JPH044477A - Image processing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is directed to a CCD (Character CCD) that images an object to be measured.
The present invention relates to a device for converting an output signal from a line image sensor (Coupled Device) into a binary signal, and particularly to a means for determining an optimal threshold for obtaining a binary signal.

[Prior Art] Various methods have been used to determine a threshold value when converting an output signal from a CCD line image sensor into a binary signal.

FIGS. 7 and 8 are block diagrams showing a schematic configuration of the main parts of a conventional image processing apparatus.

The operation of the apparatus shown in FIG. 7 will be explained below.

An image of an object placed between a light source (not shown) and a CCD line image sensor l is captured, and the CCD line image sensor l is driven by a clock pulse generated from a clock generation circuit 2 to obtain an output signal. This output signal is converted into an A/D signal by an analog/digital (A/D) converter 3.
The data is converted and taken into the CPU 5 or the like. This CP
The signal taken into U5 is an image signal in which bright and dark parts of the image are distributed, and from this signal,
The overall light amount distribution is created as a histogram, and the threshold value for binarization is set based on the average value. Then, the threshold value set in this way is applied to the comparator 4.
A binarized signal is obtained from the A>B output terminal of the comparator 4 by comparing it with the data input from the A/D converter 3 to the A input terminal of the comparator 4.

The device shown in FIG. 8 is also a conventional device for obtaining a binarized signal, but the difference from the device shown in FIG. The configuration is such that the value is fixed to an appropriate value using a switch or the like, and the other configuration and operation are the same as those shown in FIG.

[Problems to be Solved by the Invention] The output signal of a CCD line image sensor fluctuates due to aging, ambient temperature conditions, changes in the amount of light from a light source, etc.

Therefore, when the output signal from the CCD line image sensor fluctuates, if the threshold value is fixed to one value,
I can't see the subtle changes in the image.

As mentioned above, in the method of importing the data of the light intensity distribution for 1 degree and 2 minutes into the CPU, using the software to examine the distribution situation, creating a histogram, and obtaining the threshold value, It takes time to make a decision, and real-time processing is not possible. Therefore, there is a problem that it cannot follow sudden changes in light amount, temperature, etc.

In addition, it is difficult to determine the optimal threshold value with a device that fixes the threshold value, and in addition, the sensitivity is affected by changes in the amount of light over time and temperature, as well as the sensitivity of the CCD line image sensor and temperature. The problem is that it cannot keep up with changes in

This invention has been made to solve this problem, and it is an optimum method that can follow sudden changes in the light intensity of the light source and the sensitivity of the CCD line image sensor due to time, temperature, etc. An object of the present invention is to provide an image processing device that can create a high-resolution image by setting a threshold value.

[Means for Solving the Problems] In order to achieve the above object, the image processing device of the present invention includes a light shielding object placed in the middle of the optical system placed between the light source and the CCD line image sensor. Of the obtained signals, the CCD line image sensor includes a first system that samples bright areas and converts them into digital signals, and a second system that samples dark areas and converts them into digital signals, and the CCD line image sensor and an arithmetic unit comprising a clock generation circuit that drives a first system and a second system, respectively, and calculates an average value of two digital signals obtained from the first system and the second system, respectively; The apparatus includes means for comparing digital data obtained by digitally converting the output signal of the CCD line image sensor with data from the arithmetic unit to obtain a binary signal.

[Operation] By having the above configuration, it is possible to determine the threshold value each time data is read, thereby obtaining a stable binary signal.

[Examples] Examples of the present invention will be described below with reference to the drawings.

FIG. 3 is an explanatory diagram showing the outline of an apparatus in which a light source, an optical system, and a CCD line image sensor are arranged, and FIG. 4 is a waveform diagram of an output signal imaged by the apparatus of FIG. 3.

First, as shown in FIG. 3, the lens 11. An optical system consisting of a lens 12 is arranged, and the lens 11 converts light emitted from a light source 10 placed at the focal point of the lens 11 into parallel light, and the lens 12 causes the CCD line image sensor 1 to receive the light. The output signal of the CCD line image sensor 1 at this time has a waveform as shown by the solid line A in FIG.

In FIG. 4, when the light amount of the light source 10 changes, it is assumed that it changes accordingly as shown by the dotted line C in FIG. 4, or the distribution of the light amount in one line does not change.

Next, if a light blocking object is placed between the lenses 11 and 12 as shown in FIG. 5, the output of the CCD line image sensor 1 will be as shown in FIG. 6. The output signal of the CCD line image sensor shown in FIG. 6 is processed by the signal processing circuit shown in FIG.

FIG. 1 is a block diagram showing a schematic configuration of the main parts of an image processing device which is an embodiment of the present invention, and FIG. 2(a) shows a case where an image is taken with a light shield placed in the middle of the optical system. Figure 1(b) and (C) are waveform diagrams showing the output signals of the CCD line image sensor in Figure 1(a). FIG.

In FIG. 1, the output signal of the CCD line image sensor 1 is divided into three parts, one of which is input to the S/H circuit 5. The control signal of this S/H circuit 5 is the pulse signal shown in FIG. (low) to halt. Therefore, the signal in the dark (shadow) part of FIG. 2(a) is sampled and held. Another one of the three signals is input to the S/H circuit 6. The control signal of this S/H circuit 6 is the second one output from the clock generation circuit 2.
This is the pulse signal shown in Figure (c), and the signal of the part of the image signal shown in Figure (a) that has become brighter again is sampled and held.

Then, the signals sampled by the S/H circuits 5 and 6 are input to A/D converters 7 and 8, respectively, for A/D conversion.

The signal converted by the A/D converter 7 is converted into Dref, and the A/D converter 7 converts the signal into
If the signal converted by the D converter 8 is B ref, CC
The optimal threshold SL for binarizing the output signal from the D-line image sensor is SL=(Bref +Dr
ef)/2...It is determined by (1).

The calculation of this equation (1) is performed by the calculation section 9 in FIG. next,
The calculation section 9 calculates the equation (1) and sets the obtained threshold SL to the B input terminal of the digital comparator 4.

On the other hand, the other one of the output signals of the CCD line image sensor divided into three directions is input to the A/D converter 3, and the A/D converted signal is set to the input terminal of the comparator 4.

Then, the binarized signal is output to the A>B output terminal of the comparator 4.

As shown in the above embodiment, the present invention calculates and determines the threshold value each time image data is read, so that it can be easily adjusted to avoid fluctuations in CCD sensitivity due to variations in light sources, changes in time and temperature, etc. Regardless, it is possible to obtain a stable binary signal.

Therefore, by using the obtained binary signal and connecting it to an edge detector, for example, to measure the outer diameter of an object, accurate edge detection can be performed.

[Effect of the invention 1] As explained above, since this invention monitors the bright and dark areas for each line, the light intensity of the light source, the sensitivity of the CCD line image sensor, etc. change rapidly due to time, temperature, etc. Also automatically sets the optimal threshold.

Therefore, even if the amount of light from the light source is intentionally changed, the threshold value is automatically set to the optimum value.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a schematic configuration of the main parts of an image processing device that is an embodiment of the present invention, and Fig. 2 (a) shows a CCD when an image is taken with a light shield placed in the middle of the optical system.
A waveform diagram showing the output signal of the line image sensor. Figures (b) and (C) are waveform diagrams of pulses that respectively control the sample and hold (S/H) circuits 5 and 6 in Figure 1 (a). Fig. 3 is an explanatory diagram showing the outline of a device in which a light source, an optical system, and a CCD line image sensor are arranged, Fig. 4 is a waveform diagram of an output signal imaged by the device in Fig. 3, and Fig. 5
The figure is an explanatory diagram showing a state in which a light blocking object is placed in the middle of the optical system in Figure 3. - Figure 6 shows the output signal of the CCD line image sensor when imaging the state in Figure 5. The waveform diagram, FIGS. 7 and 8 are block diagrams showing the schematic configuration of the main parts of a conventional image processing device. In the figure: 1: CCD line image sensor 2: Clock generation circuit 3.7, 8: A/D converter 4: Comparator 5.6: S/H circuit 9: Arithmetic unit 10: Light source 11. 12: Lens agent Patent Attorney 1) Haru Kitatake (1'1 Section D ()V)

Claims (1)

[Claims] Among the signals obtained by placing a light shield in the middle of the optical system placed between the light source and the CCD line image sensor,
It has a first system that samples bright areas and converts them into digital signals, and a second system that samples dark areas and converts them into digital signals. a clock generation circuit for driving each of the first and second systems, an arithmetic unit that calculates the average value of two digital signals respectively obtained from the first system and the second system, and an output of the CCD line image sensor. An image processing device comprising means for comparing digital data obtained by digitally converting a signal with data from the arithmetic unit to obtain a binarized signal.