JP2600739B2 - Heat detector - Google Patents

Description

Description: (a) Industrial application field The present invention relates to a heating element detection device that detects the presence or absence of a heating element by detecting infrared energy radiated from a heating element such as a human body.

(B) Conventional technology Conventionally, a device using a pyroelectric sensor has been well known as a device for detecting infrared energy for detecting a human body or the like. However, the pyroelectric sensor detects a change in radiant energy emitted from a moving human body, and cannot detect a stationary human body in which a change in radiant energy is difficult to obtain. For this reason, thermopiles, thermistors,
Attempts have been made to detect a stationary human body using a detection element such as a bolometer. As shown in FIG. 7, the detection principle of an apparatus using this type of detection element is to output a voltage corresponding to background energy from a reference voltage unit 61 and amplify the amount of infrared light detected by an infrared light detection unit 62. The signal is amplified by the unit 63, and the reference voltage and the amount of detected infrared rays are compared by the comparison unit 64 to determine the presence or absence of a stationary human body.

(C) Problems to be Solved by the Invention However, in the above-mentioned conventional device, since the reference voltage is set to a predetermined value, the background temperature changes,
When the human body is still, a slight movement, for example, a movement of a hand, a foot, a face, or the like, and the amount of radiated energy fluctuates, a detection error may occur, and there is a problem that highly reliable detection cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is capable of detecting not only a moving heat body but also a temporary still heat body with high accuracy even when the background temperature changes. It is intended to provide a device.

(D) Means and Action for Solving the Problems The thermal element detection device of the present invention, which detects a thermal element entering and exiting a predetermined area, detects an infrared signal that outputs an output signal corresponding to infrared energy in the predetermined area. Means for inputting the output of the infrared detection means to determine and hold the level of a threshold level signal; and the predetermined area based on the output signal level of the infrared detection means exceeding the threshold level signal level. Comparing means for detecting a continuous presence of a heat body in the apparatus, wherein the holding means changes the level of the threshold level signal by following a gentle change in the output signal of the infrared detecting means. While the means does not detect the heating element, a sudden change in the output signal of the infrared detecting means causes a gentle attenuation of a predetermined time constant. However, the vicinity of the level immediately before the rapid change is held for a predetermined time determined by the time constant so that the comparing means detects the continuous presence of the heat body within the predetermined time.

In this heat detecting device, when the background temperature changes, the output level of the infrared detecting means changes. If the change in the output level is a gentle change, the threshold level changes accordingly, and the comparing means does not detect the heat. However, when the output level of the infrared detecting means changes rapidly, the threshold level is kept at a predetermined time constant or near the level immediately before the abrupt change while gently attenuating, for a predetermined time determined by the time constant. Therefore, the comparing means detects the continuous presence of the heat body within the predetermined time. Therefore, when a heat body such as a human body enters a predetermined area, temporarily stops, and exists within a predetermined time,
The presence or absence of the heat body can always be accurately determined.

(E) Examples The present invention will be described in more detail with reference to the following examples.

FIG. 1 is a schematic block diagram of a human body detection device showing one embodiment of the present invention.

This human body detecting device includes an infrared detecting element, detects an infrared energy in a monitoring area ME and converts it into an electric signal, and an inverting amplifier 2 that amplifies the detected signal.
And the output of the inverting amplifier 2, that is, the detection level,
Peak hold section for creating threshold level signals
And a comparison unit 13 for comparing the detection output of the inverting amplification unit 2 with the threshold level signal.

FIG. 2 is a specific circuit connection diagram of the human body detection device of the above embodiment. In the figure, reference numeral 11 denotes an infrared detection / amplification unit. This infrared detecting / amplifying unit 11 shows a specific example of the infrared detecting means of the present invention.

The infrared detection / amplification unit 11 includes a thermopile element (a thermistor, a bolometer, or the like may be used) 1a for detecting infrared energy, an operational amplifier 2a, and the like. The non-inverting input terminal (+) of the operational amplifier 2a has one end of the parallel circuit of the thermopile element 1a and the capacitor C ₃ is connected, an output terminal and the inverting input terminal of the operational amplifier 2a (-) between the resistor R _G3 is connected, further inverting input terminal of the operational amplifier 2a (-) and thermopile A series circuit of resistors R _G1 and R _G2 is connected between the other end of the element 1a. The resistors R _G1 and R _G3 are connected in parallel with a capacitor.
C ₂ and C ₄ are connected. The other end of the thermopile element 1a, between ground GND, and a parallel circuit of a Zener diode Zd and the capacitor C ₁ is connected. The above capacitor C ₁ ,
..., C ₄ are provided for the noise cut. The gain G of the infrared detection / amplification unit 11 is Is represented by

The peak hold unit 12 is a circuit that holds the background (peak) level of the output of the infrared detection / amplification unit 11, and is an inverting circuit including an operational amplifier 12a and a peak hold circuit including a resistor R ₀ , a capacitor C _0, and an operational amplifier 12b. It is composed of In this circuit, the hold time τ is τ = C ₀
R ₀選定 Selected around 60 seconds. This bottom hold circuit
12 shows a specific example of the holding means of the present invention.

The comparison circuit 13 includes an operational amplifier 13a and resistors _Rc1 , _Rc2 , and _Rc3. The output of the infrared detection / amplification unit 11 is connected to the inverting input terminal (-) of the operational amplifier 13a via the resistor _Rc3. On the other hand, the output terminal of the operational amplifier 12b of the peak hold unit 12 is connected to the non-inverting input terminal (+) of the operational amplifier 13a via the resistor _Rc1 , and the output terminal of the operational amplifier 13a is connected to the non-inverting input terminal (+) of the operational amplifier 13a. The resistor _Rc2 is connected between the ends.
The resistors R _c1 and R _c2 constitute a threshold level hysteresis circuit, and the threshold width V _TH is Is represented by

V _OH : High output of the operational amplifier 13 a V _OL : Low output of the operational amplifier 13 a This comparison circuit 13 is a specific example of the comparison means of the present invention.

FIG. 4 is an external perspective view of a case body in which the above-described circuit section is stored, and FIG. 5 is a sectional view of the same. Infrared energy from the monitored area passes through the PE cover 40 and window 41,
The light is reflected by the three-part concave multi-mirror 42 and irradiates the thermopile element 1a. Although not shown, the thermopile element 1a is connected to the printed circuit board 43 by a flexible board or the like. Most of the circuit of FIG. 2 is mounted on the printed circuit board 43.

Next, the operation of the above-described embodiment will be described. now,
The example device 10 is installed on the ceiling as shown in FIG. 3 (A), and the human body m moves into and enters the lower monitoring area ME, stops, and then leaves the area ME. Suppose.

First detection output V _s of the thermopile element 1a, as shown in FIG. 3 (B), up to t _1, there is no human body, background temperature hardly changes, is constant. But at time t ₁
When the human body m enters, the infrared energy increases and V ₃
There together Daito Do, The figure shows a case where a change in V _s in the human body of the fine. It reaches the point t _2, when the human body exits the detection output V _s is the level again according to the background temperature, the t ₂ ~t ₃ figures, the influence of the ambient temperature, background temperature rise An example in the case of performing is shown. t ₃ or later, shows an example where the background temperature is constant.

The output a of the infrared detector, amplifier 11, as shown in FIG. 3 (B), the waveform shape of the detected voltage V _s of the thermopile element 1a is inverted. Therefore, the output a has a high level at the background temperature, and has a lower level as the detected infrared energy becomes larger. The output signal of the infrared detection / amplification unit 11 is input to the comparison circuit 13 and also to the peak hold unit 12. In the peak hole section 12, the waveform at the point a is peak-held, and the output is as shown in FIG. 3 (B). This waveform, in the case of the background temperature is approximately output the same level of the infrared detection and amplification unit 11, and also if there is a slight change in the background temperature, the change time tau _a is tau
The levels are the same during _a > τ. However, the waveform of a point, becomes suddenly lower as shown by t ₁ ~t _2, a time constant of tau, are peak hold. Therefore, the output “b” of the peak hold unit eventually retains the background (peak).

In the comparison circuit 13, the input level is V _IN , the level at the point b is V _ref , the higher voltage (threshold voltage) of the non-inverting input terminal of the operational amplifier 13a is V _refH , the lower voltage is V _ref, and the lower voltage is V _ref. Assuming that the output is V _OH and the low output is V _OL , the level relationship between the voltages is as shown in FIG. That is, in the input voltage V _IN is level small, compared with the step shoulder de level V _refH, V _IN increases levels, until it exceeds the threshold level V _refL (A → B), the output of the comparator circuit is V _OH, input voltage V _iN is, exceeds the threshold level V _refH, the output of the comparator circuit becomes V _OL (B → C). Conversely, in turn, at the level large input voltage V _IN is compared with the threshold level V _refL, and V _IN is level decreases, until decreases beyond the threshold level V _refL (C → D), the comparator circuit The output is V _OL , and when the input voltage V _IN decreases _below the threshold level V _refL , the output of the comparison circuit becomes V _OH (D →
A).

Referring back to FIG. 3 (B), looking at the level relationship to time t _1, than the level of the point a, small V _refL, therefore, the output of this operational amplifier 13a is V _OL. However, when reaching the time point t _1, the detection level of the point a is changed in the row direction in the human body detection, a level beyond the V _refL. Therefore, the output of the operational amplifier 13a becomes V _OH . Accordingly, the threshold level also becomes _VrefH . Thus, after that between the detection level of a point is smaller than V _refH, the output of the operational amplifier 13a holds V _OH. Reaches the point t _2, the level of a point turned upward direction, eventually exceeds V _refH, the operational amplifier 1
The output of 3a again V _OL becomes even threshold level V
_refL . As described above, since the threshold level has hysteresis, the output of the operational amplifier 13a operates stably near the threshold level even if the detection level slightly changes.

In the period of t ₂ ~t _3, because of the background temperature rise, infrared detection and
Although the output of the amplifier 11 changes, the change time τ _a is larger than the hold time constant τ, and the threshold voltage follows the change, so that there is no erroneous detection.

As described above, in the human body detection device of this embodiment, even when the human body m enters the monitoring area ME and temporarily stops, the threshold level is maintained at the level before the human body enters for a predetermined time, so that the predetermined time is Detect human body. However, if the human body is still stationary for more than a predetermined time, the threshold level follows the output of the infrared detector, and thereafter, the stationary human body is no longer detected.

In the above embodiment, the human body detection device has been described as an example.
INDUSTRIAL APPLICABILITY The present invention can be widely applied to detection of living bodies such as animals and other heat bodies.

According to the present invention, the output level of the infrared detecting means is input to the comparing means, and a threshold level signal corresponding to a change in the background output level of the infrared detecting means is generated. In addition, since a thermal body such as a human body is detected by comparing the infrared detection means with a threshold level signal, the background temperature may change due to the influence of sunlight, wind, etc. ,
Even if the detection signal level fluctuates due to slight movement of the feet, face, etc.,
The influence can be minimized, and highly reliable detection can be performed. In addition, since the threshold level is gently attenuated, it is possible to quickly detect that the heating element has moved out of the detection area.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of the present invention, and FIG.
FIG. 3 is a circuit connection diagram of a human body detecting device showing an embodiment of the present invention, FIG. 3 (A) is a diagram provided for explaining the operation of the human body detecting device, and FIG. 4 is a signal waveform time chart for explaining the operation of the human body detecting device, FIG. 4 is a perspective view of the appearance of the case of the human body detecting device of the embodiment, FIG. 5 is a sectional view of the same, and FIG. FIG. 7 is a characteristic diagram for explaining the hysteresis of the comparison circuit of the detection device. FIG. 7 is a block diagram for explaining the principle of the conventional human body detection device. You. 1a: infrared detection element, 11: infrared detection / amplification unit, 12: peak hold unit, 13: comparison circuit.

Claims (1)

(57) [Claims] 1. A heating element detecting device for detecting a heating element entering and exiting a predetermined area, an infrared detecting means for outputting an output signal corresponding to the infrared energy in the predetermined area, and a threshold input to the output of the infrared detecting means. Holding means for determining and holding the level of a level signal; and comparing means for detecting the continuous presence of a heating element in the predetermined area based on the output signal level of the infrared detection means exceeding the level of the threshold level signal The holding means follows the output signal of the infrared detection means in accordance with a gentle change and changes the level of the threshold level signal so that the comparison means does not detect a heat source, while the output of the infrared detection means For sudden signal changes,
It is preferable that the level near the level immediately before the rapid change is held for a predetermined time determined by the time constant while the predetermined time constant is gradually attenuated, and the comparing means detects the continuous presence of the heat element within the predetermined time. Characteristic thermal element detection device.