JPH0560636B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a device for detecting the number of people from infrared rays emitted by the human body.

[Conventional technology and problems]

The applicant has previously published Japanese Patent Application Laid-Open No. 59-60587 "Crowding Level Detection Device" and Japanese Patent Application Laid-Open No. 59-60587 with the aim of detecting the number of people from infrared rays emitted by the human body with high precision and with a simple and inexpensive configuration. No. 83078 "Crowd level detection device" is proposed. A detailed explanation of these will be omitted, but the basic structure can be found in the fourth section.
As shown in the figure, a detection section (sensor section) 1, which includes a condensing lens 2, a scanning mirror 3 that rotates at a constant cycle, and a pyroelectric infrared detection element 4 that responds to changes in incident infrared rays, is installed at the front. a stationary amplifier 10, a bandpass filter 11 for removing noise components, etc., and a clamper 1 for providing a sample value as a reference potential for comparison.
2. A comparator 13 that outputs a pulse signal with an input signal of a predetermined level or higher, a digital multiplexer circuit (hereinafter simply referred to as a multiplexer) 14 that outputs an output 14a as a sequence of clock pulses corresponding to the pulse width of the pulse signal, and a scanning mirror 3. The synchronization circuit 15 sets the detection field of view from the synchronization signal 3a of the detection element 4. Utilizing the relationship that the width of the output signal waveform of the detection element 4 is approximately proportional to the number of people to be measured, the number of clock pulses of the output 14a is counted and the detection field is determined within the field of view. It measures the number of people. In addition,
FIG. 4 shows only one channel with one sensing element 4, and the other channels are omitted.

FIG. 5 is a diagram showing the arrangement of a scanning mirror, a lens, and a detection element of a conventional congestion level detection device. The detection element 4 is arranged on a center line 6 connecting the center of the lens 2 and the center of the scanning mirror 3, and the scanning mirror 3 rotates clockwise at a constant period with the rotation axis 5 as the axis of rotation. Assuming that the angle of the light flux incident on the lens with respect to the center line 6 is A (here, the right side toward the center line 6 is negative and the left side is positive), the optical system efficiency characteristics with respect to the lens incidence angle A at this time are as shown in Figure 6. The result will be as shown in curve A. Here, the optical system efficiency is a value indicating the proportion of the luminous flux that can be input to the detection element out of the luminous flux incident on the lens.As is clear from Fig. 6, when the detection element 4 is placed on the center line 6. , the optical system efficiency is symmetrical with respect to the center line 6, and therefore the field of view that can be measured by this congestion degree detection device is also symmetrical with respect to the center line 6.
It is symmetrical with respect to Note that the field of view refers to a range of lens incident angles in which the optical system efficiency is at a certain level or higher (at least a level that can be detected by a detection element).

By the way, since the above-mentioned crowding level detection device uses a pyroelectric type infrared detection element as a detection element, that is, a differential type infrared detection element (hereinafter simply referred to as a detection element) that detects a change in the amount of incident light,
When the scanning mirror is rotated to scan the field of view, even if there is no object to be detected within the field of view, scanning noise may be output due to the change in optical system efficiency shown in FIG. 6, resulting in false detection.

FIG. 7 is a diagram showing the rate of change of the optical system efficiency characteristic of FIG. 6. In order to reduce the scanning noise and eliminate false detection, it is necessary to keep this rate of change as low as possible.

[Means for solving problems]

The present invention is characterized in that the detection element is arranged on a circumference centered on the rotation axis of the scanning mirror, and shifted in a direction opposite to the rotational direction of the scanning mirror from the center line connecting the scanning mirror and the lens. At the point.

[Effect]

If the detection element is placed offset from the center line, the optical system efficiency characteristics will become asymmetrical with respect to the center line.Furthermore, by shifting the detection element in the direction opposite to the rotation direction of the scanning mirror, the rate of change in the optical system efficiency will be shifted to the front side of the scanning field of view. Therefore, the influence of scanning noise in the field of view is also reduced.

〔Example〕

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

FIG. 1 is a diagram illustrating an example of the arrangement relationship of a scanning mirror, a lens, and a detection element of a congestion degree detection device according to the present invention, and is a diagram corresponding to FIG. 5. In FIG. 1, the detection element 4a is left offset from the center line 6 on the circumference around the rotation axis 5 of the scanning mirror 3, and the direction of displacement is opposite to the rotation direction of the scanning mirror, that is, here. Now, assuming that the direction of rotation of the scanning mirror is clockwise,
The sensing element 4a is disposed offset from the center line 6 in a counterclockwise direction.

FIG. 2 compares the optical system efficiency characteristic (curve B) of the detection element 4a in FIG. 1 with the optical system efficiency characteristic (curve A) in FIG. As is clear from FIG. 2, when the sensing element is arranged offset from the center line 6, the optical system efficiency characteristics are asymmetrical with respect to the center line 6, that is, in this example, the lens incidence angle A is negative (in FIG. The slope of the optical system efficiency becomes gentler when the light is incident from the right side toward the center line 6. Therefore, the rate of change of the optical system efficiency characteristic curve B in FIG. 2 is as shown in FIG. 3, and when compared with FIG.
The peak value of the rate of change becomes smaller when is negative.

By the way, as shown in FIGS. 1 and 5, the scanning line 3
When rotated clockwise, the field of view is sequentially scanned from -90° to +90° at the lens incidence angle A, but at this time, due to the frequency characteristics of the detection element and detection circuit, the scanning noise output is Since it tends to lag behind changes in the amount of light, when the scanning mirror 3 is rotated clockwise, the lens incidence angle A is greatly influenced by the negative part, and when it is rotated counterclockwise, the lens incidence angle A becomes positive. greatly influenced by the parts.

Therefore, when rotating the scanning mirror clockwise as shown in Figure 1, if the sensing element is shifted counterclockwise, the rate of change in optical system efficiency in the negative portion of the lens incidence angle, which is greatly affected, is can be made smaller, resulting in lower scanning noise output.

Similarly, when scanning is performed by rotating the scanning mirror counterclockwise, running noise can be reduced by arranging the detection element clockwise from the center line.

FIG. 8 is a diagram showing another embodiment of the present invention.
An example is shown in which two sets of the optical systems shown in the figure are provided.

In Fig. 8, 2A, 2B are lenses, 3A,
3B is a scanning mirror, 4A, 4B are detection elements, 5A, 5
B is the rotation axis of the scanning mirror. In this example, two sets of optical systems are installed to expand the field of view, and the scanning mirror 3
A is rotated counterclockwise, and the scanning mirror 3B is rotated clockwise, and the detection elements 4A and 4B are arranged offset from the center line in the opposite direction to the rotation direction of the scanning mirror, in order to reduce the scanning noise output. It's on.

Note that the overlapping field of view of each optical system can be freely adjusted by adjusting the angle T shown in FIG.

〔Effect of the invention〕

According to the present invention, the influence of scanning noise can be suppressed to a low level, and detection accuracy can be improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an optical system according to the present invention;
Figure 2 is a diagram to explain the difference in optical system efficiency characteristics between the present invention and the conventional configuration, Figure 3 is a diagram showing the rate of change in optical system efficiency in the configuration of Figure 1, and Figure 4 is a diagram showing congestion. A block diagram showing the overall configuration of the temperature detection device,
FIG. 5 is a diagram showing the configuration of a conventional optical system, FIG. 6 is a diagram showing the optical system efficiency characteristics in the configuration of FIG. 5,
FIG. 7 is a diagram showing the rate of change in the optical system efficiency characteristic in the configuration of FIG. 5, and FIG. 8 is a diagram showing the configuration of the optical system according to another embodiment of the present invention. 2... Lens, 3... Scanning mirror, 4, 4a... Infrared detection element, 5... Rotation axis, A... Lens incident angle.

Claims (1)

[Scope of Claims] 1. A differential infrared sensing element that detects changes in the amount of incident light, a condensing lens, a scanning mirror that rotates at a constant cycle, and a synchronization circuit that sets the field of view of the sensing element in synchronization with the scanning mirror. in which the width of the waveform of the output signal of the detection element is converted into the number of people to count the number of people within the field of view or to determine the degree of crowding, wherein the detection element is centered around the rotation axis of the scanning mirror. 2. A congestion degree detection device, wherein the device is arranged on a circumference of the scanning mirror and shifted in a direction opposite to the rotational direction of the scanning mirror from a center line connecting the scanning mirror and the lens.