JPH11175881A - Object detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform highly accurate object detection without being affected by external environment and noise. SOLUTION: A vehicle detector is constituted of a sensor part 1 and a regression reflection plate 2 to be arranged by facing a reflection surface to the sensor part 1. The sensor part 1 is provided with a floodlighting part 3 to generate light beam by pulse light emission, a light beam scanning part 4 to scan the light beam toward the regression reflection plate 2 and a light receiving part 5 to receive reflected light from the regression reflection plate 2. A level value of light receiving quantity by every light emission timing is fetched and whether a vehicle exists or not in a scanning area of the light beam is detected by a control part 20. In addition, the level value of the light receiving quantity under condition in which no vehicle exists is constantly checked by the control part 20, when the level value of the light receiving quantity falls below a specified threshold value, a floodlighting power control part 19 is driven and a level value of light emitting quantity of a light emitting element of the floodlighting part 3 is raised.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object detector for detecting an object passing a predetermined observation position, such as a vehicle passing a tollgate.

[0002]

2. Description of the Related Art In recent years, with the proposal of non-stop toll booths that allow payments to be made through communication,
A vehicle detector for detecting a vehicle approaching a tollgate is being developed. Conventionally, as this type of vehicle detector, there is a vehicle detector having a configuration in which a sensor unit having a light emitting and receiving unit and a regression reflection plate are arranged to face each other.

FIG. 6 shows an example of installation of the above-mentioned vehicle detector, in which a sensor unit 1 and a retroreflective plate 2 are provided to face each other across a road RD. The sensor unit 1 includes a light emitting unit for irradiating a light beam, a light beam scanning unit for scanning the light beam, and a light beam scanning unit in a housing 1 ′ having a window (not shown) for transmitting and receiving light. It is configured to house a light receiving unit for receiving the reflected light, a control circuit on which a driving circuit of a light projecting unit and a light beam scanning unit and a control circuit for vehicle detection are mounted.

The regression reflection plate 2 has a function as a reflection surface by arranging reflective optical elements such as prisms in a longitudinal direction along the length of the plate surface.
The reflecting surface is provided so as to face the sensor unit 1 and the length direction of the plate is set along the vertical direction.

In the vehicle detector having the above-described structure, the light projecting unit emits light by receiving a driving pulse from the driving circuit at predetermined time intervals, and emits light.
Is scanned by the light beam scanning unit and irradiated on the regression reflection plate 2. This scanning is performed so as to spread in a fan shape in the length direction of the regression reflection plate 2. Each light applied to the regression reflection plate 2 is specularly reflected on the reflection surface, and the light received by the sensor unit 1 is received. Incident on the part.

FIG. 6 shows an example in which the vehicle 25 has not reached the scanning area of the light beam BM.
Since the reflected light corresponding to each light applied to the regression reflection plate 2 is incident on the light receiving section, a detection signal indicating "no vehicle" is output from the control circuit. Thereafter, when the vehicle 25 moves forward and reaches the scanning area of the light beam BM, the light beam is blocked by the vehicle body, so that the amount of reflected light incident on the light receiving unit is drastically reduced. As a result, the control circuit determines that the vehicle 25 exists in the scanning region of the light beam, and outputs a detection signal indicating "vehicle is present".

[0007]

Since the above-mentioned vehicle detector is installed outdoors, if a dirt adheres to the reflection surface of the regression reflection plate 2 or the window surface of the light emitting / receiving window due to long-term use, the light is not received. There is a problem that the light receiving amount of the portion is reduced and the detection accuracy is reduced. Further, when there are rainfalls such as rain and snow in the atmosphere, these precipitations obstruct the path of the light beam or the reflected light, and similarly, there is a problem that the light receiving amount of the light receiving unit is reduced.

When the vehicle 25 is located in the scanning area of the light beam BM, the light beam BM is reflected on the vehicle body of the vehicle 25, and the reflected light is incident on the light receiving portion to increase the amount of received light. There is a possibility that an erroneous detection of “no vehicle” may be made.

The object of the present invention is to provide an object detector having the above-described structure, which is capable of performing high-precision object detection without being affected by an external environment or noise by making improvements for solving the above-mentioned problems. Technical issues.

[0010]

According to a first aspect of the present invention, there is provided a sensor unit, and a recursive reflection plate provided with a reflection surface facing the sensor unit, wherein the sensor unit is configured to emit light by pulse emission. A light projecting unit for projecting a beam, a light beam scanning unit that scans the light beam in the longitudinal direction of the regression reflector, and a reflected light of the scanned light beam from the regression reflector. An object detector including a light receiving unit that receives light includes a light emission power control unit that controls a power value of a light emission amount of the light emitting unit according to a light reception amount of the light receiving unit.

The invention according to claim 3 is based on the fact that the retroreflective plate has a characteristic that the light irradiated on the reflection surface is reflected by rotating the polarization plane by 90 degrees and reflected. In the object detector having the above configuration, the first polarizing filter is provided in front of the light emitting surface of the light emitting unit, and the light passing through the first polarizing filter is provided in front of the light receiving surface of the light receiving unit. A second polarization filter for passing light having a polarization component orthogonal to the polarization direction is provided.

According to the second and fourth aspects of the present invention, the light from the light projecting unit is reflected by the light beam scanning unit at different angles at each light emission timing, and the light from the recursive reflector at each light emission timing. A reflector plate for receiving the reflected light and guiding the reflected light in a direction parallel to the light projecting path is provided, and the light receiving unit is provided at a position adjacent to the light projecting unit with the light receiving surface parallel to the light projecting surface, It is configured to receive the reflected light via the reflector.

[0013]

According to the first aspect of the present invention, the power value of the light emission amount of the light projecting unit is controlled according to the light receiving amount of the light receiving unit. When the amount of received light is reduced due to the influence of the external environment such as precipitation, it is possible to respond by increasing the power value of the amount of emitted light.

According to the third aspect of the present invention, the light beam polarized by the first polarization filter is scanned, and the light having a polarization plane rotated by 90 degrees from the light beam is received via the second polarization filter. Therefore, only the reflected light of the light beam from the regression reflection plate is received, and erroneous detection can be prevented.

According to the second and fourth aspects of the present invention, the reflected light from the recursive reflector is guided in a direction parallel to the light projecting path by the light beam scanning reflector, and the reflected light passing through the reflector is transmitted to the light projecting unit. Since light is received at a position adjacent to the optical system, the optical system can be made compact and the sensor unit can be downsized.

[0016]

FIG. 1 shows an example in which a vehicle detector according to the present invention is installed at a position before a gate (not shown) of a tollgate. 30A and 30B in the figure are concrete islands formed in front of the gate, and the sensor unit 1 is embedded in one of the islands 30A.

On the other island 30B, a first retroreflective plate 2 is provided on the upper surface in accordance with a beam irradiation area from the sensor section 1, and a second retroreflective plate 2 is provided on the inner surface. It is buried and deployed.

In the vehicle detector of this embodiment, the accuracy of detecting a vehicle is greatly improved by improving a part of an optical system and a control circuit of the sensor unit 1.
Specific examples of each configuration and the vehicle detection processing will be described step by step.

FIG. 2 shows the configuration of the optical system of the sensor unit 1 of the vehicle detector. In the figure, reference numeral 3 denotes a light projecting unit for generating a light beam to the regression reflection plate 2, which is composed of a light emitting element 6, such as an LED, a collimating lens 7, and a polarizing filter 8. Reference numeral 4 denotes a light beam scanning unit for scanning the light beam generated by the light projecting unit. The light beam scanning unit 4 includes a galvanomirror 9 and a pulse motor 10 for sequentially changing the inclination of the galvanomirror 9. It consists of possible actuators. Reference numeral 5 denotes a light receiving unit for receiving light of the light beam reflected from the regression reflector 2, and a condenser lens 12 for condensing light and a polarizing filter 13 in front of a light receiving element 11 such as a photodiode. Deployed and configured.

The light emitting element 6 of the light emitting section 3 irradiates light at predetermined time intervals upon receiving a driving pulse from a pulse driving section 16 described later. This light is collimated through a collimator lens 7, is then polarized by a polarizing filter 8 to a predetermined wavelength, and is guided to a galvanomirror 9. The pulse motor 10 rotates according to the light emission timing of the light projecting unit 3. The vertical inclination of the galvanometer mirror 9 changes with the rotation of the motor 10.
The light beam BM is scanned along the length direction of the regression reflection plate 2.

In each scanning direction, when the light beam BM is applied to the reflection surface of the regression reflection plate 2, the light is reflected regularly with the polarization plane rotated by 90 degrees due to the characteristics of the regression reflection plate 2. . The reflected light enters the sensor unit 1 from a light emitting / receiving window (not shown), and is guided by the galvanomirror 9 in a direction parallel to the light emitting path.

The light receiving section 5 is provided at a position adjacent to the light projecting section 3 on the path of the reflected light. The polarizing filter 13 on the light receiving unit 5 side is the same as the polarizing filter 8 on the light projecting unit 3 side, and is arranged with the direction orthogonal to the polarizing filter 8. Only the reflected light of the light beam BM from the regression reflector 2 is incident on the light receiving element 11, and the light receiving element 11 outputs a voltage signal corresponding to the amount of incident light.

When a vehicle having a high reflectance of the regular reflected light is located in the scanning area of the light beam BM, the reflected light from the vehicle is also guided to the light receiving unit 5. However, since the light hitting a metal part such as a vehicle body is reflected while maintaining the angle of the polarization plane, the reflected light is blocked from entering the light receiving element 11 by the polarizing filter 13 to prevent erroneous detection. Can be.

According to the optical system having the above structure, the light projecting unit 3 and the light receiving unit 5 are disposed adjacent to the position below the galvanometer mirror 9, so that the optical system can be made compact and the sensor unit 1 can be integrated. The size can be reduced. Therefore, the sensor section 1 can be buried in the concrete island 30A so as to be inconspicuous, and a practical vehicle detector can be provided.

FIG. 3 shows a specific installation example of the vehicle detector and a vehicle detection area. In the illustrated example, the road width is 350
This is an installation example in which the distance is 0 mm, and the sensor unit 1 is located at a distance of 1100 mm from the road edge and 20 mm from the road surface LD.
It is installed at a height of 0 mm. The retro-reflective plate 2, which is arranged upright, is installed such that the upper end is positioned at a height of 2500 mm from the road surface LD, and the scanning angle of the light beam BM is set to 25 degrees. The scanning region R1 of the light beam BM functions as a vehicle detection region. Note that a region R2 at a height of 230 mm from the road surface LD (here, a size of 2000 mm in width and 400 mm in height) indicates a region where a tow rod for connecting a tow vehicle can be detected.

FIG. 4 shows an electric configuration of the vehicle detector. In addition to the optical system shown in FIG.
Scan driver 14, timing controller 15, pulse driver 16, sample and hold circuit 17, A / D converter 1
8. Each circuit constituting the light projection power control unit 19 and the like is incorporated, and a control unit 20 for controlling these units and performing a vehicle detection process is provided. In the figure, reference numeral 1a denotes the above-mentioned light emitting / receiving window.

The scanning drive unit 14 drives the pulse motor 10 of the light beam scanning unit 4 and outputs a drive pulse at predetermined time intervals based on a command from the control unit 20. The control unit 20 controls the timing control unit 15 to operate at a timing synchronized with the operation of the scan driving unit 14.
Outputs a drive pulse to the light projecting unit 3 according to a timing signal from the timing control unit 15. As a result, the light emission timing of the light emitting element 6 and the galvanomirror 9
Is synchronized with the displacement timing of the inclination of the light beam, and scanning of the light beam toward the regression reflection plate 2 is realized.

The timing signal is also supplied to a sample and hold circuit 17, and the level of the amount of reflected light received at each light emission timing is sampled. This sampling value is digitally converted by the A / D conversion circuit 18 and provided to the control unit 20. The control unit 20 determines whether or not a vehicle is present in the light beam scanning area by comparing the received light level with a predetermined threshold value.

In the above configuration, the scanning drive unit 1
The timing control unit 4 and the timing control unit 15 are controlled so as to output a drive pulse at every predetermined time interval longer than the time for which the light makes one round trip between the sensor unit 1 and the regression reflection plate 2.
In this way, by scanning the light beam at predetermined time intervals and taking in the corresponding reflected light, it is possible to remove the influence of disturbance light such as sunlight.

Further, in this vehicle detector, the retroreflective plate 2
The power value of the light emission amount of the light emitting element 6 is controlled so as to be able to cope with a decrease in the light reception amount when dirt adheres to the light transmitting / receiving window 1a or when rain or the like exists in the atmosphere. This control is performed by the control unit 20 and the light projection power control unit 19. The control unit 20 receives the light in the state where the vehicle is not detected by the output value from the A / D conversion circuit 18. Always check the level. When the light receiving level falls below a predetermined threshold, the light emitting power control unit 19 is controlled to increase the power value of the light emission amount of the light emitting element 6. As a result, even when the power ratio of the reflected light to the light beam is reduced due to the external factors as described above, it is possible to secure a light receiving amount at a level required for vehicle detection and to stabilize the detection operation. it can.

Although the above-described configuration has been described as a vehicle detector in this embodiment, this configuration is not limited to vehicle detection, and can be applied as a detector for a moving object passing a predetermined observation position. It is.

FIG. 5 shows the principle of vehicle detection in the vehicle detector. (C) in the figure shows the scanning direction of the light beam BM along the time axis, and here, 18 ms.
Is set so that scanning for one cycle of lower → uper → lower is performed within the time period. (A) and (B) show the result of comparison between the received light level with respect to the light beam BM and the threshold value for vehicle detection in accordance with the timing of (C). The state in which the reflected light falls below the threshold value is determined by the level 1 signal.
, Respectively.

In a state where no vehicle exists in the scanning region of the light beam BM (shown in FIG. 7A), a light receiving amount equal to or larger than the threshold value is obtained in any scanning direction. Therefore, as shown in (A), a comparison result of level 1 is always obtained, and in response to this, the control unit 20 outputs a determination result of "no vehicle".

On the other hand, in a state where the vehicle is present in the scanning area of the light beam BM (shown by (b) in the drawing), the light beam irradiated in a direction higher than the height of the vehicle is higher than the threshold value. Is obtained, but the received light amount with respect to the light beam applied to the area where the vehicle exists is below the threshold value. Therefore, in this case, as shown in (B), a comparison result in which the level becomes 0 is obtained within a partial period of the scanning for one cycle, and a determination result of "vehicle present" is output.

[0035]

According to the first aspect of the present invention, the power value of the light emission amount of the light projecting unit is controlled in accordance with the amount of light reflected from the regression reflection plate. When the amount of received light is reduced due to contamination of the light emitting / receiving window of the unit or the influence of precipitation in the atmosphere, the power value of the amount of emitted light can be increased to secure the amount of received light required for object detection.
Therefore, the detection operation can be stabilized, and a highly reliable detection result can be obtained.

According to the third aspect of the present invention, the first polarizing filter is provided on the light projecting section side to scan the polarized light beam, and the second polarizing filter on the light receiving section side is used to scan the light beam. Since only the light whose polarization plane is rotated by 90 degrees, that is, the reflected light of the light beam from the retroreflector, is received, it is possible to prevent noise such as reflected light from an object to be detected from entering the light receiving unit. Therefore, the detection accuracy of the object can be greatly improved.

According to the second and fourth aspects of the present invention, the reflected light from the regression reflector is guided in a direction parallel to the light projecting path by the light beam scanning reflector, and the position adjacent to the light projecting portion in the path of the reflected light. Since the light receiving section is disposed to receive the reflected light via the reflecting plate, the optical system can be made compact and the sensor section can be downsized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of installation of a vehicle detector according to one embodiment of the present invention.

FIG. 2 is a perspective view illustrating a configuration of an optical system of a sensor unit.

FIG. 3 is a front view showing a specific installation example of a vehicle detector and a detection area.

FIG. 4 is a block diagram showing a configuration of a vehicle detector.

FIG. 5 is a timing chart showing the principle of vehicle detection.

FIG. 6 is a front view showing an example of installation of a conventional vehicle detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor part 2 Retroreflective plate 3 Light emitting part 4 Light beam scanning part 5 Light receiving part 9 Galvano mirror 8, 13 Polarizing plate 19 Light emitting power control part 20 Control part BM light beam

Claims (4)

[Claims] 1. A sensor device, comprising: a sensor unit; and a recursive reflection plate provided with a reflection surface facing the sensor unit, wherein the sensor unit includes a light projecting unit for projecting a light beam by pulsed light emission. An object detector comprising: a light beam scanning unit that scans the light beam in the longitudinal direction of the regression reflector; and a light receiving unit that receives the reflected light of the scanned light beam from the regression reflector. The object detector according to claim 1, further comprising a light emission power control unit that controls a power value of a light emission amount of the light emitting unit according to a light reception amount of a light receiving unit. 2. The light beam scanning section reflects light from the light projecting section at different angles for each light emission timing, and receives light reflected from a regression reflector at each light emission timing to project light. A light guide for guiding the light in a direction parallel to the light projecting portion, the light receiving portion is provided at a position adjacent to the light projecting portion with a light receiving surface parallel to the light projecting surface, and receives the reflected light via the reflector. The object detector according to claim 1. 3. A sensor unit, and a regression reflection plate provided with a reflection surface facing the sensor unit, wherein the sensor unit includes a light projecting unit for projecting a light beam by pulsed light emission. An object detector comprising: a light beam scanning unit that scans the light beam in the longitudinal direction of the regression reflector; and a light receiving unit that receives the reflected light of the scanned light beam from the regression reflector. In the above, a first polarizing filter is provided in front of a light projecting surface of the light projecting unit, and a light beam passing through the first polarizing filter is orthogonal to a front of a light receiving surface of the light receiving unit. An object detector provided with a second polarizing filter for transmitting light having a polarized light component. 4. The light beam scanning section reflects light from the light projecting section at different angles for each light emission timing, and receives light reflected from a regression reflector at each light emission timing to project light. A light guide for guiding the light in a direction parallel to the light projecting portion, the light receiving portion is provided at a position adjacent to the light projecting portion with a light receiving surface parallel to the light projecting surface, and receives the reflected light via the reflector. 4. The object detector according to claim 3, wherein: