JP3274255B2 - Defect detection method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting a defect of an inspection object arranged at a predetermined pitch.

[0002]

2. Description of the Related Art Conventionally, in a shadow mask of a color CRT, an abnormal shape of a hole through which an electron beam passes with respect to a fluorescent screen, a hole is not formed in a place where it should be formed, or a hole is originally formed. There may be a case where a defect such as a hole is made in a place where it should not be made.

[0003] This defect is detected by a defect detection device including a line sensor or area sensor, an image processing device, and the like. In this defect detection device, it is determined whether or not the luminance information for each pixel obtained by imaging the inspection target with the line sensor or the area sensor is within a predetermined range. are doing.

[0004]

However, in the conventional defect detection apparatus, when the diameter of the hole of the shadow mask is small or the abnormal shape of the hole is small, the luminance information obtained by the line sensor or the area sensor is a predetermined value. However, there is a problem that a defect cannot be detected simply by determining whether the defect is within the range.

The present invention has been made in view of the above circumstances, and an object of the present invention is to perform highly accurate defect detection by emphasizing a defect of an inspection object such as a hole of a shadow mask on an image. It is to provide a possible defect detection method and device.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to an inspection object including an area composed of a plurality of inspection objects arranged at a predetermined pitch and including the inspection object. In the defect detection method for detecting defects in the
A step of obtaining the luminance information of each of a plurality of pixels arranged in a two-dimensional array by imaging the object to be inspected by a sensor; and determining the luminance information of each pixel obtained by the sensor in a vertical and horizontal direction corresponding to the pitch. A luminance information adding step of dividing a pixel into a lattice of pixel matrices, adding luminance information of each pixel in each lattice to obtain a luminance addition value for each lattice, and a change amount of the luminance addition value between lattices Is calculated for each of the horizontal direction and the vertical direction, and a detection step of detecting as a defect when the horizontal change amount and the vertical change amount are larger than predetermined values.

[0007] Further, the invention is characterized in that the sensor is a line sensor or an area sensor.

[0008] Further, the change amount calculating step includes N (m) rows and m columns (m (m)) around a luminance addition value of an arbitrary grid.
× n), the horizontal change amount and the vertical change amount are obtained by using a first horizontal coefficient table and a vertical second coefficient table which are set in advance. It is characterized by a change amount calculating step.

An apparatus for detecting a defect in an inspection object including an inspection object, wherein the inspection area includes a plurality of inspection objects arranged at a predetermined pitch. And a sensor that obtains luminance information for each of a plurality of pixels arranged two-dimensionally and a grid composed of a predetermined number of vertical and horizontal pixel matrices each corresponding to the pitch of the luminance information for each pixel obtained by the sensor. A luminance information adding unit that divides and adds the luminance information of each pixel in each lattice to obtain a luminance addition value for each lattice, and calculates a change amount of the luminance addition value between each lattice in the horizontal direction and the vertical direction, respectively. , And a detection unit that detects a defect when the horizontal change amount and the vertical change amount are larger than predetermined values.

Further, the sensor is a line sensor or an area sensor.

[0011] Further, the change amount calculating section includes N (m.times.m.times.m) rows of m rows and n columns around a luminance addition value of an arbitrary grid.
n), using a first horizontal coefficient table and a second vertical coefficient table, which are set in advance, to determine a horizontal change amount and a vertical change amount. It is characterized in that it is a quantity calculation unit.

[0012]

According to the above construction, the luminance information adding section divides the luminance information for each pixel obtained by the sensor into a grid consisting of a predetermined number of vertical and horizontal pixel matrices corresponding to the pitch of the inspection object. (The luminance information adding step). Then, the change amount calculation unit obtains the change amount of the luminance added value between the respective lattices in each of the horizontal direction and the vertical direction (change amount calculation step). Thereafter, when the obtained horizontal change amount and vertical change amount are larger than a predetermined amount, the detection unit detects the defect (detection step).

[0013]

FIG. 1 is a block diagram showing an embodiment of a defect detection apparatus according to the present invention, in which an area sensor is used as a sensor. In this embodiment, a CRT as shown in FIG.
A case where a defect in a hole of a shadow mask for use is detected will be described as an example. Here, for convenience of description and drawings, the hole portion is inverted to black and the other portions are inverted to white.

As shown in FIG. 1, the defect detecting device 1 includes an area sensor 3, a luminance information adding unit 5, a change amount calculating unit 7,
, A detection unit 9 and a display unit 11.

The area sensor 3 picks up an image of a shadow mask (hereinafter referred to as an inspection object) composed of a plurality of holes (hereinafter referred to as an inspection object) arranged at a predetermined pitch shown in FIG. The luminance information for each of the plurality of pixels is obtained.

The luminance information adding section 5 divides the luminance information of each pixel obtained by the area sensor 3 into a lattice as shown in FIG. 3, which is composed of a predetermined pixel matrix corresponding to the pitch of the inspection object. The luminance information of each pixel in the grid is added to obtain a luminance added value for each grid.

The change amount calculating section 7 calculates the horizontal change amount and the vertical change amount of the luminance addition value between each grid in three rows and three rows.
Find in a matrix of columns.

The detecting section 9 detects a defect of the inspection object based on the vertical change amount obtained by the change amount calculating section 7 and the horizontal change amount.

The display section 11 displays the vertical change amount and the horizontal change amount obtained by the change amount calculating section 7. In addition, the luminance information for each pixel obtained by the area sensor 3 and the luminance addition value for each grid added by the luminance information addition unit 5 are displayed.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. In this case, as shown in FIG. 2, a shadow mask having a defect at the center is to be inspected.

First, an image of an object to be inspected is taken by the area sensor 3, and luminance information for each pixel whose luminance is represented by 256 tones from 0 to 255 is obtained (step ST1). When the luminance information on the line shown in FIG. 2 is displayed on the screen, it becomes as shown in FIG.

When the luminance information for each pixel is obtained, the luminance information adding section 5 divides the luminance information into a lattice as shown in FIG. 3, which is composed of a predetermined pixel matrix corresponding to the pitch of the inspection object. The luminance information of each pixel in the grid is added to obtain a luminance added value for each grid. (Steps ST3 and ST
5). Here, 27 pixels vertically and 44 pixels horizontally surrounding two holes
Although the pixel is divided into pixel grids, the present invention is not limited to this, and the dividing method can be arbitrarily changed. For example, the grid may be divided into a grid of 81 pixels vertically and 44 pixels horizontally, which is a group of three vertically.

FIG. 6 shows a screen displayed by normalizing the luminance addition value of the grid on the line shown in FIG. 2 by the maximum value of the obtained luminance addition values.

The change amount calculator 7 calculates the change amount H _ij of the luminance addition value in the horizontal direction and the change amount V _ij of the luminance addition value in the vertical direction between the respective grids in a matrix of three rows and three columns. (Step ST7).

For example, the horizontal change amount H _ij and the vertical change amount V _ij of the luminance addition value _{ij ij} of an arbitrary grid are calculated as 9 in 3 rows and 3 columns around Σ _ij as shown in FIG. Using the horizontal Sobel filter (first coefficient table) shown in FIG. 8 and the vertical Sobel filter (second coefficient table) shown in FIG. It is determined by (1) and equation (2).

H _ij = | −Σ _{i-1, j-1} −2Σ _{i, j−1} −Σ _{i + 1, j-1} + Σ _{i-1, j + 1} + 2Σ _{i, j + 1} + Σ _{i + 1 , j + 1} |... Equation (1) V _ij = | −Σ _{i−1, j−1} + Σ _{i + 1, j−1} −2j _{i−1, j} +2, _{i + 1, j} −Σ _{i−1 j + 1} + Σ _{i + 1, j + 1} | Equation (2) Then, the sum of the obtained horizontal change amount H _ij and vertical change amount V _ij is calculated as the change amount C _{ij of the} grid. I do. Then, the change amount _{Cij is obtained} for each lattice.

The change amount C _ij is obtained by using a Sobel filter, but is not limited thereto. A filter of another coefficient or a filter of another matrix (2 rows, 2 columns, 3 rows, 1 column, etc.) is used. Is also good.

Then, in the detecting section 9, the obtained change amount C
_ij is compared with a preset defect determination threshold,
If the obtained change amount C _ij is larger than a preset defect determination threshold value, it is determined that a defect exists.

On the other hand, the display unit 11 normalizes the obtained change amount C _ij for each lattice by using the following equation (3), and
(Step ST9).

S _ij = C _ij × 255 / C Max (3) where S _ij is the normalized change amount and C Max is the maximum value of the obtained change amount C _ij . At this time, when the normalized change amount S _ij of the grid on the line shown in FIG. 10 is displayed, it becomes as shown in FIG. 11, and it can be seen that the defect shown in FIG. 4 is emphasized.

As described above, the luminance information for each pixel obtained by the area sensor 3 is divided into grids corresponding to the pitch of the object to be inspected, and the luminance information for each pixel in each grid is added to add the luminance information for each grid. Defects are emphasized by calculating the luminance addition value, and the change amount H _ij of the luminance addition value in the horizontal direction between the respective lattices.
In addition, since the defect is further emphasized by _obtaining the change amount V _ij of the luminance addition value in the vertical direction in a matrix of 3 rows and 3 columns, only one inspection object (hole) is not formed.
It is possible to detect even a defect as shown in FIG.

Further, even when the lattice is set to be shifted vertically and horizontally with respect to the inspection object, the luminance addition value in the lattice is the same for all lattices when the inspection object is normal. Therefore, it is not necessary to perform a process such as pattern matching for accurately aligning the inspection target with the position of the grid, and it is possible to detect a defect with high accuracy without particularly troublesome work.

In this embodiment, the case of detecting a defect in a hole of a CRT shadow mask is described. However, the present invention is not limited to this, and slits (shown in white) at predetermined intervals as shown in FIG. Defect can also be detected for the inspection object containing the portion (the portion).

In this case, the luminance information obtained by the area sensor 3 is divided into grids indicated by dotted lines, and thereafter, the same operation as described above is performed, so that the area of the central slit as shown in FIG. Defects can be detected. In this case, it is also possible to detect a defect in which the area of the slit is smaller than a predetermined area, a chip generated by the slit, and a defect generated in a region other than the slit.

As shown in FIG. 13, even when there are a plurality of types of inspection objects, if they are regularly arranged, the defects can be detected. FIG.
In the case of 3, the defect is detected by dividing the luminance information obtained by the area sensor 3 into a grid indicated by a dotted line.

Further, even when the regions of each color of RGB are arranged and arranged like a color filter for LCD, it is possible to detect defects such as missing colors, abnormal dyeing and abnormal areas in the regions.

Further, in this embodiment, the defect of the inspection object (hole) is detected. However, the present invention is not limited to this, and the defect of the area other than the inspection object (hole) in the inspection object (shadow mask) may be detected. Can be detected.

Further, in this embodiment, the sum of the horizontal change amount H _ij and the vertical change amount V _ij is defined as the change amount C _{ij of the} lattice, and the change amount C _ij is preset. While determining a defect by comparing the defect determination threshold, it may be determined independently without adding the variation amount V _ij horizontal variation H _ij and vertical directions.

Further, in this embodiment, the area sensor 3 is used as the sensor, but the present invention is not limited to this, and a line sensor can be used.

[0040]

As described above, according to the present invention, the luminance information for each pixel obtained by imaging the object to be inspected with the sensor is divided into a lattice composed of a plurality of vertical and horizontal pixel matrices. Defects that occur in the inspection object are emphasized by adding the luminance information of each pixel to obtain a luminance addition value for each grid, and a change amount of the luminance addition value between each grid is obtained for each of the horizontal direction and the vertical direction. Since the defect is further emphasized, the defect occurring in the inspection target can be detected with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a defect detection device according to the present invention.

FIG. 2 is an explanatory diagram showing an example in which luminance information for each pixel is cut into a grid composed of a plurality of vertical and horizontal pixel matrices.

FIG. 3 is a flowchart showing the operation of the embodiment shown in FIG. 1;

FIG. 4 is a view showing a shadow mask having a defect in a central portion.

FIG. 5 is a diagram showing luminance information on a line shown in FIG. 2;

6 is a diagram in which the luminance addition value of each grid on the line shown in FIG. 2 is normalized by a maximum value and displayed.

FIG. 7 is an explanatory diagram in a case where a horizontal change amount and a vertical change amount of a luminance addition value of an arbitrary grid are obtained.

FIG. 8 is an explanatory diagram showing a Sobel filter in the horizontal direction.

FIG. 9 is an explanatory diagram showing a Sobel filter in the vertical direction.

FIG. 10 is a diagram in which a change amount for each grid is normalized and displayed.

11 is a diagram in which the amount of change of each grid on the line shown in FIG. 2 is normalized and displayed.

FIG. 12 is an explanatory diagram showing an inspection target having slits at predetermined intervals.

FIG. 13 is an explanatory diagram illustrating an inspection target when there are a plurality of types of inspection objects.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Defect detection device 3 Area sensor 5 Brightness information addition part 7 Change amount calculation part 9 Detection part 11 Display part

Continuation of the front page (56) References JP-A-63-42454 (JP, A) JP-A-1-307644 (JP, A) JP-A-2-176978 (JP, A) JP-A-4-86956 (JP) , A) JP-A-4-198744 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 9/42 G01B 11/30 G01N 21/88 G06T 1/00

Claims (6)

(57) [Claims] 1. A defect detection method for detecting a defect in an inspection target including an inspection target, wherein the inspection target is a region including a plurality of inspection targets aligned at a predetermined pitch. A step of obtaining luminance information for each of a plurality of pixels that are imaged and arranged two-dimensionally by a sensor, and the luminance information for each pixel obtained by the sensor corresponding to the pitch from a predetermined number of vertical and horizontal pixel matrices. A luminance information adding step of adding the luminance information of each pixel in each lattice to obtain a luminance addition value for each lattice, and calculating a change amount of the luminance addition value between the lattices in the horizontal and vertical directions. A defect amount calculating step for each of the directions; and a detecting step of detecting as a defect when the horizontal amount of change and the vertical amount of change are larger than predetermined values. 2. The defect detection method according to claim 1, wherein the sensor is a line sensor or an area sensor. 3. The change amount calculating step includes the step of calculating N (m × n) of m rows and n columns around a luminance addition value of an arbitrary grid.
Change amount for obtaining a horizontal change amount and a vertical change amount by using a first horizontal coefficient table and a second vertical coefficient table which are set in advance based on the luminance addition values of 3. The defect detection method according to claim 1, further comprising a calculation step. 4. An apparatus for detecting a defect in an inspection target including an inspection target, wherein the inspection target is an area including a plurality of inspection targets arranged at a predetermined pitch, wherein the inspection target is imaged. A sensor that obtains luminance information for each of a plurality of pixels arranged two-dimensionally, and a grid composed of a predetermined number of vertical and horizontal pixel matrices each corresponding to the pitch of the luminance information for each pixel obtained by the sensor. A luminance information addition unit that divides and adds the luminance information of each pixel in each lattice to obtain a luminance addition value for each lattice; and a change amount of the luminance addition value between each lattice in the horizontal direction and the vertical direction, respectively. A defect detection device, comprising: a change amount calculation unit that determines a value; and a detection unit that detects a defect when the horizontal change amount and the vertical change amount are larger than predetermined values. 5. The defect detection device according to claim 4, wherein said sensor is a line sensor or an area sensor. 6. The change amount calculation unit includes N (m × n) m rows and n columns around a luminance addition value of an arbitrary grid.
A change amount calculation unit for calculating a horizontal change amount and a vertical change amount using a preset horizontal first coefficient table and a vertical second coefficient table based on the luminance addition value of The defect detection device according to claim 4, wherein: