JPH0367597B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is based on the difference between the amount of infrared energy emitted from an object such as a moving human body and the amount of infrared energy emitted from the background such as the floor of a building. This invention relates to an infrared moving object detection device that detects objects and controls the opening and closing of automatic doors and the operation of security alarm systems.

<Conventional technology> All objects at temperatures above absolute zero (-273°C) emit infrared rays according to their temperature, but human bodies and buildings at room temperature emit far infrared rays with a wavelength of around 10 μm. There is. An infrared moving object detection device sets a predetermined detection area on the floor of a building, etc., and constantly monitors infrared rays emitted from this detection area using an optical system. A device configured to detect changes in the amount of infrared energy caused by the entry of an object such as a human body into the detection area, and issue an opening signal for an automatic door or a signal for a security alarm system. It is.

Incidentally, recently, chemically treated cloth dust absorbing mats have been increasingly installed in front of automatic doors. The fabric material of this dust-absorbing pine has a small heat capacity and has long piles, so it is susceptible to sudden changes due to direct sunlight or wind speed. For this reason, if a detection area is set outdoors that is particularly exposed to direct sunlight, and a dust suction mat is installed within this detection area, the infrared moving object detection device will catch the temperature change of the dust suction mat itself and Automatic doors sometimes operated even though no objects were moving.

Therefore, we focused on the fact that false signals caused by dust suction mats occur only when the background temperature changes rapidly and the temperature difference between the human body and the background is significantly larger than the detection sensitivity of the detector. If the change is severe, an automatic gain adjustment circuit is installed to lower the detection sensitivity of the detector or to lower the level of the signal itself depending on the degree of change, so that the signal level and detection sensitivity can be adjusted regardless of the magnitude of the temperature change. An infrared moving object detection device has been devised that maintains the constant relatively constant.

<Problems to be Solved by the Invention> In the conventional device equipped with the above-mentioned automatic gain adjustment circuit, when an object continuously moves within the detection area, automatic gain adjustment is performed using a regular signal associated with the movement of the object. As the circuit functioned, the detection sensitivity gradually decreased, eventually leading to a situation where no detection was possible at all.

<Purpose of the Invention> The present invention has been made in view of the above-mentioned problems, and is intended to provide an infrared moving object detection device equipped with an automatic gain adjustment circuit that is stable even when an object continuously moves into the detection area. The object of the present invention is to provide an infrared moving object detection device that operates as follows.

<Means for Solving the Problems> In order to achieve the above object, the infrared moving object detection device of the present invention includes an optical system that condenses an infrared beam emitted from a predetermined detection area, and this optical system. an infrared detection element that converts infrared light flux incident from An infrared moving object detection device equipped with a level detection circuit that outputs a trigger signal when the level detection circuit is activated, and an output circuit that outputs an operating signal to a controller that controls the opening and closing of automatic doors etc. using the trigger signal from the level detection circuit. a sensitivity correction circuit that corrects to reduce detection sensitivity in a low frequency band in response to fluctuations in the amplified signal of noise of the amplifier circuit; and a sensitivity correction circuit that corrects when the level detection circuit outputs a trigger signal. The gist of the present invention is to have a configuration including a sensitivity correction interrupting circuit that temporarily interrupts the output of the trigger signal to maintain the detection sensitivity at the time of outputting the trigger signal.

<Function> With the above configuration, when the temperature change of the background set as the detection area increases, the amplified signal of the amplifier circuit increases accordingly. In other words, the amplified noise signal, which has a signal level different from the normal detection signal due to the detection of a moving object such as a human body and has temporal continuity, becomes larger, and the gain of the amplifier circuit increases in response to the fluctuation of the amplified noise signal. Alternatively, the detection reference level of the level detection circuit is corrected by the sensitivity correction circuit, and the detection sensitivity is automatically adjusted. During this automatic adjustment of detection sensitivity, when the level detection circuit detects the movement of an object into the detection area and outputs a trigger signal, this trigger signal drives the sensitivity correction interrupt circuit to perform the sensitivity correction function of the sensitivity correction circuit. is stopped, and the detection sensitivity is maintained at the sensitivity at the time the level detection circuit outputs the trigger signal. Therefore,
It operates stably even if objects continuously move into the detection area. Moreover, sensitivity correction is performed only in the low frequency band corresponding to the frequency component of the noise signal from disturbance detection, and in the high frequency band corresponding to the frequency component of the regular detection signal from the detection of a moving object. Since the sensitivity is not corrected, a moving object can be detected with high sensitivity even when the sensitivity is corrected by detecting noise due to disturbance.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings.

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

An infrared beam emitted from a predetermined detection area is collected by an optical system 1 and enters an infrared detection element 2 . The infrared detection element 2 is a pyroelectric detector, a thermistor bolometer, a thermoelectric pile, or the like, and converts the incident infrared light flux into an electrical signal in proportion to the amount of variation thereof. The amplified signal amplified by the amplifier circuit 3 is monitored by a level detection circuit 4 for signal strength, that is, the amount of variation in infrared light flux, and when the level detection circuit 4 detects a variation exceeding a predetermined detection sensitivity, it generates a trigger signal having a predetermined time length. Output. The output circuit 5 is actuated by the trigger signal of the level detection circuit 4 and outputs an actuation signal to the controller 6, and the controller 6 outputs an automatic door opening signal and the like.

In the infrared moving object detection device having the basic configuration as described above, the sensitivity correction circuit 7 provided between the input and output of the amplifier circuit 3 constitutes an automatic detection sensitivity feedback control system, and the level detection circuit A sensitivity correction interruption circuit 8 is connected between the output side of 4 and the sensitivity correction circuit 7.

Next, the details of the above configuration will be explained based on its operation. When the temperature change of the background set as the detection area increases, the amplified signal of the amplifier circuit 3 increases accordingly, and the sensitivity correction circuit 7 detects noise. The output of the amplifier A2 also increases. When the output of the amplifier A2 increases, the transistor Q2 becomes conductive and the collector voltage of the transistor Q1 decreases, and as shown in FIG. 2, the gate voltage of the field effect transistor Q1 decreases and it gradually cuts off. , the impedance between the source and drain terminals increases. Therefore, when the field effect transistor Q2 is cut off, the frequency band setting capacitor C1 of the signal amplification amplifier A2 is cut off, and the amplifier A1 is turned off as shown by the dashed line in FIG. In the low range of the frequency band determined by the low range setting capacitor C2, the combined resistance value of the first and second resistors R1 and R2 and the third resistor R
The gain is determined by the ratio of the resistance values of 3 and 3. That is, when the output of the noise detection amplifier A2 increases and the impedance of the field effect transistor Q1 increases, the gain in the low frequency band of the signal amplification amplifier A1 decreases, and the amplification degree of the amplifier circuit 3 is suppressed. Malfunctions due to background temperature changes are avoided. The high frequency band of the amplifier A1 is determined by the high frequency setting capacitor C3, and in normal times when noise due to disturbance is not detected, the DC power supply +B is connected to the two bleeder resistors R4 and R5. Two capacitors C4 and C5 are charged by the reference voltage divided by and applied to the amplifier A1, and this voltage makes the field effect transistor Q1 conductive, and the frequency band of the amplifier A1 is set to the frequency band setting. Due to the capacitor C1, the structure is as shown by the solid line in FIG.

To explain the above-mentioned effect in detail, the frequency component of the noise due to the disturbance, as shown by the solid curve in FIG. 4, is in a lower frequency band than the frequency component of the signal from the human body shown by the broken line. Therefore, for example, in the frequency band of amplifier A1 shown in FIG. 5, if the overall gain is reduced as shown by the solid line in the figure due to the detection of noise due to disturbance, compared to the normal gain shown by the dashed line. , the gain is reduced to a frequency band that does not need to be reduced, resulting in the inconvenience that a signal from a human body cannot be reliably detected in a state where there is disturbance noise. Therefore, as described above, only the gain in the low frequency band is reduced by noise detection.

In such a state, if the sensitivity correction circuit 7 functions in the same way using a regular signal associated with the movement of an object into the detection area, the detection sensitivity will increase if the object continues to move into the detection area. However, if the detection circuit 4 detects the movement of an object into the detection area and outputs a trigger signal, the transistor Q3 of the sensitivity correction interrupt circuit 8 will trigger the trigger signal. The transistor Q2 of the sensitivity correction circuit 7 is turned on by a signal, and the sensitivity correction function is temporarily interrupted. At this time, each capacitor C
4. Since the time constant of C5 and each resistor R6, R7 is set large, the amplifier circuit 3 maintains the detection sensitivity at the time of outputting the trigger signal, and detects the normal signal as the object moves into the detection area. It does not function by. Note that when the trigger signal of the level detection circuit 4 returns to the basic level, the transistor Q2
is turned on and the sensitivity correction circuit 7 functions again, so the sensitivity correction interruption time of the sensitivity correction circuit 7 can be adjusted by appropriately determining the output time of the trigger signal.

In the above embodiment, an example was described in which the sensitivity correction circuit 7 was configured to adjust the amplification degree of the amplifier circuit, but the present invention is not limited to this, and the sensitivity correction circuit 7 is configured to monitor fluctuations in the amplified signal of the amplifier circuit 3. ,
A method of changing the detection level of the level detection circuit 4 according to the amount of variation, that is, when the amount of variation in the amplified signal of the amplifier circuit 3 is large, the detection level is increased, and conversely, when the amount of variation is small, the detection level is decreased. Even if the detection sensitivity is corrected by lowering the detection sensitivity, it functions in exactly the same way.

<Effects of the Invention> As explained above, according to the infrared moving object detection device of the present invention, the detection area is set outdoors under direct sunlight, and a dust suction mat is installed in the detection area. Even under conditions where the background temperature changes are extremely severe, the sensitivity correction circuit adjusts only the gain in the low frequency band, which is the frequency component of the noise signal due to this fluctuation, to the signal fluctuations caused by the background temperature changes. While correcting by
The sensitivity correction interrupt circuit interrupts the function of the sensitivity correction circuit when an object moves into the detection area, so it operates extremely stably without malfunctioning due to noise caused by external disturbances, and accurately detects moving objects. It is possible to provide an infrared moving object detection device capable of detecting a moving object.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the infrared moving object detection device of the present invention, FIG. 2 is a relationship diagram between the output of the noise detection amplifier shown in FIG. 1 and the gate voltage of the field effect transistor, and FIG. The figure is a diagram of the relationship between the frequency band in Figure 1 and the gain of the signal amplification amplifier, Figure 4 is an explanatory diagram of the frequency components of the noise signal and the signal from human body detection, and Figure 5 is the frequency shown for comparison. This is the relationship between the band and the gain of the signal amplification amplifier. DESCRIPTION OF SYMBOLS 1...Optical system, 2...Infrared detection element, 3...Amplification circuit, 4...Level detection circuit, 5...Output circuit, 6...Controller, 7...Sensitivity correction circuit, 8...Sensitivity correction interruption circuit, A1, A2...Amplifier , Q1...field effect transistor, 2,Q3...transistor.

Claims (1)

[Claims] 1. An optical system that condenses infrared light flux emitted from a predetermined detection area, an infrared detection element that converts the infrared light flux incident from this optical system into an electrical signal according to the amount of variation thereof, An amplifier circuit that amplifies the output signal of this infrared detection element, a level detection circuit that outputs a trigger signal when the output amplified signal of this amplifier circuit exceeds a predetermined level, and an automatic trigger signal from this level detection circuit. In an infrared moving object detection device equipped with an output circuit that outputs an operating signal to a controller that controls the opening and closing of a door, etc., a signal is detected in a low frequency band in response to fluctuations in the amplified signal of noise of the amplifier circuit. a sensitivity correction circuit that corrects to lower the detection sensitivity; and a sensitivity correction that controls the output of the sensitivity correction circuit to be temporarily interrupted when the level detection circuit outputs a trigger signal to maintain the detection sensitivity when the trigger signal is output. An infrared moving object detection device comprising: an interruption circuit. 2. Claim 2, characterized in that the sensitivity correction circuit is configured to control so as to reduce the gain in the low frequency band of the amplifier circuit in response to fluctuations in the amplified signal of noise of the amplifier circuit. The infrared moving object detection device according to item 1. 3. A patent characterized in that the sensitivity correction circuit is controlled to lower the detection reference level in the low frequency band of the level detection circuit in response to fluctuations in the amplified signal of noise of the amplifier circuit. An infrared moving object detection device according to claim 1.