JPH07104416B2 - Human body detection device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an infrared ray receiving type human body detecting device for detecting a human body by infrared rays emitted from the human body.

[Prior Art] An infrared ray receiving type human body detecting device detects a difference in infrared energy amount between a human body and a background (that is, a temperature difference between the human body and the background) by using an infrared detecting element such as a pyroelectric element. Then, the human body is detected, which has been widely spread in recent years, and along with this, improvement in reliability has been demanded. Possible causes of malfunction of the infrared ray detection type human body detection device are a temperature change in the background in the detection area, internal noise, and influence of disturbance light having large energy such as headlights and sunlight. Therefore, in order to eliminate these malfunction factors, various proposals have been conventionally made. As one of them, there has been proposed a method for detecting a human body by obtaining two sets of differential outputs by using four infrared detecting elements (JP-A-58-213396 or JP-A-59-94094). Gazette). An example of the detection operation of this human body detection device will be described with reference to FIGS. 3 and 4. In this human body detection device, four detection areas I to IV are set on the background, and infrared detection elements A ⁺ , A ⁻ , B ⁺ , B ^{− which} receive infrared rays from these detection areas I to IV, respectively.
Comprising a detection region I, IV and detection area II, each differential output Va for each III ^{- +} and Vb (infrared detection element B (infrared detection element A ^+, A output difference between), B ^- the output difference between ) Get. Fig. 3 (a)
As shown in, the human body M is detected from detection areas I and III to detection areas II and IV.
4A, the differential outputs Va and Vb shown in FIG. 4A are obtained, and the human body M is detected in the detection area as shown in FIG. 3B.
When moving from I and II to the detection regions III and IV, the differential outputs Va and Vb shown in FIG. 4B are obtained.

By the way, in this human body detecting device, for example, when the human body M diagonally crosses the four detection regions I to IV as shown in FIG. 3C, the differential output Va is obtained as shown in FIG. 4C. However, in the detection areas II and III, since the human body M crosses at the same time, the output is canceled and the differential output Vb does not occur. Therefore, in order to reliably detect the movement of the human body M in this human body detection device, it is necessary to determine that the human body exists when any one of the differential outputs Va and Vb produces an output. However, when the human body M is detected in this way, one of the differential outputs Va and Vb produces an output due to a temperature change occurring in one detection area, internal noise produced in one infrared detection element, or the like, and a malfunction occurs. There was a problem that caused.

Therefore, in order to solve the above-mentioned problems, the present inventors have proposed a human body detection device that detects the human body by comparing the outputs of a plurality of infrared detection elements (Japanese Patent Application No. 62-242090).
issue). FIG. 5 shows the overall structure of this human body detecting apparatus. This human body detecting device receives infrared rays from an area consisting of a plurality of detection areas A'to D ', which is sufficiently smaller than the human body M, through an optical system 1 for condensing each of the detection areas A'to D'. Infrared detector 2 including a plurality of infrared detectors A to D, an amplifier 3 that independently amplifies each output of each infrared detector A to D, and converts the amplified output into a signal suitable for human body detection. The signal processing unit 4, the determination unit 5 that detects the peak value and the output time of the converted signal and compares them with each other to determine the presence or absence of a human body, and the output unit 6 that outputs the determination result.
It consists of and.

The operation of the human body detecting device will be described with reference to FIGS. 6 and 7. In this human body detection device, the human body M passing through the area is detected regardless of the moving direction by narrowing the area composed of the detection areas A'to D'to a sufficiently smaller area than the human body M as described above. ′ To D ′, the human body M is detected by the detection areas A ′ to D ′.
After passing through, the peak values V _{A to} V _D of the respective outputs of the infrared detecting elements A to _D become almost the same value. Therefore, the fact that the peak values V _{A to} V _{D of the} outputs of the infrared detection elements A to _D show almost the same value can be the first determination condition for the presence determination of the human body M. However, in reality, there are some variations in the peak values of the outputs of the infrared detection elements A to D due to the temperature distribution on the surface of the human body M, and the peak values of the outputs V _{A to} V _D.
Is influenced by the ambient temperature, the presence of the human body M is determined by relatively comparing the outputs of the infrared detection elements A to D. Now, assuming that the maximum value of the peak values V _{A to} V _D of the respective outputs of the infrared detection elements A to _D is Vmax and the minimum value is Vmin, the ratio of Vmax and Vmin is a predetermined value S (0
If it is larger than <S <1), it is determined that the variation in each peak value V _{A to} V _D is small and the human body M exists. That is, the first determination condition for determining the presence of the human body M is expressed as follows.

Vmin / Vmax> S (1) However, 0 <S <1 Further, when the human body M passes through the detection areas A'to D ', all the detection areas A'to D'regardless of the moving direction. There is no possibility of intruding at the same time. That is, there is a time difference between the times at which the output signals of the infrared detection elements A to D rise (hereinafter, this time is referred to as the output time) t _{A to} t _D. Therefore, the presence of a time difference between the output times t _{A to} t _D can be the second determination condition for determining the presence of the human body M. The time difference is limited to a certain range in consideration of the size of the detection areas A ′ to D ′ and the moving speed of the human body M. Therefore, if the time difference between the output times t _{A to} t _D is Δt,
The second determination condition for determining the presence of the human body M shown by the following equation is obtained.

Tmin <Δt <Tmax (2) where Tmin and Tmax are the lower limit value and the upper limit value of the time difference, respectively. For example, when the outputs of the infrared detecting elements A to D shown in FIGS. 7A to 7C are obtained, the time difference Δt = t _D −t _A can be obtained in any case.

That is, in this human body detecting device, the infrared detecting element A
It is determined that the human body M exists when the peak values V _{A to} V _D of each output of _D to _D are substantially constant and the output times t _{A to} t _{D of} each output have a variation in a predetermined range. When the presence / absence of the human body M is determined in this manner, malfunction due to the influence of general temperature change, ambient light such as sunlight, or local temperature change or internal noise can be prevented, and a highly reliable human body detection device Becomes

[Problems to be Solved by the Invention] By the way, in this human body detection device, each infrared detection element A to
The output time of D was detected by the determination unit 5 as the time when those output levels exceeded a predetermined determination value. Here, the time required for the human body M to pass through the detection areas A ′ to D ′ is inversely proportional to the moving speed of the human body M, and the second time of the presence determination of the human body M is determined.
The lower limit value Tmin of the determination condition (equation (2)) is set based on the output time difference of the infrared detecting elements A to D obtained by the human body M moving at the maximum speed. Therefore, in such an output time detection method, it is necessary to set the determination value low in order to accurately detect the human body M moving at high speed. In this human body detection device, for example, 360 m / h
The human body M moving from 0.1 m) to 36 km / h (10 m / s) is detected.

Further, it is also necessary to set the above determination value low for the following reasons. For example, when infrared rays are simultaneously incident on the infrared detection elements A to D due to disturbance light, etc., and the light source is at a position greatly deviated from the center of the detection region of each infrared detection element A to D, and there is a difference in the infrared incident light amount. , Outputs of the infrared detecting elements A to D shown in FIG. 8 are obtained. Where the judgment value is
If it is set to Vth, a time difference will occur in the output time (t _A ~ t
_D ) and the peak values V _{A to} V _D satisfy the first judgment condition,
As described above, the second determination condition is also satisfied, and malfunction occurs due to ambient light. However, if the judgment value is lowered as indicated by Vth ′ in FIG. 8, at each output time of the infrared detecting elements A to D,
As shown by t _A ′ to t _D ′, the time difference disappears and the judgment condition of the expression (2) is not satisfied, so that malfunction due to ambient light can be prevented. Therefore, it is necessary to set the determination value low in order to prevent the malfunction due to the ambient light as described above.

However, when the determination value for detecting the output time is set low as described above, for example, when noise having different output times as shown in FIG. 9 and having a substantially constant peak value is input to the determination unit 5. In some cases, both the first and second determination conditions are satisfied, and therefore noise may cause malfunction. In other words, if the judgment value is set low, it will react to noise.

The present invention has been made in view of the above points, and an object of the present invention is to provide a human body detection device that is less likely to malfunction due to noise.

[Means for Solving the Problem] In order to achieve the above-mentioned object, the present invention is the latest in which the increasing / decreasing direction of the change of each output is reversed until the determination unit determines that the output of the infrared detection element exceeds the determination value. The time point of is determined to be the output time.

Even if the determination unit determines that the latest time when the increase / decrease rate of the change in each output increases until the output exceeds the determination value for determining that the output of the infrared detection element has occurred is the output time, it is the same as the above case. The purpose of can be achieved.

[Operation] According to the present invention, as described above, the determination unit determines that the latest time point at which the increasing / decreasing direction of the change in each output is reversed until the output value of the infrared detecting element exceeds the determination value is the output time. By doing so, it is possible to prevent malfunction due to noise by making a determination that the output of the infrared detection element has occurred with a relatively high determination value that can remove noise.

In addition, even if the determination unit determines that the output time is the point at which the increase / decrease rate of the change in each output until the output exceeds the determination value for determining that the output of the infrared detection element has occurred, the output of the infrared detection element occurs. It is possible to prevent malfunction due to noise by making a determination with a relatively high determination value that can remove noise.

[Embodiment 1] The human body detection apparatus of the present embodiment is structurally the same as the conventional human body detection apparatus shown in FIG. 5, and in the case of the present embodiment, the determination unit 5 is used.
The method is characterized by the method of determining the presence of the human body M by. In the following description, the case where four infrared detecting elements are used will be described, but the present invention can be applied even when the number of infrared detecting elements is other than four.

First, a description will be added regarding the specific configuration of the present embodiment. In this embodiment, an inexpensive pyroelectric element that can operate at room temperature is used as the infrared detecting element. A thermopile may be used instead of the pyroelectric element. As the optical system 1, a mirror or a lens is used, and more specifically, a multi-division mirror or a multi-division lens is used. The infrared detection elements A to D are arranged on the focal plane of the optical system 1, and four detection areas A ′ to D ′ are arranged on the background through the optical system 1 in the same arrangement as the infrared detection elements A to D. Will be formed in. Here, when the human body M passes through the detection areas A'to D ', the infrared detection elements A to D generate outputs corresponding to changes in the temperature difference between the human body M and the background. The signal processing unit 4 is composed of a bandpass filter, a multiplexer and an A / D converter. The bandpass filter extracts only necessary frequency components in the outputs of the infrared detection elements A to D, and the bandpass filter is used by the multiplexer and the A / D converter. The outputs of the infrared detection elements A to D that have passed through the filter are sequentially A / D converted. Judgment unit 5
Then, the output times t _{A to} t _D and the peak values V _{A to} V _D are obtained from the respective outputs of the infrared detection elements A to D processed by the signal processing unit 4,
It is determined whether or not the determination conditions of the above equations (1) and (2) are satisfied.

By the way, in the case of the present embodiment, the determination unit 5 detects the output times of the infrared detection elements A to D as follows. For example, if the outputs of the infrared detecting elements A to D change as shown in FIG.
The output time is determined to be the latest time point at which the increasing / decreasing direction of the change in each output is reversed until the output exceeds the determination value Vth. Specifically, the infrared detection elements A to D
The slope of the output change is calculated and the time when the polarity of the slope is reversed is stored. At the time of polarity reversal, the previously stored time is erased and a new polarity reversal time is stored.
Then, when the outputs of the infrared detecting elements A to D exceed the predetermined voltage Vth, the time (ts in the case of FIG. 1) stored at that time is determined to be the output time t _{A to} t _D. To do. By doing so, the determination value Vth for determining that the outputs of the infrared detection elements A to D have been made relatively high, so that malfunction due to noise can be prevented. That is,
Since noise has a low peak value, it can be removed as described above. In addition, the output time is the infrared detection element A to
Since the detection is performed from the time when the increasing / decreasing direction of the change in the output of D is reversed, it can be reliably detected separately from the case where the output of the infrared detection elements A to D is detected. The presence determination of the human body M after the detection of the output time is performed by the above-described fifth determination.
Similar to the example of the related art, it is performed depending on whether or not the determination condition is satisfied.

[Second Embodiment] This embodiment is different from the first embodiment in the method of detecting the output time, and in the above-described first embodiment, the determination unit determines that the infrared detection elements A to D output. The latest time point when the increasing / decreasing direction of the change of each output until it exceeds the value is reversed is determined to be the output time, but in the present embodiment, in addition to that, the outputs of the infrared detecting elements A to D occur. The output time is also determined when the increase / decrease rate of the latest change in each output until the determination value is exceeded. Specifically, in this embodiment, the infrared detection element A
Until the outputs D to D occur, the slope of the output change is obtained in the same manner as in the first embodiment, and the time at which the polarity of the slope is reversed and the time at which the absolute value of the slope exceeds the previous value are updated and stored. Then, the time stored when the output of the infrared detection elements A to D exceeds the determination value Vth is set as the output time. Therefore, in the case of FIG. 2, the determination unit 5 determines the time t _{K at} which the increase / decrease rate of the change in output increases as the output time. In the case of this embodiment, the same effect as that of the first embodiment can be obtained.

[Effects of the Invention] As described above, in the present invention, the latest time point at which the increasing / decreasing direction of the change in each output is reversed until the determination unit determines that the output of the infrared detection element has exceeded the determination value is the output time. Therefore, it is possible to prevent malfunction due to noise by determining that the output of the infrared detection element has occurred with a comparatively high judgment value capable of removing noise.

In addition, even if the determination unit determines that the latest time when the increase / decrease rate of the change in each output increases until the output exceeds the determination value for determining that the output of the infrared detection element has occurred, the output of the infrared detection element does not occur. It is possible to prevent malfunction due to noise by making a determination with a relatively high determination value that can remove noise.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an output time detection method according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of an output time detection method according to another embodiment, and FIG. 3 is a conventional human body detection method. 4 and 5 are output waveform diagrams of the same as above, FIG. 5 is a block diagram showing the configuration of another conventional example, and FIG. 6 is an explanatory diagram of the human body detecting method of the same as above.
FIG. 8 is an output waveform diagram of the above, FIG. 8 is an explanatory diagram of a method of detecting an output time, and FIG. 9 is an explanatory diagram of problems in the same. Reference numeral 5 is a determination unit, A to D are infrared detection elements, and Vth is a determination value.

Claims (2)

[Claims] 1. A plurality of infrared detecting elements, each of which detects infrared rays from an area which is composed of a plurality of detecting areas and is sufficiently smaller than a human body, for each detecting area, and a peak value of each output of these infrared detecting elements. In a human body detection device having a determination unit that determines that a human body is present when the output times of the outputs are substantially constant and varies in a predetermined range, the determination unit determines that the output of the infrared detection element has occurred. The human body detection device configured to determine that the latest time point at which the increasing / decreasing direction of each output change is reversed until it exceeds the determination value is the output time. 2. A plurality of infrared detecting elements, each of which has a plurality of detecting areas and receives infrared rays from an area sufficiently smaller than a human body, for each detecting area, and peak values of outputs of the infrared detecting elements. In a human body detection device having a determination unit that determines that a human body is present when the output times of the outputs are substantially constant and varies in a predetermined range, the determination unit determines that the output of the infrared detection element has occurred. The human body detection device configured to determine the latest time when the increase / decrease rate of each output change increases until the output exceeds the determination value as the output time.