JP3446619B2 - Infrared detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detecting device for detecting infrared energy radiated from a human body to detect the presence or movement of the human body.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram of a conventional infrared detecting device of this type. The pyroelectric element 1 is widely used as an infrared detection unit, and infrared rays from the detection area are collected in the pyroelectric element 1 by using a lens system or the like, and the amount of infrared rays collected from the pyroelectric element 1 is detected. A current corresponding to the change is output. The electric current output from the pyroelectric element 1 is converted into a voltage by the I / V conversion circuit 2 and then further amplified by the voltage amplification circuit 3. When the output amplified by the voltage amplification circuit 3 exceeds a predetermined value Vh or Vl set in advance as shown in FIG. 10 (b), the alarm unit 4 detects that a human body exists or moves within the detection area. 10C, the alarm signal Q0 shown in FIG.
Is output.

The frequency characteristic of the infrared detecting device is set in accordance with the movement of the human body, and the voltage amplifying circuit 3 is provided with a bandpass filter centered at about 1 Hz. As a result, it is possible to increase the sensitivity to the human body, and it is possible to prevent a malfunction from occurring due to a signal in a band that is considered to be unrelated to the movement of the human body.

However, a single noise output called popcorn noise may occur from the pyroelectric element.
As a measure for that, the output from the pyroelectric element due to popcorn noise rises much faster than the output from the human body, etc., so popcorn noise is detected by another system as shown in FIG. 11, and popcorn noise is detected. In addition to reducing the gain of the IV conversion circuit 2 from the output control circuit 6 for a certain period of time or prohibiting the output of the alarm signal for a certain period of time depending on the detection signal, a method of reducing the gain of the voltage amplifying unit 3a can be considered. ing.

Here, a method of lowering the gain of the IV conversion circuit 2 for a certain period of time will be described as an example. When popcorn noise occurs, the popcorn noise detection unit 5
When the signal output from the second voltage amplification unit 3b as shown in FIG. 12B exceeds a predetermined value Vh1 set in advance, it is assumed that popcorn noise is output from the pyroelectric element 1 and the output control circuit is output. 6 is shown in FIG. 12 (e).
And outputs a popcorn noise detection signal P1 a cormorant. When the popcorn noise detection signal is input from the popcorn noise detection unit 5, the output control circuit 6 passes through the switch circuit 7 to the I / V conversion circuit 2 for a few seconds T,
An output control signal Q1 as shown in FIG. 12 (f) is output.

In the switch circuit 7, while the output control signal Q1 is being output from the output control circuit 6, the conversion impedance of the I / V conversion circuit 2 is lowered to lower the output.
As a result, the first voltage amplification unit 3a shown in FIG.
Even if the signal output from is input to the alarm unit 4,
Since the predetermined value Vh0 or Vl0 is not exceeded, the alarm signal is not output to the outside as shown in FIG. 12D, and it is possible to prevent malfunction due to popcorn noise. Become.

[0007]

However, in reality, I
The V conversion circuit 2 and the voltage amplification section 3a are composed of several operational amplifiers, and when the gain of the circuit is changed, the bias voltage and bias current of the operational amplifiers change the output DC state. Then, the input of the next amplification section is
As shown in the output of the IV conversion circuit 2 (a), the signal changes in steps and the signal is amplified to output the alarm signal.

The present invention has been made to solve the above problems, and an object thereof is to apply a bias voltage to an amplifier or the like constituting the IV conversion circuit 2 or the amplification section 3a in the infrared detection section. Even if there is a problem, or if popcorn noise occurs until the signal stabilizes, it eliminates the so-called false alarm that outputs the alarm signal as if the detection target is detected, and these factors make detection sensitivity unnecessary. It is an object of the present invention to provide an excellent infrared detection device that prevents so-called false alarms in which the original presence or movement of the human body cannot be detected due to a long-term reduction.

[0009]

According to a first aspect of the present invention, there is provided a pyroelectric element, an I / V conversion circuit for converting a current signal output from the pyroelectric element into a voltage signal, and the I / V conversion circuit. a first voltage amplifier for amplifying the output, and an infrared detector comprising a alarm unit output from the voltage amplifier of said first outputs a alarm signal exceeds a predetermined value, the The signal having a higher frequency than that of the first voltage amplifying unit is passed and the I / V
A second voltage amplifier for amplifying the output of the conversion circuit;
When the output of the voltage amplifying unit exceeds a predetermined value, a popcorn noise detection unit configured to determine that popcorn noise has occurred and output a popcorn noise detection signal, and the popcorn noise detection unit A timer circuit that creates a plurality of types of time that differ depending on the signal, and the first time created by the timer circuit
The output signal of the first part of the infrared detector is
It is controlled so that it is suppressed during the second time, which is longer than the first time.
The infrared detecting section located after the first portion.
When a popcorn detection signal is output, which includes a control circuit that controls so as to suppress the output signal of the second part of , the timer circuit creates a plurality of types of time, and the step output that occurs in the amplification unit in the previous stage is generated. This is to ensure that false alarms are suppressed by lowering the gain of the amplifying unit in the subsequent stage until it is settled.

According to a second aspect of the present invention, in the infrared detecting apparatus according to the first aspect, the gain of the I / V conversion circuit is first lowered by the popcorn detection signal, and the bias voltage of the amplifier constituting the I / V conversion circuit and the like are detected. Due to the influence, by reducing the gain of the first voltage amplifying unit that amplifies the step-like output while the step-like signal is generated, a stable signal is sent to the reporting unit to prevent false alarms. It is characterized by being able to.

According to a third aspect of the present invention, in the infrared detecting device according to the first aspect, the gain of the I / V conversion circuit is first lowered by the popcorn detection signal, and the bias voltage of the amplifier constituting the I / V conversion circuit and the like are detected. It is characterized in that false alarms are prevented by prohibiting the alarm signal generated by the stepwise output due to the influence for a certain period of time.

According to a fourth aspect of the present invention, in the infrared detecting device according to the first aspect, the output of the IV conversion circuit output by the popcorn detection signal can be ignored by lowering the gain of the first voltage amplifying section. In addition, with respect to an erroneous alarm caused by an output variation due to the bias voltage of the voltage amplification unit or the like, the erroneous output can be prevented by prohibiting the output of the alarming unit.

According to a fifth aspect of the present invention, in the infrared detecting device according to the first aspect, the I / V conversion circuit and the first voltage amplifying section are the same as in the first aspect, and the output from the alarming section is also provided. Similarly, by prohibiting for a certain period of time, false alarms can be more surely prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of an infrared detector according to the present invention will be described below with reference to FIGS. 1 and 2, a second embodiment will be described with reference to FIGS. 3 and 4, and a third embodiment will be described. FIG. 5 and FIG.
The fourth embodiment will be described in detail with reference to FIGS. 7 and 8.

[First Embodiment] FIG. 1 is a block diagram of an infrared detector. FIG. 2 is a timing chart explaining the operation of the infrared detection device. The infrared detection device includes a pyroelectric element 1, an IV conversion circuit 2, a first voltage amplification unit 3a, a second voltage amplification unit 3b, a reporting unit 4, a popcorn noise detection unit 5, a timer circuit 6, and a switch circuit 8.
And a switch circuit 9.

The pyroelectric element 1 outputs a current according to a change in the amount of infrared rays radiated from the detection area. The I / V conversion circuit 2 converts the detection current output from the pyroelectric element 1 into a voltage. The voltage-converted signal is branched, one of which is input to the first voltage amplifier 3a and the other of which is input to the second voltage amplifier 3b. The alarm unit 4 compares the signal output from the first voltage amplification unit 3a with a predetermined value set in advance by a comparator, and the output of the first voltage amplification unit 3a has an amplitude equal to or larger than a predetermined value. If so, an alarm signal is output.

The second voltage amplification section 3b selects and amplifies a signal having a frequency higher than that of the first voltage amplification section 3a, and outputs it to the popcorn noise detection section. In the popcorn noise detection unit, when the output of the second voltage amplification unit 3b is equal to or more than a predetermined value set in advance as shown in FIG.
A popcorn noise detection signal as shown in (c) is output.

When a popcorn noise detection signal is output from the popcorn noise detection section 5, the timer circuit 6 outputs the timer outputs T11 and T12 from the timer circuit T1.
1 outputs a pulse signal having a preset time width of T1 to the switch circuit 8 and timer output T11 outputs a pulse signal having a preset time width of T2 to the switch circuit 9.
Here, the timer output T11 is T as shown in FIG.
The pulse having a width of 1 is input to the switch circuit 8 and reduces the gain of the I / V conversion circuit 2 over the time T1. As a result, even if the signal output from the first voltage amplification unit 3a is input to the alarm unit 4 as shown in FIG. 2 (f), the signal does not exceed the predetermined value. No report signal is output. The time width of T1 is set longer than several ms which is the output time of the popcorn signal, and the output of the I / V conversion circuit 2 is not affected by the signal level of the popcorn noise, and the bias voltage of the amplifier, etc. Only the effect of is output. Further, the timer output T12 has a pulse having a width of T2 as shown in FIG. 2E, is input to the switch circuit 9, and reduces the gain of the first voltage amplification unit 3a over the time T2.

Here, T2 is set to have a longer time than T1, and the step input signal generated by the influence of the bias voltage of the I / V conversion circuit 2 is the first voltage amplification section 3.
It is set so that the gain of the first voltage amplification unit 3a is reduced over a time period of several seconds which is amplified by a and is not detected by the alarm unit 4. Further, the influence of the bias fluctuation in the first voltage amplification unit 3a is configured to be smaller than the predetermined value set in the reporting unit 4.

[Second Embodiment] FIG. 3 is a block diagram of an infrared detector. FIG. 4 is a timing chart explaining the operation of the infrared detection device. The infrared detection device according to the embodiment of the present invention includes a pyroelectric element 1, an I / V conversion circuit 2, a first voltage amplification section 3a, and a second voltage amplification section 3b.
A notification unit 4, a popcorn noise detection unit 5, a timer circuit 6, an output prohibition circuit 7, a switch circuit 8 and a switch circuit 1.
It consists of zero. The basic configuration of the infrared detector of the present embodiment is very similar to that of the first embodiment, and the same parts are designated by the same reference numerals and detailed description thereof will be omitted.

As in FIG. 2, when the popcorn noise detection signal is output from the popcorn noise detection unit, the timer circuit 6 outputs the pulse signals having the preset time width of T1 as the timer outputs T11 and T13. To the switch circuit 8, the timer output T13 outputs a pulse signal having a preset time width of T3 to the switch circuit 10, respectively. The signal having the pulse width T1 is the same as that of the above-described first embodiment, the gain of the IV conversion circuit 2 is reduced by the time T1, and the output from the I / V conversion circuit is not popcorn noise. Irrespective of the influence of the bias voltage of the amplifier. Therefore, the output of the first voltage amplification unit 3a is, as shown in FIG.
The output of the IV conversion circuit 2 exceeds the predetermined value of the reporting unit 4.

Therefore, the timer output T13 has a pulse having a width of T3 as shown in FIG. 4 (g), and by being input to the switch circuit 10, the output prohibiting circuit 7 is controlled and generated for the time T3. Prohibit the output of the report signal. The time of the pulse of T3 is set to have a longer time width than the time of the pulse of T1.

[Third Embodiment] FIG. 5 is a block diagram of an infrared detector. FIG. 6 is a timing chart for explaining the operation of the infrared detection device. The infrared detection device according to the embodiment of the present invention includes a pyroelectric element 1, an I / V conversion circuit 2, a first voltage amplification section 3a, and a second voltage amplification section 3b.
A notification unit 4, a popcorn noise detection unit 5, a timer circuit 6, an output prohibition circuit 7, a switch circuit 9, and a switch circuit 1.
It consists of zero. The basic configuration of the infrared detection device according to the present embodiment is very similar to that of the first embodiment, and the same parts will be denoted by the same reference numerals and detailed description thereof will be omitted.

In the third embodiment, when the popcorn noise detection section 5 outputs a popcorn noise detection signal, the timer circuit 6 outputs the timer outputs T14 and T15, and the timer output T14 is the preset time T4. The pulse signal of the width is output to the switch circuit 9, and the timer output T15 outputs the pulse signal of the preset time width of T5 to the switch circuit 10. Here, the timer output T14 has a pulse having a width of T4 as shown in FIG.
The gain is input to the switch circuit 9 connected to the first voltage amplification unit 3a, and the gain of the first voltage amplification unit 3a decreases for the time T4. In this case, the width of T4 is set to several seconds to several tens of seconds in order to deal with a sufficiently large popcorn noise signal. Here, as shown in FIG. 6A, in the portion where the output of the IV conversion circuit 2 rises and then gradually falls, the voltage that falls per constant time is the larger the generated popcon noise signal is. growing. Therefore,
When the gain of the first voltage amplification unit 3a is restored while the output of the IV conversion circuit 2 is decreasing, the falling signal of the output of the IV conversion circuit 2 is amplified and the threshold value is increased depending on the magnitude of the popcon noise. Will be exceeded. To prevent this,
It is necessary to make the time of T4 sufficiently long, and it takes about ten seconds or more. The timer output T15 is shown in FIG.
The pulse having the width of T5 as shown in (f) is inputted to the switch circuit 10 connected to the output prohibiting circuit 7, and the output from the alarm unit 4 is prohibited during the time of T5. Note that T5 is set to a time slightly longer than T4.

[Fourth Embodiment] FIG. 7 is a block diagram of an infrared detector. FIG. 8 is a timing chart explaining the operation of the infrared detection device. The infrared detection device according to the embodiment of the present invention includes a pyroelectric element 1, an I / V conversion circuit 2, a first voltage amplification section 3a, and a second voltage amplification section 3b.
A notification unit 4, a popcorn noise detection unit 5, a timer circuit 6, an output prohibition circuit 7, a switch circuit 8 and a switch circuit 9
And a switch circuit 10. The basic configuration of the infrared detector of the present embodiment is very similar to that of the first embodiment, and the same parts are designated by the same reference numerals and detailed description thereof will be omitted.

In the fourth embodiment, the timer circuit 6 outputs timer outputs T11, T12, and T16, and the timer output T11 outputs a pulse signal having a preset time width of T1 to the switch circuit 8 and the timer circuit. The output T12 outputs a pulse signal having a preset time width of T2 to the switch circuit 9, and the timer output T16 outputs a pulse signal having a preset time width of T6 to the switch circuit 10. The pulse having the time width T1 is input to the switch circuit 8 and reduces the gain of the IV conversion circuit 2. The time of T1 is several ms as in the first and second embodiments, and by lowering the gain of the IV conversion circuit 2, the step-like output unrelated to the popcorn noise signal is converted into the IV conversion circuit. Output from 2. T2 is a pulse of several seconds as in the first embodiment, and is input to the switch 9 to reduce the gain of the first voltage amplification unit 3a. Therefore, the output of the first voltage amplification section 3a becomes only the bias fluctuation of the amplifier in this section, and this output is input to the reporting section 4. T6
Has a pulse width of time until the signal of the first voltage amplification section 3a settles down, and the pulse signal of T6 inhibits the output of the reporting section 4 for a certain time.

[0027]

As described above, according to the first aspect of the present invention, when there is a bias voltage in the amplifier or the like which constitutes the I / V conversion circuit or the amplification section, or when the signal becomes stable, the popcorn Even if noise occurs, the detection target is detected and the so-called false alarm that outputs a warning signal is eliminated, and the detection sensitivity is unnecessarily reduced for a long period of time, which results in the presence or movement of the original human body. There is an effect of providing an excellent infrared detection device that prevents so-called false alarms in which the detection of the above can not be performed.

According to the invention of claim 2, in addition to the effect of claim 1, the detection sensitivity is unnecessarily reduced for a long period of time, so that the original presence or movement of the human body cannot be detected. This has the effect of shortening the so-called false alarm time.

According to the invention of claim 3, in addition to the effect of claim 1, since the output inhibition circuit is used, there is an effect that false alarm can be surely prevented.

According to the invention of claim 4, in addition to the effect of claim 1, there is no need to connect the switch circuit to the IV conversion circuit which requires very high impedance, so that the switch is relatively easy. In addition, it is possible to reduce the influence of noise or the like that affects the output due to the influence of the leakage current caused by connecting an unnecessary one.

According to the invention of claim 5, the false alarm time can be shortened as in the case of claim 2, and the false alarm can be more surely prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an infrared detection device according to a first embodiment of the present invention.

FIG. 2 is a timing chart explaining the operation of the infrared detection device.

FIG. 3 is a block diagram showing an infrared detection device according to a second embodiment of the present invention.

FIG. 4 is a timing chart for explaining the operation of the infrared detection device.

FIG. 5 is a block diagram showing an infrared detection device according to a third embodiment of the present invention.

FIG. 6 is a timing chart illustrating the operation of the infrared detection device.

FIG. 7 is a block diagram showing an infrared detection device according to a fourth embodiment of the present invention.

FIG. 8 is a timing chart explaining the operation of the infrared detection device.

FIG. 9 is a block diagram showing a conventional infrared detector.

FIG. 10 is a timing chart illustrating the operation of the infrared detection device.

FIG. 11 is a block diagram showing an example of a conventional infrared detection device having a popcorn detection circuit.

FIG. 12 is a timing chart illustrating the operation of the infrared detection device.

[Explanation of symbols]

1 Pyroelectric element 2 I / V conversion circuit 3a First voltage amplification unit 3b Second voltage amplification unit 4 reporting department 5 Popcorn noise detector 6 timer circuit 7 Output inhibit circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-149455 (JP, A) JP-A-2-272330 (JP, A) JP-A-6-187578 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G08B 13/191 G01J 1/42

Claims (5)

(57) [Claims] 1. A pyroelectric element, an I / V conversion circuit for converting a current signal output from the pyroelectric element into a voltage signal, and the I / V.
A first voltage amplification unit for amplifying an output of the conversion circuit;
An infrared detector consisting of an alarm unit for output from the voltage amplifier outputs the alarm signal exceeds a predetermined value set in advance of, the passed through a signal of the first frequency higher than the voltage amplifier A second voltage amplification unit that amplifies the output of the I / V conversion circuit, and when the output of the second voltage amplification unit exceeds a predetermined value, it is determined that popcorn noise has occurred and popcorn noise is generated. a popcorn detection unit consisting of a popcorn noise detector for outputting a detection signal, a timer circuit that produces the popcorn noise detection plurality of types of time different by the signal, created by said timer circuit
The first part of the infrared detecting section for the first time when it has started
Minute output signal is controlled to be longer than the first time.
Before being located after the first part for a second time
An infrared detecting device, comprising: a control circuit for controlling an output signal of the second portion of the infrared detecting section . Wherein if the popcorn noise detection signal is outputted, the timer circuit which produces two kinds of time, the
2. The infrared detection device according to claim 1, wherein the control circuit operates so as to reduce the conversion impedance of the I / V conversion circuit over the first time period and reduce the gain of the first voltage amplification section over the second time period . . 3. If the popcorn noise detection signal is outputted, the timer circuit which produces two kinds of time, the
2. The infrared detection device according to claim 1, wherein the control circuit operates so as to lower the conversion impedance of the I / V conversion circuit for the first time and inhibit the output of the alarm unit for the second time . 4. If the popcorn noise detection signal is outputted, the timer circuit which produces two kinds of time, the
2. The infrared detection device according to claim 1, wherein the control circuit operates so as to reduce the gain of the first voltage amplification unit for the first time and inhibit the output of the alarm unit for the second time . 5. If the popcorn noise detection signal is output by the timer circuit to produce three kinds of time, the
The conversion impedance of the I / V conversion circuit is reduced over a first time period, the gain of the first voltage amplification unit is reduced over the second time period , and the first time period and the second time period are reduced.
The infrared detection device according to claim 1, wherein the control circuit operates so as to prohibit the output of the alarm unit for a third time longer than the time .