JPH0357993A - Human body detector - Google Patents

Abstract

PURPOSE:To reduce the effect of noise and to enable detection of a human body moving at a low speed, by a method wherein threshold values prescribing the upper limits of a time difference between output times and being used for removing the noise and detecting the human body are changed over by outputs of infrared ray detecting elements delivered from a signal processing unit. CONSTITUTION:Two kinds of upper-limit threshold values T'MAX and TMAX of a time difference between output time are set beforehand in a decision unit 5. When a mutual time difference t of times tA to tD when outputs of infrared ray detecting elements A to D exceed a threshold value Vgamma does not satisfy a second determining condition TMIN < t < T'MAX ( where TMIN is the lower limit of the time difference t) on a human body, the respective output values FK(t) of all the elements A to D at the time when the time of the threshold value T'MAX passes from an output start time nt of an element (n) outputting first are checked up by an inequality ¦FK(tn +T'MAX¦ > Vgamma, and when no elements A to D satisfy this inequality, it is determined that the human body is absent. If any one of the elements A to D satisfies this inequality, the second determining condition is checked up again by using the threshold value TMAX. When this condition and further a first determining condition VMIN/VMAX > S (where VMIN and VMAX are the minimum and maximum values of peak values of the elements, and S a threshold value) are satisfied, it is determined that the human body is present.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is an infrared receiving type that detects the difference between the amount of infrared rays emitted from the human body and the amount of infrared rays emitted from the background such as the floor surface by the movement of the human body. The present invention relates to a human body detection device.

[Prior Art] An infrared receiving type human body detection device is a device that detects a human body by detecting the temperature difference between the human body and the background as a difference in the amount of infrared energy using an infrared detection element such as a pyroelectric element. , which has become widely popular in recent years, has also required improvements in reliability. Possible causes of malfunction of the infrared receiver 2 human body detection device include background temperature changes within the detection area, internal noise, and the influence of high-energy disturbance light such as headlights and sunlight. Various proposals have been made in the past to remove this.

As one of them, a method has been proposed that uses four infrared detection elements to obtain two sets of differential outputs (Japanese Patent Application Laid-Open No. 58-1989-1).
Publication No. 213396, JP-A-59-94094
Publication No.). An example of the detection operation of this human body detection device is shown in FIGS. 6 and 7. 4 infrared detection elements A+ on the object surface
．． A-, B+. Four detection areas ■ to ■ according to B- are set, and detection areas I. The differential outputs Va (output between infrared detection elements A+.A and 1) and Vl (output between infrared detection elements B+ and .degree.B) are obtained by the detection areas II and III. In the case of FIG. 6(a), the human body M moves from the detection areas 1 and II[ to the detection areas ■ and ■, and differential outputs vA+vl as shown in FIG. 7(a) are obtained. In the case of FIG. 6(b), the human body M moves from the detection area I, ■ to the detection area ■, ■, and the differential output vA, ■ as shown in FIG. 7(b). are obtained together. However,
In the case of Fig. 6(c), the differential output vA is obtained as shown in Fig. 7(c), but the differential output V, is canceled because the human body M crosses the detection area ■■ at the same time. and the differential output vll is not generated. Therefore, in order to reliably detect the movement of a human body, it is necessary to output a human body detection output when any one of the differential outputs vA+V produces an output.

However, in this case, the differential outputs vA, v. There was a problem in that one of the two would produce an output, causing malfunction.

Therefore, the present applicant has proposed a highly reliable human body detection device by using a plurality of infrared detection elements and comparing their respective outputs (Japanese Patent Application No. 62-242090). 8th
The figure shows an overall horizontal block diagram of this human body detection device.

Infrared rays from a detection area are collected by an optical system 1, and the collected infrared rays are received using an infrared detection element section 2 consisting of a plurality of infrared detection elements A-D. After each output is independently amplified by the amplification section 3,
The signal processing unit 4 converts the signal into a signal suitable for human body detection, the determining unit 5 detects the peak value and the output time, compares these with each other to determine the presence or absence of a human body, and outputs the determination result to the output unit 6. It is output from. Detection operation of this human body detection device? This will be explained based on FIGS. 3 and 4.

First, attention will be paid to each output of the infrared detection elements A to D. The detection areas A' to D' corresponding to the infrared detection elements A to D are narrowed down to a sufficiently small area compared to the human body M.

When the human body M moves, it is considered that the human body M passes through the entire detection area A' to D° regardless of the direction of movement.
Approximately similar peak values are obtained for each output of the infrared detection elements A to D. In reality, the peak value of each output varies to some extent due to the temperature distribution on the surface of the human body. The peak value VA-VD is also affected by the ambient temperature. Therefore, a relative comparison may be made for each peak value VA~■. That is, the peak value ■
．． ~The maximum value at VD is VMAX, the minimum value is VMIN
Then, the ratio of ■■8 and VMIN is the threshold S (Q<S<
1), it is determined that the variation in each of the peak values VA to VD is small, and that a human body is present. The condition for determining the presence of a human body can be expressed by the following equation.

■■N / V WAX > S - ■? To,
Attention is paid to the output time t A% t . When a human body moves through the detection areas 8° to D, it will not enter all the detection areas A to D at the same time, regardless of the direction of movement.

That is, there is a time difference between the times (output times) tA to 1D at which the output signals of the infrared detection elements A to D rise (output times). This time difference can be limited to a certain range by considering the width of the detection area A~D" and the moving speed of the human body. If the time difference between output time 1 A-1. is Δt, then the second The judgment condition can be expressed by the following equation.

T■8kuΔt<THAX. - ■However, T■,
, T', and 4ax are the lower and upper limits of the time difference, respectively. In the example of FIG. 4, (a), (b). In either case (c), the time difference is obtained as Δt""to tA, and it is determined whether or not this ΔL satisfies the following formula. By detecting the presence or absence of a human body according to the above judgment conditions, it is possible to prevent malfunctions caused by general temperature changes, ambient light such as sunlight, local changes, internal noise, etc., and highly reliable human body detection. It becomes a device.

? Problems to be Solved by the Invention] In the human body detection device described above, the presence or absence of a human body is determined from the output time and peak value of each infrared detection element. The time required for the human body to pass through the detection area is inversely proportional to the moving speed of the human body, which is 360 m/h (0.1 m/s).
In order to detect a human body moving at speeds from m) to 36 km/h (10 m/s), it is necessary to set the upper limit threshold TMA of the human body judgment condition (■) based on the output time difference of each element at the lowest speed. did not become. However, the larger the threshold value TMo is, the more malfunctions due to noise will occur, and conversely, if the threshold value T8 is smaller, there is a problem that a human body moving at low speed cannot be detected.

For example, as shown in FIG. 5(a), the output signals of the infrared detection elements A-D due to the human body are output at output times tA to 1D and at peak values VA-V. If the peak value satisfies the human body determination condition, and the time difference upper limit threshold is TMAX, it can be detected as a human body since it satisfies the human body determination condition (2), but if the time difference upper limit threshold is T'■8 If so, it cannot be detected as a human body because the human body determination condition (3) is not satisfied.

Further, as shown in FIG. 5(b), the output signals of the infrared detection elements A-D due to noise are output at the output time t+. ~tl, and peak value Vl. ~ ■f+, and when the peak value satisfies the human body judgment condition, the upper threshold of the time difference is T,l
If AX satisfies the human body determination condition (■), it will be mistakenly detected as a human body, but the upper threshold of the time difference is T.
) If it is IAX, it can be removed as noise because it does not satisfy the human body judgment condition (2).

The present invention has been made in view of these points,
The purpose is to provide a highly reliable human body detection device that suppresses the influence of noise and can reliably detect a human body moving at low speed.

[Means for Solving the Problems] A human body detection device according to the present invention includes an optical system that collects infrared rays from a detection area, and a plurality of infrared detection elements that receive the infrared rays collected by the optical system. , an amplification unit that amplifies each output of the plurality of infrared detection elements, a signal processing unit that processes each output of the infrared detection elements amplified by the amplification unit into a signal passed through human body detection, and the signal processing unit a determining unit that determines the presence or absence of a human body by comparing the peak value and output time of each output of the infrared detection element processed by the unit; and an output unit that outputs the determination result of the determining unit. In the human body detection device, the determination unit sets a threshold for noise removal and a threshold for human body detection as thresholds that are the upper limit of the time difference between the output times of each infrared detection element, and sets a threshold for noise removal and a threshold for human body detection to determine whether the output from the signal processing unit is The invention is characterized in that the threshold value is switched by an output signal corresponding to each infrared detection element.

[Effect]

In the present invention, the presence or absence of a human body is determined by switching the threshold value that defines the upper limit of the time difference between the output times used in the determination unit based on each output of the infrared detection element from the signal processing unit, thereby reducing noise. This makes it possible to reliably detect human bodies moving at low speeds while minimizing the impact.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. Although this embodiment shows a case in which there are four infrared detecting elements, the present invention can also be applied to a case in which a number of infrared detecting elements other than four is used.

1 is an optical system that condenses infrared rays using a mirror or lens. In the case of this embodiment, infrared rays are collected from a plurality of detection areas using a multi-segment ξ beam or a multi-segment lens. 2
is an infrared detecting element section, which is different from a plurality of infrared detecting elements, and this embodiment shows a case where four infrared detecting elements A to D are used. As the infrared detection elements A to D, inexpensive pyroelectric elements that can operate at room temperature are used. In addition to the pyroelectric element, a thermopile can also be used. By arranging the infrared detecting elements A to D on the focal plane of the optical system 1, a plurality of detection areas A' to D° are formed on the object plane through the optical system 1. It is shaped in the same arrangement as the arrangement,
As the human body moves within the detection areas A' to D'', each infrared detection element A to D produces an output as a change in temperature difference with the background.
The outputs of each are amplified independently. 4 is a signal processing unit, which is equipped with a bandpass filter to remove noise, and extracts only a certain portion of the necessary frequency from each output, and each output that has passed through the bandpass filter is sent to a multiplexer and an A/D converter. A/D conversion is performed sequentially using

Reference numeral 5 denotes a determining section, which obtains the peak value and output time from each output of the infrared detecting elements A to D processed by the signal processing section 4, and uses these information to determine the presence or absence of a human body.

Here, regarding the output time, two types of thresholds TMAX and T'MAX are used as the upper limit threshold of the time difference between the output times.
Set. In other words, the threshold for noise removal T'l. I
AX and threshold value T. for human body detection. AX is provided.

Reference numeral 6 denotes an output unit that outputs the determination result from the determination unit 5.

The human body determination operation in this human body detection device will be explained based on FIG. First, attention will be paid to each output of the infrared detection elements A to D. The detection area is narrowed down to a sufficiently small area compared to the human body M. When the human body M moves, it is considered that the human body M passes through the entire detection area A° to D' regardless of the direction of movement, so the peak values of each output of the infrared detection elements A to D are almost the same. . In reality, the peak value of each output varies to some extent due to the temperature distribution on the surface of the human body. Also, the peak value ■. ~v0 is also affected by ambient temperature. Therefore, a relative comparison may be made for each peak value V A - V . That is, the peak value■.

It is sufficient that the ratio between the maximum value VMAX and the minimum value VMIN in ~VI, is larger than the threshold value S (0<S<1).

VMIN/VMAyt>S-
■Next, the output time t A/'w t. Focus on.

When a human body moves through detection areas A~D, it will not invade all detection areas at the same time, regardless of the direction of movement. In other words, at the output of each infrared detection element? LA””
T. There is a time difference in o. This time difference is determined by considering the size of the detection area and the speed of movement of the human body.
It can be limited to a certain range. Assuming that the time difference between the output times is Δt, it is determined that a human body is present when the following equation is satisfied.

T■8kuΔt<TMAX'- ■However,
TIN+TNAX are the lower and upper limits of the time difference, respectively. In the example of Figure 4, (a), (b), (c
), the time difference is determined as ΔL=LDLA, and it is determined whether or not this satisfies the equation (2).

Here, the process of switching the upper limit threshold of the time difference between output times in the determining unit 5 and detecting the presence or absence of a human body in the determining unit 5 is shown in the flowchart of FIG. In the judgment section 5,
The upper limit threshold T' NA of the time difference between two types of output times is set in advance.
II. TMAX (T″WAX <TMAX is set. The threshold T and IAX are the upper limit values of the time difference between the output times when it is assumed that the human body moves at the minimum speed,
The threshold value T'MAX is a value smaller than TMA)l, for example, assuming that the human body moves at the maximum speed)? Set to the upper limit of the time difference between the output times.

When the determination unit 5 detects that the output of any one of the infrared detection elements A to D exceeds a preset threshold value VT from a flat state near 0, the determination unit 5 determines that the output of one of the infrared detection elements A to D exceeds a preset threshold value VT.
Store K as the output time of element K. However, threshold V7
is the minimum level of the signal component, and outputs below ■7 are considered noise.

When all elements start outputting, use T'Ml4AX as the upper limit threshold of the time difference between output times to check whether the human body judgment condition (T HI N <Δt<T'■X) is satisfied. Sometimes, an alarm is issued only when the human body criteria are also met. If the human body determination condition (2) is not satisfied, the following process is performed.

That is, the element that first started outputting among the infrared detecting elements A-D is defined as n, and the output value of element K at time t is Ft.
(t). First, time t when element n starts outputting,
Regarding the outputs of all the elements when T'■8 has passed since ,
Check whether output is occurring. That is, for each element K, Fx (tn+T' WAX) l >
Examine the inequality of Vt ---■. When there is no element that satisfies formula (2), it is determined that these outputs are not caused by the human body. However, if there is even one element that satisfies the formula (■), use TMAX as the upper limit threshold for the time difference between output times and check the human body judgment condition (T s I N <Δt<T.AX) again. ,
When this and the judgment conditions are also satisfied, an alarm is issued.

The operation of the determining section 5 will be explained using FIG. 5. As shown in FIG. 5(a), the infrared detection elements A to D rise at times tA to tD, and the peak value of each element is VA~■. It is. Element A is the first to rise, and at time (tA+T'MAX), the other three elements have not yet risen. Therefore, time (tA+T'l
Looking at the output of each element at lAll ), it can be seen that only element A produces an output, satisfying the inequality (2). Furthermore, the time ( t A f TMA)
Since all the elements have risen by then, the judgment unit 5 checks whether or not the human body judgment condition (2) is satisfied, and if it is satisfied, it issues an alarm.

Moreover, in FIG. 5(b), each infrared detection element A-
D has the output time +,,jl. , peak value y+, ~V'
. The output is caused by some noise. In this case, from time tj, when the first element rises, T', IAX
After a certain period of time, no output is produced in element A, and the other elements have not yet risen, so the determination condition (2) is not satisfied. Therefore, it is not determined to be a human body.

Conventionally, the presence or absence of a human body was determined based only on the upper limit of the time difference between the output times of each element depending on the moving speed of the human body, so when trying to detect a human body moving at low speed, it was easily affected by noise etc. Ta. In this embodiment, the presence or absence of a human body is determined by switching the threshold value that defines the upper limit of the time difference between the output times used in the determination unit based on each output of the infrared detection element from the signal processing unit, so the influence of noise is eliminated. Even human bodies moving at low speed can be detected reliably.

[Effects of the Invention] As described above, according to the present invention, an optical system that collects infrared rays from a detection area, a plurality of infrared detection elements that receive the infrared rays collected by the optical system, and a plurality of an amplification section that amplifies each output of the infrared detection element, a signal processing section that processes each output of the infrared detection element amplified by the amplification section into a signal suitable for human body detection, and processing by the signal processing section. A human body detection device comprising: a determination unit that determines the presence or absence of a human body by comparing the peak values and output times of the outputs of the infrared detection elements, and an output unit that outputs the determination results of the determination unit. The determination unit sets a threshold for noise removal and a threshold for human body detection as the upper limit of the time difference between the output times of each infrared detection element, and sets each infrared ray output from the signal processing unit to a threshold for noise removal and a threshold for human body detection. Since the threshold value is switched according to the output signal corresponding to the detection element, it is possible to provide a highly reliable human body detection device that suppresses the influence of noise and can reliably detect a human body moving at low speed.

[Brief explanation of drawings]

Figure 1 shows Figure 2 shows Figure 3 shows Figure 4 shows Figure 5 shows Figure 6 shows Figure 7 shows Figure 8 shows 11 optical system 3.1.Amplification section 5-・Judgment Department A block diagram showing an embodiment of the present invention, Flowchart for explaining the operation of the same as above to, The detection area is shown to explain the operation of the same as above. Schematic diagram, Waveform diagram according to the above, A wave showing an example for explaining the operation of the same as above. shape diagram, The detection area for explaining the operation of the conventional example Schematic diagram showing, Waveform diagram according to the above, FIG. 2 is a block diagram showing another conventional example. 2.1.Infrared detection element part 41 signal processing section 6.--Output section

Claims (1)

[Claims] (1) An optical system that collects infrared rays from a detection area, a plurality of infrared detection elements that receive the infrared rays collected by the optical system, and an amplification that amplifies each output of the plurality of infrared detection elements, respectively. a signal processing section that processes each output of the infrared detection element amplified by the amplification section into a signal suitable for human body detection; and a peak value of each output of the infrared detection element processed by the signal processing section; A human body detection device comprising: a determination unit that compares output times with each other to determine the presence or absence of a human body; and an output unit that outputs a determination result of the determination unit, the determination unit comprising A threshold for noise removal and a threshold for human body detection are set as the upper limit of the time difference between the output times of the elements, and the threshold is set by the output signal corresponding to each infrared detection element output from the signal processing section. A human body detection device characterized by being configured to switch.