JPH0216459B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention attempts to detect an intruder by detecting infrared rays emitted from a human body using an infrared detection element that responds to changes in infrared energy.

Intrusion detection devices using infrared detection elements have been known for some time. The conventional example shown in Figure 1 A and B is as follows:
Two infrared sensing elements B and C are located vertically near the focal point of the parabolic reflector A, and are connected so that the outputs of these infrared sensing elements B and C have opposite polarities, and their outputs are are amplified in width D and D', and their outputs are outputted through level detection circuits E and E', so that they are activated only when both infrared detection elements B and C simultaneously output an output of a predetermined level or higher. It is an intrusion detector.

In this conventional example, since both infrared sensing elements have opposite polarities, it is possible to eliminate noise generated from components in the signal processing circuit and malfunctions due to power supply noise, but when both infrared sensing elements output simultaneously, Since the structure is such that infrared energy is incident on both detection elements at the same time, such as when an incandescent light is turned on near the detector or when sunlight enters, it may malfunction. .

This invention aims to improve the above-mentioned drawbacks.

An embodiment of the infrared detector of the present invention will be described in detail below.

In the figure, numeral 1 is a parabolic reflector that constitutes the optical system. This optical system 1 does not need to be a parabolic reflector and may be, for example, a semi-parabolic reflector.
2 and 3 are infrared detection elements, such as pyroelectric elements, which generate voltage when infrared rays are incident thereon. The pyroelectric elements 2 and 3 are arranged parallel to the moving direction P of the person. Therefore, the infrared rays emitted from a human body moving in the P direction are
Since it passes through the heat receiving range 4 of the pyroelectric element 3, an output is output from the pyroelectric element 3. Then, since it passes through the heat receiving range 5, an output is output from the pyroelectric element 2. The outputs of these two pyroelectric elements 2 and 3 are input to the signal processing circuit 13. This signal processing circuit 13 is comprised of an amplification circuit 6, a waveform shaping circuit 8, an integration and synthesis circuit 14, and an output circuit. Therefore, the two pyroelectric elements 2,
3 is input to the amplifier 6. At this time, the pyroelectric elements 2 and 3 are connected so that their outputs have opposite polarities.
Therefore, at the output terminal 7 of the amplifier 6, an output shown by a waveform a is produced as shown in FIG. 5i. This output is input to a waveform shaping circuit 8, for example, a window comparator as shown in FIG. When the input Vx is higher than the predetermined level Va, input from comparator 9.
When Vx is lower than the predetermined level Vb, a rectangular wave is output from the comparator 10 (see the left column of FIG. 5). The outputs of each of these are integrated into integration circuits 11 and 1.
1' and synthesized by a synthesis circuit 12. For example, as shown in FIG. 7, the voltage VF across charging capacitors C ₁ and C ₂ is a composite voltage output. A transistor that shorts both ends of this capacitor C ₁ and C ₂
The configuration is such that both outputs of the window comparator are inverted and inputted to the bases B ₁ and B ₂ of Tr ₁ and Tr ₂ . By doing so, the transistors Tr ₁ and Tr ₂ become non-conductive when there is an output from the waveform shaping circuit 8, and charge the capacitor C ₁ or C ₂ . When this combined output exceeds the voltage VG, an output is generated.

Next, when power supply noise occurs with the same polarity and a time lag (see waveform b in the right column of Figure 5), since there is no negative side waveform, the integrated and synthesized output does not exceed level VG and no output is produced. In addition, in the case of lighting or sunlight, both infrared detection elements 2 and 3
Since infrared energy is supplied to both elements at the same time, the outputs of both elements are cancelled, which is the same as no output, and no malfunction occurs.

Note that FIG. 8 shows an embodiment in which the outputs of the pyroelectric elements 2 and 3 are input to the amplification circuits 6' and 6'' separately. Note that a semiconductor infrared sensor is used as the infrared detection element. If so, the power supply voltage will be divided by this semiconductor infrared sensor and the resistor, and the voltage at this voltage division point will be input to the amplification circuit.

As described above, according to the present invention, the detection areas are arranged at intervals in the direction of passage of the person.
an optical system that allows infrared rays from the human body to be collected at different infrared detection elements at different times;
The outputs of the two infrared detecting elements are connected so that they have opposite polarities, and the output waveforms of the infrared detecting elements are waveform-shaped and then integrated by respective integrating circuits. The infrared detector is made up of a signal processing circuit that synthesizes signals so that the intruder is detected, and outputs an output if the output of this synthesis circuit exceeds a predetermined level, making it possible to reliably detect intruders. It is possible to obtain a highly reliable infrared detector that does not malfunction due to electrical noise such as power supply noise, and does not malfunction even when exposed to lighting or sunlight.

[Brief explanation of drawings]

Figures 1A and 1B show conventional examples of the present invention;
Figure A is a schematic diagram of a means for concentrating heat onto infrared detecting elements B and C in optical system A, and Figure B is a signal processing circuit diagram thereof. 2 to 8 are drawings for explaining one embodiment of the present invention, in which FIG. 2 is a schematic diagram of the optical system, FIG. 3 is a block diagram, and FIG. 4 is a circuit diagram of the amplifier circuit 6. , FIG. 5 shows the output waveforms of each circuit in FIG. 3, and FIGS. 6 to 8 show electrical circuit diagrams.

Claims (1)

[Claims] 1. An optical system that collects infrared rays from a human body at different times on two infrared detecting elements whose detection areas are arranged at intervals in the direction in which the person passes; The outputs of the infrared sensing elements are connected so that they have opposite polarities, and the output waveforms of these infrared sensing elements are waveform-shaped and then integrated by each integrating circuit, so that the outputs of each integrating circuit have the same polarity. An infrared detector consisting of a signal processing circuit that performs synthesis and outputs an output if the output of the synthesis circuit exceeds a predetermined level.