JPS63266589A - Detector for number of persons - Google Patents

Abstract

PURPOSE:To form small-sized detector for the number of persons which has large optical gain by providing a mirror with a concave surface which has focal length much smaller than the distance to an objective plane as a reflecting surface in a radial direction of the circular scan of the mirror, and making the center position of the concave surface in the radial direction of the circular scan nearly coincident with the center of rotation of the mirror. CONSTITUTION:The reflecting surface in the radial direction of the circular scan of the mirror M used for a circular scanning optical system is the concave surface which has the focal length much smaller than the distance to the objective plane. An optical path viewed from the photodetection surface S of an infrared detecting element is reflected by the reflecting surface of the reflecting surface of the mirror M, converged once in front of the mirror M, and diverged again to spread in the radial direction of the circular scan, so that a very wide visual field is obtained. Further, the center position of the circular scan of the concave surface in the radial direction is nearly coincident with the center of rotation of the mirror M, so the scanning optical system is reduced in size greatly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an infrared receiving type people detection device that detects the number of people by detecting infrared rays emitted from a detected human body.

(Background Art) The present inventors have developed a highly accurate number of people detection device having a wide detection area with a simple and inexpensive configuration (Japanese Patent Application No. 61-281301).
) has already been proposed. FIG. 13 is a block diagram showing its configuration. This number of people detection device includes an infrared detection element 2, a circular scanning optical system 1 that circularly scans the field of view of the infrared detection element 2, a preamplifier 3 that amplifies the output signal of the infrared detection element 2, and a preamplifier 3 that amplifies the output signal of the infrared detection element 2. a signal processing section 4 that converts the output signal of the stationary amplifier section 3 into a signal necessary for detecting the number of people;
Consisting of a determining section 5 that determines the number of people based on the output signal of the signal processing section 4, and an output section 6 that outputs the number of people information from the output signal of the determining section 5, it is possible to accurately determine the number of people within a wide detection area. It is designed to be detectable.

FIG. 14 shows an example of a circular scanning optical system. As shown in FIG.
The rotary plate 10 is placed at a position of 1iRb, and the rotating shaft 11 of the rotary plate 10 is aligned with the field of view center C of the light-receiving surface of the infrared detection element 2.
The rotating plate 10 is rotated by a drive mechanism such as a motor. As shown in FIG. 14(b), a rectangular slit A having a length La and a width Da is provided in the rotary plate 10, and only the infrared rays radiated from the object surface B that pass through the slit A are infrared rays. It is configured so that it enters the detection element 2. The instantaneous visual field on the object plane is similar to the shape of the slit A, and if the distance from the rotary plate 10 to the object plane B is Ra, then the instantaneous visual field length Lv and visual field width Dv on the object plane are expressed by the following equation. It becomes like this.

Further, in the radial direction in circular scanning, if the instantaneous field of view is the viewing angle at which the object surface B is seen, θ is expressed as in the following equation.

The above-mentioned instantaneous field of view is circularly scanned with the field center C of the light-receiving surface of the infrared detection element 2 as an axis, and therefore, the total viewing angle looking into the object surface B by the circular scanning method is 2θ.

When detecting people, the instantaneous field of view Dv on the object surface is the main factor that determines the number of people resolution.In order to increase the number of people resolution, the smaller the instantaneous field of view Dv, the better.Therefore, the aperture width Da of slit A should be made smaller. However, the amount of infrared light received decreases in proportion to this, and a sufficient S/N ratio may not be obtained. In that case, a cylindrical lens is placed in the slit A to have a condensing effect in the scanning direction to obtain a predetermined instantaneous field of view width Dv and a necessary optical gain. In Fig. 14, when a convex cylindrical lens is placed in the slit A, and if the diameter of the light-receiving surface of the infrared detection element 2 is d, the field length Lv and field width Dv of the instantaneous field on the object surface are calculated by the following equations. It becomes like this. -As can be seen from the above equation, instantaneous visual field width D
v is determined by selecting an appropriate Rb or d to obtain a predetermined instantaneous visual field width DV, regardless of the aperture width Da of the cylindrical lens.
can be obtained. Furthermore, the optical gain can be increased by increasing the aperture width Da of the cylindrical lens.

As another means for obtaining optical gain, as shown in FIG.
It has also been proposed to rotate around an axis. The distance from the mirror surface of the cylindrical mirror M° to the light receiving surface of the infrared detection element 2 is Rb, the distance from the mirror surface of the cylindrical mirror M° to the object surface B is Ra, the mirror length of the cylindrical mirror M" is Lm, the mirror width When Dta is the diameter of the light-receiving surface of the infrared detection element 2, and d is the diameter of the light-receiving surface of the infrared detection element 2, the instantaneous visual field length Lv and visual field width Dv on the object surface are expressed by the following equations as in the case of using a cylindrical lens.

Rh + Ra Lv= □ Lm −<6) Rb Ra Dv= □d ... (7) R
b Therefore, by selecting an appropriate Rb or d, a predetermined instantaneous field width Dv can be obtained, and by increasing the mirror width DI11 of the cylindrical mirror M°, the optical gain can be increased. In the radial direction during scanning, the viewing angle θ at which the instantaneous visual field looks at the object surface B is expressed by the following equation.

In addition, the total viewing angle of the object surface B using the circular scanning method is 2
becomes θ.

In order to obtain a wide detection area, in the circular scanning method,
It is necessary to take a large total viewing angle when looking at object surface B, and to do so, the angle θ at which the light-receiving surface looks at object surface B at an instant must be increased.
It is necessary to take a large value.

From equations (3) and (8), in order to increase θ, the slit length or the lens length of the cylindrical lens L
a, or the mirror length of the cylindrical mirror M" may be increased. However, the infrared detection element 2
According to the directional sensitivity characteristics with respect to incident light, as the angle between the incident light and the center C of the field of view of the light-receiving surface increases, the sensitivity decreases, and the sensitivity becomes zero above a certain angle. An example of the directional sensitivity characteristics of the pyroelectric element used as the infrared detection element 2 is shown in Fig. 16. As is clear from this figure, in the circular scanning optical system, the total viewing angle looking onto the object surface is the same as that of the infrared detection element 2. It is limited by the directional sensitivity characteristics of the sensor, and cannot be made sufficiently wide.Furthermore, in the field of view, the sensitivity in the peripheral area decreases, resulting in non-uniformity in sensitivity within the detection area.

In order to solve these problems, the present inventors have developed a modified saddle shape in which one direction is a concave surface with a continuous curvature change and the other perpendicular direction is a convex surface, as shown in FIG. We proposed that the field of view in the radial direction be expanded by rotating the mirror M'' with the direction in which the convex surface is formed as the radial direction ('
(See Pf Application No. 61-281302). As a result, it has been possible to provide a people detection device that has a wide detection area with a uniform sensitivity distribution, but there is a desire for a people detection device that is smaller and has an optical system with a large optical gain.

(Object of the invention) The present invention has been made in view of the above points, and
The purpose is to provide a small number of people detection device that has a simple and inexpensive configuration, has a wide detection area with a uniform sensitivity distribution, and has a large optical gain.

(Disclosure of the Invention) In order to achieve the above object, the number of people detecting device according to the present invention has an infrared detecting element 2 and a reflective surface as shown in FIGS. a circular scanning optical system 1 that circularly scans the field of view of the infrared detection element 2 by rotating a mirror M facing the element 2 around the field of view center C of the infrared detection element 2; and a circular scanning optical system 1 that amplifies the output signal of the infrared detection element 2. a preamplifier 3 that converts the output signal of the preamplifier 3 into a signal necessary for detecting the number of people.
A number of people detecting device comprising a determining unit 5 that determines the number of people based on the output signal of the signal processing unit 4, and an output unit 6 that outputs number of people information from the output signal of the determining unit 5,
The reflecting surface of the mirror M in the circular scanning direction is a concave surface having a continuous curvature change, and the reflecting surface in the radial direction of the circular scanning is a concave surface having a sufficiently small focal length compared to the distance to the object surface. The mirror is characterized in that the center position of the circular scan of the concave surface in the radial direction substantially coincides with the rotation center of the mirror.

In the present invention, as described above, the reflecting surface in the radial direction of circular scanning in the mirror M used in the circular scanning optical system 1 is a concave surface having a sufficiently small focal length compared to the distance to the object surface. As shown in FIG. 5, the optical path seen from the light-receiving surface S of the infrared detection element 2 is reflected by the reflective surface of the mirror M, is once condensed in front of the mirror M, and then diverges again into a circular shape. It extends in the radial direction of scanning and therefore provides a very wide field of view.

In other words, in the conventional example using the modified saddle-shaped mirror M'''', the field of view in the radial direction is expanded by making the reflecting surface in the radial direction of circular scanning a convex surface, and this reflecting surface is made into a concave surface. It was thought that the field of view in the radial direction would become narrower if Since the infrared rays are once focused in front of the mirror M, the field of view in the radiation direction can be expanded. In addition, since the center position in the radial direction of the circular scanning of this concave surface is made to approximately coincide with the rotation center of the mirror M, as shown in FIG. 8(a), the conventional example (FIG. 8(b)) In comparison, the scanning optical system can be dramatically downsized.

Examples of the present invention will be described below.

x1 Takumi 1 FIG. 1 is a perspective view showing the shape of a mirror M used in an embodiment of the present invention. This mirror M has a concave reflecting surface in the direction of the X-X'' line, and a concave surface having a continuous curvature change in the reflecting surface in the direction perpendicular to the xx' line, and the overall shape is a modified toric mirror. FIG. 2 is a diagram showing a cross section of the mirror M in FIG. The mirror M is directed toward the light-receiving surface S of the infrared detecting element 2, and the mirror M is
By rotationally driving the x'-ray direction as the radial direction, the field of view of the infrared detection probe 2 can be circularly scanned. The concave surface in the xx' line direction has the effect of expanding the instantaneous field of view in the radial direction, and the reflective surface in the direction perpendicular to the xx' line has the function of condensing light in the scanning direction. The incident light that enters from point B1 on the object side enters the light receiving surface S via the mirror one end point M1, and the incident light that enters from the object surface side point B2 enters the light receiving surface S via the mirror one end point M2. 0 point B1 shall be incident on
Assuming that the incident light from point B2 to the mirror end point M1 is perpendicular to the X axis, the angle θ formed by the incident light from point B2 to the mirror end point M2 and the Y axis is the instantaneous viewing angle in the radial direction in the instantaneous visual field. . The mirror surface has an arc shape, and the center of curvature is N.

The light receiving surface S is arranged directly below the center of the mirror surface. That is,
As shown in Figure 2, take the X-Y coordinates, and calculate the coordinates of point M1 as (x + , y + ), the coordinates of point M2 as (X2°Y2), and the coordinates of light receiving surface S as (Xs, Ys). Then, X
2=XI...(9)Xs
=O...(10) Set so that. Thereby, the mirror can be efficiently arranged on the rotary plate of the Mtt scanning optical system, and a compact optical system with a large optical gain can be provided. The cross-sectional shape of the mirror M is uniquely determined by setting its length in the X-axis direction, the position of the light-receiving surface S, and a desired instantaneous viewing angle θ, and the center of curvature N is determined.

In FIG. 3, a point at an angle t from the starting diameter NM1 on the circular arc representing the mirror surface is designated as ML. It is assumed that incident light from a point P on the object surface enters the light receiving surface S via the point ML, and the point M
1, the distance Rh from the light-receiving surface S to the point Mt on the mirror surface, and from the point Mt to the point P on the object surface.
Find the distance to @Ra. Here, the distance 1iiRb is
It varies depending on the position of point Mt on the mirror surface. That is, Rb=Rb(t)...(11
), the concave surface of the mirror M in the scanning direction is arcuate, and in order to condense the incident light from the point P on the object surface onto the light receiving surface S, at the point Mt on the mirror surface, the following equation is written. What is necessary is just to form a concave surface having a focal length ft that satisfies the scanning direction.

In order to have the focal length rt, the radius of curvature Rt at the point Mt on the mirror surface is Rt=2ft (13)
On the mirror surface, a point ML is located at the center of the scanning direction of the mirror M, and the center of concave curvature Nt is placed on an extension of the line segment NMt, and the line segment NtMt has a radius of curvature Rt. It is sufficient to form a concave surface that matches the .

From equations (11), (12), and (13), we get Rh(
t) changes continuously, and the radius of curvature Rt also needs to change continuously. Furthermore, the object surface B to be focused on is
If the plane is parallel to the horizontal plane and the distance from the point ML on the mirror surface to the plane in focus is R, then the distance R and the distance w
The relationship of IRa is that the angle between one line segment and the normal line nt is θH2
If the angle between the line segment M〒P and the center of field of view of the light-receiving surface C is θF, then the distance 911Ra also changes continuously. In this way, the concave surface of the mirror M in the scanning direction may be formed by continuously changing the radius of curvature, taking into consideration the surface to be focused.

FIG. 4 shows a specific example of the cross-sectional shape of the mirror M in the present embodiment in the radial direction. The distance to the center of the field of view is 3On++a,
The radius of concave curvature is 28.5...In, and the starting diameter of the arc is NMI
If the angle that it makes with the horizontal plane is 76°7175°, then the angle that the incident light from point B2 on the object surface makes with the center of visual field C is 71.6°.
464°, and the angle at which the object plane B is viewed through the mirror M is 71,6464°.
The total viewing angle is 143.2928°. Fifth
The figure shows the state of convergence of light from the object surface B by the mirror M of this embodiment.

FIG. 6 shows the radius of curvature of the concave surface of the mirror M in the scanning direction whose curvature changes continuously, and the position on the mirror surface is expressed by the angle t from the starting diameter NMI. The radius of curvature at the end points Ml and M2 of the mirror M is 64.
It has 2108m wheels and 45.4898a+m. Further, the mirror width in the scanning direction was set to 30111M.

Figure 7 shows the calculation result of the incident power from the human body when the human body stands upright on the floor in three rows directly below the scanning optical system.The horizontal axis is the horizontal distance of the human body from the center of visual field C, and the vertical axis The axis is the relative value of the incident power. The characteristics plotted with black circles are the characteristics when using the modified saddle-shaped mirror M'' shown in FIG. 17, and the characteristics plotted with white circles are the characteristics when using the mirror M shown in FIG. 1. .If you look at Figure 7,
It can be seen that by using the mirror M of this example, the optical gain is dramatically improved.

FIG. 8 shows a situation where the mirror M is placed on the rotary plate 10. When the mirror M is installed as shown in FIG. 8(a),
If the rotary plate 10 is circular, it will have a minimum diameter of 42.4 m. On the other hand, the modified saddle-shaped mirror M'' shown in FIG. 17 requires a rotary plate 10 having a diameter of at least 72.1wl11 (see FIG. By using this, the optical system can be made significantly smaller.

Here, the overall configuration of the number of people detection device using the above optical system will be explained based on the block diagram of FIG. , converted into an electrical signal. The output of the infrared detection element 2 is amplified by the preamplifier 3 and then input to the bandpass filter in the signal processing unit 4 to cut unstable low frequency components and unnecessary high frequency components, and improve the S/N. improve the ratio. The output of the bandpass filter is A/D converted and output to the microcomputer that constitutes the judgment section 5.

This microcomputer is synchronized with the rotation of the circular scanning optical system 1 and sequentially captures the A/D converted waveform for each rotation. In the 0 judgment section 5, the output waveform when there is no human body within the detection area is determined in advance. The input waveform is stored in the memory as reference waveform data, and the input waveform is compared with the reference waveform in the memory to determine the presence or absence of a human body and the number of people at the same time.In this embodiment, the input waveform data and the reference waveform data are Perform a comparison calculation, use the result as new comparison processing waveform data, detect the local maximum value in the comparison processing waveform data,
The number of maximum values is counted as the number of people. In the comparison processing waveform data, if the detected number of people is O, the current input waveform data is updated as reference waveform data and stored in the memory. By performing comparison calculations with the input waveform data using the reference waveform data in this way, it is possible to detect the number of people with high precision without being affected by environmental changes within the detection area. The output section 6 displays the number of people information based on the number of people information given from the judgment section 5. In a conference room, etc., the number of people or the degree of congestion is displayed outside the room so that others can grasp the usage status of the room. In addition, in rooms used by individuals, the room status is determined as ``absent'', ``occupied'', or ``visitor'' based on the number of people information ``0 person'', ``1 person'', and ``more than 2 Å''.
By displaying the information outside the room, others can easily and simply grasp the indoor situation. Furthermore, various environmental facilities such as air conditioning can be operated stably and effectively based on the information on the number of people.

21I is a sectional view in the radial direction of a mirror M used in a number of people detection device according to another embodiment of the present invention.

This mirror M has an elliptical concave surface in the radial direction, and widens the instantaneous viewing angle in the radial direction. Incident light from point B1 on the object surface side enters the light receiving surface S via one end point M1 of the mirror, and incident light from point B2 on the object surface side enters the light receiving surface S via one end point M2 of the mirror. shall be. Here, as shown in FIG.
Y2), and if the coordinates of the light-receiving surface S are (Xs, Ys), then
2=-X, ...(16)XS
=O...(17) If it is set as follows, that is, one end point Ml,
If the field of view center C is placed in the center of M2 and the light-receiving surface S of the infrared receiving element 2 is placed on the field of view center C, the mirror M can be efficiently placed on the rotating plate of the scanning optical system, resulting in a small size and a large optical gain. An optical system can be provided.

n, , n2 are the normal vectors at the end points Ml and M2 of the mirror M, and the rays enter from point B1 on the object surface side to one end point M1 of the mirror, and the rays enter from point B2 on the object surface side to one end point M2 of the mirror. Letting the intersection point with the ray of light be Q, we can see that the concave surface should have an elliptical shape with two focal points at points S and Q.0
If the midpoint of the line segment SQ connecting points S and Q is N, point N becomes the center of the ellipse. This elliptical shape is determined by the length of the mirror M in the X-axis direction, the position of the light receiving surface S, and the desired instantaneous viewing angle θ.
It is uniquely determined from .

FIG. 10 shows a specific example of the cross-sectional shape of the mirror M of this embodiment in the radiation direction. From the visual field center C to the mirror end point Ml
, M2 are each 15 mm in the horizontal direction, and the vertical distance from the light receiving surface S to one end point M1 of the mirror is 30+m. The focal points of the elliptical shape are points S and Q, and point Q is located 22 degrees directly below the mirror end point M1. The elliptical shape is expressed by the following equation.

By setting the straight line passing through points S and Q as the X axis, and taking the X-Y coordinates with the center N of the ellipse as the origin, this ellipse shape can be calculated as follows: a = 27.7705 (+sm), b = 26.43
Any point M(X,
Y) is expressed by the following formula using α as a parameter.

X = a −cosa −(19
)Y = b-sin α-= (20) α = 47.2436° at point M1, α = 118.
It is 041°. The instantaneous viewing angle θ in the radial direction is 70.7
It becomes 977°. Therefore, the total viewing angle of the scanning optical system with respect to the object plane B is 141°5954°.

FIG. 11 shows the state of convergence from the object surface B when the mirror M of this embodiment is used. All the light incident on the light receiving surface S from the object surface B passes through the focal point Q. Therefore, in order to protect the scanning optical system, if a protective cover made of infrared transmitting material is attached to the light-transmitting part, only the part through which the focal point Q passes according to the rotation of the scanning optical system should be made into a window. , only a small amount of infrared transmitting material is required, and the structure is strong. The shape of the protective cover is not particularly limited as long as it covers the entire scanning optical system. It is arranged on the rotation center axis of the lens, and only the part at a predetermined height (and its vicinity) through which the focal point Q passes is an annular window part, and an infrared transmitting material is arranged in this window part, and the other parts are lightweight. It can be made of a strong light-shielding material.

The concave surface shown in FIG. 9 in the direction orthogonal to the direction in which the concave surface is formed is a concave surface that has a continuous change in curvature, and has a light condensing effect in the scanning direction. This continuous curvature change of the concave surface is determined in the same manner as in the first embodiment. FIG. 12 shows the relationship between the angle t from the starting diameter and the radius of curvature of the concave surface in the scanning direction, with the butterbur 1 as the starting diameter. Even in this embodiment, where the mirror width in the scanning direction is 30 eam, As in the case of Example 1, the optical gain is improved and the optical system can be made smaller.

(Effects of the Invention) As described above, in the present invention, the reflecting surface of the mirror in the circular scanning direction for circularly scanning the field of view of the infrared detecting element is a concave surface having a continuous curvature change, and Since the reflective surface of is a concave surface with a sufficiently small focal length compared to the distance to the object surface, it can be constructed easily and inexpensively, and a large optical gain and uniform carbon sensitivity distribution can be obtained over a wide detection area. Moreover, since the radial center position of the concave surface in the radial direction of circular scanning is made to approximately coincide with the rotation center of the mirror, the rotation radius of the scanning optical system becomes small, making it possible to make the scanning optical system compact. There is an effect that there is.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a mirror used in an embodiment of the present invention, FIGS. 2 to 4 are cross-sectional views of the same, FIG. Fig. 7 is a characteristic diagram showing the light-gathering power of the mirror shown above; Fig. 8 is an explanatory drawing showing how the mirror is attached to the rotary plate; 9 and 10 are cross-sectional views of mirrors used in other embodiments of the present invention, FIG. 11 is an explanatory diagram showing the state of convergence by the same mirror, and FIG. 12 is a diagram showing changes in the radius of curvature of the same mirror. 13 is a block diagram of the conventional example, FIG. 14(a) is a schematic configuration diagram of the optical system used in the conventional example, FIG. 14(b) is a bottom view of the main parts of the same, and FIG.
Figure (a) is a schematic configuration diagram of an optical system used in another conventional example, Figure (b) is a bottom view of the main parts of the same, Figure 16 is a directivity characteristic diagram of the infrared detection element used in the same, and Figure 17 is FIG. 7 is a perspective view of a modified saddle-shaped mirror used in yet another conventional example. 1 is a circular scanning optical system, 2 is an infrared detecting element, 3 is a preamplification section, 4 is a signal processing section, 5 is a judgment section, 6 is an output section, and M is a mirror.

Claims (1)

[Claims] (1) an infrared detection element and a circular scanning optical system that rotates a mirror with a reflective surface facing the infrared detection element around the center of the field of view of the infrared detection element to circularly scan the field of view of the infrared detection element; a preamplifier that amplifies the output signal of the infrared detection element; a signal processor that converts the output signal of the preamplifier into a signal necessary for detecting the number of people; and a signal processor that calculates the number of people based on the output signal of the signal processor. In the number of people detection device, which includes a judgment unit that makes a judgment, and an output unit that outputs number of people information from an output signal of the judgment unit, the reflective surface of the mirror in the circular scanning direction is a concave surface having a continuous change in curvature; The reflecting surface in the radial direction of the circular scan is a concave surface having a sufficiently small focal length compared to the distance to the object surface, and the center position of the concave surface in the radial direction of the circular scan is approximately the rotation center of the mirror. A device for detecting the number of people, characterized in that they match.