JPH03238391A - Human body detector - Google Patents

Abstract

PURPOSE:To prevent the erroneous operation due to noise by judging the latest points of time when the increase and decrease directions of the change in respective outputs until the outputs of infrared detection elements exceed a judging value are inverted as output times. CONSTITUTION:When the outputs of infrared detection elements A - D change, a judging part 5 judges the latest points when the increase and decrease directions of the change in respective output until the outputs of the infrared detection elements A - D exceed a judging value Vth judging the generation of the outputs are inverted as output times. Concretely, the inclinations of the output changes of the detection elements A - D are calculated and times when the polarities of the inclinations are inverted are stored. The times stored previously are erased at the inversion time of polarity and new polarity inversion times are stored. At the point of time when the outputs of the detection elements A - D exceed predetermined voltage Vth, the times ts stored at that time are judged to be output times tA - tD. By this method, the judging value Vth judging the generation of the outputs of the detection elements A - D can be made relatively high. That is, since a peak value is low, noise can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an infrared receiving type human body detection device that detects a human body using infrared rays emitted from the human body.

[Prior art 1 An infrared receiving type human body detection device uses an infrared detection element such as a pyroelectric element to detect the difference in the amount of infrared energy between the human body and the scenery (that is, the temperature difference between the human body and the background). It detects the human body and has become widespread in recent years, and as a result, there has been a demand for improved reliability. Possible causes of malfunction of this infrared receiving type 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. Therefore, various proposals have been made to eliminate these causes of malfunction. One such method has been proposed to detect a human body by obtaining two sets of differential outputs using four infrared detection elements (Japanese Patent Application Laid-Open No. 58-213396
(or wWi No. 59-94094). An example of the detection operation of this human body detection device will be explained based on FIGS. 3 and 4. In this human body detection device, four detection areas I to ■ are set on the background, and infrared detection elements A'', A-, B+, and B- are provided to receive infrared rays from these detection areas I to ■, respectively. , differential output ■a (output difference between infrared detecting elements A", A-) and \'b (infrared detecting elements B", B-) Figure 3 (output difference) is obtained.
, ), the human body M is located in the detection area 1. When the human body M moves from the detection area It, rV to the detection area It, rV, the differential outputs Va, Vb shown in FIG. 4(a) are obtained, and as shown in FIG. 3(b), the human body M moves to the detection area 1. Detection area from It■,■
When moving to , the differential outputs Va, vh shown in FIG. 4(b)
is obtained.

By the way, in this human body detection device, when the human body M diagonally crosses the four detection areas I to ■ as shown in FIG. 3(c), the differential output Va is obtained as shown in FIG. 4(c). However, since the human bodies M cross at the same time in the detection areas (2) and (2), the outputs are canceled and no differential output vb is generated. Therefore,
In order to reliably detect the movement of the human body M, the body detection device needs to determine that a human body is present when either of the differential outputs Va and Vb produces an output. However, when detecting the human body M in this way, one of the differential outputs Va and Vb will generate an output due to temperature changes occurring within one detection area or internal noise occurring in the infrared detection element 1@, resulting in malfunction. There was a problem that it could cause

Therefore, in order to solve the above-mentioned problems, the present inventors have proposed a human body detection device that detects a human body by comparing the outputs of a plurality of infrared detection elements (Japanese Patent Application No. 62-242
09 (No. 1). FIG. 5 shows the overall configuration of this human body detection device. This human body detection device has multiple detection areas A° to D.
An infrared detection fIS2 consisting of a plurality of infrared detection elements A to D which receive infrared light from an area sufficiently small compared to the human body M through an optical system 1 for condensing the infrared light from a region sufficiently small compared to the human body M. , an amplification section 3 that independently amplifies each output of each infrared detection element A-D, a signal processing section 4 that converts the amplified output into a signal suitable for human body detection, and a peak value and output time of the converted signal. It consists of a determination section 5 that detects and compares these with each other to determine the presence or absence of a human body, and an output section 6 that outputs the determination result.

The operation of this human body detection device will be explained based on FIGS. 6 and 7. In this human body detection device, by narrowing down the area consisting of detection areas A to D to a sufficiently small area compared to the human body M as described above, the human body M passing through the area can be detected in the detection area A regardless of the direction of movement. The human body M passes through the entire area from ゛ to D゛, so that the human body M passes through the entire detection area from A to D''.
, the peak values VA to VD of the respective outputs of the infrared detection elements A to D become approximately the same value. Therefore, the peak value vA~\7 of each output of the infrared detection elements A-D. The first determination condition for determining the presence of the human body M may be that the values are the same. However, in reality, there is some variation in the peak value of each output of the infrared detection elements A to D due to the temperature distribution on the surface of the human body M, and the peak value of each output ■8 to VD is affected by the ambient temperature. Because I receive it,
Regarding this presence determination, the presence of the human body M is determined by relatively comparing the outputs of the respective infrared detection elements A to D. Now, the peak value V^~V of each output of the infrared detection element AT-D
If the maximum value of D is V wax and the minimum value is Vein,
The ratio of Vmax and Vwin is a predetermined value S (o<S<1)
If it is larger, it is determined that the variation in each peak value VA~1 is small and that the human body M is present. In other words, the first judgment condition for determining the presence of the human body M is expressed as follows.

V sin/V wax > S - (1) However, 0<S<1 In addition, when the human body M passes through the detection areas A'' to D'', all the detection areas A to D'' regardless of the direction of movement. It is impossible for both to invade at the same time. In other words, there is a time difference between the times at which the output signals of each infrared detection element A to D rise (hereinafter, this time will be referred to as output time) t^~1(,).Therefore, the output time t^~ The presence of a time difference in tD can be used as the criterion @2 for determining the presence of the human body M.The above time difference is based on the width of the detection areas A'' to D'' and the moving speed of the human body M. Considering this, it is limited to a certain range.

Therefore, output time 1. If the time difference of -10 is set to 6t, the second determination condition for determining the presence of the human body M is obtained as shown in the following equation.

Twin < 4t < Tmax = 12) However,
TvintTs+a is the lower limit value and upper limit value of the time difference, respectively. For example, when the outputs of the infrared detection elements A-D shown in FIGS. 7(a) to (c) are obtained, the time difference is determined as 1:J t = tL+ -tA in any case.

That is, in this human body detection position i, the infrared detection element A
If the peak value \・'6~Vo of each output of -D is approximately - constant, and there is variation within a predetermined range at the output time t7~[,3 of each output, it is determined that the body M exists. be. Determining the presence or absence of a human body M in this way prevents malfunctions caused by general temperature changes, disturbance light such as sunlight, local temperature changes, internal noise, etc., and makes the human body detection device highly reliable. becomes.

[Problems to be Solved by the Invention] By the way, in this human body detection device, each infrared detection element A-
The determination unit 5 detected the output time of D as the time when their output levels exceeded a predetermined determination value. Here, the time required for the human body M to pass through the detection areas A゛~D° is inversely proportional to the moving speed of the human body M, and the second
The lower limit T sin of the determination condition (Equation (2)) is set based on the output time difference of the infrared detection elements A and D obtained with the human body M moving at the highest speed. Therefore,
In such an output time detection method, the determination value needs to be set low in order to accurately detect the body M moving at high speed. Note that this human body detection device has a speed of 36 mph, for example.
The body M is detected when the vehicle moves from 0II+ (0.1 wheels per second) to 36i (10 kilometers per second).

Furthermore, it is necessary to set the above-mentioned judgment value low for the following reason as well. For example, when infrared rays are simultaneously incident on infrared detection elements A-D due to disturbance light, etc., and the light source is located far away from the center of the detection area of each infrared detection element A-D, and there is a difference in the amount of infrared incident light. , the outputs of the infrared detection elements A to D shown in FIG. 8 are obtained. Here, if the judgment value is set to vth, a time difference will occur in the output time (t
^~to), when the peak value VA-VD satisfies the first determination condition, the determination condition of vi2 is also satisfied as described above, and a malfunction occurs due to the disturbance light. However, the judgment value is Vt in Figure 8.
When lowered as shown by h', the infrared detection element A-[)
There is no time difference between the output times of tA' to ttl, as shown by tA' to ttl'', and the judgment condition of equation (2) is no longer satisfied, which makes it possible to prevent malfunctions caused by ambient light. The determination value must be set low to prevent malfunctions.

However, if the judgment value for detecting the output time is set low as described above, for example, if noise with different output times and a substantially constant peak value is input to the judgment unit 5 as shown in FIG. , the first and the second determination conditions may both be satisfied, and therefore there is a possibility of malfunction due to noise. 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-mentioned points, and its purpose is to provide a human body detection device that is less likely to malfunction due to noise.

[Means for Solving the Problems 1] In order to achieve the above object, the present invention provides a new method in which the direction of increase/decrease in each output is reversed until the determination unit exceeds the determination value for determining that the output of the infrared detection element has occurred. The point in time is determined to be the output time.

Note that even if the output time is determined to be the latest point in time at which the increase/decrease rate of change in each output increases until it exceeds the determination value at which the determination unit determines that the output of the infrared detection element has occurred, the above case will not occur. can achieve the same purpose.

[Operation 1] As described above, the present invention determines that the latest point in time at which the increase/decrease direction of the change in each output is reversed until the determination unit exceeds the determination value for determining that the output of the infrared detection element has occurred is the output time. By doing so, it is possible to determine whether the output of the infrared detection element has occurred using a relatively high determination value that can remove noise, thereby preventing malfunctions due to noise.

Furthermore, even if the determination unit determines as the output time the point in time when the increase/decrease rate of the latest change in each output increases until it exceeds the determination value for determining that the output of the infrared detection element has occurred, the output of the infrared detection element has not occurred. By using a relatively high judgment value that can remove noise, malfunctions due to noise can be prevented.

[Example 1] The human body detection device of this example is structurally the same as the conventional human body detection device shown in FIG.
This method is characterized by a method for determining the presence of a human body M according to the present invention. In addition, although the following description explains the case where four infrared detecting elements are used, 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 this embodiment. In this embodiment, an inexpensive pyroelectric element that can operate at room temperature is used as the infrared detection element.

Note that a thermopile can also be used in addition to the pyroelectric element. As the optical system 1, a mirror or lens is used,
More specifically, a multi-segment mirror or a multi-segment lens is used. The infrared detecting elements A-D are arranged on the focal plane of the optical system 1, and on the background, through the optical system 1, four detection areas A''-D'' are infrared #! It will be formed in the same arrangement as the arrangement of detection elements A to D. Here, the detection area A~
When the body M passes through D, each of the infrared detection elements A to D generates an output corresponding to a change 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 outputs of each of the infrared detection elements A to D that have passed through the filter are sequentially A/D converted. The determination unit 5 determines the output time L^~1 from each output of the infrared detection elements A to D processed by the signal processing unit 4.
° and the peak values V, ~vD were determined, and the above-mentioned (1), (
2) Determine whether the determination condition of the expression is satisfied.

By the way, in the case of this embodiment, the determination unit 5 detects the output times of the infrared detection elements A to D in the following manner. For example, if the outputs of the infrared detecting elements A-D change as shown in FIG. The latest point in time at which the direction of increase/decrease in change is reversed is determined to be the output time. Specifically, infrared detection elements A-D
The slope of the output change is determined, and the time when the polarity of the slope reverses is memorized. In addition, at the time of polarity reversal, the previously stored time is deleted and a new polarity reversal time is stored.

Then, the output of the infrared detection elements A-D is set to a predetermined voltage Vth.
At the point in time when the time exceeds , the time stored at that time (ts in the case of FIG. 1) is determined to be the output time t^-tO. In this way, the determination value vth for determining whether the output of the infrared detection elements A to D has occurred can be made relatively high, and therefore malfunctions due to noise can be prevented.

In other words, since noise has a low peak value, it can be removed as described above. In addition, since the output time is detected from the point in time when the increase/decrease direction of the change in the output of the infrared detection elements A to D is reversed, it can be reliably determined separately from the case where the output of the infrared detection elements A to D is detected. can be detected. The presence of the human body M after the output time is detected is determined based on whether or not the determination conditions are met in the same manner as in the conventional example shown in FIG.

[Example 2] This example differs from the first example in the method of detecting the output time. In the first example described above, the determination unit determines that the output of the infrared detection elements A-D has occurred. The latest point in time when the direction of increase/decrease in each output until it exceeds the value is reversed is determined to be the output time, but in this embodiment, in addition to that, the output time of the infrared detection elements A to D is determined to have occurred. The output time is also determined at the time when the increase/decrease rate of the latest change in each output increases until the determination value is exceeded. Specifically, in this example, the infrared detection element A
-D until the output is generated, the slope of the output change is determined in the same manner as in the first embodiment, and the time when the polarity of the slope is reversed and the time when the absolute value of the slope exceeds the previous value are updated and stored. Then, the time stored at the time 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 point t) at which the rate of increase/decrease in the output change increases as the output time. In the case of this embodiment as well, the same effects as in the first embodiment can be obtained.

(Advantageous Effect 1 of the Invention As described above, in the present invention, the output time is the latest point in time at which the direction of increase/decrease in the change in each output is reversed until the determination unit exceeds the determination value at which it determines that the output of the infrared detection element has occurred. Therefore, it is possible to determine whether the output of the infrared detection element has occurred using a relatively high determination value that can eliminate noise, thereby preventing malfunctions due to noise.

Furthermore, even if the determination unit determines as the output time the latest point in time at which the increase/decrease rate of change in each output increases until it exceeds the determination value for determining that the output of the infrared detection element has occurred, the output of the infrared detection element has not occurred. By using a relatively high judgment value that can remove noise, malfunctions due to noise can be prevented.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an output time detection method according to one 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 an explanatory diagram of a conventional human body detection method. 4 is an output waveform diagram same as above, FIG. 5 is a block diagram showing the configuration of another conventional example, FIG. 6 is an explanatory diagram of the human body detection method same as above, FIG. 7 is an output waveform diagram same as above, @Figure 8 is an explanatory diagram of the method of detecting the output time, and Figure 9 is an explanatory diagram of the same problem. 5 is a determination unit, A-D is an infrared detection element, and vth is a determination value. Deputy k Patent attorney Ishi 1) Chief Shichie 1:〆(0) 4I7j (b) (C) q 5Lbe1 Figure 3 (0) Figure 6 Condolence 7 IK+ (b) (C) Figure 8

Claims (2)

[Claims] (1) Multiple infrared detection elements that are composed of multiple detection areas and receive infrared rays from an area sufficiently small compared to the human body, and the peak value of each output of these infrared detection elements is approximately constant. and a determination unit that determines that a human body is present when the output times of the respective outputs vary within a predetermined range, wherein the determination unit determines that an output of the infrared detection element has occurred. A human body detection device that determines the latest point in time at which the increase/decrease direction of each output change until exceeding the value is reversed to be the output time. (2) Multiple infrared detection elements that are composed of multiple detection areas and receive infrared rays from an area sufficiently small compared to the human body, and the peak value of each output of these infrared detection elements is approximately constant. and a determination unit that determines that a human body is present when the output times of the respective outputs vary within a predetermined range, wherein the determination unit determines that an output of the infrared detection element has occurred. A human body detection device that determines the latest point in time at which the rate of change in each output increases until it exceeds the value as the output time.