JPH06189129A - Image input device - Google Patents

Abstract

PURPOSE:To quickly respond even to a work with large density change and to stably output an image signal by providing a table part which corrects the density of the image signal of the work by inputting the representative density of the image signal. CONSTITUTION:The image signal with representative density is inputted from a representative density calculation part 5 to the table part 6. The signal is compared with the image signal from an A/D converter 2, and an image signal waveform from the converter 2 is controlled so as to set difference between them at zero. A signal of stabilized density is set by extending the waveform when the maximum value of the waveform is set at a low level and compressing it when the waveform is set at a high level by the table part 6. Therefore, it is possible to output the image signal by which the image display of the inspecting plane of the work can be performed on an image display device even when the image signal density of the work is remarkably fluctuated due to, for example, the change of the light quantity of an illumination lamp with which the work is irradiated or the difference of reflected light by the work to an image processing device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to an image input device for inputting an image signal of a work having a large change in density to an image processing device.

[0002]

2. Description of the Related Art As is well known, an automatic gain control circuit is used in a camera or the like in an image input device for inputting an image signal of a work having a large change in density to an image processing device.
In this automatic gain control circuit, after holding the average level of the image signal in the capacitor, it is fed back to the amplification section to control the gain.

[0003]

However, in the image input device using the automatic gain control circuit, the circuit is simple, but the response is delayed by 3 to 5 scans.

Further, when the cycle of change in the density of the work becomes short, the change in the density of the input image signal becomes large. Then, for example, when the threshold value is fixed to the density data and the binarization processing is performed, it is necessary to suppress the change in the density, and a faster response (for example, 1 scan, 1
(For each screen) is required.

Therefore, an object of the present invention is to provide an image input device which can respond to a work having a large change in density at high speed with a simple circuit and can output a stable image signal to an image processing device. That is.

[0006]

SUMMARY OF THE INVENTION The present invention is an image input device for converting an image signal of a workpiece input from an image pickup device by an A / D converter and outputting the image signal to an image processing device. It is characterized by adding a representative density detecting section for detecting a representative density of the image signal of the work and a table section for correcting the density of the image signal of the work by inputting the representative density of the image signal detected by the representative density detecting section. And

[0007]

When the density of the image signal input from the image pickup device is low, the image signal subsequently input to the table section is
The image is expanded according to the representative density input from the representative density detecting unit to the table unit, and is compressed according to the representative density input from the representative density detecting unit when the density of the image signal input from the imaging device is high.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image input device of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the image input device of the present invention.

As shown in FIG. 1, the image input device of the present invention comprises a buffer amplifier 1 to which an image signal of a work imaged by an image pickup device for picking up an image of the work by a CCD camera or the like is input, and the buffer amplifier 1. An analog signal of the amplified image is input and an A / D converter 2 for converting it into a digital signal, and a part of the analog signal of the image amplified by the buffer amplifier 1 is also input, and a representative density detection unit 15 described later in detail. Then, the output signals of the representative density detecting unit 15 and the A / D converter 2 described above are input, and by using the representative density data of the image to be described later input from the representative density detecting unit 15, AD
A table unit 6 for correcting an image signal input from the converter 2 and outputting the corrected image signal to an image processing apparatus (not shown) is roughly configured.

Among them, the representative density detecting section 15 receives the analog signal output from the buffer amplifier 1 and receives the analog signal output from the buffer amplifier 1. A / D converter 4 for converting the analog image signal output from the filter 3 into a digital signal and the A / D converter 4
The representative density calculation section 5 outputs the representative density in one scan obtained by calculating the maximum value of the density of the image signal in one scan output from the table to the table section 6.

Next, the operation of the image input device thus constructed will be described. When the image signal of the representative density is input from the representative density calculation unit 5, the table unit 6 compares this signal with the image signal input from the A / D converter 2 so that the difference becomes zero. The waveform of the image signal input from the A / D converter 2 is controlled.

2 and 3 are explanatory views for explaining the waveform control in the table section 6. That is, FIG.
(A) shows the case where the maximum value of the waveform of the image signal input from the A / D converter 2 is the low level signal 7, and in this case, the table section 6 shows the waveform of the signal 7 in FIG. The conversion characteristic 11 shown in the graph expands as shown in FIG. On the contrary, when the image signal input from the AD converter 2 is the high level signal 8 as shown in FIG. 2B, the conversion characteristic 10 shown in the graph of FIG. Thus, the signal 9 having the stabilized density is obtained.

Therefore, in the image input apparatus having such a structure, for example, even if the density of the image signal of the work greatly changes due to the change of the light amount of the illumination lamp irradiating the work or the difference of the reflected light by the work. The image display device can output an image signal capable of clearly displaying the image of the inspection surface of the work to the image processing device.

Note that the control of the waveform of the image signal in the table 6 is performed by the conversion characteristic curves 12 and 13 shown in FIG.
By using a curved line, control by non-linear calculation such as logarithmic conversion may be performed. In this case, there is an advantage that it is possible to cope with a case where the difference between the maximum value and the minimum value of the density of the image signal is large.

In the above embodiment, the representative density is set to the maximum value of the image signal during one scan, but depending on the irradiation part of the inspection object, the typical density (maximum value) up to several scans before. From this, the representative density of the next scan may be predicted, and the conversion characteristic shown in FIG. 3 may be selected and output to the table unit 6.

Further, in the case of a work in which there is not a large change in density depending on the material of the irradiation portion of the inspection object, the average value of the image signal densities during one scan is used as the representative density, and based on the average value of the densities during several scans. The representative density of the next scan is predicted, the conversion characteristic shown in FIG.
May be output to.

FIG. 5 is a block diagram showing another embodiment of the image input apparatus of the present invention. 5, the difference from FIG. 1 is that the address information of the image signal is input from the address counter 14 to the table section 6.

In this case, there is an advantage that the shading phenomenon caused by the position of the screen of the CRT that finally displays the image signal output from the image input device can be corrected to reduce the difference in shade of the screen. .

At this time, the conversion characteristic in the table portion 6 is f (i), and the conversion characteristic for shading correction is g.
Assuming that (p), the output characteristic h (i, p) of the image signal from the table unit 6 can be represented by h (i, p) = f (i) · g (p) (1). FIG. 6A is a graph showing the conversion characteristic regarding the density, and FIG. 6B is a graph showing the conversion characteristic regarding the position.

Of these, in FIG. 6B, the density of the image signal in the central portion of the image pickup portion is reduced and the density of the image signal near the outer periphery of the image pickup portion is increased based on the position information input from the address counter 14. The case where the shading phenomenon of the CRT displayed by the image signal output from the table unit 6 is corrected is shown. Further, a binarization function may be added to the table unit 6 to omit the processing of the image processing device.

[0021]

As described above, according to the present invention, in the image input device for converting the image signal of the work input from the image pickup device by the AD converter and outputting it to the image processing device, the image input device receives the image signal. By adding a representative density detection unit that detects a representative density of the image signal of the work and a table unit that inputs the representative density of the image signal detected by the representative density detection unit and corrects the density of the image signal of the work, When the density of the image signal input from the image pickup device is low, the image signal input to the table unit is expanded in accordance with the representative density input to the table unit from the representative density detection unit, and the image input from the image pickup device is expanded. When the signal density is high, it is compressed according to the representative density input from the representative density detector, so even a workpiece with a large density change can respond quickly with a simple circuit. , It is possible to obtain an image input apparatus which can output a stable image signal to the image processing apparatus.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an image input device of the present invention.

FIG. 2 is a diagram showing an image density level showing an effect of correcting the density of an image signal in the image input apparatus of the present invention.

FIG. 3 is a graph showing the correction function of the density of the image signal in the image signal of the image input apparatus of the present invention.

FIG. 4 is a graph showing another embodiment of the image input device of the present invention.

FIG. 5 is a block diagram showing another embodiment of the image input device of the present invention.

FIG. 6 is a graph showing the operation of another embodiment of the image input device of the invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Buffer amplifier, 2, 4 ... AD converter, 3 ... Low-pass filter, 5 ... Representative density calculation part, 6 ... Table part,
7 ... Low level signal, 8 ... High level signal, 9 ... Stabilized density signal, 15 ... Representative density detection unit.

Claims (1)

[Claims] 1. An image input device for converting an image signal of a work input from an image pickup device by an A / D converter and outputting the image signal to an image processing device. A representative image signal of the work input from the image pickup device. An image input characterized by adding a representative density detecting section for detecting the density and a table section for correcting the density of the image signal of the workpiece by inputting the representative density of the image signal detected by the representative density detecting section. apparatus.