optical nonuniformity inspecting apparatus according to the third aspect of the present invention is the configuration of the optical nonuniformity inspecting apparatus according to the first or second aspect of the invention. It is further provided with an input means.

In this case, from input of image data corresponding to the image of the object to determination of the existence of optical nonuniformity is automatically performed.

(4) fourth invention

In the optical non-uniformity inspection apparatus according to the fourth invention, in the configuration of the optical non-uniformity inspection apparatus according to the first, second or third invention, the normalization means performs normalization by removing low frequency components from image data.

As a result, the low frequency component of the image data due to the property of the object and the low frequency component of the image data due to the optical system are eliminated, so that the determination of the presence or absence of optical nonuniformity is accurately performed.

(5) Fifth invention

An optical nonuniformity inspection method according to a fifth aspect of the invention is an optical nonuniformity inspection method for inspecting optical nonuniformity of an object, wherein the normalized image data is calculated by standardizing the image data corresponding to the image of the object, and the pixel of the calculated normalized image data. A first threshold value lower than the average value and a second threshold value higher than the average value are set by one or more sets on the basis of the average value of the values, and pixels having a value lower than the first threshold value of each set set in the calculated standardized image data Pixels having a value higher than the threshold of? Are extracted for each group, the number of extracted pixels is counted for each group, and the presence or absence of optical nonuniformity is determined based on the count value obtained for each group.

In the optical non-uniformity inspection method according to the fifth aspect of the present invention, in the normalized image data, a pixel having a value lower than the first threshold and a pixel having a value higher than the second threshold are extracted for each pair of pixels. The number is counted for each pair, and the presence or absence of optical nonuniformity is determined based on the count value. In this case, the count value represents an area of nonuniformity having a larger variation than the difference between the first threshold value and the second threshold value.

In this way, the presence or absence of the optical nonuniformity is determined based on the area of the nonuniformity having a variation width larger than the width determined by the first and second threshold values. In this case, by setting the first and second threshold values to arbitrary values, it is possible to detect nonuniformity having an arbitrary variation range. Therefore, it is possible to automatically determine whether there is an optical nonuniformity exceeding a certain criterion automatically and without change with a high degree of freedom.

(6) Sixth invention

In the optical nonuniformity inspection method according to the sixth invention, in the optical nonuniformity inspection method according to the fifth invention, a plurality of sets of first and second thresholds are set, the weighted sum of the coefficient values obtained for each group is calculated, and the weighted sum Is compared with a criterion for determining the presence or absence of optical nonuniformity.

In this case, in calculating the weighted sum, by setting the weighting coefficient and the determination reference value given to the count value of each group to arbitrary values, it becomes possible to selectively detect the optical nonuniformity having an arbitrary variation width and an arbitrary magnitude.

1 is a front view of an optical non-uniformity inspecting apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing an electrical configuration of the optical non-uniformity inspecting apparatus of FIG. 1.

The optical nonuniformity inspection apparatus of FIG. 1 is composed of an optical measurement apparatus 10 for photographing an inspection object to obtain image data, and a data processing apparatus 20 that performs various data processing based on the image data.

In the optical measuring device 10, a light source 13 is disposed on the surface plate 11, and a diffusion plate 12 made of glass or the like is provided above the light source 13. As the light source 13, a high frequency lighting type fluorescent lamp is used, for example. On the diffusion plate 12, as shown in FIG. 2, the mask plate 14 which has the opening part 14a is mounted, and the test | inspection object 100 is fixed on this mask plate 14. As shown in FIG. In addition, the following description demonstrates the case where the test | inspection object 100 is a shadow mask. In this case, the inspection object 100 has a transmission hole area 100a in the center portion.

The support arm 15 which stands upward is provided in the surface plate 11, and the camera holding member 16 is provided in this support arm 15 so that a movement to an up-down direction is possible. The camera holding member 16 is provided with a CCD camera 17 so as to be movable in the horizontal direction. Thereby, the CCD camera 17 can be moved up and down and left and right so that the inspection area | region of the inspection object 100 of various sizes and the imaging area of the CCD camera 17 may correspond.

The CCD camera 17 has a two-dimensional CCD (charge coupled device), and outputs a light and shade of an image as image data.

The data processing apparatus 20 includes a camera control apparatus 21 for controlling gain and shutter speed of the CCD camera 17, an image processing apparatus 22 for performing image processing described later, and a display for displaying an image ( 23).

As shown in FIG. 2, the light emitted from the light source 13 sequentially passes through the transmission holes of the diffusion plate 12 and the inspection object 100 and enters the CCD camera 17. In this case, the transmission hole area 100a of the inspection object 100 is positioned in the opening 14a of the mask plate 14. Therefore, the peripheral region of the through hole region 100a of the inspection object 100 is masked by the mask plate 14.

The CCD camera 17 outputs the image of the inspection object 100 as image data of multiple values. This image data is input to the image processing apparatus 22 through the camera control apparatus 21. FIG.

The image processing apparatus 22 includes a CPU (central processing unit) 31 which performs a determination process described later in accordance with a program stored in advance, a random access memory (RAM) for temporarily storing image data and other data. A main memory device 32, a keyboard 33 for inputting data and various instructions, an auxiliary storage device 34 for storing image data and other data, and a printer 35 for outputting test results. These are connected to each other via the bus line 36. In addition, the camera control device 21 and the display 23 are connected to the bus line 36.

In this embodiment, the CPU 31 constitutes the normalizing means, the setting means, the counting means, and the determining means, and the CCD camera 17 constitutes the image input means.

Next, the operation of the optical non-uniformity inspection device of FIG. 1 will be described with reference to FIGS. 3, 4, and 5. 3 is a waveform diagram showing an example of normalization processing of image data, FIG. 4 is a flowchart showing the determination processing of optical nonuniformity, and FIG. 5 is a waveform diagram showing the data processing in the determination processing of optical nonuniformity.

First, the inspection object 100 provided on the diffusion plate 12 of FIG. 1 is photographed by the CCD camera 17, and the image of the inspection object 100 is input. The CCD camera 17 transfers the image of the inspection object 100 to the image processing apparatus 22 as image data. The image processing apparatus 22 removes large variations (low frequency components) of image data due to the illumination characteristics of the light source 13, the optical characteristics of the lens system of the CCD camera 17, and the properties of the inspection object 100. Normalization processing is performed.

Fig. 3A shows the waveform of the image data output from the CCD camera 17, Fig. 3B shows the waveform of the smoothing data obtained by smoothing the image data, and Fig. 3C shows the normalization process. The waveform of the normalized data obtained is shown. In each waveform of FIG. 3, the horizontal axis corresponds to the pixel position, and the vertical axis corresponds to the pixel value.

In the normalization process of FIG. 3, the normalized image data D3 is obtained by dividing the image data D1 into the smoothing data D2. The standardized image data D3 thus obtained is stored in the main memory 32 and the auxiliary storage device 34 of the image processing device 22.

Next, the CPU 31 calculates an average value of the pixel values of the standardized image data, and sets one or more threshold values, respectively, up and down based on the average value. That is, at least one threshold is set at a level higher than the average value of the pixel values by a preset value, and at least one threshold is set at a level lower than the average value.

In this embodiment, as shown in Fig. 5A, two thresholds thH1 and thH2 are set at a level higher than the average value, and two thresholds thL1 and thL2 are set at a level lower than the average value. Here, thH2> thH1 and thL2> thL1. The thresholds thH1, thH2, thL1, and thL2 set in this way are stored in the main memory 32 and the auxiliary memory 34.

Hereinafter, the CPU 31 determines the optical nonuniformity shown in the flowchart of FIG. 4 based on the normalized image data stored in the main memory device 32 and the auxiliary memory device 34 and the threshold values thH1, thH2, thL1, thL2. The process is performed.

First, normalized image data and threshold values thH1, thH2, thL1, and thL2 stored in the main memory 32 or the auxiliary storage device 34 are read (step S1).

Next, in the standardized image data, a pixel having a value equal to or less than the threshold thL1 and a pixel having a value equal to or greater than the threshold thH1 are extracted, and the extracted pixel is referred to as the first region Ra (step S2). Specifically, as shown in Fig. 5B, the values of pixels having a threshold thL1 or lower value and a pixel having a threshold thH1 or higher value are replaced with "1", and the remaining pixel values are replaced with "0". do.

At this time, you may perform a predetermined noise removal process as needed. As the noise removal process, well-known means, such as shrinkage of a binary image, an expansion process, and a process of removing a small area element after labeling (labeling) to a closed area, are used.

Next, the number of pixels (pixel whose value is "1") of the 1st area | region Ra is counted, and a count value is set to A (step 3).

Next, in the standardized data, a pixel having a value equal to or less than the threshold thL2 and a pixel having a value equal to or greater than the threshold thH2 are extracted, and the extracted pixel is referred to as the second region Rb (step S4). Specifically, as shown in Fig. 5C, the values of pixels having a threshold thL2 or lower and pixels having a threshold thH2 or higher are replaced with "1" and the remaining pixels are replaced with "0". do. At this time, a predetermined noise removing process may be performed as necessary.

Next, the number of pixels (pixels whose value is "1") in the second region Rb is counted, and the count value is set to B (step S5).

Thereafter, the presence or absence of optical nonuniformity is determined based on the count values A and B (step S6). For example, as shown in the following equation, the weighted sum S of the count values A and B is calculated.

S = mA + mB ..... (1)

In the formula (1), m and n are weighting coefficients having an arbitrary value of 0 or more. The weighted sum S is compared with a predetermined criterion value, and when the weighted sum S is equal to or greater than the criterion value, the inspection object 100 is judged to be a defective product, and when the weighted sum S is smaller than the criterion value, the inspection is performed. The object 100 is determined to be good quality.

In this case, when the weighting factor m is set large, optical nonuniformity with a large area is selectively detected. When the weighting factor n is set high, optical nonuniformity with a large variation is selectively detected.

In addition, by passing the count value A and the count value B separately from the predetermined determination reference value, the quality of the inspection object 100 may be determined.

Finally, the determination result of both parts is displayed on the display 23 and output to the printer 35 (step S7).

In this way, in the optical nonuniformity inspection apparatus of this embodiment, the presence or absence of optical nonuniformity exceeding a predetermined standard is automatically determined without change.

In this optical nonuniformity inspection apparatus, the thresholds thH1, thH2, thL1, and thL2 are set to arbitrary values, and the judgment reference value is set to an arbitrary value to thereby set an optical nonuniformity of arbitrary variation and an arbitrary size. It is possible to detect selectively.

This makes it possible to selectively detect nonuniformities of different properties, such as optical nonuniformity having a small fluctuation range of the pixel value but a large change in area, and optical unevenness having a small fluctuation range of the pixel value.

Moreover, although two sets of thresholds are used in the said embodiment, three or more sets of thresholds may be used as needed, or only one set of thresholds may be used. In addition, when it is anticipated that the optical nonuniformity to be examined may exist in any one of contrast, the same value may be set to the some threshold value above and below the average value of a pixel value. In addition, the difference between the average value and the upper threshold value and the difference between the average value and the lower threshold value may be different.

In addition, when the inspection target area (transmission hole area 100a) exists in a part of the inspection object 100 as in the present embodiment, a threshold for setting the inspection object area is set in the standardized image data, and is larger than the threshold value. The mask process may be performed so that only the part having a value becomes an inspection object.

In the above embodiment, the case where the inspection object is a shadow mask has been described, but the optical non-uniformity inspection apparatus and the optical non-uniformity inspection method of the present invention include a nonuniformity in concentration of sheet-like objects such as a display panel, a film and paper, a nonuniformity in light transmittance, and the like. The same applies to the inspection of optical nonuniformity, and is also applicable to the inspection of two-dimensional nonuniformity of an arbitrary object without being limited to the sheet-like object.

According to the optical nonuniformity inspection apparatus which concerns on the 1st invention of this invention, the presence or absence of an optical nonuniformity is determined based on the area of the nonuniformity which has a fluctuation range larger than the width determined by the 1st and 2nd threshold value. In this case, by setting the first and second threshold values to arbitrary values, it is possible to detect nonuniformity having an arbitrary variation range. Therefore, it becomes possible to determine whether there exists an optical nonuniformity exceeding a predetermined standard automatically and without change with a high degree of freedom.

According to the optical non-uniformity inspection apparatus according to the second invention of the present invention, in calculating the weighted sum, the weighting coefficient and the determination reference value given to the coefficient value of each pair are set to arbitrary values, respectively, so as to have an optical variation having an arbitrary variation width and an arbitrary magnitude. It becomes possible to selectively detect the nonuniformity.

According to the optical nonuniformity inspection apparatus which concerns on the 3rd invention of this invention, it is automatically performed from input of image data corresponding to the image of a target to determination of the presence or absence of optical nonuniformity.

According to the optical nonuniformity inspection apparatus according to the fourth aspect of the present invention, since the low frequency component of the image data due to the property of the object and the low frequency component of the image data due to the optical system are removed, the presence or absence of optical nonuniformity is accurately determined.

According to the optical nonuniformity inspection method which concerns on the 5th invention of this invention, presence or absence of optical nonuniformity is determined based on the area of the nonuniformity which has a fluctuation range larger than the width determined by the 1st and 2nd threshold value. In this case, by setting the first and second threshold values to arbitrary values, it is possible to detect nonuniformity having an arbitrary variation range. Therefore, it is possible to automatically determine whether there is an optical nonuniformity exceeding a certain criterion automatically and without change with a high degree of freedom.

According to the optical non-uniformity inspection method according to the sixth invention of the present invention, in calculating the weighted sum, the weighting coefficient and the determination reference value given to the coefficient values of the respective sets are set to arbitrary values, respectively, so as to have an optical width having an arbitrary variation width and an arbitrary size. It becomes possible to selectively detect the nonuniformity.

Claims (6)

In the optical non-uniformity inspection device for inspecting the optical non-uniformity of the object, Standardization means for obtaining standardized image data by standardizing image data corresponding to an image of the object; Setting means for setting one or more sets of a first threshold value lower than the average value and a second threshold value higher than the average value on the basis of an average value of pixel values of standardized image data obtained by the standardizing means; Extraction means for extracting, for each pair of pixels having a value lower than the first threshold value of each set and each pixel having a value higher than the second threshold value, from the standardized image data obtained by the standardizing means, And counting means for counting the number of pixels extracted by said extracting means for each group, and determining means for determining the presence or absence of optical nonuniformity based on the count value obtained for each group by said counting means. Non-uniformity Inspection Device. According to claim 1, The setting means sets a plurality of sets of first and second thresholds, And said determining means calculates the weighted sum of the count values obtained for each group by said counting means, and determines the presence or absence of optical nonuniformity by comparing said weighted sum with a determination reference value. According to claim 1, And an image input means for capturing the object and inputting an image, and supplying the input image as image data to the normalization means. The method according to any one of claims 1 to 3, wherein And said normalization means performs normalization by removing low frequency components from said image data. In the optical nonuniformity inspection method for inspecting the optical nonuniformity of the object, Normalized image data is calculated by standardizing image data corresponding to the image of the object, On the basis of the average value of the calculated pixel values of the normalized image data, one or more sets of the first threshold value lower than the average value and the second threshold value higher than the average value are set. From the calculated normalized image data, a pixel having a value lower than the first threshold of each set and a pixel having a value higher than the second threshold are extracted for each pair, Counting the number of the extracted pixels for each pair, An optical nonuniformity inspection method comprising determining the presence or absence of optical nonuniformity on the basis of a count value obtained for each group. The method of claim 5, Set a plurality of first and second thresholds, Calculate the weighted sum of the coefficients obtained for each group, And determining the presence or absence of optical nonuniformity by comparing the weighted sum with a determination reference value.

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