JPH0654356B2 - Hot wire detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat ray detector for detecting the heat ray radiated from a human body or the like to identify the presence or absence of an intruder and prevent theft or the like. .

(Prior Art) In a conventional heat ray type detector, a plurality of warning beam areas are set by a reflecting mirror, and a heat ray emitted when an intruder from outside crosses the warning beam area is detected by a light receiving element. Then, the presence or absence of an intruder is identified by obtaining a detection pulse having an amplitude corresponding to the intensity of the heat ray and processing this detection pulse by a predetermined signal processing means.

By the way, in such a heat ray type detector, it is required to reliably distinguish noise from a detection signal and always operate stably with respect to noise to give a highly reliable alarm without false alarm. For this reason, conventionally, the detection signal from the detection element is compared with a predetermined threshold to distinguish between noise and the detection signal, or a detection signal exceeding a predetermined threshold is detected within a predetermined time. In addition, signal processing means is provided to distinguish between noise and a detected signal, assuming that the detected signal is correctly detected only when a predetermined number is counted.

As shown in FIG. 7, the light receiving element 1 generates a detection signal having an amplitude corresponding to the strength of the heat ray as a means for discriminating noise from the detection signal by comparing with the predetermined threshold value. The detection signal is amplified by the amplifier 2 to a level at which signal processing is possible, rectified by the absolute value circuit 3 into a signal having the same polarity, and then supplied to the comparator 4. Then, when the output signal from the absolute value circuit 3 exceeds the threshold value of the comparator 4, it is determined that a true detection signal is obtained, and the comparator 4 supplies an alarm signal to the alarm circuit 5 to issue an alarm. It is designed to be used.

On the other hand, the latter means for discriminating between noise and detection signals by counting a predetermined number of detection signals within a predetermined time is, as shown in FIG.
The detection signal output from is amplified to a predetermined level by the amplifier 2 and rectified into a signal of the same polarity by the absolute value circuit 3,
The pulse signal is output from the comparator 4 only when the rectified signal exceeds a predetermined threshold value. The timer circuit 7 is activated based on this pulse signal and supplies a rectangular signal having a predetermined time width to the counting circuit 8. The counting circuit 8 outputs the rectangular signal from the comparator 4 only within the time set by this rectangular signal. Count pulse signals. When the count result is a preset count, an alarm signal is supplied from the counting circuit 8 to the alarm circuit 5 to issue an alarm. That is, even if instantaneous noise is applied to the counting circuit 8 and the counting circuit 8 erroneously counts, it is reset after a predetermined time set by the rectangular signal from the timer circuit 7 and an alarm signal is supplied to the alarm circuit 5. Therefore, false alarms can be prevented.

(Problems to be Solved by the Invention) However, in such a conventional heat ray type detector, in the case of the configuration shown in FIG. 7, there is a problem such as popcorn noise generated inside the light receiving element 1. The noise that occurs instantaneously and sporadically and that has a relatively large amplitude cannot be removed even by the pass band limitation of the frequency set in the amplifier 2, and the noise and the detection signal are compared in the comparator 4. It was extremely difficult to identify. Also, the eighth
In the case of the configuration shown in the figure, for example, when a single popcorn noise is applied to the input side of the amplifier 2, the amplitude of the amplitude of the first noise peak is vibrated and subsequently attenuated by the AC amplification of the amplifier 2. Therefore, the counting circuit 8
When the alarm signal is output at 2 counts, there is a problem that the alarm signal is output at the count of the first noise peak and the subsequent attenuating amplitude peak, and an erroneous alarm is issued.

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned conventional problems, and it is possible to eliminate noise generated in the light receiving element, such as popcorn noise, which is generated instantaneously and sporadically. It is an object of the present invention to provide a hot-wire detector that can effectively discriminate a desired detection signal detected by a light-receiving element, operate stably against noise, and give an accurate alarm. In order to achieve this object, the present invention has a reflection mirror that forms a warning beam region and a light receiving unit that is formed by closely connecting two pyroelectric infrared sensors to each other in a differential pair connection. When the object to be detected crosses, the heat ray radiated from the object to be detected is detected by the light receiving section, and a detection signal including a small amplitude corresponding to a change in the intensity of the heat ray and a vibration with a large amplitude following the detection signal are detected. Signal detection that generates a light-receiving circuit and a signal that exceeds a predetermined threshold value, holds the peak value at the same time, and generates an alarm signal only when a signal with an amplitude larger than the peak value is detected within a predetermined time And a circuit are provided.

(Embodiment) An embodiment of a heat ray detector according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a heat ray detector according to this embodiment, which includes a light receiving circuit 9 for generating a detection signal having an amplitude corresponding to the intensity of the detected heat ray, and an amplifier 10 for amplifying the detection signal. , An absolute value circuit 11 for rectifying the output signal from the amplifier 10 into a signal of the same polarity, and a signal identifying circuit 12 and a signal identifying circuit 12 for signal processing the output signal from the absolute value circuit 11.
And an alarm circuit 13 for issuing an alarm based on an alarm signal supplied from

Here, the light receiving circuit 9 has the circuit configuration shown in FIG. In FIG. 2, the light receiving circuit 9 is an integrally structured light receiving section in which one contact of each of two pyroelectric infrared sensors 14 and 15 provided extremely close to each other is connected in series with opposite polarities.
16, the other contact of the pyroelectric infrared sensor 15 is connected to the ground terminal 17, the other contact of the pyroelectric infrared sensor 14 is connected to the gate terminal of the field effect transistor 18 and the resistor 19. . The drain terminal of the field effect transistor 18 is connected to the output terminal 20 connected to the input terminal of the amplifier 10 shown in FIG. 1, and also connected to the ground terminal 17 via the resistor 21, and the source terminal is connected to the power supply terminal 22. Connected.
As described above, the light receiving unit 16 is composed of the pyroelectric infrared sensors 14 and 15 connected in series with opposite polarities, and therefore has differential characteristics, and each of the pyroelectric infrared sensors 14 and 15 generated. A differential signal of the signals is output to the output terminal 20 via the field effect transistor 18.

FIG. 3 is an explanatory diagram showing the operation of the light receiving circuit having this differential characteristic. As shown in FIG. 3A, an object that radiates heat rays traverses in front of the light receiving section 16 in the XY directions. In that case, the detection signal as shown in FIG.
That is, when an object penetrates in front of the first pyroelectric infrared sensor 14, the infrared sensor 14 generates a differential waveform signal corresponding to the amount of change of the heat ray due to the movement of the object, and the differential waveform signal is received. It is output in a state of being integrated by the time constant and the like inside the circuit 9. Next, while the object is away from the first pyroelectric infrared sensor 14, the second pyroelectric infrared sensor
When entering the infrared ray sensor 15, both infrared sensors 14 and 15 both generate a differential waveform signal corresponding to the amount of change of the heat ray, so that the differential signal of these differential waveform signals is output in an integrated state. Therefore, a detection signal having a larger amplitude and a reverse polarity than the detection signal detected by only the first pyroelectric infrared sensor 14 is output to the output terminal 20. When the object moves away from the second pyroelectric infrared sensor 15, the infrared sensor 15 generates a differential waveform signal corresponding to the amount of change of the heat ray, and the differential waveform signal is generated by the time constant of the light receiving circuit 9 or the like. The integrated signal is output to the output terminal 20, and a detection signal having a waveform as shown in FIG. That is, with the waveform of FIG.
The waveform of FIG. 9D is obtained as a waveform obtained by adding and synthesizing the waveform of FIG. The light receiving section 16 is a pyroelectric infrared sensor with extremely uniform characteristics.
Since it is configured by connecting 14 and 15 in a differential pair, it is not easily affected by changes in ambient temperature and voltage fluctuations of the power supply, and a stable detection signal is generated. In FIG. 3 (a), for convenience,
Although the pyroelectric infrared sensors 14 and 15 are shown separated from each other, they are actually provided very close to each other.

Next, the circuit configuration of the signal identifying circuit 12 will be described with reference to FIG. In the figure, 23 is an input terminal connected to the output terminal of the absolute value circuit 11, and 24 is an output terminal connected to the input terminal of the alarm circuit 13. Reference numeral 25 is a comparator that connects the non-inverting input terminal to the input terminal 23 and connects the inverting input terminal to the reference voltage source 26. The output terminal of the comparator 25 is the input terminal I _{C of the} 2-bit binary counter circuit 27. Also, it is connected to the input terminal I _M of the monostable multivibrator (hereinafter referred to as one-shot multi) 28. One shot multi 28 output terminal
Q _M is connected to the set terminal SC of the counter circuit 27 and the set terminal SP of the peak hold circuit 29. The input terminal I _P of the peak hold circuit 29 is connected to the input terminal 23 via the switch element 30 such as an analog switch whose opening and closing is controlled by the control signal from the lower bit output terminal Q ₁ of the counter circuit 27, and the output terminal Q _P is connected to the inverting input terminal of the second comparator 31. Further, the non-inverting input terminal of the comparator 31 is connected to the input terminal 23 via a switch element 32 such as an analog switch whose opening and closing is controlled by a control signal supplied from the upper bit output terminal Q ₂ of the counter circuit 27. The output terminal of the comparator 31 is connected to the alarm circuit 13 via the output terminal 24.

The second comparator 31 always generates an alarm signal only when the voltage applied to the non-inverting input terminal is higher than the voltage applied to the inverting input terminal. Offset voltage Vos is set.

In the signal identification circuit 12 having such a configuration, the one-shot multi-28 outputs a rectangular signal having a preset width,
While outputting this rectangular signal, the start signal is input
A so-called non-retriggerable monostable multivibrator that does not restart when supplied to I _M is used.
The counter circuit 27 and the peak hold circuit 29 perform a predetermined operation only while the rectangular signals from the one-shot multi 28 are supplied to the respective set terminals SC and SP. That is, while the rectangular signal is supplied, the counter circuit 27 counts the rectangular signal from the comparator 25 and outputs the lower bit output terminal Q ₁
Also, the result of the binary count is output to the high-order bit output terminal Q ₂ , and this output serves as a control signal for the switch elements 30 and 32. When the outputs of the respective output terminals Q ₁ and Q ₂ are at the “H” level, the switch elements 30 and 32 are closed and in the conductive state, and when the outputs of the output terminals Q ₁ and Q ₂ are at the “L” level,
The switch elements 30 and 32 are opened to be in a non-conductive state. When the conductive state switching device 30, holds a peak voltage of the supplied detection signal to the input terminal 23, and outputs the holding voltage from the output terminal Q _P. The comparator 31 compares the level of the detection signal supplied to the input terminal 23 with the level of the holding voltage of the peak hold circuit 29 when the switch element 32 is in the conductive state, and outputs an alarm signal when the level of the detection signal is high. Is output to the output terminal 24. As described above, the counter circuit 27 performs the counting operation during the period in which the rectangular signal is generated by the one-shot multi 28, and the operation of the switch elements 30 and 32 according to the output levels of the output terminals Q ₁ and Q ₂ of the counter circuit 27. Is controlled. The voltage held in the peak hold circuit 29 when the switch element 30 is conducting and the switch element 32 is non-conducting,
Only when the detection signal supplied to the input terminal 23 has a larger amplitude when the switch element 30 is non-conductive and the switch element 32 is conductive, the comparator 31 detects that the true detection signal has been detected, and outputs the alarm signal. Is output.

Next, the operation of the hot-wire detector shown in FIG. 1 will be described based on the signal identification circuit shown in FIG. 4 and the timing charts of FIGS. 5 and 6.

5 and 6, (a) is the output signal of the amplifier 10, (b) is the output signal of the absolute value circuit 11, and (c) is the first comparator.
25 output signal, (d) one-shot multi 28 output signal, (e) counter circuit 27 lower bit output terminal Q ₁ output signal, (f) counter circuit 27 upper bit output terminal Q ₂
Output signal, (g) is the output terminal Q _{P of the} peak hold circuit 29
, And (h) shows the output signal of the second comparator 31.

First, in FIG. 5, the heat ray radiated from an object that has entered the warning beam region is detected by the light receiving circuit 9, and the amplifier 10
The detection signal [(a) in the figure] amplified by [1] is converted into a signal of the same polarity [(b) in the figure] by the absolute value circuit 11 and supplied to the signal identifying circuit 12. At time t ₁ , when the level of the detection signal exceeds the threshold value V _REF of the reference voltage power supply 26, the comparator 25
A rectangular signal is output from, and at the rising edge of this rectangular signal,
The one-shot multi 28 is activated to generate a rectangular signal having a predetermined time width T. Here, the time width T of this rectangular signal is
Statistical examination of the moving speed when a person crosses the warning beam area, it is set based on this statistical result, after considering the size of the room where this heat ray type detector is installed,
It is set to be slightly longer than the time required for the intruder to move through the warning beam area at the slowest speed, and in this embodiment, T =
It is set to 3 seconds. Thus, the intruder passes through the guard beam region, so that the rectangular wave signal output from the light receiving circuit 9 detects signals after time t ₄ when disappear from time t ₅ to the one-shot multi 28 falls There is. In this way, when the rectangular wave signal is generated from the one-shot multi 28 at time t ₁ , the counter circuit 27 and the peak hold circuit 29 start a predetermined operation. Since the counter circuit 27 counts the rectangular wave signal output from the comparator 25, at time t ₁ , the output of the lower bit output terminal Q ₁ becomes “H” level and the switch element 30 becomes conductive. On the other hand, the peak hold circuit 29 holds the peak voltage of the detection signal and
Until time t ₅ the rectangular signal is "L" level falls from 28, and outputs the holding voltage from the output terminal Q _P. Between times t ₁ and t _2, one square signal is supplied from the comparator 25 to the counter circuit 27, so that the output of the upper bit output terminal Q ₂ is at “L” level, and the switch element 32 is It becomes non-conductive. Therefore, the voltage applied to the inverting input terminal becomes higher than the voltage applied to the non-inverting input terminal of the second comparator 31, and the second comparator 31 does not output an alarm signal. Next, at time t ₂ , when the signal from the absolute value circuit 11 exceeds the threshold value V _REF of the reference voltage source 26, the first comparator 25 outputs a rectangular signal, and the counter circuit 27 outputs this rectangular signal. Therefore, the output of the lower bit output terminal Q ₁ of the counter circuit 27 becomes “L” level and the output of the upper bit output terminal Q ₂ becomes “H” level. Therefore, the switch element 30 becomes non-conductive, the switch element 32 becomes conductive,
The signal supplied from the absolute value circuit 11 via the input terminal 23 is supplied to the non-inverting input terminal of the comparator 31. In this case, at time t _'2 which towards the voltage of the signal peak-hold circuit 29 is applied to the non-inverting input terminal than the holding voltage to the output from the output terminal Q _P is increased from the second comparator 31 "H"
A level alarm signal [Fig. 5 (h)] is output. next,
At time t ₃ , the output signal of the absolute value circuit 11 is the reference voltage source.
When the threshold value V _REF of 26 is exceeded, the first comparator 25 outputs a rectangular signal and the counter circuit 25 counts this rectangular signal.
Output of lower bit output terminal Q ₁ and higher bit output terminal Q ₂
Output changes to "H" level, and both switch elements 30 and 32 become conductive. Therefore, the peak hold circuit
The peak voltage of the output signal from the absolute value circuit 11 supplied to the input terminal 23 is held in 29, and this held voltage is applied to the non-inverting input terminal of the comparator 31 via the output terminal Q _P. The signal voltage of the input terminal 23 is applied to the non-inverting input terminal of the comparator 31. At this time, an equal voltage is applied to the comparator 31, but an alarm signal is not generated from the comparator 31 due to the offset voltage set in the comparator 31.

Then, at time t ₅ , the output signal of the one-shot multi 28 falls, so the counter circuit 27 and the peak hold circuit 29 are reset, and the output terminal of the counter circuit 27.
The output of Q ₁ and Q ₂ goes to “L” level, and the switching element 30,
32 are both rendered non-conductive, the holding voltage of the peak hold circuit 29 is discharged, the voltage of the output terminal Q _P is equal to the ground voltage. As described above, the signal identifying circuit 12 detects the first small-amplitude detection signal exceeding the predetermined threshold value V _REF with the first comparator 25, and then detects the detection signal with a larger amplitude than the small-amplitude signal. The alarm signal is generated from the second comparator 31 only when it is detected. That is, by detecting the characteristic of the radiation pattern of the heat ray emitted when the intruder crosses the warning beam area, the intruder is surely discriminated from the noise and the false alarm is prevented.

FIG. 6 is a timing chart for explaining the operation of this heat ray type detector when a single pulse noise is instantaneously generated in the light receiving circuit 9. In the figure, noise is amplified by the amplifier 10 and rectified by the absolute value circuit 11,
When noise exceeding the threshold value V _REF is supplied to the signal identifying circuit 12 as shown in FIG. 6B, the first comparator 25 generates a rectangular signal at times t ₆ and t ₇ . First, time t ₆
At this time, the one-shot multi 28 generates a rectangular signal of the time width T, and based on this, the counting operation of the counter circuit 27 and the holding operation of the peak hold circuit 29 are started. Time t ₆
, The output of the lower bit output terminal Q ₁ becomes "H" level and the output of the higher bit output terminal Q ₂ becomes "L" level by the counting operation of the counter circuit 27.
Is in the conductive state, and the switch element 32 is in the non-conductive state.
The peak voltage of noise at t ₆ is held in the peak hold circuit 29. Next, at time t ₇ , when the counter circuit 27 counts the rectangular signal output from the first comparator 25,
The output of the lower bit output terminal Q ₁ is at “L” level, and the output of the upper bit output terminal Q ₂ is at “H” level. Therefore, the switch element 30 is turned off, the switch element 32 is turned on, the noise voltage at time t ₇ is applied to the non-inverting input terminal of the second comparator 31, and the peak hold is applied to the inverting input terminal. The holding voltage of the circuit 29 is applied. At this time t ₇ , the holding voltage of the peak hold circuit 29 is higher than the voltage applied to the non-inverting input terminal, so the comparator
No alarm signal will be output from 31.

In this way, even if noise that differs from the radiation pattern of the heat ray emitted by the intruder occurs when it crosses the inside of the warning beam area,
The noise is identified so that it does not cause false alarms. Thus the fifth
By detecting only the change in the heat ray pattern radiated by the intruder as shown in FIGS. 6 and 6, noise can be well identified and false alarms can be prevented.

(Effects of the Invention) As described above, according to the hot-wire detector of the present invention,
When the object to be detected crosses the beam area formed by the reflecting mirror, the heat ray emitted from the object to be detected is detected by the light receiving circuit, and a small amplitude corresponding to the change in the intensity of the heat dose and a large amplitude following it are detected. Generate a detection signal that includes the amplitude signal,
At the same time as detecting a signal that exceeds a specified threshold value, its peak value is held, and if an intruding object is identified only when a signal with an amplitude larger than that peak value is detected within a specified time, it is possible to detect Instantaneous and sporadic noise generated in the element can be distinguished from the true detection signal, and it can always operate stably against noise to give an accurate alarm and output from the light receiving circuit. Since the detection signal is processed in substantially real time, there is an effect that the response speed for identifying the detection signal can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a hot wire detector according to the present invention, FIG. 2 is a circuit diagram showing a circuit configuration of the light receiving circuit of FIG. 1, and FIG. 3 is an operation of the light receiving circuit of FIG. 4 is a circuit diagram showing the circuit configuration of the signal discrimination circuit of FIG. 1, FIG. 5 is a timing chart showing the operation of the hot-wire detector of FIG. 1, and FIG. 6 is of FIG. 7 is a timing chart showing the operation when noise is generated in the heat ray detector of
FIG. 8 and FIG. 8 are block diagrams showing an example of a conventional hot-wire detector. 9: Light receiving circuit, 10: Amplifier 11: Absolute value circuit, 12: Signal identification circuit 14, 15: Pyroelectric infrared sensor 16: Light receiving part, 25, 31: Comparator 26: Reference voltage source, 27: Counter circuit 28 : Monostable multivibrator 29: Peak hold circuit 30,32: Switch element

Claims (1)

[Claims] 1. An optical system such as a reflecting mirror for forming a warning beam region, and a light receiving section formed by closely connecting two pyroelectric infrared sensors to each other in a differential pair, and within the warning beam region. When the object to be detected crosses, the heat ray emitted from the object to be detected is detected by the light receiving unit, and a detection signal including a small amplitude signal and a large amplitude signal corresponding to the change in the intensity of the heat ray is generated. Light receiving circuit and a signal identifying circuit that detects a signal exceeding a predetermined threshold value, holds the peak value at the same time, and generates an alarm signal only when a signal having an amplitude larger than the peak value is detected within a predetermined time A heat ray detector characterized by being provided with.