JP5598100B2 - Object detection device - Google Patents

Description

  The present invention relates to an apparatus for detecting an object present in a monitoring area.

  A technique for detecting an object by analyzing reflected light of a scanning light using a laser radar that scans a three-dimensional space in a main scanning direction and a sub-scanning direction with a scanning light for distance measurement is, for example, an intruder in a monitoring area This technique can also be used in the field of monitoring (for example, Patent Document 1).

JP 2004-212129 A

  The above-mentioned laser radar is installed at a height where the line of sight from the entire monitoring area is good. When the monitoring area covers a wide area from near to far of the laser radar, the scanning light irradiated to the monitoring area from the light emitting means of the laser radar is diffusely reflected on the surface of the irradiated object, and the reflected light Is received by the light receiving means of the laser radar. Since the reflected light reaches the laser radar while diffusing, the intensity of the reflected light received by the light receiving means becomes weaker in inverse proportion to the square of the distance from the laser radar to the scanning light irradiation point. Therefore, in order for the light receiving means to receive the reflected light from the distant monitoring area with the intensity that can be analyzed, the scanning light output from the light emitting means needs to have an appropriate intensity.

  However, if the intensity of the scanning light is increased in accordance with the remote monitoring area, the intensity of the reflected light received from the nearby monitoring area may be too strong. If the intensity of the reflected light received is too strong, the output signal of the light receiving means corresponding to the received light intensity of the reflected light is optically saturated and the output waveform is distorted, and correct object detection cannot be performed. As a result, there arises a problem that, for example, it is erroneously determined that the ground surface of the nearby monitoring area is at a higher position than the actual position.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to irradiate scanning light from a laser radar to a monitoring area, and receive and analyze the reflected light by the laser radar, thereby detecting an object present in the monitoring area. It is an object of the present invention to provide an object detection device capable of accurately detecting an object in a monitoring area even when the monitoring area is widely distributed from near to far in the laser radar.

In order to achieve the above object, the object detection apparatus according to the first aspect of the present invention scans the monitoring area in a predetermined scanning direction by reflecting the laser beam output from the laser projection unit by the scanning mirror. and light, by receiving the reflected light of the scanning light to the light receiving unit is reflected by the scanning mirror, the apparatus for detecting the position of those bodies present in the monitoring area, said scanning mirror, the laser With respect to the light projecting unit and the light receiving unit, the scanning light having the same beam diameter is applied to an irradiation point closest to the laser light projecting unit in the monitoring region and an irradiation point farthest from the laser light projecting unit in the scanning direction. The reflected light of the scanning light that is reflected and is farther from the laser projection unit in the scanning direction is larger in the scanning area. Characterized in that it is arranged in a relative positional relationship which reflects toward the light receiving unit in the light flux width.

  According to the object detection device of the present invention as set forth in claim 1, the larger the luminous flux width of the reflected light reflected by the scanning mirror toward the light receiving unit, the higher the efficiency with which the light receiving unit receives the reflected light. . Therefore, the reflection of the scanning light irradiated to the part far from the laser projecting unit is larger than the intensity of the reflected light of the scanning light irradiated to the part near the laser projecting unit in the scanning direction in the scanning region. The light receiving efficiency, in other words, the optical intensity gain is increased.

  Therefore, the intensity of the scanning light and the electrical gain of the light receiving unit are dynamically changed depending on whether the scanning light is applied to the monitoring region near the laser projection unit in the scanning direction or the remote monitoring region. The reflected light is received with a high intensity from a remote monitoring area where the degree of diffusion of the reflected light is large, and the reflected light with a low intensity is received from a nearby monitoring area where the degree of diffusion of the reflected light is small. Can be received. Thereby, the reflected light from the distant monitoring region can be analyzed to an intensity that can be analyzed, and the reflected light from the nearby monitoring region can be suppressed to an intensity that does not optically saturate. Therefore, even if the monitoring area scanned by the scanning light from the laser radar is widely distributed from near to far of the laser radar, the object in the monitoring area is reflected by the reflected light of the scanning light received by the laser radar from the monitoring area. It can be detected accurately.

  The object detection device of the present invention described in claim 2 is the object detection device of the present invention described in claim 1, wherein the laser projection unit and the light receiving unit output the laser projection unit. Laser light and the reflected light received by the light receiving unit are respectively irradiated on the same reflecting surface of the plurality of reflecting surfaces of the scanning mirror at intervals in the rotation axis direction of the scanning mirror, and The optical paths are arranged so as not to interfere with each other.

  According to the object detection device of the present invention described in claim 2, in the object detection device of the present invention described in claim 1, the laser beam from the laser projection unit reflected by the same reflecting surface of the scanning mirror. And the optical path of the reflected light received by the light receiving unit can be arranged on the same path in a plane orthogonal to the rotation axis of the scanning mirror. Thereby, the magnitude | size of the light beam width of the reflected light which a light-receiving unit light-receives can be changed with the rotation angle of the scanning mirror synchronized with the irradiation location of the scanning light in a monitoring area | region changing in a scanning direction.

  Furthermore, the object detection device of the present invention described in claim 3 is the object detection device of the present invention described in claim 1 or 2, wherein the light receiving unit has a lens diameter at least equal to or greater than the maximum luminous flux width of the reflected light. It has the focusing lens which has.

  According to the object detection device of the present invention described in claim 3, in the object detection device of the present invention described in claim 1 or 2, the focusing lens of the light receiving unit that receives the reflected light is greater than or equal to the maximum luminous flux width of the reflected light. Therefore, even if the beam width of the reflected light changes in accordance with the change in the scanning direction in the scanning area, the light receiving unit can reliably receive the reflected light. it can.

  According to the present invention, even when the monitoring area scanned by the scanning light from the laser radar is widely distributed from near to far from the laser radar, the monitoring is performed by the reflected light of the scanning light received by the laser radar from the monitoring area. An object in the area can be detected accurately.

It is a schematic block diagram which shows the object detection apparatus which concerns on one Embodiment of this invention. It is explanatory drawing which shows the relationship between the monitoring area | region scanned with the scanning light of FIG. 1, and the installation position of a laser radar head. (A), (b) is the top view and side view which show the positional relationship of the laser projection unit of FIG. 1, a light reception unit, and a polygon mirror. (A), (b) shows the state of reflection of laser light from the laser projection unit by the polygon mirror of FIG. 1, when the scanning light scans the scanning start end in the main scanning direction of the monitoring region and the scanning end end. It is explanatory drawing each shown when scanning. (A), (b) shows how reflected light is reflected to the light receiving unit by the polygon mirror in FIG. 1, when the scanning light scans the scanning start end in the main scanning direction of the monitoring region and the scanning end end. It is explanatory drawing each shown about when.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an object detection apparatus according to an embodiment of the present invention. The object detection apparatus shown in FIG. 1 scans a monitoring area with scanning light and detects an object that has entered the monitoring area with reflected light. The laser radar head 5 outputs scanning light and receives the reflected light. And a control device 6 that performs detection processing of an object in the area based on the scanning light and the reflected light.

  When the object detection apparatus of FIG. 1 is used, for example, for detecting an intruding object in a monitoring area in a site, the laser radar head 5 has an upper end of a support B that can see the entire monitoring area A as shown in the explanatory diagram of FIG. Installed in the vicinity. By installing the laser radar head 5 at such a high place, the entire monitoring area A can be scanned with the scanning light LB1 from the laser radar head 5. In the present embodiment, it is assumed that the laser radar head 5 is installed at the ground height H [m] of the column B.

  In the present embodiment, the monitoring area A is Lmin [m] to Lmax [m] from the column B in the main scanning direction X (corresponding to the scanning direction in the claims) of the scanning light LB1 from the laser radar head 5. Extends to the range. This Lmin [m] may be set to Lmin = 0 [m]. That is, if the scanning light LB1 from the laser radar head 5 arrives, the monitoring area A can be extended from the base of the column B.

Further, θ in FIG. 2 indicates a scanning angle in the main scanning direction X with respect to the monitoring region A of the scanning light LB1. This scanning angle θ can be expressed as θ = tan ⁻¹ (L / H), where L is the distance from the laser radar head 5 to the column B of the scanning portion of the scanning light LB1 in the main scanning direction X. The scanning angle θ is smaller as the scanning position of the scanning light LB1 in the main scanning direction X is closer to the laser radar head 5 to the column B, and is larger as the scanning position is farther (provided that θ <90 °).

  As shown in FIG. 1, the laser radar head 5 includes a laser projection unit 1 that intermittently outputs the laser beam LB, and a polygon mirror that scans the laser beam LB in the vertical and horizontal directions to form the scanning beam LB1. 11 and the galvanometer mirror 12, the light receiving unit 2 that receives the reflected light LB2 of the scanning light LB1 irradiated on the object after being reflected by the galvanometer mirror 12 and the polygon mirror 11, a polygon scanner 11a that rotates the polygon mirror 11, and a galvanometer. A galvano scanner 12a for rotating the mirror 12;

  The polygon mirror 11 (corresponding to the scanning mirror in the claims) has a hexahedron that rotates at high speed, and the center of two opposing surfaces (upper and lower surfaces) excluding the mirrored four side surfaces is the rotation axis. It is configured to be rotated by the polygon scanner 11a. The laser beam LB is reflected by any one of the four side surfaces of the polygon mirror 11 so that the laser beam LB is scanned in the main scanning direction (vertical scanning direction) X.

  The galvanometer mirror 12 is connected to a side surface of a rotating shaft that is reciprocally rotated within a limited angular range by the galvano scanner 12a, and is reciprocally oscillated by the reciprocating rotation of the rotating shaft. The laser light LB is reflected by one surface of the galvanometer mirror 12 so that the laser light LB is scanned in the sub-scanning direction (horizontal scanning direction) Y.

  The polygon scanner 11a and the galvano scanner 12a rotate the polygon mirror 11 and oscillate the galvano mirror 12 at a rotational speed commanded by a speed command from a controller 13 of the controller 6 to be described later. Further, the polygon scanner 11 a and the galvano scanner 12 a output angle information indicating the rotation angle of the polygon mirror 11 and the swing angle of the galvanometer mirror 12 to the controller 13. The polygon mirror 11 and the galvanometer mirror 12 described above are merely examples, and the scanning optical system of the laser beam LB is not limited to the illustrated configuration.

  In the laser radar head 5 having the configuration shown in FIG. 1, the scanning direction (main scanning direction X) of the laser beam LB by the polygon mirror 11 coincides with the direction of approaching and separating from the column B in the monitoring area A as shown in FIG. It attaches to the support | pillar B so that it may do. Therefore, the scanning direction (sub-scanning direction Y) of the laser light LB by the galvanometer mirror 12 extends in the width direction of the monitoring area A in FIG. 2, that is, the front and back direction of the paper surface in FIG.

  The control device 6 shown in FIG. 1 has a controller 13 and a distance calculator 14. The controller 13 and the distance calculator 14 can be configured by separate microcomputers, or can be configured by a single microcomputer.

  The controller 13 intermittently outputs a projection command to the laser projection unit 1. This light projection command is also output to the distance calculator 14 in parallel.

  The distance calculator 14 receives the above-described light projection command from the controller 13 and a light reception timing signal output from the light receiving unit 2 when the reflected light LB2 is received. The distance calculator 14 is a laser radar head of an object present on the optical path of the scanning light LB1 based on the time difference from the input of the light projection command to the input of the light reception timing signal and the light velocity V [m / sec]. The distance from 5 is calculated, and distance information indicating the calculated distance is output to the controller 13.

  As described above, the controller 13 outputs speed commands to the polygon scanner 11a and the galvano scanner 12a, respectively. The rotation speed of the polygon mirror 11 and the oscillating speed of the galvano mirror 12 commanded by each speed command are the pitch of the scanning light LB1 that is intermittently irradiated in the main scanning direction X and the sub-scanning direction Y of the monitoring area A in FIG. That is, it is determined according to the spatial resolution of the scanning light LB1 in the monitoring area A.

  Further, the controller 13 can calculate the rotation angle of the polygon mirror 11 and the swing angle of the galvano mirror 12 based on the angle information respectively input from the polygon scanner 11a and the galvano scanner 12a. Therefore, the controller 13 determines the coordinate value of the part of the monitoring area A to which the scanning light LB1 is irradiated by the light projection command output to the laser light projection unit 1 based on the angle information received from the polygon scanner 11a or the galvano scanner 12a. Can be specified. The identified coordinate value is used when detecting an object that has entered the monitoring area A based on the distance information from the distance calculator 14.

  Here, the spatial resolution of the scanning light LB1 in the main scanning direction X out of the spatial resolution of the scanning light LB1 in the monitoring region A will be described. When the rotational angular velocity of the polygon mirror 11 is ω [° / sec] (optical angle) and the output frequency of the laser beam projection unit 1 of the laser beam LB that is the source of the scanning beam LB1 is S (Hz), the main frequency is The spatial resolution D in the main scanning direction X of the scanning light LB1 that scans a position at a distance L from the laser radar head 5 or the support column B in the scanning direction X is D≈L × tan (ω / S) [m].

  As is apparent from this equation, the spatial resolution D of the scanning light LB1 increases as the location where the scanning light LB1 scans is farther from the laser radar head 5 in the main scanning direction X. Therefore, the repetition frequency S is determined so that the necessary spatial resolution D can be obtained when the scanning light LB1 scans the monitoring area A that is a distance Lmax away from the laser radar head 5 in the main scanning direction X.

  Also, since the speed of light is V [m / sec], the time required for the scanning light LB1 to reach the monitoring area A that is a distance Lmax away from the laser radar head 5 and the reflected light LB2 return to the laser radar head 5. Can be represented by approximately 2 L / V [sec]. Therefore, the repetition frequency S is set to V / 2L [Hz] or less.

  By the way, the intensity of the reflected light LB2 received by the light receiving unit 2 becomes weaker as the location in the monitoring area A irradiated with the scanning light LB1 is farther from the laser radar head 5 in the main scanning direction X. This is because the reflected light LB2 from the irradiation spot of the scanning light LB1 arrives at the laser radar head 5 while diffusing, and its intensity is inversely proportional to the square of the distance L from the laser radar head 5 to the irradiation spot of the scanning light LB1. Because it weakens.

  Therefore, the intensity of the scanning light LB1 irradiated to a position farthest from the laser radar head 5 in the main scanning direction X and at a distance Lmax from the laser radar head 5 in the monitoring area A is an intensity that can be detected by the reflected light LB2 therefrom. Therefore, it is necessary that the light intensity is received by the light receiving unit 2. Therefore, the intensity of the laser beam LB output from the laser projection unit 1 is such that the reflected light LB2 from the monitoring region A farthest from the laser radar head 5 in the main scanning direction X is received by the light receiving unit 2 with sufficient intensity. Determine the strength.

  On the other hand, when the irradiation position of the scanning light LB1 is close to the laser radar head 5 in the main scanning direction X, the distance L from the laser radar head 5 to the irradiation position of the scanning light LB1 is short. The degree of diffusion until reaching the position is smaller than that in the case where the irradiated portion of the scanning light LB1 is far from the laser radar head 5 in the main scanning direction X. Therefore, for example, when the scanning light LB1 is irradiated to the other monitoring area A with the same intensity as the irradiation of the scanning light LB1 at the distance Lmax farthest from the laser radar head 5 in the main scanning direction X, the distance L There is a possibility that the intensity of the reflected light LB2 that is inversely proportional to the square is too strong, and the light reception timing signal output from the light receiving unit 2 that receives the reflected light LB2 is optically saturated. When the light reception timing signal is optically saturated, the accuracy of the three-dimensional object recognition by the laser radar is adversely affected.

  For this reason, it is necessary to reduce the intensity of the reflected light LB2 of the scanning light LB1 as the portion of the monitoring area A irradiated with the scanning light LB1 is closer to the laser radar head 5 in the main scanning direction X. Therefore, in the object detection apparatus of the present embodiment, the laser projection unit 1 and the light receiving unit 2 and the polygon mirror 11 are arranged so as to have a positional relationship as shown in FIGS. 3 (a) and 3 (b). Yes.

  As shown in the plan view and the side view in FIGS. 3A and 3B, the laser projection unit 1 and the light receiving unit 2 are arranged in the direction of the rotation axis of the polygon mirror 11 (the horizontal direction in FIG. 3B). It arrange | positions so that it may space and may overlap in the plane orthogonal to a rotating shaft direction.

  The laser projection unit 1 has a laser light source 1a and a focusing lens 1b for correcting the beam diameter. The laser beam LB corrected to a desired beam diameter by the focusing lens 1 b is irradiated on one of the four reflecting surfaces 11 b of the rotating polygon mirror 11 and reflected toward the galvanometer mirror 12.

  The light receiving unit 2 includes a light receiving element 2a and a condenser lens 2b. The reflected light LB2 guided from the monitoring area A through the galvanometer mirror 12 is irradiated on the same reflecting surface 11b as the laser beam LB of the rotating polygon mirror 11 is irradiated, and is reflected toward the light receiving unit 2. The As shown in FIG. 3 (b), the irradiation position of the laser beam LB and the irradiation position of the reflection light LB2 on the reflecting surface 11b are spaced apart in the direction of the rotation axis of the polygon mirror 11, so that the optical path of the laser beam LB And the optical path of the reflected light LB2 do not interfere with each other. The reflected light LB2 reflected by the polygon mirror 11 is condensed by the condenser lens 2b, guided to the light receiving element 2a, and received.

  Since the laser projection unit 1 is arranged with respect to the polygon mirror 11 as described above, the beam diameter of the laser beam LB (scanning beam LB1) after being reflected by the polygon mirror 11 is the scanning shown in FIG. When the light LB1 is irradiated to the position closest to the laser radar head 5 in the monitoring area A in the main scanning direction X, and when the light LB1 is irradiated to the position farthest from the laser radar head 5 shown in FIG. The same. Although not described with reference to the drawings, the laser beam LB (scanned after reflection) by the polygon mirror 11 is also performed while the scanning light LB1 scans the monitoring area A in the main scanning direction X from the scanning start end to the scanning end end. The beam diameter of the light LB1) does not change.

  In addition, as described above, the light receiving unit 2 is arranged with respect to the polygon mirror 11, so that the light flux width of the reflected light LB2 that can be reflected by the reflecting surface 11b of the polygon mirror 11 toward the light receiving unit 2 is as shown in FIG. As shown in FIG. 5 (b), the scanning light LB1 is irradiated to the position farthest from the laser radar head 5 as shown in FIG. When it is done, it becomes bigger. Although the description with reference to the drawings is omitted, the reflection surface 11b of the polygon mirror 11 faces the light receiving unit 2 while the scanning light LB1 scans the monitoring area A in the main scanning direction X from the scanning start end to the scanning end end. The luminous flux width of the reflected light LB2 that can be reflected from the width shown in FIG. 5 (a) in synchronization with the rotation of the polygon mirror 11 from the angle shown in FIG. 5 (a) to the angle shown in FIG. 5 (b). The width continuously changes to the width shown in FIG.

  As a result, the light receiving efficiency of the reflected light LB2 of the scanning light LB1 is lowered at a position closer to the laser radar head 5 in the monitoring region A where the degree of diffusion that occurs in the reflected light LB2 before reaching the laser radar head 5 is small. It is possible to prevent the light receiving timing signal output from the light receiving unit 2 that has received the light LB2 from being optically saturated.

  Then, the controller 13 uses the distance information from the distance calculator 14 and the coordinate value of the irradiation position of the scanning light LB1 in the monitoring area A specified based on the angle information received from the polygon scanner 11a or the galvano scanner 12a. The object that has entered the monitoring area A is detected, and the detection result is output.

  In the present embodiment, the laser beam LB and the reflected light LB2 are applied to the same reflecting surface 11b of the polygon mirror 11 with an interval in the rotation axis direction of the polygon mirror 11. However, for example, the laser beam LB and the reflected light LB <b> 2 may be configured to irradiate separate reflective surfaces of the polygon mirror 11. In that case, the laser projecting unit 1 and the light receiving unit 2 are arranged separately on both sides of the polygon mirror 11.

  Further, in the present embodiment, a configuration in which the light receiving efficiency of the reflected light LB2 received by the light receiving unit 2 changes depending on the distance from the laser radar head 5 in the main scanning direction X of the monitoring area A will be described as an example. did.

  However, the light receiving efficiency of the reflected light LB2 received by the light receiving unit 2 may be changed depending on the distance from the laser radar head 5 in the sub-scanning direction Y of the monitoring area A. In that case, the sub-scanning direction Y corresponds to the scanning direction in the claims. The laser radar head 5 is configured to scan in the main scanning direction X after scanning the laser beam LB from the laser projection unit 1 in the sub-scanning direction Y. Therefore, in this case, the mirror that scans the laser beam LB in the sub-scanning direction Y corresponds to the scanning mirror in the claims.

DESCRIPTION OF SYMBOLS 1 Laser projection unit 1a Laser light source 1b Condensing lens 2 Light receiving unit 2a Light receiving element 2b Condensing lens 5 Laser radar head 6 Control apparatus 11 Polygon mirror 11a Polygon scanner 11b Reflecting surface 12 Galvano mirror 12a Galvano scanner 13 Controller 14 Distance calculator A Monitoring area B Post LB Laser light LB1 Scanning light LB2 Reflected light X Main scanning direction Y Sub-scanning direction

Claims (3)

The laser beam output from the laser projection unit is reflected by a scanning mirror to form a scanning beam for scanning the monitoring area in a predetermined scanning direction, and the reflected light of the scanning beam is reflected by the scanning mirror to the light receiving unit. by to be received, the device for detecting the position of those bodies present in the monitoring area,
The scanning mirror has an irradiation spot closest to the laser projection unit in the monitoring region and an irradiation spot farthest from the laser projection unit in the scanning direction with respect to the laser projection unit and the light receiving unit. The reflected light of the scanning light that reflects the scanning light having the same beam diameter and whose irradiation spot in the monitoring region is farther from the laser projection unit in the scanning direction is directed toward the light receiving unit with a larger luminous flux width. Arranged in a relative positional relationship to reflect,
An object detection apparatus characterized by that.   In the laser projection unit and the light receiving unit, the laser beam output from the laser projection unit and the reflected light received by the light receiving unit are the same reflection surface among the plurality of reflection surfaces of the scanning mirror. 2. The object detection apparatus according to claim 1, wherein the scanning mirror is irradiated with an interval in the direction of the rotation axis of the scanning mirror and arranged so that the optical paths do not interfere with each other.   The object detection apparatus according to claim 1, wherein the light receiving unit includes a focusing lens having a lens diameter that is at least equal to or larger than a maximum light flux width of the reflected light.

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