JPH02157978A - Shading correcting device - Google Patents

Abstract

PURPOSE:To automatically confirm a correction position by visual observation by providing a monitoring means to decide a detecting signal on the correction position as defective when the level of an output signal exceeds a prescribe range in the output side of an arithmetic means. CONSTITUTION:On the output side of an arithmetic means 6, a monitoring means 12 is provided to monitor the level of the output signal from the arithmetic means 6. Accordingly, when the level of the output signal exceeds the prescribed range, it is decided that there is a cause such as dust or an unnecessary pattern to distrub the signal level in the correction position. For example, the correction position is changed again as a correction defect and shading correction is continued. Thus, without depending on the unreliable method of the confirmation by the visual observation, the propriety of correcting operation can be automatically judged and efficiency is widely improved.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a shading correction device that electronically corrects (shading correction) unevenness in illumination light, sensitivity differences in a detection system, etc. The present invention relates to a shading correction device used in visual inspection devices and the like.

In devices such as visual inspection devices for printed circuit boards that detect images using sensors such as CCDs, non-uniformity in illumination and sensor sensitivity leads to a decrease in the inspection accuracy of the device.

However, these illumination unevenness and sensitivity hardly change for each substrate to be inspected. Therefore, these devices use their shading correction device to correct the non-uniformity in advance,
Eliminates sensitivity errors due to position.

[Conventional technology]

Conventional shading correction devices of this type include those shown in FIGS. 4 to 6, for example. Figure 4 is an overall configuration diagram of the shading correction device, Figure 5 (a) is a diagram showing an example of a signal before correction at the calibration position, and Figure 5 (b) is an example of a signal after correction at the calibration position. FIG. 6(a) is a diagram showing an example of a signal including shaveve, and FIG. 6(b) is a diagram showing an example of the signal after correction. In FIG. 4, reference numeral 1 is a shave-eave correction device, and the shave-eave correction device 1 is a COD
an amplifier 2 that amplifies an image signal detected by a sensor such as the like, and an A/D that converts the image signal amplified by the amplifier 2 into a predetermined (e.g., 8 bit) digital value.
A converter 3, a correction value memory 4 that stores the signal of the base material portion without a pattern before the start of inspection, a scan address counter 5 that counts scan addresses, and an A/D converted value S.
ig (8bit) and the value Cmp (8bit) read from the correction value memory 4 are input manually, Sig is corrected based on Cmp, and the output signal Out (8b
It consists of an arithmetic circuit 6 which outputs an output as (it) to the outside.

With the above configuration, the CCD signal detected by the COD or the like is amplified by the amplifier 2 and then converted into a digital value by the 8-bit A/D conversion 3.

First, before starting the inspection, a signal from a portion of the base material without a pattern is taken into the correction value memory 4.

Next, during inspection, the contents of the correction value memory 4 are read out according to the scanning of the COD, and the A/D converted value Sig (8
bit) are both input to the arithmetic circuit 6. The arithmetic circuit 6 sets the correction reference value α to the value C read out from the correction value memory 4.
The result of division by mp (8 bits) is used as a correction coefficient and multiplied by the A/D converted signal Sig (see equation 0).

However, α: correction reference value. In order to make the dynamic range as wide as possible, α is set to 70% of the full scale, specifically 28×0°7=179.

FIG. 5(a) shows a normal signal before correction at the calibration position, and FIG. 5(b) shows the signal after correction. In this way, the shave is corrected, resulting in a flat signal. When an inspection is performed in this state, a signal containing shaved waves as shown in FIG. 6(a) is corrected as shown in FIG. 6(b). Here, although the signal examples shown in FIG. 5.6 and FIG. 2, which will be described later, are represented in an analog manner, digital signal processing is actually performed.

[Problem to be solved by the invention]

However, in such a conventional shading correction device, when performing the above-mentioned shave-even correction (
During the calibration process (hereinafter referred to as the calibration process), if there is dust or unnecessary patterns in the reference location (screen), it will be imported as a correction value, and subsequent corrections will not be performed normally, instead it will be judged as abnormal. The situation will be such that

That is, conventionally, when performing a calibration process, the calibration position was visually checked to confirm that there was no dust or unnecessary patterns, and then the calibration operation was performed. However, if the resolution of the imaging system is as fine as about 10 μm, this confirmation becomes extremely difficult, and oversights are likely to occur. For example, if an incorrect value is read as a correction value due to dust as shown in Figure 2 (a) (a), the same position as shown in Figure 5 (
Although a flat signal as shown in FIG. 2(b) can be obtained, if the position changes, over-correction occurs as shown in FIG. 2(b) and (a), and normal operation does not occur. In addition, if dust, such as metal powder, is attached to the calibration position, incorrect correction values as shown in Figures 2(a) and (B) will be read. As shown in (a), the correction is undercorrected and the system does not operate normally.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a shading correction device that can automate the visual confirmation of the calibration position and perform complete correction confirmation.

[Means for Solving the Problems] In order to achieve the above object, the shading correction device according to the present invention includes a storage means for storing a detection signal at a predetermined calibration position among the detection signals detected by a predetermined light detection means as a correction value. and the detection signal detected by the light detection means and the correction value read from the storage means are input,
A shading correction device that corrects shading for unevenness in the amount of detected illumination light, sensitivity differences in the detection system, etc., comprising: arithmetic means for correcting the detection signal based on the correction value and outputting an output signal; The shading correction apparatus is provided with a monitoring means for determining that the detection signal at the calibration position is defective when the level of the output signal exceeds a predetermined range on the output side of the calculation means.

[Effect]

In the present invention, a monitoring means for monitoring the level of the output signal of the arithmetic means is provided on the output side of the arithmetic means.

Therefore, when the level of the output signal exceeds a predetermined range,
It is determined that there is a factor that disturbs the signal level, such as dust or an unnecessary pattern, at the calibration position, and, for example, it is determined that the calibration is defective, and the calibration position is recalibrated and the shave-eve correction is continued. As a result, it is possible to automatically judge whether the calibration operation is good or bad, without using the uncertain method of visual confirmation.
Efficiency is greatly improved.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

Fig. 1.2 is a diagram showing a first embodiment of the shading correction device according to the present invention, Fig. 1 is an overall configuration diagram thereof, and Fig. 2 (a) is a diagram showing a first embodiment of the shading correction device according to the present invention. Figure 2 shows an example of the signal before correction at the calibration position in the state where
Figure (b) is a diagram showing an example of a signal when the position after correction at the calibration position is moved. In explaining the first embodiment,
Components that are the same as those in the conventional example shown in FIG. 4 are given the same numbers and will not be described again.

First, the configuration will be explained. In FIG. 1, numeral 11 is a shave-eave correction device, and the shave-eave correction device 11 is
An amplifier 2 that amplifies the CCD signal detected by the CD sensor (light detection means) and an 8bi
An A/D converter 3 that performs A/D conversion into a digital value of t, a correction value memory (storage means) 4 that stores the signal of the base material portion without a pattern before the start of inspection, and a scan address that counts the scan address. Counter 5 and A/D converted value Si
-g (8 bits) is corrected based on the value Cmρ (8 bits) read from the correction value memory 4 and outputted to the outside as an output signal Out (8 bits); and a comparator (monitoring means) 12 that compares the reference voltage with a predetermined reference voltage.The comparator 12 outputs an error signal when the comparison voltage becomes "minus" than the reference voltage. A device that outputs Err (see Fig. 2(b)) is used.In this embodiment, a value (-0.71V) higher than the calibration reference value (-0.7V in this example) is used as the reference voltage input to the comparator 12. ).Here, it is appropriate that the reference voltage input to the comparator 12 be about ±0.1V with respect to the calibration reference value.

Next, the effect will be explained.

First, after performing a calibration operation, the position of the board to be inspected is moved a little, and the output signal Out is compared with the reference voltage (-0.71V) shown in FIG. It is checked whether there is a position where the state of (Err) is "ON".

If there is a position that is "'ON", an error signal (Err) is output from the comparator 12 as a calibration failure, and the control device (unit ) to judge. Based on this judgment, the calibration position is changed to search for a place where there is no dust or pattern (where the comparator 12 becomes "OFF") and the calibration operation is performed automatically.In this case, the retry (retry) is set in advance. By predetermining the number of times and having a human perform calibration only after a predetermined number of errors have occurred, the human burden and time involved in shave-eve correction can be significantly reduced.

As described above, in this embodiment, by adding a simple circuit called the comparator 12, it is possible to automate the confirmation of the calibration position, which was previously done visually by humans. It becomes possible to completely correct and confirm things that could not be confirmed before, such as sagging. In particular, when calibrating while overlooking the presence of dust or unnecessary patterns, it would be fine if the abnormality could be recognized as an abnormality, but as shown in Figure 2 (b) (a), the abnormality correction signal due to dust etc. If this were to disappear, it would result in a large loss in terms of cost, since printed circuit boards with a large number of laminated layers (that is, high-cost printed circuit boards) are now often used. According to the apparatus of this embodiment, such mistakes can be prevented as much as possible.

FIG. 3 is a diagram showing a second embodiment of the shading correction device according to the present invention, and is an example in which a comparator is further added to prevent undercorrection. Components that are the same as those of the first embodiment shown in FIG. 1 are given the same numbers and their explanations will be omitted.

In FIG. 3, 21 is a shave correction device;
The shave-eave correction device 21 differs from the shave-eve correction device 11 shown in FIG. 1 only in that a comparator (monitoring means) 22 is added. The output signal Out of the arithmetic circuit 6 is input as a comparison voltage to one end of the comparator 22, and the comparator 22 receives the comparison voltage as a reference voltage (for example, -
0.69V (see the two-dot chain line in FIG. 2(b)), the output becomes "'ON" and an error signal Err is output.

Therefore, although it is less frequent than when dust or unnecessary patterns are present at the calibration position, it is possible that metal powder or the like is attached to the calibration position and an abnormal signal as shown in Figure 2 (a) (b) is read. Also, by comparing the output signal Out from the arithmetic circuit 6 with the comparator 22, a calibration failure can be appropriately determined. As a result, the effects of the first embodiment can be further improved.

〔Effect of the invention〕

According to the present invention, visual confirmation of the calibration position can be automated, and the correction can be completely confirmed.

[Brief explanation of the drawing]

Fig. 1.2 is a diagram showing a first embodiment of the shading correction device according to the present invention, Fig. 1 is an overall configuration diagram thereof, and Fig. 2 is a diagram showing an example of signals before and after correction at the calibration position. , FIG. 3 is an overall configuration diagram showing a second embodiment of a shading correction device according to the present invention, FIGS. 4 to 6 are diagrams showing a conventional shading correction device, FIG. 4 is an overall configuration diagram thereof, FIG. 5 is a diagram showing an example of a signal before and after correction at the calibration position, and FIG. 6 is a diagram showing an example of a signal including shaveve and an example of a signal after correction. 2...Amplifier, 3...A/D converter, 4...Correction value memory (storage means), 5...
...Scanning address counter, 6... Arithmetic circuit (
calculation means), 11.21... Shave correction device, 12. 22 --- Comparator (monitoring means) (1 (a) Figure 2 shows an example of signals before and after correction at the calibration position of the first embodiment. Kai p Signals before and after correction at the conventional calibration position Figure 5 shows an example.

Claims (1)

[Scope of Claims] Storage means for storing, as a correction value, a detection signal at a predetermined calibration position among the detection signals detected by a predetermined light detection means; and the detection signal detected by the light detection means and the storage means. a calculation means that receives a correction value read out from the correction value, corrects the detection signal based on the correction value, and outputs an output signal, and the calculation means corrects the detection signal based on the correction value and outputs an output signal, and the calculation means corrects the detection signal based on the correction value and outputs an output signal. A shading correction device for shading correction, characterized in that monitoring means is provided on the output side of the calculation means for determining that the detection signal at the calibration position is defective when the level of the output signal exceeds a predetermined range. Shading correction device.