JPH06222159A - Human body detecting device - Google Patents

Abstract

PURPOSE:To enhance detection sensitivity by determining the high-band cut-off frequency of a band-pass filter from the frequency spectrum of an incoming infrared ray which is calculated from the width of an object for detection, the width of a detecting beam, and the upper limit speed of movement of the object for detection. CONSTITUTION:When an object for detection with width Ls passes a detecting beam of width Lr at a moving speed V, the fundamental wave component fs(fr) of the frequency spectrum of the temperature (detecting beam sensitivity) distribution characteristic of the object for detection V/Ls (fr V/Lr). The fundamental wave component fx of the frequency spectrum Y(f) of an incoming infrared ray = fs (Ls>Lr) or = fr (Ls<Lr). When frequencies lower than the peak level of the spectrum Y(f) by several dB, e.g. those in a band higher than near fx/2 are eliminated, infrared outputs can be taken out efficiently. Therefore, the high-band cut-off frequency of a band-pass filter 13 is theoretically supported and determined by the spectrum Y (f) calculated from the widths Ls, Lr and the upper limit speed of movement of the object for detection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects infrared rays emitted from a human body and infrared rays emitted from a background such as a floor by detecting movement of the human body or movement of a part of the human body. The present invention relates to an improvement of a light receiving type human body detection device.

[0002]

2. Description of the Related Art An infrared ray receiving type human body detecting device obtains a sensor output based on a difference between a background temperature and a human body temperature. That is, by using an optical system, the field of view is limited, infrared rays emitted from the human body passing through the range are detected by an infrared ray receiving element such as a pyroelectric element, and the output of the infrared ray receiving element is amplified. The output signal is obtained by removing unnecessary low-frequency components and high-frequency components with a bandpass filter.

Since such an infrared ray receiving type human body detecting device is intended to detect a human body located relatively close to the human body detecting device in the purpose of lighting control, FIG.
As shown in, the center frequency of the bandpass filter is around 1 Hz,
The frequency band is set to a relatively narrow band of 0.7 to 1.6 Hz. Further, in crime prevention applications, since it is necessary to detect a slow motion of a human body to a fast motion in a wide area, as shown in FIG. 10, the frequency band of the bandpass filter is 0.08 to 15 Hz, which is a relatively wide band. Is set to.

However, in order to determine the frequency band of the bandpass filter as described above, it is necessary to consider the infrared characteristic incident on the infrared light receiving element and the output characteristic of the infrared light receiving element. Is an empirical one that conducts a practical test assuming that the human body passes through the detection area at a predetermined moving speed, and adopts the one having the best S / N ratio among several kinds of amplifiers. It was doubtful that the band was set to a truly optimum range for a human body detection device.

As an example thereof, the human body detecting device for the above-mentioned lighting control will be considered. Generally, the slower the moving speed of the sensing object, the lower the frequency component of infrared rays emitted by the sensing object, and the higher the speed, the higher the frequency range. , The frequency band of the bandpass filter should be determined.
However, since the high cutoff frequency of the conventionally used bandpass filter is as low as 1.6 Hz, a sufficient output cannot be obtained when the moving speed is 2.0 m / sec as shown in FIG.
It was difficult to detect moving objects.

Therefore, in order to detect even at a moving speed of 2.0 m / sec, it seems that the high cutoff frequency should be set to a higher band, but the high cutoff frequency should be set to a higher band. If set, the infrared output is amplified, and at the same time, the high frequency noise is also amplified, and there is a problem that the S / N ratio is deteriorated and the margin ratio against malfunction is reduced.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a human body detecting device which has high detection sensitivity and does not cause malfunction due to high frequency noise.

[0008]

A human body detecting apparatus according to claim 1, which is proposed to achieve the above object, has an optical system for condensing infrared rays from a detection area, and a condensing system for the optical system. Infrared light receiving element for receiving the received infrared ray, an amplification section for amplifying the output of the infrared light receiving element, and a band for removing unnecessary low frequency components and high frequency components from the output of the infrared light receiving element amplified by the amplification section. A filter, a comparison unit that compares the output of this bandpass filter and a reference voltage to determine the presence or absence of a human body, an output unit that outputs the determination result of this comparison unit, and a reference voltage generation unit that generates the above reference voltage. In the infrared receiving type human body detection device, the high-frequency cutoff frequency of the bandpass filter is determined by the width of the detection object, the width of the detection beam, and the maximum moving speed of the detection object. It has a configuration which is determined by the vector.

A human body detecting apparatus according to a second aspect of the present invention is an optical system for condensing infrared rays from a detection area, an infrared light receiving element for receiving the infrared rays collected by the optical system, and an infrared receiving element for the infrared light receiving element. An amplification unit that amplifies the output, a bandpass filter that removes unnecessary low-frequency components and high-frequency components from the output of the infrared light receiving element amplified by this amplification unit, and compares the output of this bandpass filter and the reference voltage, In the infrared ray detection type human body detection device including a comparison unit that determines the presence or absence of a human body, an output unit that outputs the determination result of the comparison unit, and a reference voltage generation unit that generates the reference voltage, the bandpass filter The high cutoff frequency fh of the detected object width L
s, the detection beam width Lr, and the moving upper limit speed Vh of the detection object
Thus, fh = Vh / 2Ls (when Ls> Lr) or fh = Vh / 2Lr (when Ls <Lr) is determined.

[0010]

In the human body detecting apparatus according to the present invention as set forth in claim 1, the high cutoff frequency of the bandpass filter is determined by the frequency spectrum of the incident infrared rays, which is obtained from the detection object width, the detection beam width and the moving upper limit speed of the detection object. Since it is determined, high detection sensitivity can be realized while suppressing malfunctions due to high-frequency noise without resorting to practical tests.

In the human body detecting apparatus according to the present invention as defined in claim 2, the high cutoff frequency fh of the bandpass filter is fh = Vh / depending on the detection object width Ls, the detection beam width Lr, and the detection object upper limit speed Vh. 2Ls (when Ls> Lr)
Alternatively, since it is determined by fh = Vh / 2Lr (when Ls <Lr), high detection sensitivity can be realized while suppressing malfunction due to high-frequency noise without relying on a practical test or the like.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a configuration example of an embodiment of the human body detecting device according to the present invention as set forth in claim 1. In the figure, 10 is an optical system such as a lens that collects infrared rays from the detection area, and 11 is an optical system 10 such as a lens.
Infrared light receiving element such as a pyroelectric element arranged on the focal plane of the
2 is an amplifying section for amplifying the output signal of the infrared light receiving element 11,
Reference numeral 13 is a bandpass filter that removes unnecessary low frequency components and high frequency components from the output signal of the infrared light receiving element 11 amplified by the amplification unit 12, and 14 is a peak voltage of the signal output from the bandpass filter 13 and a preset value. A comparison unit that compares the reference voltages to determine the presence or absence of a human body, and 15 is a reference voltage generation unit that outputs the reference voltage to the comparison unit 14. The band filter 13, the comparison unit 14, and the reference voltage generation unit 15 perform processing. The judgment unit 16 is configured. An output unit 17 outputs the comparison result of the comparison unit 14 as the determination result of the processing determination unit 16.

The high cutoff frequency fh of the band-pass filter 13 of the human body detecting device having such a structure is determined as follows. As shown in FIG. 2, the detected object having the width Ls is the width Lr.
The infrared ray y (t) incident on the infrared light receiving element 11 when passing through the detection beam at the moving speed V is the convolution integral of the detection object temperature distribution characteristic s (t) and the detection beam sensitivity distribution characteristic r (t).

[0014]

[Equation 1]

Can be represented by Than this,
The frequency spectrum Y (f) of the incident infrared ray is obtained by detecting the temperature distribution characteristic s (t) of the sensing object and the sensing beam sensitivity distribution characteristic r (t).
Of each Fourier transform of S (f) and R (f), Y (f) = S (f) × R (f).

By the way, when the shapes of the detection object and the detection beam are selected as shown in FIG. 2, the detection object temperature distribution characteristic s (t) and the detection beam sensitivity distribution characteristic r (t) are respectively shown in FIG. 3 (a), Since it becomes a square wave as shown in (b), the respective frequency spectra S (f) and R (f) are shown in FIG.
As shown in (b). From this, the fundamental wave component fs of the frequency spectrum S (f) of the detected object temperature distribution characteristic s (t) is fs≈V / Ls, and the detected beam sensitivity distribution characteristic r
The fundamental wave component fr of the frequency spectrum R (f) of (t)
Is represented by fr≈V / Lr. Therefore, the fundamental wave component fx of the frequency spectrum Y (f) of the incident infrared ray is fx
= Fs (when Ls> Lr) or fx = fr (Ls <L
r)), as shown in FIG. 4 (c).

Here, referring to FIG. 4 (c), it can be considered that the frequency spectrum Y (f) of the incident infrared rays can be neglected at frequency components higher than the fundamental wave component fx. Also, from the viewpoint of removing high-frequency noise higher than the fundamental wave component fx, it is lowered by several dB (4 dB to 8 dB) from the peak level of the frequency spectrum Y (f) of the incident infrared light, for example, in the high range near fx / 2. If the frequency is removed, the infrared output can be extracted efficiently.

Therefore, the high cutoff frequency fh of the bandpass filter 13 is calculated from the width Ls of the detected object, the beam width Lr of the detected object, and the moving upper limit speed Vh of the detected object (at this time, the fundamental frequency becomes maximum). With the frequency spectrum Y (f) of 1, the human body detection device can be realized with high detection sensitivity, which is determined empirically but not empirically. The above high cutoff frequency fh = fx / 2 is an example, and the optimum value may be determined by looking at the frequency spectrum Y (f) of the incident infrared rays that is determined by the usage conditions at that time.

Further, the low cutoff frequency fL of the bandpass filter 13 is preferably as low as possible from the viewpoint that it can be detected even when the moving speed of the sensing object is slow. However, since the infrared light receiving element such as the pyroelectric element contains a lot of low frequency noise as shown in FIG. 5, if the low cutoff frequency fL is set too low, the S / N ratio becomes worse. Therefore, it is advisable to select the low cutoff frequency fL by referring to the light reception output of the infrared light receiving element and the frequency characteristic of noise as shown in FIG.

Since the structure of the human body detecting device according to the present invention as defined in claim 2 is the same as that of the human body detecting device according to claim 1 shown in FIG. 1, the description thereof will be omitted. The high cutoff frequency fh of the bandpass filter 13 of the human body detecting device according to claim 2 is determined in the same manner as the human body detecting device according to claim 1, and the detection object width Ls, the detection beam width Lr, and the movement upper limit of the detection object are determined. If the speed is Vh (see FIG. 2), fh = Vh /
2Ls (when Ls> Lr) or fh = Vh / 2Lr
It is represented by the mathematical expression (when Ls <Lr).

Here, as one embodiment, the detected object is 0.
2m x 0.2m square, detection beam 0.276m x
Rectangle of 0.138m, upper limit speed of movement of sensing object is 2.
It is assumed that the temperature difference between the detection object and the background is set to 0 ° C./sec and 3 ° C., and the detection object is moved in the short side direction of the detection beam as shown in FIG. Then, in this case, L
Since s = 0.2 m, Lr = 0.138 m, and Vh = 2.0 m, the high-frequency cutoff frequency fh of the bandpass filter 13 is fh = Vh / 2Ls = 2.0 / (2 × 0.2) = 5.
(∵Ls> Lr), and set around 5Hz.

On the other hand, the low cutoff frequency fL is 0..0 from the received light output characteristics and noise characteristics of the infrared light receiving element shown in FIG.
Set around 2Hz. Therefore, the frequency band characteristic of the band filter 13 in this case is as shown in FIG. Further, the moving speed V of the detection object of the bandpass filter 13 is V =
The output at 1.0 m / sec and 2.0 m / sec is as shown in Fig. 7, and the peak value is about 1.5 times higher than that of a conventional bandpass filter with a center frequency of 1 Hz. Can be done.

The S / N ratio of the band-pass filter 13 when the moving speed of the detected object is 0.3 m / sec to 2.0 m / sec is as shown in FIG. A sufficiently good value is obtained from the S / N ratio of the bandpass filter (frequency band characteristic is shown in FIGS. 9 and 10) used in the human body detection device for crime prevention.

[0024]

According to the human body detection apparatus of the present invention as set forth in claim 1, the high-frequency cutoff frequency of the bandpass filter is determined by the incident infrared ray, which is obtained from the detection object width, the detection beam width, and the maximum moving speed of the detection object. Since it is determined by the frequency spectrum of, high detection sensitivity can be realized while suppressing malfunction due to high frequency noise without depending on a practical test or the like.

In the human body detection apparatus according to the present invention as defined in claim 2, the high-frequency cutoff frequency fh of the bandpass filter is fh = Vh / depending on the detection object width Ls, the detection beam width Lr, and the detection object upper limit speed Vh. 2Ls (when Ls> Lr)
Alternatively, since it is determined by fh = Vh / 2Lr (when Ls <Lr), high detection sensitivity can be realized while suppressing malfunction due to high-frequency noise without relying on a practical test or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a human body detection device according to the present invention as defined in claims 1 and 2.

FIG. 2 is a diagram showing how a detection object passes through a detection beam.

FIG. 3A is a diagram showing a temperature distribution characteristic of a detection object. FIG. 7B is a diagram showing the sensitivity distribution characteristic of the detection beam. (C) is an intensity distribution characteristic diagram of infrared rays incident on the infrared light receiving element.

FIG. 4A is a diagram showing frequency characteristics of a temperature distribution of a detected object. (B) is a diagram showing the frequency characteristics of the sensitivity distribution of the detection beam. (C) is a frequency characteristic diagram of the intensity distribution of infrared rays incident on the infrared light receiving element.

FIG. 5 is a diagram comparing the light receiving output characteristic and the noise characteristic of the infrared light receiving element.

FIG. 6 is a diagram showing frequency band characteristics of a band filter of the human body detection device according to the present invention as defined in claim 2;

7 is a diagram showing the output characteristic of the bandpass filter having the frequency band characteristic shown in FIG. 6;

8 shows a band filter of the human body detecting apparatus according to the present invention as defined in claim 2 (frequency band characteristic is FIG. 6) and a band filter of a conventional human body detecting apparatus (frequency band characteristic is FIG. 9 and FIG. 1).
It is a figure which compared the S / N ratio characteristic of 0).

FIG. 9 is a diagram showing frequency band characteristics of a conventional bandpass filter for illumination control.

FIG. 10 is a diagram showing a frequency band characteristic of a conventional bandpass filter for crime prevention.

11 is a diagram showing the output characteristic of the bandpass filter showing the frequency band characteristic of FIG. 9;

[Explanation of symbols]

 10 ... Optical system 11 ... Infrared light receiving element 12 ... Amplification unit 13 ... Band filter 14 ... Comparison unit 15 ... Reference voltage generation unit 17 ... Output unit

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[Procedure amendment]

[Submission date] June 23, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 10

[Correction method] Change

[Correction content]

[Figure 10]

Claims (2)

[Claims] 1. An optical system for collecting infrared rays from a detection region, an infrared light receiving element for receiving the infrared light collected by the optical system, an amplification section for amplifying the output of the infrared light receiving element, and A bandpass filter that removes unnecessary low-frequency components and high-frequency components from the output of the infrared light receiving element amplified by the amplification unit, and a comparison unit that compares the output of this bandpass filter and a reference voltage to determine the presence or absence of a human body. In the infrared light receiving type human body detection device including an output unit that outputs the determination result of the comparison unit and a reference voltage generation unit that generates the reference voltage, the high cutoff frequency of the bandpass filter is a detection object. A human body detection device characterized by being determined from a frequency spectrum of incident infrared rays, which is obtained from a width, a detection beam width, and a moving upper limit velocity of a detection object. 2. An optical system for collecting infrared rays from a detection region, an infrared light receiving element for receiving the infrared light collected by the optical system, an amplification section for amplifying an output of the infrared light receiving element, A bandpass filter that removes unnecessary low-frequency components and high-frequency components from the output of the infrared light receiving element amplified by the amplification unit, and a comparison unit that compares the output of this bandpass filter and a reference voltage to determine the presence or absence of a human body. In an infrared ray receiving type human body detecting device comprising an output section for outputting the judgment result of the comparing section and a reference voltage generating section for generating the reference voltage, a high cutoff frequency f of the bandpass filter is provided.
h is fh = Vh / 2Ls (Ls due to the detection object width Ls, the detection beam width Lr, and the moving upper limit speed Vh of the detection object.
> Lr) or fh = Vh / 2Lr (when Ls <Lr), the human body detecting device.