JPH02128124A - Heat body detector - Google Patents

Abstract

PURPOSE:To prevent erroneous detection by arranging an infrared rays detection means, a reference signal generation means, a comparison means and a reference signal control means. CONSTITUTION:An infrared rays detection means 1 contains a detector to generate an electrical signal according to an infrared energy radiated from within a specified area. A reference signal generation means 2 generates a reference signal to be compared with an output of the detection means 1. A comparison means 3 compares an output of the detection means 1 with the reference signal to judge whether a heat body exists within a specified area. A reference signal control means 4 changes the reference signal based on a maximum value of a temperature change presumable within the specified are after the detection of the heat body by the comparison means 3, which means that the reference signal is changed allowed for the largest presumable change on the assumption that a background temperature varies to approach the temperature of he heat body. Thus an output of the detection means 1 falls below a reference voltage so much that a detection output from the comparison means 3 is turned OFF when the heat body is removed under such a condition.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a heat body detection device that detects the presence or absence of a heat generating body by detecting infrared energy emitted from a heat generating body such as a human body.

(B) Prior Art Conventionally, a device using a pyroelectric sensor is well known as a type of device that detects infrared energy to detect a human body or the like. However, the pyroelectric sensor detects changes in radiant energy emitted from a moving human body, and cannot detect a stationary human body for which changes in radiant energy are difficult to obtain. For this reason, in recent years, attempts have been made to detect a stationary human body using detection elements such as thermopiles, thermistors, and bolometers. The detection principle of a device using this type of detection element is as shown in FIG. A comparison section 84 compares the reference voltage and the amount of detected infrared rays to determine whether there is a stationary human body.

(c) Problems to be Solved by the Invention However, in the conventional device described above, the reference voltage is set to a predetermined value, so the background temperature may change or the human body may move slightly while the human body is stationary, such as hands or feet. If the face or the like moves and the amount of radiated energy fluctuates, detection errors may occur, making it impossible to perform highly reliable detection.

In particular, if the background temperature changes in a direction approaching the temperature of the moving heat body after a moving heat body such as a human body is detected, even if the moving heat body leaves the predetermined area, it will still output a detection output, resulting in false detection. There was a risk that it would happen.

The present invention has been made by focusing on the above-mentioned problem, and is a heating element that does not cause false detection even if the temperature within a predetermined area changes to approach the temperature of the moving heating element after the detection of the moving heating element. The purpose is to provide a detection device.

(d) Means and operation for solving the problems The hot body detection device of the present invention comprises an infrared detection means (1) including a detection element that generates an electric signal in response to infrared energy radiated from within a predetermined area; A reference signal generating means (2) for generating a reference signal for comparison with the output of the infrared detecting means, and comparing the output of the infrared detecting means with the reference signal to determine whether a heating body is present within the predetermined area. and a reference signal control means (4) for changing the reference signal based on the maximum possible temperature change within the predetermined area after the comparison means detects the hot body. (See Figure 1).

In this heating body detection device, when the moving heating body enters a predetermined area, infrared energy from the moving heating body is detected by the infrared detection means, and its output increases, for example. When the output (output change) of the infrared detection means exceeds the reference voltage, the comparison means outputs a detection output indicating that a hot body is present in the area. After the hot body is detected, the reference signal is changed so as to approach the detection output of the infrared detection means, taking into consideration the maximum possible temperature change in the monitoring area. Therefore, even if the background temperature changes to approach the heating body temperature, the reference signal is changed taking into account the maximum possible change.
If the heating element is removed under this situation, the output of the infrared detection means will be below the reference voltage, and the detection output from the comparison means indicating the presence of the heating element will be reliably turned off.

(E) Examples The present invention will be explained in more detail with reference to Examples below.

FIG. 2 is a block diagram of a human body detection device in which the present invention is implemented. In the figure, the detection section 11 is composed of an infrared detection section 12 and a temperature detection section 13. The infrared detection section 12 includes an infrared detection element such as a thermopile element that detects infrared rays within a predetermined monitoring area ME, and the temperature detection section 13 includes a temperature measurement element such as a thermistor that detects the temperature of the detection section 11. We are prepared. The detection signal from the infrared detection section 12 is amplified by the amplification section 14 and then sent to the analog switch circuit 1.
5. The data is taken into the CPU 17 via the A/D converter 16.

The temperature signal detected by the temperature detection section 13 is converted into an electrical signal by the temperature/voltage conversion section 18, and similarly taken into the CPU 17 via the analog switch circuit 15 and the A/D converter 16. The analog switch circuit 15 is switched by a command from the CPU 17 and inputs a detection signal from the infrared detection section 12 or the temperature detection section 13 to the A/D converter 16. The CPU 17 includes a ROM 19 that stores programs.
, and a RAM 20 for storing read data. The CPU 17 executes a series of processing operations in accordance with a program stored in the ROM 19 to determine whether a person has entered or left the monitoring area ME.

The details of this program will be explained later along with its operation. Further, a reference signal is inputted to the CPU 17 from a reference signal generating section 21 . This reference signal is configured to be controllable by the CPU 17. In addition, power supply section 2
Power supply voltage is supplied from 2 to each circuit via a power switch 23. A signal indicating human body detection is outputted from the CPU 17 via the output control unit 24,
It is given to CD display etc. 25 is a reset switch.

FIG. 3 is an external perspective view of the case body in which the circuit section described above is housed, and FIG. 4 is a sectional view thereof. Monitoring area M
The infrared energy from E is transmitted to the window 31 of the PE cover 30.
The light is then reflected by the concave multi-mirror 32 and irradiated onto the thermopile element 11a. Although not shown, the thermopile element 11a is connected to the printed circuit board 33 using a flexible board or the like.

On the printed circuit board 33, in addition to the temperature measuring element, most of the circuit shown in FIG. 2 is mounted.

Next, the software configuration and operation of the hot body detection device of the above embodiment will be explained with reference to the flowcharts shown in FIGS. 5(a) to 5(d).

When the power switch 23 or the reset switch 25 is turned on, initialization processing is first performed [Step S
T (hereinafter abbreviated as ST) 1]. In this initialization process, the high temperature range flags A and 1, the low temperature range flag AL, the detection flags D and t, the environmental instability flag D en, and the dead zone flag D exa are all set to "0°", and the temporary
Area registers Dr, DS, p+, , p+ are all P. shall be. Here, Po is the initial value of the infrared energy data.

After initialization, select the analog switch circuit 15 to the temperature measurement side (5T2), read the temperature data at every sampling time (Sr1), and store it in the RAM as T.
20 (Sr1).

Next, 1 (T, −T, −, “)/Δt1≧ΔT e n
Then, it is determined whether there is a drastic temperature change (Sr1). Here, T1 is the nth temperature data, T, , is the n-1th temperature data, ΔL is the sampling time (or an integral multiple thereof), and ΔT8° is the criterion for rapid temperature change. If the temperature suddenly changes due to, for example, an air conditioner or sunlight, the determination of Sr1 becomes YES, and the environmental instability flags D, . . . are set to “l”. If the temperature change is small, Sr1 judgment is NO.
Move on to 7. For Sr7, T, -ΔT≦T7≦TM+ΔT
The background temperature T is determined. It is determined whether or not the human body surface temperature Ti and the human body surface temperature Ti are very close to each other. If the judgment is YES in Sr7, the dead band flag D, 4 is set as “work” 5T8)
, if No, the process directly moves to Sr1. T in Sr1
1≦T, and determine whether the background temperature T7 is lower than the human body surface temperature TM, that is, in a low temperature range, or conversely, whether it is higher than the human body surface temperature TM.
In other words, it is determined whether or not the temperature is in the high temperature range. If it is in the low temperature range, it is determined whether it is AL-“1°” (5TIO), and if the low temperature range flag AL is not set yet, the flag A is set.
Set L to "'1" 5TII), and if it is already set, set the high temperature range flag A to 0" (ST12)
.

If Sr1 is in the high temperature range, it is determined whether "A, = 1"" (5T13), and if the high temperature range flag A□ has not been set yet, the flag A is set to 1°". 5T
14) If the cent has already been sent, the low temperature range flag AL is set to "0" (ST15). This completes the temperature processing that detects the current background temperature, determines whether the environment is unstable, whether the background temperature is in a dead zone, whether the background temperature is in a low temperature range or a high temperature range, etc., and then infrared detection processing. Move to.

In the infrared detection process, as shown in Figure 5), first the analog switch circuit 15 is selected as the infrared detection side (ST
16). Then, each time the sampling time arrives (ST1
7) Read the infrared energy data and store it in the RAM 20 as P (STlB). Then, the FI in which infrared energy data P,...P,, 1 from the current sampling time to m times before is formed in the RAM 20.
It is stored in FO (ST19). Next, in Sr10, it is determined whether the detection output is already ON. When the human body has not entered the monitoring area, this determination is NO at the beginning of the operation, and peak hold processing or bottom hold processing is executed from 5T27 to Sr14. That is, set variable 2 to O, 5T27) take register Dp, and store data P and l this time.5T2B, 5T29), the contents of register D, and P7-! Compare Sr10), Dr.
<P-, then store P n-j' in register D, 5T31), DP≧P7-! If so, skip Sr11 and move on to 5T32. And in Sr12, register D
Compare the contents Pn-, of , and if DI>P, ,-, then P7
−, in register D, 5T33), Da ≦P
□.

If so, skip Sr13. Then, until l=m (ST34), l is incremented by 1 in 5T34a, returns to Sr10, and the processing of 5T30-3T34 is repeated, and the peak value and bottom value of the infrared energy data Pn-P, , are held. .

Next, move to Sr11 l (P,, -Pfi-,)/
It is determined whether ΔL1≧ΔPs or not, and it is determined whether the infrared energy signal has changed by a predetermined value or more. This determines whether a human body has entered the monitoring area.

, ΔP, or more signal changes, and the judgment of Sr11 is YE.
If it is S, then set the detection flag Dot to “1” and set it to 5T2.
2) Transfer the contents of register D to register D", and transfer the contents of register D to register p+, respectively.
23.5T24), move on to 5T25. Judgment Y with Sr10
In the case of ES, the process similarly moves to Sr15.

At 5T25, it is determined whether the flags D and t are °'1', and if no, the process returns to Sr1. However, the flag D−t=
In the case of 1, that is, if the entry of a human body has already been detected, then the flag AL="0" and the flag A o="
1” (Sr26) This determination determines whether the processing is in a high temperature range or a low temperature range.

If the determination at 5T26 is YES, the low temperature range processing from 5T35 onward is selected (see FIG. 5(C)), and when the determination at 5T26 is NO, the high temperature region processing from 5T49 onwards is selected (see FIG. 5). (d)].

When low temperature range processing is selected, detection is performed when the background temperature is lower than the human body temperature. In this case, as shown in Figure 6, when the human body enters the monitoring area at point a, The infrared energy P, . also increases and remains approximately at a predetermined value until exiting.

In the low temperature range processing, first, the contents of the register D'B are compared with the infrared energy data Pn as a threshold level. In other words, it is determined whether D',<P,, (Sr
35). Immediately after a human body is detected, this judgment is normally YES, and therefore the process moves to 5T36, where 8f (T) is added to the contents of the previous register p+8, and a new register D゛,
The contents shall be as follows. Here, Δf (T) is a function of the maximum value of the ambient temperature change, assuming the worst case of ambient temperature change, that is, the maximum value at which the ambient temperature can approach the human body temperature.
D′ l obtained by adding this Δf (T) is set as the threshold level. Therefore, D+ increases from point a, as shown in FIG. As time passes, when D' l reaches P7 [point b in Figure 6], 5T
35 is NO, and this time, in 5T37, [)l, is compared with P, . In this case, it is determined that the human body that entered the monitoring area has not yet left. Δf (T) may be set to a fixed value if the maximum value at which the temperature changes in the monitoring area ME can be estimated in advance, or it may be set to a fixed value depending on the temperature measured by the temperature detection unit 13 during the measurement process or the temperature change It may be estimated from etc.

When the human body in the monitoring area leaves, the infrared energy data P7 decreases [point C in FIG. 6].

Therefore, the determination of Sr17 is YES, the detection flag Del is set to "0" (5T38), and the infrared energy data P, is stored in the register D (Sr39).

Then, move on to Sr10.

At 5T40, it is determined whether the dead zone flag D_sad is "1" or the instability flag D, . . . is "1".

If the determination is No, the detection flag Dat is further set to 1'.
5T41), and if this judgment is also NO, the detection output is set to 0FFL (ST/I 2), Sr1
Return to If the detection flag D e L is 1 in Sr11, the detection output is turned on (S748) and the process returns to Sr1. If the determination of Sr10 is YES, the detection flag D a
I want to judge whether L is 1°°5T43), and this judgment is YE.
In the case of Sr1, turn on the detection output (ST4B) and
Return to

On the other hand, if the determination is No in 5T43, that is, the flag Da
is 0'', a check process is performed to see if there are multiple changes greater than a specified value in the data interval of P.
T45). Here, if there is a plurality of changes greater than a specified value, it is determined that there is a slight tremor.

When the output level is low, even if a human body exists within the monitoring area, it cannot be detected, and even if Sr13 and L = "0"', if a human body is present, the infrared energy will be emitted due to its minute movement. Since data P1 also fluctuates slightly,
P,, ~P 11-1, even if Del="0°°, if there are multiple pieces of previous data P, ~p n-+* whose fluctuation exceeds the specified value, the human body is still It is determined that the target exists within the monitoring area.

Therefore, the determination of whether 5T45 has slight movement is YES.
In this case, it is further determined in 5T46 whether the detection output is ON or not, and if the detection output is ON in the previous process, set the flag I)at to 1° (5T47) and leave the detection output ON ( Sr48), return to Sr1. 5T45, Sr16
If the judgment is No, turn off the detection output (Sr12
), return to Sr1.

When high temperature range processing is selected, detection is performed when the background temperature is higher than the human body temperature, and in this case, as shown in Figure 7, when the human body enters the monitoring area at point a, the detection is performed accordingly. Infrared energy P also decreases due to the temperature difference.

In the high temperature range processing, first, the contents of the register D'P are set as a threshold level and compared with the infrared energy data Pn. In other words, it is determined whether D',>P,, (Sr
49). Immediately after a human body is detected, this judgment is usually YES.
Therefore, moving to Sr10, Δf (T) is subtracted from the contents of the previous register D" at each sampling time to obtain the new contents of the new register DI. This Δf
(T) is the same as that explained in the above low temperature range treatment.

Therefore, DIP decreases from point a as shown in FIG. After time t passes, D'P becomes P. When it reaches (point b in Fig. 7), the judgment of 5T49 becomes NO, and this time D'P is compared with Pl-β at Sr11,
If pl,≦P,,-β is not satisfied, proceed to 5T40. In this case, it is determined that the human body that entered the monitoring area has not yet left.

When a human body in the monitoring area leaves, infrared energy data P is generated. increases (point C in Figure 7). Therefore Sr11
The judgment is YES, and the detection flag DSL is set to "0" (5T52), and the infrared energy data P is stored in the register D (Sr53).Then, the process moves to Sr10.The processing after 5T40 is a low temperature range process. As explained.

(f) Effects of the Invention According to this invention, after detecting a hot body such as a human body, the reference signal approaches the detection output with the maximum possible change within a predetermined area. Even if the background temperature changes toward the heating body temperature, the reference signal is brought closer to the detection output than the change in background temperature, so even if the heating body leaves the predetermined area, the detection output can continue to be output. false detection can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a schematic configuration of the present invention, and FIG.
3 is a block diagram of a human body detection device in which the present invention is implemented, FIG. 3 is an external perspective view of the case of the human body detection device, and FIG.
5(a), 5(b), 5(C) and 5(d) are flowcharts for explaining the software configuration and operation of the human body detection device. , FIG. 6 is a diagram for explaining the operation of low temperature region processing, FIG. 7 is a diagram for explaining the operation of high temperature region processing, and FIG. 8 is a diagram for explaining the principle of the conventional human body detection device. FIG. 1: Infrared detection means, 2: Reference voltage generation means, 3: Comparison means, 4: Reference voltage control means. (d) (d)

Claims (1)

[Claims] (1) Infrared detection means including a detection element that generates an electric signal in response to infrared energy radiated from within a predetermined area; and reference signal generation means that generates a reference signal for comparison with the output of the infrared detection means. , a comparison means for comparing the output of the infrared detection means with a reference signal and determining whether or not a hot body is present within the predetermined area; A hot body detection device comprising: reference signal control means for changing the reference signal based on a maximum value of temperature change obtained.