JPS638542A - Fine flaw detector - Google Patents

Abstract

PURPOSE:To detect the finest of darker flaws in the light color and lighter flaws in the dark color, by providing a plurality of threshold levels before an imaged signal is binary-coded to detect a flaw by being compared with a reference signal. CONSTITUTION:After being amplified by a buffer amplifier 2, a signal inputted from a TV camera 1 is binary-code by a binary-coding circuit 3 to be compared with a reference graphic signal by a comparator 4 and when a defect is identified, an output signal of the comparator is outputted through an OR circuit 6. Binary-coding circuits 10 and 20 each have a threshold level different from the threshold level of the binary-coding circuit 3: that slightly lower (lighter) than that of the dark color set for the former 10 and that slightly higher (darker) than that of the light color for the latter 20. Detection circuits 11 and 12 take in binary-coded signals separately to detect a fine flaw by a signal processing.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a micro-flaw detection device for detecting micro-flaws in the inspection of printed wiring boards after etching, semiconductor quanos, masks, etc. [Prior art] Japanese Patent Application Laid-Open No. 52-11984 as a device for detecting minute scratches
The one disclosed in Publication No. 4 has been proposed in the past. In this method, a detection target is imaged, the obtained signal is binarized, and this binarized signal is compared with a certain threshold level. In this case, the threshold level is generated based on data of non-defective products.

[Problem that the invention seeks to solve]

However, in the imaging results of such conventional devices, for example, there may be thin scratches on conductor parts that are imaged as thin dark lines in light colors, or thin conductors left in non-conductor parts that are imaged as thin dark lines in dark colors. If there is a portion that is imaged as a thin, light-colored line, the amount of change in that portion is extremely small, so the amount of change may not be able to cross the threshold level.

To solve this problem, you can enlarge the image by increasing the camera's lens magnification, but this method reduces the range of images that can be captured at once) and reduces the processing power of the detection device. This leaves the problem of a decline in performance.

The present invention was made to solve this problem, and its object is to provide a device that can quickly detect even thin scratches.

[Means for solving problems]

In order to solve these problems, the present invention divides the threshold level into a plurality of types.

[Effect]

Even if the amount of change in the detection signal is small, a minute flaw is detected when it crosses one of a plurality of threshold levels.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, 1 is a television camera for capturing an image, 2 is a buffer amplifier, and 3 is a binarization circuit having a predetermined threshold level.The Sonos threshold level is shown in dark colors and light colors c.

Set it approximately in the middle of the section. Reference numeral 4 denotes a comparator that compares the binarized signal with the standard figure signal generated from the standard figure signal generator 5. The standard figure signal is obtained by imaging and recording a good object with no scratches. use.

The signal input from TV camera 1 is sent to buffer amplifier 2.
After being amplified by the binarization circuit 3, the comparator 4
The output signal is compared with a standard graphic signal by , and if it is found that there is a defect, the output signal is outputted via the OR circuit 6. 10.20 is a binarization circuit having a threshold level different from the threshold level of the binarization circuit 3, and the binarization circuit 10 is on the slightly lighter side of the dark color, and the binarization circuit 20 The threshold level is set on the slightly darker side of the light color. 11 and 21 are detection circuits that each take in a binary signal and perform signal processing to find thin scratches.

The detection circuit 11.21 is composed of a vertical flaw detection circuit 50, a horizontal flaw detection circuit 51, and an OR circuit 52, as shown in FIG. As shown in FIG. 3, the vertical flaw detection circuit 50 includes a shift register 31, inverters 32 to 34, and an AND circuit 35.
37, 39, and an OR circuit 38. As shown in FIG. 4, the horizontal scratch detection circuit 51 includes shift registers 40 to 40 that can provide a delay of 256 clocks.
d1 Inverters 41-43, AND circuits 41-46.
48, an OR circuit 47, and a counter 49 that passes only 256 clocks per horizontal scanning line.

Now, the image inputted by the television camera 1 is shown in Fig. 5 (1), and the image signal of the portion corresponding to the horizontal scanning line of the dashed dot line indicated by symbol A is shown in Fig. 5 (b). (Figure 5(b) is shown in the television standard format with light color on the top and dark color on the bottom). Figure 5 (phantom symbol) The minute scratches shown by C are extremely slight changes in the image signal. Binarization with a threshold level between the dark and light colors shown in Figure 1 The circuit 3 can only extract the signal shown in Fig. 5(f), and cannot detect minute scratches.The binarization circuit 10 has a symbol hotel shown in Fig. 5(b), which is located slightly darker than the light color. The input signal is binarized according to the threshold hold level, and a signal corresponding to the scratch is output as shown in FIG. 5(e), and this output is supplied to the detection circuit 11.

The signal supplied to the vertical flaw detection circuit 50 of the detection circuit 11 is transferred to the adjacent output terminal of the shift register 31 shown in FIG. 3 every time the clock signal CL is supplied. Here, the clock signal is approximately 6MH2, and when the number of scanning lines is 256, the length of one pixel is the same in the vertical and horizontal directions.The input binary signal corresponds to the scratch, and one pixel 9, and when both sides are at the rHJ level, the terminals 1 and d of the shift register 31 go to the "H" level.
At this level, the terminal C becomes "L" level. Since the output of terminal C is inverted by the inverter 32, if the output of the AND circuit 35 does not go to "H" level, the signal is outputted via the OR circuit 38 and the AND circuit 39, which indicates that there is a scratch. be done.

When two pixels are at the "L" level and the elements adjacent to both sides are at the rHJ level, the AND circuit 36 becomes active and outputs the result of "scarring". The AND circuit 37 also becomes active when three pixels are at the rLJ level, and it is determined that there is a scar.

In this way, the circuit shown in FIG. 3 outputs a result indicating a scratch when there is a light-colored scratch within a width of 1 to 3 pixels in the horizontal scanning line direction. The clock is operated by a counter 49 so that 256 counts are input during one scanning line. And shift register 40&~4
Since 0d is a shift register having 256 stages of 7 lip-flops, the binary signal is output from the shift register 401 at the same location after one scanning line. This is the pixel immediately above the pixel corresponding to the current binary input signal. In this way, by comparing the contents of each shift register in FIG. 4, changes in the vertical positional relationship on the image can be grasped. Then, by the same operation as described above, when the rLJ level of 1 to 3 pixels in the vertical direction is input, and a binary signal with rHJ level at both ends is input, a flawed signal is output. In other words, this circuit is prepared for cases where thin scratches extend horizontally.

The binarization circuit 20 in FIG. 1 performs binarization using a threshold V level set from the dark side to the light color side, as indicated by the symbol in FIG. As shown,
The output of this circuit is used to find fine scratches in dark colors.The output of this circuit is then supplied to a detection circuit 21 which has the same function as the detection circuit 11, and detects minute scratches in the vertical and horizontal directions. The outputs of the comparator 4 and the detection circuits 11 and 21 are outputted via the OR circuit 6.

FIG. 6 is a block diagram showing another embodiment, in which 60 is a combiner, configured as shown in FIG. 7, and 61
m and 61b are delay circuits for 2 pixels in the vertical direction), and the binary signal moves downward by 2 pixels on the screen. Specifically, it uses a 256-stage shift register like shift registers 40m and 40b. There are two sets. 62m and 62b are processing circuits that shift the binary signal by two pixels in the right direction, which can be realized by a circuit that inputs from the terminals of the shift register 31 and performs a table operation similar to that output from the terminal d. The outputs of the processing circuits 52m and 52b move each binary image two pixels at a time in the lower right direction. Note that the input indicated by symbol a in Fig. 7 corresponds to Fig. 5 (e), and the input indicated by the symbol 0, which sets the threshold level from the light color side to a slightly dark color side, corresponds to Fig. 5 (e). This corresponds to d). These two input signals are shown in Figures 8 (&) and (d), and (&) in Figure 9.
~(h) corresponds to the symbol ~h in FIG.

63 is a processing circuit with a function of shifting 4 pixels downward; 64
65 is a processing circuit that shifts 4 pixels to the right, and 65 shifts 4 pixels toward the bottom.
This is a processing circuit that shifts pixels pixel by pixel, and these are configured in the same manner as the shift register described above. The OR circuit 66 combines these output signals, and the symbol breath signal moves slightly to the lower right and becomes thicker. This is inverted by an inverter 67, and added to the signal moved to the lower right of the signal at symbol 68 by an AND circuit 68. In the OR circuit 69, the signal of symbol a is added to the signal moved to the lower right, and the signal shown in symbol 1 is synthesized, containing minute scratches that have the characteristics of both the signal of symbol breath and the signal of symbol A. I get a signal. This embodiment attempts to perform similar processing by combining two binary signals having different threshold levels into one binary signal as in the prior art.

〔Effect of the invention〕

As explained above, the present invention has a plurality of threshold levels, so it has the effect of being able to detect even minute scratches among dark color side scratches in light color and light color side scratches in dark color.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of this invention, tJX
FIG. 2 is a block diagram showing an example of the detection circuit in FIG. 1, FIGS. 3 and 4 are block diagrams showing examples of the vertical flaw detection circuit and the horizontal flaw detection circuit, FIG.
7 is a block diagram showing another embodiment, FIG. 7 is a block diagram showing an example of the synthesizer shown in FIG. 6, and FIG. 8 is a waveform diagram of each part. 1@@-・TV camera, 2-0・・Buffer amplifier,
3, 10, 20...Binarization circuit, No. 11゜21...
・Detection circuit, 31.40a-40d @-...Shift register 5 Q * * Fist/vertical wound detection circuit, 51@
... Lateral flaw detection circuit, 61a, 61b, 62m. 62b@...processing circuit.

Claims (1)

[Claims] There is a means for detecting flaws by binarizing the imaged signal at approximately the median value and comparing it with a standard signal, a means for detecting flaws by binarizing the imaged signal at a level slightly higher than the median value, and means for detecting flaws by binarizing them at a slightly lower level.