JPS63304766A - Correction circuit for picture - Google Patents

Abstract

PURPOSE:To attain the correction of picture unevenness which occurs by means of an illumination system, an image pickup system and an object to be inspected by giving a picture signal to an A/D converter with setting the characteristic of background luminance and the reflective characteristic of the object of inspection as for correction. CONSTITUTION:A reference surface in a light part and that in a dark part are previously image-picked up and an analogue picture signal is digital-converted in the A/D converter 1. They are respectively fetched into memories 2A and 2B and the reference surface signals in the light part are set to the plus reference signals of the A/D converter 1 as the reflective characteristic of the object of inspection, and the reference surface signals in the dark part are set to the minus reference signals of the A/D converter 1 as the characteristic of the background luminance. The plus reference signals and the minus reference signals are synchronized with the analogue picture signals and are inputted to the A/D converter 1. Next the object of inspection is image- picked up, and the picture is set to be corrected when the analogue picture signals are digital-converted in the A/D converter 1. Thus, the influence of background luminance can be corrected if the distribution luminance of background luminance and the reflective characteristic of the object of inspection differ.

Description

Detailed Description of the Invention (a1 Technical Field of the Invention The present invention relates to a circuit for correcting image unevenness caused by an illumination system, an imaging system, and an object to be inspected when binarizing images of bright and dark areas. It is something.

(b) Prior Art and Problems FIG. 2 shows an example of the waveform of image unevenness obtained by optically reading an inspection object having portions with different reflection characteristics using an imaging device such as a CCD camera.

In FIG. 2(A), the vertical axis represents the density values of bright and dark areas, and the horizontal axis represents the sensor position.

Next, FIG. 2(B) shows a diagram in which the waveform of the image unevenness in FIG. 2(A) has been binarized at a certain threshold level.

In Figure 2 (A), after binarizing Figure 2 (A), parts a and C should be "1" but are instead "0"], and part b becomes "0". The expected value is “1”.

Therefore, as a method for correcting image unevenness read by an imaging device, there is the following conventional example.

For example, as a method for correcting images, a subtractive binarization method is disclosed in Japanese Patent Application Laid-open No. 81-193569.

FIG. 3 shows an example of the waveform of image unevenness read by the low Tf and binarization method.

FIG. 3(1) shows the density on the vertical axis and the sensor position on the horizontal axis, and is a diagram in which the background brightness curve 12 of the image is calculated for the original image 11.

FIG. 3(a) is a diagram in which the background brightness curve is subtracted from the original image in FIG. 3(a) to eliminate the influence of the background brightness.

Figure 3 (T) is a binary representation of Figure 3 (A) with a threshold set at a certain value.
The distance d at the center of the sensor is detected to be narrower than the distance e at the periphery of the sensor.

Therefore, in this method, although the influence of the background brightness is corrected, the variation in the brightness of the object is not corrected.

Another method for correcting images, disclosed in Japanese Patent Laid-Open No. 81-237577, is a shading distortion correction method.

FIG. 4 shows an example of the waveform of image unevenness read by the aging distortion correction method.

Figure 4 (1) shows the reflection curve of the test object that matches the original image 13 and the reflection characteristics of the test object in the original image, with 11 degrees on the vertical axis and the sensor position on the horizontal axis. FIG. 14 is a diagram.

FIG. 4(a) is a diagram showing the result of correcting the original image using the reflection curve of the object to be inspected.

Figure 4 (c) is a binary representation of Figure 4 (a) with a threshold set at a certain value. If the bright parts of the object are equally spaced,
The distance f at the center of the sensor is detected wider than the distance g around the sensor periphery.

Therefore, with this method, if the distribution characteristics of the background brightness and the reflection characteristics of the object to be inspected are different, the influence of the background brightness cannot be corrected.

(c) Purpose of the Invention This invention images the reference plane of the bright part and the reference plane of the dark part in advance, converts the analog image signal into digital with an A/D converter, and then imports each into a memory. The reference plane signal of the part is used as the reflection characteristic of the object to be inspected and is used as the positive reference signal of the A/D converter, and the reference plane signal of the dark part is used as the background luminance characteristic and is used as the negative reference signal of the A/D converter. A positive reference signal and a negative reference signal are input into an A/D converter in synchronization with the image signal, and then the inspection object is imaged, and when the analog image signal is digitally converted by the A/D converter, the image is corrected. The purpose of the present invention is to provide an image correction circuit that can perform the following functions.

(d) Embodiment of the invention At the beginning, a configuration diagram of a printed wiring board that can be read optically is shown in the fifth figure.
As shown in the figure.

6 in Figure 5 is a printed wiring board, and 7 is! 141 portion, 8 is a base material portion, and 9 is a pattern forming portion.

The printed wiring board 6 is an object to be inspected, and before the external shape is processed, it consists of a copper foil portion 7, a base material portion 8, and a pattern forming portion 9.

A pattern circuit is formed in the pattern forming portion 9, and there are a copper foil portion 7 and a base material portion 8 around it.

In FIG. 5, the copper foil portion 7 is used as the reference plane for the bright part, and the base material part 8 is used as the reference plane for the dark part.

Next, a block diagram of an embodiment according to the present invention is shown in FIG.

1 in Figure 1 is an A/D converter, 2A, 2B are memories, 3A
, 3B is a D/A converter, and 4 is an amplifier.

In FIG. 1, an analog image signal of a signal obtained by first imaging the reference plane of the bright part with a CCD camera, etc. of the image of the object to be inspected, which consists of a bright part and a dark part, is sent to the amplifier 4. It enters the IN input of the A/D converter 1 through the .

The A/D converter 1 converts the analog image signal into a digital image signal and writes it into the correction reference signal area of the mesori 2A.

Next, the analog image signal of the signal obtained by imaging the reference plane of the dark part with a CCD camera etc. is sent via the amplifier 4 to the A/
Enters the IN input of D converter 1.

A/Df converter 1 converts analog image signals into digital ones.

The image signal is converted into an image signal and input into the correction reference signal area of the memo U 2 B.

The A/D converter 1 of this embodiment uses a commercially available MP7882 manufactured by Micro Power Stems.

Memories 2A and 2B have a reference signal area for data import, which is used when importing data to create a reference signal for correction, and a reference signal area for correction, which is used when actually performing correction. .

The memories 2A and 2B of this embodiment are commercially available Toshiba 111
I am using Tc5564.

In the reference signal area for data import of memory 2A, CC
The sensor of the D camera is set so that it remains at a constant level higher than the input voltage of the It A/D converter 1 during scanning.

In the reference signal area for data import of memory 2B, CC
The D camera sensor is set to remain at a constant 0 level during scanning.

1] The /A converters 3A and 3B convert the reference signals stored in the memories 2A and 2B from digital signals to analog signals, and use the +R of the A/D converter 1 as the reference signal for image correction.
Add to EF and -REF in synchronization with the analog image signal.

At this time, when the analog image signal is input to the IN input of the A/D converter 1, the analog signal is converted into a digital signal and an image signal with image distortion corrected is outputted from the output side.

Next, the operation of FIG. 1 will be explained with reference to FIGS. 6, 7, and 8.

The analog image signal 15 in FIG. 6(1) has a waveform that is applied to the IN input of the A/D converter 1 via the amplifier 4. At this time, since the sensor is scanning, the A/D converter 1
The plus reference signal 17 for data capture shown in FIG. 6(A) is added to +REF of the A/D converter 1, and the minus reference signal 17 for data capture shown in FIG. 6(A) is added to -REF of the A/D converter 1.
8 is a waveform diagram in which 8 is added.

Therefore, the analog image signal 15 of the bright reference plane is converted into a digital image signal of the bright reference plane without being corrected.

The correction plus reference signal 19 in FIG. 7 is a signal written in the correction reference signal area of the memo 1J2A as the reflection characteristic of the object to be inspected.

Next, FIG. 6(a) Analog image signal 16 of the dark reference plane
is a waveform applied to the IN input of the A/D converter 1 via the amplifier 4. At this time, +RE of A/D converter 1
F is the plus reference signal 1 for data capture in Figure 6 (A)
7 is added to -REF, and the minus reference signal 18 for data acquisition shown in FIG. 6(A) is added to -REF.

Therefore, the analog image signal 16 of the dark reference plane in FIG. 8(a) is converted into a digital image signal of the dark reference plane without being corrected. .

The correction minus reference signal 20 in FIG. 7 is a signal written in the correction reference signal area of the memo U 2 B as a background luminance characteristic.

FIG. 8(7) shows a waveform diagram applied to the A/D converter 1.

The analog image signal 21 is an image of the object to be inspected captured by a CCD camera or the like, and is a waveform applied to the IN input of the A/D converter 1.

The plus reference signal 22 for correction is the plus reference signal 1 in FIG.
9 is a waveform written into the memory 2A and converted to analog by the D/A converter 3A, and +RE of the A/D converter 1.
This is the waveform added to F.

The minus reference signal 23 for correction is obtained by writing the minus reference signal 20 in FIG.
This is the waveform converted into analog at , and is the waveform added to -REF of the A/D converter 1.

FIG. 8(A) represents the output signal of the A/D converter 1 as an analog signal, and shows a diagram of an image signal in which the reflection characteristics of the object to be inspected and the background brightness characteristics have been corrected.

Figure 8 (T) is a binary representation of Figure 8 (A) with a threshold set at a certain value. If the bright parts of the object are equally spaced,
The distance between the central part of the sensor and the distance around the sensor are detected to be equal.

te1 Effects of the Invention According to this invention, the image signal is given to the A/D converter for correction based on the characteristics of the background brightness and the reflection characteristics of the object to be inspected. It is possible to correct image unevenness that occurs.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment according to the present invention, Fig. 2 is a waveform diagram of image unevenness, Fig. 3 is a waveform diagram of the conventional subtractive binarization method, and Fig. 4 is a conventional shading distortion correction method. FIG. 5 is a configuration diagram of the printed wiring board, and FIGS. 6 to 8 are waveform diagrams of each part of FIG. 1. ■...A/D converter, 2...Memory,
2av 2b...Memory% 3a13b...
...D/A converter, 4...Amplifier, 6...
...Printed wiring board, 7...Copper foil part, 8.
...Substrate part, 9...Pattern forming part. Agent Patent Attorney Kin Tsukasa Omata 1 Figure 2 Figure 3 Figure 4 Sensor position Figure 5 Figure 6 Sensor position Sensor position Figure 7 Figure 8

Claims (1)

[Scope of Claims] 1. In a device that converts a signal obtained by capturing an image consisting of a bright part and a dark part with a CCD camera or the like into an analog signal, which is created in advance in synchronization with the analog signal outputted by the device. an A/D converter (1) capable of inputting the two reference signals and digitally converting the analog signal to correct image distortion; and a memory (1) that stores a continuous curve signal of the first reference surface data.
2A), and a memory for storing the continuous curve signal of the second reference surface data (
2B), a D/A converter (3A) that reads out the continuous curve signal of the first reference plane data digitized in the memory (2A) and converts it into analog to create a reference signal for first correction; A D/A converter (3B) that reads out the continuous curve signal of the second reference plane data digitized in the memory (2B) and converts it into analog to create a second reference signal for correction. Features an image correction circuit.