JPH02116000A - Photoelectric detector - Google Patents

Abstract

PURPOSE:To prevent a malfunction by composing the title device so that a light beam projected from a projector can be reflected on a reflector and made incident to a light receiver, detecting the output of the light receiver, and extracting the intermittent component of the output. CONSTITUTION:A projector 1 projects an intermittent infrared ray beam 5 in a prescribed direction. Further, a reflector 6 for the infrared ray beam 5 is arranged, for example, at a position at the distance of several ten meters from a pedestal 4, the reflection beam 7 is made incident to a light receiver 2, and the output of this light receiver 2 is applied to a detector 3. Further, when an illegal invader 11 interrupts one of the beams 5 and 7, the detector 3 detects the interruption and ceases the beam 7 made incident to the light receiver 2. Thus, the malfunction caused by a light beam reflected on the detected body 11 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoelectric moving object detection device using invisible light, etc., which is used, for example, to detect illegal intruders and send out a warning.

For example, infrared detection devices are used to detect illegal intruders into houses and issue alarms. In such a device, the projected infrared beam is incident on the receiver through the reflector, and an alarm is generated when the incident beam is interrupted by an intruder.
Since the projector, the receiver, the detection circuit for the output thereof, etc. can be arranged at the same position, for example, the manufacturing and installation of the device is facilitated. However, if the intruder's clothing has a high reflectance of the light beam, the beam incident on the reflector may be blocked by the intruder, and at the same time the reflected light beam from the intruder may enter the receiver, causing malfunction. . Therefore, the present invention attempts to prevent such malfunctions.

The present invention is constructed so that the light beam projected from the projector is reflected by a reflector and enters the receiver, and a liquid crystal shutter or a mechanical chopper is provided in front of the reflector that repeatedly opens and closes at high speed. etc., and the reflected light beam is intermittent at a constant high speed. Therefore, by detecting the output of the photoreceiver and extracting this intermittent component, the light reflected by the clothes of the intruder can be removed, and only the presence or absence of the reflected light by the reflector can be reliably detected to prevent malfunctions. Can be done. Because of the parentheses, it is possible to reliably detect the presence or absence of weak light reflected by the reflector, so the distance between the emitter and receiver and the reflector can be increased to perform detection over a wide range. Since it can be easily operated using a small capacity battery power source, the reflector part is also simple and easy to construct.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, in which a projector 1, a receiver 2, and a detector 3 for its output are integrally constructed on the same base 4, and the projector I is oriented in a predetermined direction. For example, an intermittent infrared beam 5 is projected towards. Furthermore, a reflector plate 6 for the infrared beam 5 is arranged at a distance of, for example, several tens of meters from the base 4, and the reflected beam 7 is made incident on the photoreceiver 2, and the output of the photoreceiver is transmitted to a detector. This is in addition to 3. Further, in front of the reflection plate 6, there is provided an optical modulator 1O consisting of, for example, a liquid crystal plate 8 and its driving circuit 9. The circuit 9 is composed of, for example, a small-capacity dry cell battery and a simple oscillation circuit, and the liquid crystal plate 8 repeats a transparent state and an opaque state at a frequency of, for example, several hundred to several thousand hertz, and operates as an intermittent shutter against infrared rays. It is designed to work.

In the above device, the projector l projects an intermittent infrared beam 5 of, for example, several tens or hundreds of hertz, as shown in FIG. The infrared rays reflected by the reflecting plate 6 pass through the liquid crystal plate 8 again and enter the light receiver 2. A rectangular wave voltage of several thousand hertz, for example, as shown in FIG. 2 is applied to the liquid crystal plate 8 from a drive circuit 9. Therefore, the liquid crystal plate 8 repeats transparent and opaque states at the above-mentioned frequency and acts as a shutter that cuts off the light beam, so that the beam 7 has the waveform shown in FIG. 2C. That is, since the light receiver 2 sends out an output as shown in FIG. 2C, the detector 3 detects this and obtains an output d having the same waveform as a.

In other words, the detector 3 in FIG. 1 always detects the signal shown in FIG. , the beam 7 incident on the photoreceiver 2 disappears. Furthermore, even if the beam 12 reflected by the intruder II is incident on the light receiver 2, this beam 12 does not pass through the liquid crystal plate 8 and is therefore not modulated by the voltage shown in FIG.

Therefore, the output of the photoreceiver 2 has the waveform shown in the figure a, and since it is not subjected to high frequency modulation, the detector 3 cannot be operated to obtain the signal d. In the above embodiment,
Although the liquid crystal plate 8 is used as the optical modulator, it is of course possible to use, for example, a mechanically operated high-speed shutter.

As described above with respect to the embodiments, the device of the present invention is free from the risk of malfunction due to light rays reflected by the detected object, and can reliably detect the interruption of the light beam by the detected object and obtain accurate information. can. Furthermore, objects to be detected whose movement speed is extremely low or objects that remain stationary for a long period of time can be reliably detected. Furthermore, since there is no risk of malfunction due to reflected light from the object to be detected, it is possible to project a powerful light beam and increase the detection distance, and the reliability of detection is also improved. In addition, the detection range can be arbitrarily selected by placing the emitter, receiver, and reflector at appropriate positions, and at the same time, by placing the emitter and receiver at the same location as in the example, they can be integrated. By configuring this, the device can be manufactured in a small size and at low cost.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a diagram showing the configuration of an embodiment of the present invention.
FIG. 3 is a signal waveform diagram of each part in the device shown in the figure. In the figure, 5 is an infrared beam, 6 is a reflector, 7 is a reflected beam, 8 is a liquid crystal board, IO is an optical modulator, 11 is an illegal intruder, 1
2 is a reflected beam.

Claims (1)

[Claims] a light projector that projects a light beam in a predetermined direction; a reflector that is arranged so that the light beam is incident thereon; a light receiver that is arranged so that the light beam reflected by the reflector is incident thereon; It consists of an optical modulator placed on the front and intermittent at a predetermined frequency of at least one of the light rays incident on the reflector or the light rays reflected, and a detector that extracts the component of the frequency from the output of the light receiver. Photoelectric detection device