JPH0345763B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an apparatus for inspecting the appearance of an object to be inspected for scratches, dirt, etc.

[Background of the invention]

Conventionally, in pattern determination of an object to be inspected, it is common to extract features from video information, align the positions, and then match the pattern with a standard pattern. However, this method has the disadvantage that the apparatus is complicated and the processing time is long.

[Purpose of the invention]

The present invention solves the above-mentioned drawbacks and provides a visual inspection device that can identify and inspect isolated defects and chipped defects with a simple configuration without being affected by quantization errors. There is something to do.

[Summary of the invention]

That is, in order to achieve the above object, the present invention provides an imaging device that captures an image of an object to be inspected having a predetermined pattern while scanning, and a binary image signal obtained from the imaging device at a predetermined threshold value. The above pattern is calculated by counting the level of one of the binary pixel converting circuit that samples and converts into pixels at a predetermined period, and the binary pixel converting signal output from the binary pixel converting circuit. a first means for calculating the area; and a second means for calculating the length of the outline of the pattern based on the binary pixelization signal output from the binary pixelization circuit.
means, a first comparing means for determining whether or not the area value calculated from the first means exists within a first reference range, and a contour calculated from the second means. a second comparing means for determining whether the length value is within a second reference range;
The comparison means determines that the area is within the first reference range, and the second comparison means determines that the contour length is within the second reference range.
When the outline length is not within the reference range, it is determined that an isolated defect exists in the pattern, and the second comparison means determines that the outline length is within the second reference range, and the first comparison means determines that an isolated defect exists in the pattern. and a determination processing means for determining that a chipping defect exists in the pattern when the area is not within the first reference range.

[Embodiments of the invention]

The present invention will be explained below based on embodiments shown in the drawings. FIG. 1 is a block diagram of an apparatus for inspecting the appearance of an object to be inspected. In the figure, a video input device 1 is an imaging device such as a commonly used TV camera, which captures an image of the object to be inspected formed of bright and dark areas while scanning each row, and outputs a video signal 1.
It outputs 0. Analog comparator 2 is
The voltage from a set voltage circuit 12 in which a power supply E and a variable resistor R are connected in series is compared with the video signal 10, and the video signal 10 is converted into a binarized black and white signal 11 of bright and dark parts. It is something that converts. The sampling circuit 3 receives this binary black and white signal 11.
This circuit samples the image using a clock pulse having a predetermined period, and converts the dark image portion of the object to be inspected into an image pulse signal 13 corresponding to an x mark, as shown in FIGS. 2 and 3. The area counting counter 4 counts the pulse signals 13 of the video corresponding to the x marks shown in FIGS. 2 and 3 over all scanned columns, and converts this into an area value digital binary. It is output as signal 14. The value counted by the area counting counter 4 corresponds to the area of the object to be inspected covered by the dark area. The digital comparator 5 stores the upper and lower limits of the inspection standard for the area of the dark area, which is the external appearance of the object to be inspected, in a separate counter or the like in advance, and uses the stored upper and lower limits for the area counting. It compares it with the value of the binary signal 14 from the counter 4 to determine whether it is good or bad and outputs it as a binary signal 15.
The electric circuit 6 detects the outline of the image where the object to be inspected is covered by the dark area based on the pulse signal 13 from the sampling circuit 3, as shown by the cross mark in FIGS. 4 and 5. The pulse signal 16 is extracted and output as a pulse signal 16. The contour length counting counter 7 counts the contour pulse signals 16 extracted from the electric circuit 6 and outputs a contour length digital binary signal 17. The digital comparator 8 stores the upper and lower limit values of the inspection standard for the outline length of the dark part, which is the appearance of the object to be inspected, in advance in another counter, etc., and uses the stored upper and lower limit values as described above. Compare it with the value of the binary signal 17 from the contour length counting counter 7 to determine whether it is good or bad.
It is output as a value signal 18. The comprehensive judgment circuit 9 is composed of an arithmetic circuit, a digital comparator, etc., and receives binary signals 15 and 18 from the digital comparators 5 and 8, a binary signal 14 from the area counting counter 4, and a contour length count. This circuit receives the binary signal 17 from the counter 7 and comprehensively determines the appearance image figure of the object to be inspected.

With the above configuration, if the object to be inspected is a good item as shown in FIG.
The area count value of the binary signal 14 outputted from the digital comparator 5 is a value within the range from the upper limit value to the lower limit value set in the digital comparator 5, and the binary signal outputted from the contour length counting counter 7. The contour length count value 17 is a value within the range from the upper limit value to the lower limit value set in the digital comparator 8. On the other hand, if the object to be inspected has an isolated defect as shown in FIG. As shown in FIG. 5, the digital comparator circuit 8 sends a binarized signal 18 to the general judgment circuit 9, which determines that the product is defective due to the large increase in the length of the contour as shown in FIG. be done. On the other hand, if the object to be inspected has a chipped defect such as a partially chipped part as shown in FIG. 6, the digital comparison circuit 5 determines that it is a defective product with a chipped defect because the area is greatly reduced. The binary signal 15 is sent to the overall judgment circuit 9, and the digital comparison circuit 8 outputs the binary signal 18, which is determined to be a good product because the length of the contour hardly changes, as shown in FIG. It is transmitted to the determination circuit 9. In this way, since the external appearance image of the object to be inspected is inspected by combining the area and contour, the comprehensive judgment circuit 9 can be made very simple and can make four different judgments.

In addition, the comprehensive judgment circuit 9 calculates the value obtained by calculating the binary signal 14 from the area counting counter 4 and the binary signal 17 from the contour length counting counter 7 as described below. The exterior image can be inspected strictly. First, the appearance image figure of the object to be inspected is roughly divided into two types: a circular shape as shown in FIG. 8a, and a square shape as shown in FIG. 8b. In the case of Figure 8a, if the radius is r, the area Sr is πr ² and the length Lr of the contour is 2πa
becomes. On the other hand, in the case of FIG. 8b, if the length of one side is h, the area Sh is h ² and the length Lh of the contour is 4h.

Here, if K = (contour length L) ² /area S, then
For Figure 8a, K ₁ = (2πa) ² /πa ² = 4π, the 8th
For figure b, K ₂ =(4a) ² /a ² =16. this
K ₁ and K ₂ are constants that are not related to the values of r and h, and can determine the complexity of the external image figure of the object to be inspected to some extent. For example, as shown in FIG. 8, by selecting a region 19 within a predetermined area range and in which the value of K is within a predetermined range, a certain predetermined area of the external image figure of the object to be inspected can be selected. It is also possible to inspect and select only the figures. That is, the arithmetic circuit of the comprehensive judgment circuit 9 multiplies the binary signal 14 from the contour length counting counter 7,
This multiplied value is calculated as 2 from area counting counter 4.
By dividing by the decimal signal 17, the above K is obtained. Next, the digital comparator of the comprehensive judgment circuit 9
The upper limit value Kmax and lower limit value Kmin are stored in a separate counter etc. in advance, and the stored upper limit value
Kmax and lower limit value Kmin are compared with the value of K from the above calculation circuit, and upper limit value Kmax and lower limit value Kmin are determined.
Select the external appearance image figure of the object to be inspected when it is included in . In this way, the comprehensive judgment circuit 9 uses the digital comparator and the upper limit value Smax of the area S to determine the lower limit value.
The external image figure of the specific object to be inspected which falls within the area 19 shown in FIG. Inspect and judge.

As explained above, the present invention has the effect of being able to simultaneously identify and inspect whether or not an isolated defect exists in a pattern and whether or not a chipping defect exists with a very simple configuration. .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an appearance inspection apparatus which is an embodiment of the present invention, FIG. 2 is a diagram showing the dark area area of the inspected object in the case of a non-defective item by the number of X marks, and FIG. The figure shows the area of the dark part of the object to be inspected, which is formed by a bright part with a convex shape in the center, by the number of x marks. Figure 4 is the outline of the dark part of the object to be inspected shown in Figure 2. Figure 5 shows the outline length of the dark part of the object to be inspected shown in Figure 3 by the number of × marks. Figure 7 is a diagram showing the area of the dark part of the object to be inspected formed by the number of x marks, and Figure 7 is a diagram showing the length of the dark part outline of the object to be inspected in Figure 6 by the number of × marks. Figures a and b are
Figure 9 is a diagram for explaining the area and outline length for cases in which the shape of the dark part of the object to be inspected is circular and square. Figure 9 shows the relationship between area and outline length by varying K. FIG. DESCRIPTION OF SYMBOLS 1... Imaging device, 2... Analog comparator, 3... Sampling circuit, 4... Area counting counter, 5... Digital comparator, 6... Electric circuit, 7... Contour length counting counter, 8... Digital comparator, 9 ...Comprehensive judgment circuit.

Claims (1)

[Claims] 1 An imaging device that scans and captures an image of an object to be inspected having a predetermined pattern, and a video signal obtained from the imaging device that is binarized using a predetermined threshold and sampled at a predetermined period to generate picture elements. a binary pixel converting circuit for converting into a pixel; a first means for calculating the area of the pattern by counting one level of the binary pixel converting signal output from the binary pixel converting circuit; a second means for calculating the length of the outline of the pattern based on the binary pixelization signal output from the value pixelization circuit; A first comparing means for determining whether the outline length value is within a reference range, and determining whether the contour length value calculated from the second means is within a second reference range. a second comparison means;
When the first comparison means determines that the area is within the first reference range and the second comparison means determines that the contour length is not within the second reference range, the area is isolated within the pattern. It is determined that a defect exists, and furthermore, the second comparison means determines that the contour length is within the second reference range, and the first comparison means determines that the area does not exist within the first reference range. and a determination processing means for determining that a chipping defect exists in the pattern.