JPS5914790B2 - optical identification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical identification device that optically identifies an object to be recognized.

There are two main types of optical methods for optically identifying the object's color, including its color. One is to illuminate the object with a DC light source and detect the reflected light. This method has the disadvantage that it is extremely difficult to stabilize the DC level due to changes in the power of the DC amplifier and detector, changes in disturbance light, etc., and accurate identification is not possible.

Another method uses a modulated light source to AC amplify the output of the detector, then rectifies it, and uses the rectified output to perform identification. Although the shortcomings can be improved, there is a certain upper limit to the modulation frequency of the light source because the sensitivity and response of the detector conflict with each other in terms of performance, so it is difficult to recognize small no-turns moving at high speed. There is a drawback. Also, applying modulation 15
The light source that can do this is limited to light-emitting diodes. That is, when an incandescent lamp is used as a light source, the light must be mechanically chopped, which increases the size of the device, lowers the reliability ratio, and makes it impossible to increase the modulation frequency very high20. Also, lasers are expensive,
It is not easy to operate stably. The present invention improves the drawbacks of the conventional example as described above, and its purpose is to enable stabilization of the DC level with a simple configuration, and to enable high-precision identification without any restrictions on the light source or detector 25 used. The goal is to make it possible.

Examples will be described in detail below. FIG. 1 is a block diagram of an embodiment of the present invention, in which 1 is a light source such as an incandescent lamp, discharge lamp, light emitting diode, or laser; 2 is an object to be recognized having 30 pieces of information such as shape, color, and surface pattern; 3 is a photodiode, a phototransistor, a photomal,
A detector such as a diode array or an image pickup tube, 4 a DC amplifier, 5 a sampling circuit, 6 a hold circuit, 7 a difference circuit, 8 a sampling/timing circuit, and 935 a reset circuit. Irradiating the object 2 with light from the light source 1,
The reflected light is detected by the detector 3, and the object to be recognized is c.

Scanning by transporting the frame 2, scanning by deflecting the light from the light source 1 by a deflecting means, self-scanning by a diode array or an image pickup tube, etc. can be adopted, and the output of the detector 3 is It is amplified by a DC amplifier 4.

The output of the DC amplifier 4 is branched into two, one being applied to the sampling circuit 5 and the other being applied to the difference circuit 7.

The sampling circuit 5 performs a sampling operation using the sampling pulse from the sampling timing circuit 8, and is composed of an analog switching element such as a field effect transistor and a gate circuit. The output of this sampling circuit 5 is held in a hold circuit 6 and reset by the output of a reset circuit 9. It is also possible to omit the resetting circuit 9, perform resetting using the sampling pulse, and hold the output of the DC amplifier 4 sampled by the sampling nogle. The above-mentioned sampling pulse is set to occur at the timing immediately before the detection output signal of the object 2 to be recognized is obtained. For example, the timing immediately before the optical scanning line hits the object 2 to be recognized is set to It is set based on the relationship between the starting position of the line and the position of the object to be recognized 2.

In the case of scanning when the object 2 to be recognized is being transported, the object position detector detects when the object 2 to be recognized comes just before the scanning position, and that point is set as the generation timing of the sampling pulse. . In addition, in the case where the object 2 to be recognized is stationary and scanning is performed by deflecting the light from the light source 1 by the deflection means, a light flux position detector is provided immediately before the scanning light input side of the object 2 to be recognized. , the timing at which the beam position detector detects the scanning light is the timing for generating the sampling pulse. Furthermore, in the case of self-scanning with an image pickup tube, etc., if the object 2 to be recognized is placed at a predetermined position within the field of view of the image pickup tube, the point immediately in front of the object 2 will be Since the time required for scanning by the beam is determined, the horizontal synchronizing signal is delayed and the timing at which this time elapses is set as the generation timing of the sampling pulse. Therefore, the output signal of the hold circuit 6 is
A level is maintained due to the light from the light source 1 and the disturbance light reflected from the background immediately in front of the object to be recognized 2 and the offset of the DC amplifier 4, and this level is maintained at the time when the light scanning of the object to be recognized 2 ends. Alternatively, it is held until the next optical scanning starts. FIG. 2 is a waveform diagram explaining the operation. FIG. 2A shows an example of the output signal waveform of the DC amplifier 4, FIG. 2B shows an example of the output signal waveform of the hold circuit 6, and FIG. 2C shows an example of the output signal waveform of the difference circuit 7. It shows. In the figure, Tl and Tl' are sampling timings, T2 and T2' beam setting timings, L is the length of the object to be recognized 2, DO and DO' are disturbance light, offset of the detector 3, and DC amplifier. The levels Ds and Ds' of unnecessary fluctuations due to the offset etc. of 4 are the detection signal levels of the object 2 to be recognized. The output signal of the DC amplifier 4 is sent to the sampling circuit 5 at the timing of Tl and Tl'.
When sampled at , the output signal of the hold circuit 6 is at level D, which is the amount of unnecessary fluctuation.

, DJ, and is held until the next timing T2, T2'. Therefore, by performing calculations such as A-B in the difference circuit 7, the output signal of the difference circuit 7 is determined to be the object to be recognized between T1 and T2 and between T1' and T2', as shown in FIG. 2C. By adding the output signal of this difference circuit 7 to an identification processing circuit (not shown), identification can be performed without being affected by offset fluctuations of the DC amplifier. Further, in the case of identifying the color of the object to be recognized 2, by providing the above-described configuration for each wavelength of each color, it becomes possible to identify color patterns with high accuracy.

As explained above, according to the present invention, not only the light source can be freely selected, but also the detector can be freely selected, and by performing DC amplification, there is no need for complex light source modulation, and the drift of the DC amplifier can be eliminated. There is also an advantage that the output signal of the difference circuit essentially becomes the detection signal of the object to be recognized, making it possible to accurately identify the object.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 A-C
is a waveform diagram illustrating operation. 1 is a light source, 2 is an object to be recognized, 3 is a detector, 4 is a DC amplifier, 5 is a sampling circuit, 6 is a hold circuit, 7 is a difference circuit, 8 is a sampling timing circuit, and 9 is a resetting circuit.

Claims (1)

[Claims] 1 A light source that irradiates light onto an object to be recognized, a detection means that scans the object relatively to detect reflected light, and a DC amplifier that amplifies the output signal of the detection means, In a device that identifies the object to be recognized based on a detection output signal from reflected light, a sampling timing for generating a sampling pulse by detecting the point in time when the point immediately before the object to be recognized is being scanned for each scan. means, a sampling circuit that samples the output signal of the DC amplifier at the time when the sampling pulse is generated, a hold circuit that holds the output signal of the sampling circuit at least while the detection signal of the object to be recognized is obtained, and the hold circuit. An optical identification device comprising a difference circuit for adding the output signal of the DC amplifier and the output signal of the DC amplifier.