JPS6057527B2 - Reflective photoelectric detector - Google Patents

Description

[Detailed description of the invention] The present invention relates to a reflective photoelectric detector.

Conventionally, the light emitter and receiver are integrated so that the light from the emitter is modulated by an oscillation circuit, the modulated light is reflected by the human body, and the reflected light is received by the receiver. In a reflective photoelectric detector with an integrated emitter and receiver, which detects and outputs changes in the modulated light that is received, a differentiating circuit or an integrating circuit is used to detect only the changes. A configuration that detects the change is also used.
For this reason, it has the disadvantage that it operates even when there is an instantaneous change in the output of the light receiver, such as lightning, flashing illumination, light emission from a flash bulb, or electrical noise input, resulting in false alarms being generated. Conventionally, the solution to these problems was to provide a separate detection circuit for instantaneous changes so that it acts as a negative circuit for instantaneous changes, but this conventional circuit complicates the overall circuit configuration. There was a drawback. The present invention has been provided in view of the above-mentioned points, and is intended to be used when lightning, flashing illumination light, flash bulb light emission, or pulsed electrical To provide a reflection type photoelectric detector which does not issue a false alarm even when there is a pulsed output change in a photodetector due to input of noise into the photodetector circuit, etc., and has a simplified circuit configuration. The purpose is to

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment circuit of the present invention, in which a light receiver composed of a light receiving element such as a solar cell receives reflected light from a human body or other detected object of modulated light emitted from a projector. The output of the photoreceiver is then amplified by a suitable AC amplification circuit and then input to the detection circuit 2. The detection circuit 2 is mainly composed of a transistor 7, and the collector resistance of the transistor 7 is constituted by three voltage dividing resistors 8, 9, and 10, so that the output voltage of the detection circuit 2 is divided into three parts. be. Reference numeral 1 denotes a change detection circuit which inputs each output of the detection circuit 2 divided into three voltages, and includes two comparators 3 and 4 for setting upper and lower limits;
The OR outputs of both comparators 3 and 4 are input to an integrating circuit 11 at the next stage.

In this change detection circuit 1, the output voltage on the high potential side of the detection circuit 2 divided into three voltages is inputted to the positive input terminal of the upper limit comparator 3 via the time constant circuit 5, and the output voltage on the intermediate potential side is directly input to the negative input terminal of the upper limit comparator 3 and the positive input terminal of the lower limit comparator 4, and the output voltage on the low voltage side is further inputted to the negative input terminal of the lower limit comparator 4 via the time constant circuit 6. The outputs of both comparators 3 and 4 are commonly connected to the next stage integration circuit 1.
1, and its output is input to an integration time constant circuit consisting of a resistor 13 and a capacitor 14. The output of this integration circuit 11 is the detection circuit 15
When the output of the integrating circuit 11 exceeds a predetermined level, an output signal is generated in the level detecting circuit 15. In the circuit shown in FIG. 1, the input voltage of the comparator 3 for setting the upper limit threshold via the time constant circuit 5 is a, and the input voltage of both comparators 3 and 4 corresponding to the input signal is set to the time constant circuit b1. When the input voltage of the comparator 4 for setting the lower limit threshold value via 6 is cm, the input voltage b is equal to the input voltage a for setting the threshold value as shown in Fig. 2A.
or when c is exceeded to the upper or lower side, both comparators 3
, 4 generates an output signal corresponding to the temporal change in the input signal as shown in Figure 1. This results in an integral output like this. Therefore, the level detection circuit 15 generates a detection output signal as shown in FIG. 2 when the output of the integration circuit 11 exceeds a predetermined level L. As described above, the present invention includes a light receiver that receives the reflected light of the modulated light projected from the light emitter, a detection circuit that detects a signal obtained by amplifying the output of the light receiver, and a change in which the output of the detection circuit is input. In a reflective photoelectric detector consisting of a minute detection circuit and a detection means for detecting the movement of a detected object such as a human body based on the output of the change detection circuit, a voltage dividing circuit is provided to divide the output voltage of the detection circuit into three parts. , a change detection circuit is formed by comparators for setting upper and lower limits that detect level changes based on the output of the voltage dividing circuit, and an integrating circuit that integrates the OR output of both comparator outputs, and an integrating circuit that detects level changes at a predetermined level. A detection means is formed with a level detection circuit that outputs a detection signal when the voltage exceeds 3, and a voltage signal between the voltages divided into three voltages is directly input to both comparators, and the upper side of the voltage divided into three voltages is directly input to both comparators. Since the lower and lower voltage signals are input to the input terminals for threshold setting of each comparator via time constant circuits, the output signal corresponding to the change in the photoreceiver output is output as the OR output of both comparators. This has the effect that the object to be detected can be accurately detected without being influenced by aging or external conditions.

Furthermore, since the present invention performs a detection operation when the output obtained by integrating the OR outputs of the two comparators exceeds a predetermined level, it is possible to suppress and eliminate the pulsed output of the photodetector by the integration operation of integrating the OR outputs. Therefore, there is no possibility of false alarms caused by lightning, flashing lights, flash bulb emissions, or pulsed electrical noise, and stable and highly reliable detection operation can be achieved. Furthermore, there is no need to provide a separate detection circuit for the output of the pulsed photoreceiver or a circuit for suppressing the alarm operation based on the output of this detection circuit as in the past, and the circuit configuration can be greatly simplified. It is something.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the same operation. 1 is a change detection circuit, 2 is a detection circuit, and 3
, 4 are comparators, and 5 and 6 are time constant circuits.

Claims (1)

[Claims] 1. A light receiver that receives the reflected light of the modulated light projected from the light emitter, a detection circuit that detects a signal obtained by amplifying the output of the light receiver, and a change detection circuit that receives the output of the detection circuit.
In a reflective photoelectric detector comprising a detection means for detecting the movement of a detected object such as a human body based on the output of a change detection circuit, a voltage dividing circuit is provided to divide the output voltage of the detection circuit into three parts,
A change detection circuit is formed by comparators for setting upper and lower limits that detect level changes based on the output of the voltage dividing circuit, and an integrating circuit that integrates the OR output of both comparator outputs, and an integrating circuit that detects level changes when the output of the integrating circuit reaches a predetermined level. A detection means is formed with a level detection circuit that outputs a detection signal when the voltage exceeds the level, and a voltage signal between the voltages divided into three voltages is directly input to both comparators, and the voltage signal above the voltage divided into three voltages and A reflective photoelectric detector characterized in that a lower voltage signal is inputted to an input terminal for setting a threshold value of each comparator via a time constant circuit.