JP2006046961A - Human body sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a human body sensor inhibited from misdetecting and capable of surely detecting a person in sensing area. <P>SOLUTION: The human body sensor 1 comprises: a light emission source 5 for irradiating objective space with the light periodically varying intensity modulated light; a photodetector element 3 arranged with a plurality of photosensitive parts for generating the electric power corresponding to the received ligh amount for imaging the objective space; a distance image sensor part 2 for forming the distance image, the pixel value of which is the distance value, by converting the phase difference of the intensity modulated light from the light emitted from the light source 5 till received by each light receiving part after reflected by the object in the object space into the distance to the object; and a signal processing circuit 10 for detecting the existence of the person in the sensing area on the basis of the distance image of the distance image sensor part 2. The signal processing circuit 10 eliminates the area from the sensing area till approximately a constant height using the installation height of the distance image sensor part 2 and information in a direction of viewing direction of each pixel. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a human body detection sensor.

As this type of human body detection sensor, for example, a sensor that is installed on an invisible wall or ceiling of a building and used to detect the presence or absence of a person in an approach path to an automatic door has been provided (for example, a patent) Reference 1).
Japanese Patent No. 3458738

  By the way, as a human body detection sensor used for automatic door opening / closing applications, it is necessary to detect a person or a cart, so that an infrared reflection type sensor is mainly used. There was a problem that the automatic door would malfunction by detecting only people passing through the aisle. In addition, since a human body detection sensor using an infrared detection element such as a pyroelectric element cannot detect a stationary person, a sensor for preventing pinching is auxiliary installed when used for opening and closing an automatic door. There was a need.

  Further, in the human body detection sensor, if a small animal such as a dog or a cat moves in the detection area or a sudden temperature change occurs in the detection area, there is a possibility that a false detection occurs.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a human body detection sensor that can prevent erroneous detection and reliably detect a person in the detection area. is there. Furthermore, an object of the inventions of claims 4 and 5 is to provide a human body detection sensor capable of detecting only a person approaching a specific point in addition to the above object.

  In order to achieve the above object, the invention of claim 1 is a distance image sensor unit that captures a target space and generates a distance image having a distance value as a pixel value, and the installation height and distance image of the distance image sensor unit. Is set by the area setting means based on the area setting means for removing the range up to a substantially constant height from the detection area using the information on the line-of-sight direction for each pixel and the distance image input from the distance image sensor unit. And a human body detection unit for detecting the presence or absence of a person in the detection area.

  According to a second aspect of the present invention, in the first aspect of the invention, the area setting means divides the horizontal plane into a plurality of areas at concentric boundaries centering on the installation position of the distance image sensor unit, and for each area. The upper limit value of the pixel value of the pixel corresponding to each area is set stepwise so that the upper limit value becomes larger as the area is farther from the installation position.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the area setting means limits the detection area within a certain distance from the installation position of the distance image sensor unit in the horizontal plane.

  According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, a direction detection unit that detects a moving direction of the person detected by the human body detection unit, and a detection signal from the human body detection unit are output to the outside. And a signal output unit, wherein the signal output unit determines whether or not to output a detection signal to the outside according to the moving direction detected by the direction detection unit.

  According to a fifth aspect of the present invention, in the fourth aspect of the invention, the signal output unit does not output a detection signal to the outside if the moving direction detected by the direction detection unit is a direction away from a specific point in the target space. Features.

  The invention according to claim 6 is detected by the human body detection unit using the installation height of the distance image sensor unit, the pixel value of each pixel, and information on the line-of-sight direction in any one of the inventions of claims 1 to 5. A height information detection unit for detecting the height information of a person and a height information output unit for outputting the height information detected by the height information detection unit to the outside are provided.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the distance image input from the distance image sensor unit at the timing of at least one of power-on or warning set is used as a background image. A background image registration unit for registration is provided, and the human body detection unit detects the presence or absence of a person from a difference image between the distance image and the background image input from the distance image sensor unit.

  According to the first aspect of the invention, the area setting means removes the range up to a substantially constant height from the detection area by using the installation height of the distance image sensor unit and the information on the line-of-sight direction for each pixel of the distance image. Therefore, it is possible to prevent false detection of small animals by removing the range up to a certain height higher than the height of small animals such as dogs and cats from the detection area. Since the presence or absence of a person is detected in the detection area based on the distance image input from the sensor unit, there is an effect that erroneous detection due to a sudden temperature change in the surroundings can be prevented.

  According to the invention of claim 2, the area setting means has an upper limit value of a pixel value of a corresponding pixel for each of a plurality of areas obtained by dividing the horizontal plane by a concentric boundary centered on the installation position of the distance image sensor unit. Since the upper limit value is set stepwise so that the area farther from the sensor installation position becomes larger, the range up to a substantially constant height can be removed from the detection area.

  According to the invention of claim 3, it is possible to detect only a person within a range of a certain distance from the installation position of the distance image sensor unit in a horizontal plane, and it is possible to prevent detection of an irrelevant person located at a place more than a certain distance. .

  According to the invention of claim 4, since the signal output unit determines whether or not to output the detection signal to the outside according to the moving direction detected by the direction detecting unit, depending on the moving direction of the person The output of the detection signal can be stopped, and an unnecessary detection signal can be prevented from being output to the outside.

  According to the invention of claim 5, since the detection signal is not output to the outside if the moving direction detected by the direction detection unit is away from the specific point, the unnecessary detection signal is prevented from being output to the outside. it can.

  According to the sixth aspect of the present invention, the height information of the person detected by the human body detection unit is detected by the height information detection unit, and the detected height information is output to the outside from the height information output unit. Therefore, the external device can perform control according to the detected height of the person. For example, in an apparatus that controls the opening and closing of an automatic door, the opening and closing speed is changed according to the detected height of the person, so that the opening and closing speed can be moderated for a child and safety can be improved.

  According to the seventh aspect of the present invention, as the background image used by the background image registration means for the human body detection unit to determine the presence or absence of a person, the distance image at the timing of at least one of power-on and warning set Since the distance image input from the sensor unit is registered, it is possible to prevent erroneous detection of an environmental change in the target space by updating the background image when the power is turned on or when the warning is set.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram of one embodiment of a human body detection sensor. The human body detection sensor 1 includes a distance image sensor unit 2 and a signal processing circuit 10 as main components, and the operation of the load 12 from the signal processing circuit 10. A human body detection signal is output to the load control circuit 11 for controlling the control. The human body detection sensor 1 according to the present embodiment is installed, for example, on an unfinished wall, ceiling, or eaves ceiling of a building, and detects the presence or absence of a person in the vicinity of an opening such as an access path to an automatic door or a window. FIG. 3 shows a construction example in the case of detecting the approach of the suspicious person 100 to the window 32 on the lower side, which is installed on the unidentified wall surface 31 on the outdoor side of the building 30.

  First, the configuration of the distance image sensor unit 2 used in the present embodiment will be described. As shown in FIGS. 1 and 2, the distance image sensor unit 2 includes a light emitting source 5 that irradiates light to a target space 33 set outside the window 32, and receives light from the target space 33 to obtain a received light amount. The light detection element 3 that can obtain an electrical output of the reflected output value is provided, and the distance to the target object (such as the human body 100) existing in the target space 33 is that the target space 33 is irradiated with light from the light emitting source 5. To the time from when the reflected light from the object enters the light detection element 3 (referred to as “time of flight”). However, since the flight time is very short, the intensity modulated light modulated so that the intensity of the light irradiating the target space 33 periodically changes at a constant period, and the phase when the intensity modulated light is received is used. Seeking flight time.

  That is, as shown in FIG. 11A, it is assumed that the intensity of light radiated from the light emitting source 5 to the space changes as shown by curve A, and the amount of received light received by the light detecting element 3 changes as shown by curve B. For example, since the phase difference ψ corresponds to the flight time, the distance to the object can be obtained by obtaining the phase difference ψ. Further, the phase difference ψ can be calculated using the received light quantity of the curve B obtained at a plurality of timings of the curve A. For example, it is assumed that the received light amounts of curve B obtained with the phases of curve A at 0 degrees, 90 degrees, 180 degrees, and 270 degrees are A0, A1, A2, and A3, respectively. However, the received light amount A0, A1, A2, A3 in each phase uses the received light amount integrated at a predetermined time Tw instead of the instantaneous value. Now, while obtaining the received light amounts A0, A1, A2, and A3, the phase difference ψ does not change (that is, the distance to the object does not change), and the reflectance of the object does not change. To do. Further, it is assumed that the intensity of light emitted from the light emitting source 5 is modulated with a sine wave, and the intensity of light received by the light detection element 3 at time t is represented by A · sin (ωt + δ) + B. Here, A is the amplitude, B is the external light component, ω is the angular frequency, and δ is the phase. If the received light amounts A0, A1, A2, A3 received by the light detecting element 3 are instantaneous values instead of the integrated values of the time Tw, the received light amounts A0, A1, A2, A3 can be expressed as follows.

A0 = A · sin (δ) + B
A1 = A · sin (π / 2 + δ) + B
A2 = A · sin (π + δ) + B
A3 = A · sin (3π / 2 + δ) + B
Since δ = −ψ, A0 = −A · sin (ψ) + B, A1 = A · cos (ψ) + B, A2 = A · sin (ψ) + B, A3 = −A · cos (ψ ) + B, and as a result, the relationship between the received light amounts A0, A1, A2, A3 and the phase difference ψ is expressed as follows.

ψ = tan ⁻¹ {(A2−A0) / (A1−A3)} (1)
In the above equation (1), the instantaneous values of the received light amounts A0, A1, A2, A3 are used, but even if the integrated values at the time Tw are used as the received light amounts A0, A1, A2, A3, the equation (1) ) To obtain the phase difference ψ.

  By the way, in order to modulate the intensity of the light irradiated to the target space 33, the light source 5 is, for example, one in which a large number of light emitting diodes are arranged on one plane or a combination of a semiconductor laser and a diverging lens. Use. The light emission source 5 is driven by a modulation signal having a predetermined modulation frequency output from the control circuit unit 7, and the intensity of the light emitted from the light emission source 5 is modulated by the modulation signal. The control circuit unit 7 modulates the intensity of light emitted from the light source 5 with, for example, a 20 MHz sine wave. The intensity of the light emitted from the light source 5 may be modulated by a triangular wave, a sawtooth wave, or the like in addition to the modulation by a sine wave. In short, any configuration is possible as long as the intensity is modulated at a constant period. May be adopted.

  The light detecting element 3 includes a plurality of photosensitive portions 3a regularly arranged. A light receiving optical system 4 is disposed in the light incident path to the photosensitive portion 3a. The photosensitive portion 3a is a portion where light from the target space 33 enters through the light receiving optical system 4 in the light detection element 3, and the photosensitive portion 3a generates an amount of electric charge corresponding to the amount of received light. Further, the photosensitive portions 3a are arranged on lattice points of a planar lattice, and are arranged in a matrix in which, for example, a plurality are arranged at equal intervals in the vertical direction (that is, the longitudinal direction) and the horizontal direction (that is, the lateral direction). Is done.

  The light receiving optical system 4 associates the line-of-sight direction when viewing the target space 33 from the light detection element 3 with each photosensitive portion 3a. That is, the range in which light is incident on each photosensitive portion 3a through the light receiving optical system 4 can be regarded as a conical field of view having a small apex angle set for each photosensitive portion 3a with the center of the light receiving optical system 4 as a vertex. it can. Therefore, if the reflected light emitted from the light source 5 and reflected by the object existing in the target space 33 enters the photosensitive portion 3a, the optical axis of the light receiving optical system 4 depends on the position of the photosensitive portion 3a that has received the reflected light. It is possible to know the direction in which the object exists with reference to.

  Since the light receiving optical system 4 is generally arranged so that the optical axis is orthogonal to the plane on which the photosensitive portion 3a is arranged, the center of the light receiving optical system 4 is set as the origin, and the vertical and horizontal directions of the plane on which the photosensitive portion 3a is arranged If an orthogonal coordinate system is set in which the optical axis of the light receiving optical system 4 is in the direction of three axes, the angle (so-called azimuth and elevation) when the position of the target existing in the target space 33 is expressed in spherical coordinates. It corresponds to each photosensitive portion 3a. The light receiving optical system 4 can also be arranged so that the optical axis intersects at an angle other than 90 degrees with respect to the plane on which the photosensitive portions 3a are arranged.

  In the present embodiment, as described above, in order to obtain the distance to the object, the received light amounts A0, A1, and A2 are synchronized at four timings synchronized with the intensity change of the light emitted from the light source 5 to the target space 33. , A3. Therefore, it is necessary to control the timing to obtain the desired received light amount A0, A1, A2, A3. Further, since the amount of charge generated in the photosensitive portion 3a is small in one cycle of the intensity change of light irradiated from the light source 5 to the target space 33, it is desirable to accumulate the charges over a plurality of cycles. Therefore, as shown in FIG. 2, by providing a plurality of charge accumulating portions 3c for accumulating the charges generated in each photosensitive portion 3a, and changing the area of a region for generating charges that can be used in each photosensitive portion 3a. A plurality of sensitivity control units 3b for adjusting the sensitivity of each photosensitive unit 3a are provided.

  In each sensitivity control unit 3b, the sensitivity of the photosensitive unit 3a corresponding to the sensitivity control unit 3b is increased at any one of the four points described above, and in the photosensitive unit 3a with increased sensitivity, the received light amount A0, Since charges corresponding to A1, A2, and A3 are mainly generated, charges corresponding to the received light amounts A0, A1, A2, and A3 can be accumulated in the charge accumulating portion 3c corresponding to the photosensitive portion 3a.

  By the way, the sensitivity control unit 3b changes the amount of charge generated in each period by changing the area (substantial light receiving area) of the region that generates charge that can be used in the photosensitive unit 3a. The charges accumulated in 3c are not necessarily mixed with the charges generated in the period in which the received light amounts A0, A1, A2, A3 are obtained, but also the charges generated in other periods. Now, in the sensitivity control unit 3b, the sensitivity in the period for generating the charges corresponding to the received light amounts A0, A1, A2, A3 is α, the sensitivity in the other periods is β, and the photosensitive unit 3a is a charge proportional to the received light amount. Is generated. Under this condition, the charge accumulating unit 3c that accumulates charges corresponding to the received light amount A0 is proportional to αA0 + β (A1 + A2 + A3) + βAx (Ax is the received light amount other than the period during which the received light amounts A0, A1, A2, and A3 are obtained). Charges proportional to αA2 + β (A0 + A1 + A3) + βAx are accumulated in the charge accumulating unit 3c that accumulates charges and accumulates charges corresponding to the received light quantity A2. As described above, when obtaining the phase difference ψ, (A2−A0) is obtained, and A2−A0 = (α−β) (A2−A0), and similarly, A1−A3 = (α−). β) Since (A1-A3), (A2-A0) / (A1-A3) theoretically has the same value regardless of the presence or absence of charge mixing. The phase difference ψ has the same value.

  The photodetecting element 3 including the photosensitive unit 3a, the sensitivity control unit 3b, and the charge accumulating unit 3c is configured as one semiconductor device, and the photodetecting element 3 receives charges accumulated in the charge accumulating unit 3c outside the semiconductor device. A charge extraction portion 3d is provided for extraction. The charge extraction unit 3d has the same configuration as the vertical transfer unit and horizontal transfer unit in the CCD image sensor.

  As described above, since each photosensitive unit 3a generates an amount of electric charge corresponding to the amount of received light, each of the received light amounts A0, A1, A2, A3 reflects the brightness of the object. That is, the added value or average value of the received light amounts A0, A1, A2, A3 corresponds to the density value in the grayscale image. In other words, in addition to obtaining the distances from the received light amounts A0, A1, A2, A3 to the object at each photosensitive portion 3a, it is also possible to obtain the density value of the object. In addition, since the distance and density value of the object are obtained using the photosensitive portion 3a at the same position, information on both the density value and the distance can be obtained for the same position.

  The charges extracted from the charge extraction unit 3d in this way are converted into digital quantities by the A / D conversion unit 9, and then given as image signals to the image generation unit 8 made of DSP. The distance to the object in 33 is calculated from the received light amounts A0, A1, A2, A3 using the above-described mathematical formula. That is, the image generation unit 8 calculates the distance to the object in each direction corresponding to each photosensitive unit 3a, and calculates the three-dimensional information of the target space 33. By using this three-dimensional information, it is possible to generate a distance image in which the pixel values of the pixels matching in each direction of the target space 33 are distance values. Further, the image generation unit 8 generates a grayscale image of the target space 33 as necessary based on the density value obtained by each photosensitive unit 3a. In this embodiment, the control circuit unit 7 and the image generation unit 8 are configured by a one-chip ASIC 6.

  Then, the distance image of the target space 33 obtained by the image generation unit 8 of the distance image sensor unit 2 is input to the signal processing circuit 10, and processing for detecting the presence / absence of a person in the target space 33 is performed by the signal processing circuit 10. Is called.

  Here, the signal processing circuit 10 limits the detection range of the sensor to a predetermined upper limit value or less by limiting the input range of the pixel value (distance value) of each pixel to a predetermined upper limit value or less. As shown in FIG. 3B, the detection area 34 is limited to a sphere having a radius R centered on the installation position P0 of the human body detection sensor 1 in a quadrangular pyramid shape. Note that the detection area of the human body detection sensor 1 is not intended to limit the detection area to the above-described area, but the detection area of the sensor is changed by changing the upper limit value of the pixel value according to the line-of-sight direction of each pixel. ), The installation position P0 may be set as the apex, and the area 33 may be set to a quadrangular pyramid area 33 having a hypotenuse length of L.

  Further, in the signal processing circuit 10, a range (dead zone) up to a substantially constant height H is excluded from the detection area 34 using the installation height of the human body detection sensor 1 and data of the line-of-sight direction for each pixel. (See FIG. 4). For example, as shown in FIG. 5A, the signal processing circuit 10 divides the horizontal plane into a plurality of areas S1, S2, and S3 at concentric boundaries C1, C2, and C3 centering on the installation position of the human body detection sensor 1. For each area S1, S2, S3, the height from the ground (floor surface) is determined based on the line-of-sight direction of the pixels corresponding to each area S1, S2, S3 and the installation height H0 of the human body detection sensor 1. The pixel values of the pixels corresponding to the areas S1, S2, S3 are limited to a certain distance L1, L2, L3 or less so that the range up to H deviates from the detection area. In this case, when each of the areas S1, S2, S3 is viewed in the vertical plane, each of the areas S1, S2, S3 has a sector shape with radii L1, L2, L3 centered on the installation position P0 of the human body detection sensor 1. Each area S1, S2, and S3 may be divided so that the width in the horizontal plane becomes a substantially constant value W as shown in FIG. 5B, or as shown in FIG. The central angles θ1, θ2, and θ3 when viewed in a vertical plane may be divided so as to be substantially equiangular. In order to reduce the variation in the height of the dead zone, it is desirable to divide each area S1. Further, the concentric boundary C1 that divides each of the areas S1, S2, and S3 may be a circular boundary centered on the installation position of the human body detection sensor 1, or the installation position of the human body detection sensor 1 may be a single fixed point. An elliptical boundary may be used.

  As described above, the detection area 34 ′ from which the dead zone area up to the height H is removed is set. The signal processing circuit 10 performs the following determination process based on the distance image in the detection area 34 ′. Do. First, as shown in FIGS. 10 (a) and 10 (b), the signal processing circuit 10 sets the detection area to the above-described area 34 based on the distance image input from the distance image sensor unit 2 when the power is turned on or when the warning is set. An image limited to 'is created and registered as a background image, and a difference calculation is performed between the background image and an image in which the distance image input from the distance image sensor unit 2 is limited to the detection area 34'. The presence / absence of a person in the detection area is determined by performing template matching between the difference image and a template image registered in advance. When the signal processing circuit 10 detects the presence of a person in the detection area, the signal processing circuit 10 sends an alarm signal to the load control circuit 11 to cause the load control circuit 11 to control the load 12. Here, when using it for control of an automatic door, the load control circuit 11 drives the load 12 like a motor based on the alert signal from the signal processing circuit 10, and opens and closes an automatic door. When used for warning around the window 32, the load control circuit 11 drives the load 12 such as a speaker or a lamp on the basis of the alarm signal from the signal processing circuit 10, so that an intruder can be detected by sound or light. It notifies you that it has been detected and threatens the intruder.

  In this way, the signal processing circuit 10 determines the presence or absence of a person in an area outside the range from the detection area 34 to the substantially constant height H, and determines the height H of the dead zone region as a dog or a cat. By setting the height higher than the height of the small animal 110, the false detection of the small animal 110 can be prevented, and the presence or absence of a person is determined using the distance image. A sudden temperature change in the environment is not erroneously detected, and a stationary person can also be detected. Here, the signal processing circuit 10 includes area setting means for removing a range up to a substantially constant height from the detection area, a human body detection unit for detecting the presence or absence of a person in the detection area based on the distance image, and a distance image sensor. It functions as background image registration means for registering the distance image input from the unit 2 as a background image.

  In this embodiment, the signal processing circuit 10 prevents the detection of the small animal 110 by removing the range from the detection area 34 to the height H, but as shown in FIGS. 6 (a) and 6 (b). The detection area 34 may be limited within a range S10 having a radius R1 centered on the installation position P0 of the human body detection sensor 1 in the horizontal plane, and is outside the range S10 and not near the window 32 or the automatic door. It can prevent even unrelated people from being detected.

  The signal detection circuit 10 determines the presence or absence of a person in the detection area 34 by taking the background difference between the distance image input from the distance image sensor unit 2 and the background image. In this case, the direction of movement of the detected person is obtained by performing inter-frame difference, and if the direction of movement is close to a specific point in the detection area (for example, an opening such as an automatic door or window), The detection information may be output to the load control circuit 11. Since the human body detection sensor 1 is generally installed above an opening such as an automatic door or window, if human movement direction is close to the installation position of the human body detection sensor 1, load human detection information. You may make it output to the control circuit 11. FIG.

  Here, FIG. 7 shows a person who moves in the detection area. The signal processing circuit 10 detects the two persons 100a and 100b in the detection area by performing the above-described determination process, and also displays a distance image. The movement directions D1 and D2 of the two persons 100a and 100b are detected by performing the inter-frame difference, and the movement directions D1 and D2 are detected at specific points in the detection area (for example, openings such as automatic doors and windows). That is, if it is in a direction approaching a point immediately below the human body detection sensor 1, human detection information is output to the load control circuit 11. For example, the moving direction D1 of the person 100a is a direction that intersects the direction perpendicular to the eyeless wall surface 31 toward the eyeless wall surface 31 at an angle α, and a direction approaching the installation position of the human body detection sensor 1. Therefore, the detection information of the person 100a is output from the signal processing circuit 10 to the load control circuit 11. On the other hand, since the moving direction D2 of the person 100b is substantially parallel to the plain wall 31 and is not oriented to approach the installation position of the human body detection sensor 1, the detection information of the person 100b is transmitted from the signal processing circuit 10 to the load control circuit 11. Is not output. Accordingly, the load control circuit 11 receives a detection signal only when the direction of movement of the person is a direction approaching a specific point in the detection area (for example, an opening of an automatic door or window). It is possible to prevent an irrelevant person who does not go to the opening of the door from opening an automatic door or issuing an alarm.

  In addition, when the signal detection circuit 10 performs the above-described processing to detect the movement direction of the person in the detection area, the movement direction is away from a specific point in the detection area (for example, the installation position of the human body detection sensor 1). If so, human detection information may not be output to the load control circuit 11. For example, as shown in FIGS. 8 (a) and 8 (b), when the human body detection sensor 1 is installed on the invisible wall 31 on the upper side of the automatic door 35 and detects the presence or absence of a person on the approach path to the automatic door 35, When the detection sensor 1 detects a person moving in the direction of approaching the automatic door 35 in the approach path, the load control circuit 11 opens the automatic door 35 based on the detection signal. Since the detection signal of the person 100 is not output from the signal detection circuit 10 to the load control circuit 11 when the person who has moved is moving in the direction away from the human body detection sensor 1 on the approach path to the automatic door 35, the automatic door 35 It is possible to prevent the automatic door 35 from being opened by a signal that detects a person leaving.

  Furthermore, when the signal detection circuit 10 detects the presence of a person in the detection area 34, the detected height information of the person may be output to the load control circuit 11. Since the signal detection circuit 10 determines the presence / absence of a person based on the distance image of the detection area 34, as shown in FIG. 9, information on the installation height H0 of the human body detection sensor 1 and the persons 100a and 100b By using the distance information L10 and L11 of the corresponding pixels and the information of the line-of-sight directions D4 and D5, the height information of the detected persons 100a and 100b can be obtained. At this time, the signal processing circuit 10 classifies the person's height by a plurality of threshold levels h1 to h5 (H <h1 <h2 <h3 <h4 <h5), and the classification includes the detected heights of the persons 100a and 100b. Is output to the load control circuit 11 together with the detection signal. For example, when the load control circuit 11 controls the opening and closing of the automatic door 35, the detected height information of the persons 100a and 100b is included. Since the load 12 is controlled so that the opening / closing speed of the automatic door is slowed down as the height information is low, the opening / closing speed of the automatic door can be slowed down in the case of a child with a short height. This has the effect of improving safety.

  In this embodiment, the signal processing circuit 10 creates a background image based on the distance image input from the distance image sensor unit 2 when the power is turned on or at the time of a warning set, and registers a new background image. Therefore, by updating the background image at the time of power-on or warning set, even if the environment in the target space changes due to the potted plant 36 being placed, this environmental change is erroneously detected. Can be prevented.

  Next, a specific structural example of the light detection element 3 used in the present embodiment will be described with reference to FIGS. The light detection element 3 shown in FIG. 12 has a plurality of (for example, 100 × 100) photosensitive portions 3a arranged in a matrix, and is formed on, for example, a single semiconductor substrate. In each column in the vertical direction of the photosensitive portion 3a, the semiconductor layer 21 that is integrally continuous is shared, and the semiconductor layer 21 is used as a transfer path for charges in the vertical direction (using electrons in this embodiment). It is possible to employ a configuration in which a semiconductor substrate is provided with a horizontal transfer portion Th that is a CCD that receives charges from one end of the semiconductor layer 21 and transfers the charges in the horizontal direction.

  That is, as shown in FIG. 13, the semiconductor layer 21 is used as both the photosensitive portion 3a and the charge transfer path, and is similar to a frame transfer (FT) type CCD image sensor. Similarly to the FT-type CCD image sensor, a light-shielded storage region Db is provided adjacent to the imaging region Da in which the photosensitive portions 3a are arranged, and charges accumulated in the storage region Db are transferred to the horizontal transfer unit Th. To do. The transfer of charges from the imaging area Da to the storage area Db is performed at once in the vertical blanking period, and the horizontal transfer unit Th transfers charges for one horizontal line in one horizontal period. The charge extraction unit 3d illustrated in FIG. 2 represents a function including a horizontal transfer unit Th as well as a function as a charge transfer path in the vertical direction in the semiconductor layer 21. However, the charge accumulation unit 3c does not mean the accumulation region Db, but represents a function of accumulating charges in the imaging region Da. In other words, the accumulation region Db is included in the charge extraction unit 3d.

  The semiconductor layer 21 is doped with impurities, the main surface of the semiconductor layer 21 is covered with an insulating film 22 made of an oxide film, and a plurality of control electrodes 23 are arranged on the semiconductor layer 21 via the insulating film 22. . This light detection element 3 has a structure known as a MIS element, but a normal MIS element is that a plurality of (five in the illustrated example) control electrodes 23 are provided in a region functioning as one light detection element 3. Is different. A material is selected for the insulating film 22 and the control electrode 23 so that light having the same wavelength as the light irradiated from the light source 5 to the target space can be transmitted. When light enters the semiconductor layer 21 through the insulating film 22, the semiconductor layer 21. A charge is generated inside the. The conductivity type of the semiconductor layer 21 in the illustrated example is n-type, and electrons e are used as charges generated by light irradiation. FIG. 12 shows only the region corresponding to one photosensitive portion 3a. As described above, a plurality of regions having the structure of FIG. 12 are arranged on the semiconductor substrate (not shown) and the charge extraction is performed. A structure to be the part 3d is provided. The vertical transfer unit provided as the charge extraction unit 3d is assumed to transfer charges in the left-right direction in FIG. 12, but it is also possible to adopt a configuration in which charges are transferred in a direction orthogonal to the plane in FIG. is there. In addition, when transferring charges in the horizontal direction in the figure, it is desirable to set the width dimension of the control electrode 23 in the horizontal direction to about 1 μm.

  In the photodetecting element 3 having this structure, when a positive control voltage + V is applied to the control electrode 23, a potential well (depletion layer) 24 that accumulates electrons e in a portion corresponding to the control electrode 23 is formed in the semiconductor layer 21. The That is, when light is applied to the semiconductor layer 21 with a control voltage applied to the control electrode 23 so as to form the potential well 24 in the semiconductor layer 21, a part of the electrons e generated in the vicinity of the potential well 24. Are captured in the potential well 24 and accumulated in the potential well 24, and the remaining electrons e disappear due to recombination in the deep part of the semiconductor layer 21. Further, the electrons e generated at a location away from the potential well 24 are also extinguished by recombination in the deep part of the semiconductor layer 21.

  Since the potential well 24 is formed at a portion corresponding to the control electrode 23 to which the control voltage is applied, the potential well 24 along the main surface of the semiconductor layer 21 is changed by changing the number of the control electrodes 23 to which the control voltage is applied. (In other words, the area of a region that generates a charge that can be used on the light receiving surface) can be changed. That is, changing the number of control electrodes 23 to which the control voltage is applied means adjusting sensitivity in the sensitivity control unit 3b. For example, when the control voltage + V is applied to three control electrodes 23 as shown in FIG. 12A, and when the control voltage + V is applied to one control electrode 23 as shown in FIG. The area occupied by the potential well 24 on the light receiving surface changes, and the area of the potential well 24 is larger in the state shown in FIG. As a result, the ratio of the charge that can be used increases and the sensitivity of the photosensitive portion 3a is substantially increased. Thus, it can be said that the photosensitive portion 3 a and the sensitivity control portion 3 b are constituted by the semiconductor layer 21, the insulating film 22, and the control electrode 23. Since the potential well 24 holds charges generated by light irradiation, it functions as the charge accumulating portion 3c.

  In order to extract charges from the potential well 24, a technique similar to that of the FT type CCD may be employed. After the electrons e are accumulated in the potential well 24, a control voltage of an applied pattern different from that during charge accumulation is controlled. By applying the voltage to the electrode 23, the electrons e accumulated in the potential well 24 can be transferred in one direction (for example, the right direction in the figure). That is, the semiconductor layer 21 can be used as a charge transfer path in the same manner as the vertical transfer portion of the CCD. Further, the electric charge is transferred through the horizontal transfer portion Th shown in FIG. 13 and is taken out of the photodetecting element 3 from an electrode (not shown) provided on the semiconductor substrate. In short, by controlling the application pattern of the control voltage to the control electrode 23, the sensitivity of each photosensitive portion 3a is controlled, charges generated by light irradiation are integrated, and the integrated charges are transferred. Can do.

  The sensitivity control unit 3b according to the present embodiment switches the sensitivity of the photosensitive unit 3a between two levels, high and low, by switching the area for generating available charges into two levels, that is, the received light amounts A0, A1, A2, and A3. High sensitivity is set only during a period in which the charge corresponding to any of the photosensitive portions 3a is to be generated (the area for generating charges is increased), and low sensitivity is set in other periods. The period of high sensitivity and the period of low sensitivity are set in synchronization with the modulation signal for driving the light source 5. Further, after the charges are accumulated in the potential well 24 over a plurality of periods of the modulation signal, the charges are taken out of the light detection element 3 through the charge extraction portion 3d. The charge is accumulated over a plurality of periods of the modulation signal because the period for generating the usable charge in the photosensitive portion 3a is short within one period of the modulation signal (for example, if the frequency of the modulation signal is 20 MHz). This is because less than a quarter of 50 ns is generated. That is, by integrating charges for a plurality of periods of the modulation signal, signal charges (charges corresponding to light emitted from the light emission source 5) and noise charges (external light components and shots generated inside the light detection element 3). A large signal-to-noise ratio can be obtained, and a large SN ratio can be obtained.

  By the way, if the charges corresponding to the four kinds of received light amounts A0, A1, A2, and A3 necessary for obtaining the phase difference ψ are generated by one photosensitive portion 3a, the resolution with respect to the line-of-sight direction is increased. There arises a problem that the time difference for obtaining the charges corresponding to the received light amounts A0, A1, A2, A3 becomes large. On the other hand, if the charges corresponding to the received light amounts A0, A1, A2, A3 are respectively generated by the four photosensitive portions 3a, the time difference for obtaining the charges corresponding to the received light amounts A0, A1, A2, A3 becomes small. However, a shift occurs in the line-of-sight direction for obtaining the four types of charges, and the resolution in the line-of-sight direction decreases. Therefore, in the present embodiment, a configuration is adopted in which two types of charges corresponding to the received light amounts A0, A1, A2, and A3 are generated within one cycle of the modulation signal by using the two photosensitive portions 3a. . That is, two photosensitive portions 3a are used as a set, and light from the same line-of-sight direction is incident on the two photosensitive portions 3a.

  By adopting the above-described configuration, the resolution in the line-of-sight direction can be made relatively high, and the time difference for generating charges corresponding to the received light amounts A0, A1, A2, and A3 can be reduced. In other words, by reducing the time difference for generating charges corresponding to the received light amounts A0, A1, A2, and A3, the distance detection accuracy can be kept relatively high even for an object moving in the object space. Can do. In the configuration of this embodiment, the resolution in the line-of-sight direction is lower than that in the case where the charge corresponding to the four types of received light amounts A0, A1, A2, and A3 is generated by one photosensitive unit 3a. The resolution can be improved by downsizing the photosensitive part 3a or designing the light receiving optical system 4.

  The operation of the light detection element 3 will be specifically described below. The example shown in FIG. 12 shows an example in which five control electrodes 23 are provided for one photosensitive portion 3a, but the two control electrodes 23 on both sides are charged (electrons e) by the photosensitive portion 3a. Is used to form a barrier for preventing the electric charge from flowing out to the adjacent photosensitive portion 3a, and when the two photosensitive portions 3a are used as a set, the adjacent photosensitive portion Since a barrier is formed by any one of the photosensitive portions 3a between the potential wells 24 of 3a, it is sufficient to provide three control electrodes 23 for each photosensitive portion 3a. With this configuration, the occupation area per one photosensitive portion 3a is reduced, and it is possible to suppress a decrease in resolution in the line-of-sight direction while using two photosensitive portions 3a as a set.

  Here, as shown in FIG. 14, the numbers (1) to (6) are assigned to the control electrodes 23 in order to distinguish the three control electrodes 23 provided in the two photosensitive portions 3a. Attached. The two photosensitive portions 3a having the control electrodes 23 to which the numbers (1) to (6) are assigned correspond to one line-of-sight direction and constitute pixels in the image sensor. It is desirable to provide an overflow drain in association with the photosensitive portion 3a for each pixel.

  14A and 14B show a state in which a control voltage + V is applied to the control electrode 23 in a different application pattern (a state in which the control voltage + V is applied between a substrate electrode (not shown) provided on the semiconductor substrate and the control electrode 23). As can be seen from the shape of the potential well 24, a positive control voltage + V is applied to the control electrodes (1) to (3) of the two photosensitive portions 3a to be one pixel in FIG. In addition, a positive control voltage + V is applied to the central control electrode (5) among the remaining control electrodes (4) to (6). In (b), a positive control voltage + V is applied to the central control electrode (2) of the control electrodes (1) to (3), and positive to the remaining control electrodes (4) to (6). The control voltage + V is applied. That is, the application pattern of the control voltage + V applied to the two photosensitive portions 3a constituting one pixel is alternately replaced. The timing of switching the application pattern of the control voltage + V applied to the two photosensitive portions 3a is the timing of the opposite phase (the phase is 180 degrees different) in the modulation signal. In addition, except for the period in which the control voltage + V is simultaneously applied to the three control electrodes 23 provided in each photosensitive portion 3a, one central control electrode 23 (that is, the control electrode) provided in each photosensitive portion 3a. (2) The control voltage + V is applied only to (5)), and the other control electrodes 23 are kept at 0V.

  For example, in the case where charges corresponding to the received light amounts A0 and A2 are alternately generated in the two photosensitive portions 3a constituting one pixel, as shown in FIG. 11, one of the photosensitive portions 3a corresponds to the received light amount A0. While the control voltage + V is applied to the three control electrodes (1) to (3) in order to generate charges, the other photosensitive portion 3a has one to hold the charge corresponding to the received light quantity A2. A control voltage + V is applied only to the control electrode (5). Similarly, while the control voltage + V is being applied to the three control electrodes (4) to (6) in order to generate a charge corresponding to the received light amount A2 in one photosensitive portion 3a, the other photosensitive region is exposed. In the unit 3a, the control voltage + V is applied only to one control electrode (2) in order to hold the charge corresponding to the received light quantity A0. In addition, the control voltage + V is applied only to the control electrodes (2) and (5) except for the period in which charges corresponding to the received light amounts A0 and A2 are generated. FIGS. 3B and 3C show the timing of applying the control voltage + V to the control electrodes (1) to (6) when accumulating charges corresponding to the received light amounts A0 and A2. In the figure, the hatched portion indicates a state where the control voltage + V is applied, and the blank portion indicates a state where no voltage is applied to the control electrodes (1) to (6).

  The same applies to the case where the charges corresponding to the received light amounts A1 and A3 are generated in the two photosensitive portions 3a constituting one pixel, and the case where the charges corresponding to the received light amounts A0 and A2 are generated is different from the control electrode 23. The only difference is that the timing at which the control voltage + V is applied differs by 90 degrees in the phase of the modulation signal. In addition, the charge is transferred from the imaging region to the accumulation region between a period for generating charges corresponding to the received light amounts A0 and A1 and a period for generating charges corresponding to the received light amounts A1 and A3. That is, charges corresponding to the received light amount A0 are accumulated in the potential well 24 corresponding to the control electrodes (1) to (3), and charges corresponding to the received light amount A2 correspond to the control electrodes (4) to (6). When accumulated in the potential well 24, the charges corresponding to the received light amounts A0 and A2 are taken out. Next, charges corresponding to the received light amount A1 are accumulated in the potential well 24 corresponding to the control electrodes (1) to (3), and charges corresponding to the received light amount A3 are applied to the control electrodes (4) to (6). When accumulated in the corresponding potential well 24, charges corresponding to these received light amounts A1 and A3 are taken out to the outside. By repeating such an operation, the charges corresponding to the received light amounts A0, A1, A2, and A3 in the four sections can be taken out of the light detecting element 3 by two reading operations, and the extracted charges are used. The phase difference ψ can be obtained. For example, in order to obtain an image of 30 frames per second, the period for generating charges corresponding to the received light amounts A0 and A1 and the period for generating charges corresponding to the received light amounts A1 and A3 are shorter than 1/60 second. A short period.

  In the above example, the control voltage applied simultaneously to the three control electrodes 23 ((1) to (3) or (4) to (6)) and one control electrode 23 ((2) or (5)) Since the control voltage applied only to is equal, the area of the potential well 24 changes, but the depth of the potential well 24 is equal. In this case, the charges generated at the control electrode 23 ((1) (3) or (4) (6)) to which no control voltage is applied flow into the potential well 24 with a similar probability. That is, by applying the control voltage + V to only one of the three control electrodes 23 constituting the photosensitive portion 3a, the region functioning as the charge accumulation portion 3c and all the three control electrodes 23 are applied. A similar amount of charge flows into both the region to which the control voltage + V is applied. That is, since the noise component flowing into the potential well 24 holding the charge is relatively large, the dynamic range is lowered.

  Therefore, as shown in FIG. 15, the control voltage applied simultaneously to each of the three control electrodes (1) to (3) or (4) to (6) provided in the two photosensitive portions 3a in the set is 1 It is set to be lower than the control voltage applied only to the individual control electrodes (2) or (5), and the depth of the small area potential well 24 is set to be smaller than the depth of the large area potential well 24. Is desirable. As described above, the potential well 24 that mainly generates charges (electrons e) is made deeper than the potential well 24 that mainly holds charges, so that the control electrode (1) to which no control voltage is applied is applied. Charges generated at the sites corresponding to (3) or (4) and (6) are likely to flow into the deeper potential well 24. That is, as compared with the case where a constant control voltage + V is applied to the control electrode 23, the noise component flowing into the potential well 24 holding the charge can be reduced.

  In the configuration example of the distance image sensor described above, four periods corresponding to the received light amounts A0, A1, A2, and A3 are set so that the phase interval is 90 degrees in one cycle of the modulation signal. If the phase with respect to the modulation signal is known, the four periods can be set at appropriate intervals other than 90 degrees. However, the formula for obtaining the phase difference ψ differs if the interval is different. In addition, the period of taking out the charge corresponding to the amount of received light in the four periods is within one period of the modulation signal as long as the reflectance of the object and the external light component do not change and the phase difference ψ does not change. It is not essential to take out four signal charges. Furthermore, when there is an influence of disturbance light such as sunlight or illumination light, it is desirable to arrange an optical filter that transmits only the wavelength of light emitted from the light source 5 in front of the photosensitive portion 3a. In the configuration example described with reference to FIGS. 14 and 15, three control electrodes 23 are associated with each photosensitive portion 3a. However, four or more control electrodes 23 may be provided. In the above example, the same configuration as the FT type CCD image sensor is adopted, but the same configuration as the interline transfer (IT) method and the frame interline transfer (FIT) method is adopted. Is also possible.

It is a block diagram of the human body detection sensor of this embodiment. It is a block diagram of the principal part same as the above. (A) (b) is explanatory drawing of a detection area same as the above. It is explanatory drawing of a detection area same as the above. (A)-(c) is explanatory drawing explaining the setting method of a dead zone. (A) (b) is explanatory drawing which showed the dead zone in a horizontal surface. It is operation | movement explanatory drawing same as the above. (A) (b) is operation | movement explanatory drawing explaining another operation | movement same as the above. It is operation | movement explanatory drawing explaining another operation | movement same as the above. (A) (b) is operation | movement explanatory drawing explaining another operation | movement same as the above. It is operation | movement explanatory drawing of the photon detection element used for the same as the above. It is operation | movement explanatory drawing of the principal part of the photon detection element used for the same as the above. It is a top view of the photon detection element used for the same as the above. It is operation | movement explanatory drawing of the principal part of the photon detection element used for the same as the above. It is operation | movement explanatory drawing of the principal part of the photon detection element used for the same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Human body detection sensor 2 Distance image sensor part 3 Photodetection element 5 Light emission source 10 Signal processing circuit

Claims (7)

A distance image sensor unit that images a target space and generates a distance image having a distance value as a pixel value;
Area setting means for removing the range up to a substantially constant height from the detection area using information on the installation height of the distance image sensor unit and the line-of-sight direction for each pixel of the distance image;
A human body detection sensor comprising: a human body detection unit that detects the presence or absence of a person in the detection area set by the area setting unit based on a distance image input from the distance image sensor unit .   The area setting means divides the horizontal plane into a plurality of areas at concentric boundaries centering on the installation position of the distance image sensor unit, and for each area, the upper limit value of the pixel value of the pixel corresponding to each area The human body detection sensor according to claim 1, wherein the upper limit value is set in a stepwise manner so that an upper limit value increases in an area farther from the installation position.   The human body detection sensor according to claim 1, wherein the area setting unit limits a detection area within a range of a certain distance from an installation position of the distance image sensor unit in a horizontal plane.   A direction detection unit that detects a movement direction of the person detected by the human body detection unit; and a signal output unit that outputs a detection signal of the human body detection unit to the outside, and the signal output unit is detected by the direction detection unit. The human body detection sensor according to claim 1, wherein it is determined whether or not to output a detection signal to the outside in accordance with the moved direction.   5. The human body detection sensor according to claim 4, wherein the signal output unit does not output the detection signal to the outside if the moving direction detected by the direction detection unit is a direction away from a specific point in the target space. .   A height information detection unit that detects height information of a person detected by the human body detection unit using the installation height of the distance image sensor unit and the pixel value and line-of-sight direction information of each pixel; The human body detection sensor according to claim 1, further comprising a height information output unit configured to output height information detected by the information detection unit to the outside.   A background image registration unit that registers a distance image input from the distance image sensor unit as a background image at a timing of at least one of when the power is turned on or when a warning is set, and the human body detection unit includes the distance image sensor The human body detection sensor according to claim 1, wherein presence / absence of a person is detected from a difference image between a distance image input from a unit and the background image.

Images