JPH06109847A - Optical distance-measuring apparatus - Google Patents

Abstract

PURPOSE:To capture an object under test such as a preceding vehicle or the like by a method wherein the existence direction of the object under test such as the preceding vehicle or the like is estimated and an optical system is operated automatically to the direction. CONSTITUTION:A light-emitting element 2 and a plurality of photodetectors 3, 4 are arranged transversely on a turntable 14, and photodetection areas 43, 44 for the individual photodetectors 3, 4 are set in respectively different ranges so as to be overlapped partly with each other. A mechanism which turns the turntable 14 and its driving motor as well as an operating and control part which turns and controls the driving motor on the basis of the combination of magnitude relationships of the distance measured value or the photodetection intensity of the individual photodetectors 3, 4 are installed. They are operated so that a reflecting body 40 such as a preceding vehicle or the like is always captured inside the overlapped region of the photodetection areas 43, 44.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical distance measuring device which is mounted on a vehicle and is useful for measuring the distance to a preceding vehicle or an obstacle existing in the traveling direction of the vehicle.

[0002]

2. Description of the Related Art Generally, it is necessary to widen a sensing area in an optical distance measuring device that detects a preceding vehicle or an obstacle existing in a traveling direction of a vehicle and measures a distance to the preceding vehicle or the obstacle. is there.

In response to the above demand, if the light emitting area is expanded by devising an optical system, it becomes difficult to receive light due to a decrease in light emitting power density. Therefore, conventionally, a method of scanning a narrow light emitting beam at a wide angle (beam scanning method). It has been known. However, in this beam scanning method, it is necessary to process the position (direction) of the emission beam and the light reception information at the speed of light, and the signal processing system becomes large-scale. Therefore, a method (a multi-beam method) that includes a plurality of light emitting elements to obtain a wide-angle light emitting region is being studied.

FIG. 4 shows a multi-beam type optical distance measuring device (JP-A-61-259185). This device is provided with a plurality of light emitting elements a, b, c, such as laser diodes, in a light transmitter 50, and light beams A, B, from the respective light emitting elements a, b, c driven by a drive circuit 51. C is emitted through the condenser lens 52. On the side of the light receiver 53, the light beams A, B, C
Light reflected by the reflector 53 such as a preceding vehicle or an obstacle,
Light is received by the light receiving element 55 through the condenser lens 54, and the output signal is sent to the distance measuring circuit 57 through the amplifier circuit 56, and the distance measuring circuit reaches the reflector 53 based on the propagation delay time from light emission to light reception. It is configured to measure the distance.
According to the configuration of the light transmitter 50, the measurement can be performed in a wide range, and the condenser lens system 52 is used for the light emitting elements a, b, c.
The size of the entire device can be reduced.

[0005]

However, in the case of the above-described multiple beam system, it is indispensable to provide a plurality of light emitting elements such as laser diodes. The unit price of the current laser diode is much higher than that of the light receiving element, and installing a plurality of laser diodes makes a mass-produced device with high cost. Further, if there is only one light receiving element, the light receiving area cannot be deflected in the direction in which the preceding vehicle exists and the preceding vehicle cannot be captured efficiently.

The present invention has been made in view of the above problems, and a desired wide sensing area can be secured by providing a plurality of light-receiving elements having a low unit price, and the light-receiving areas are different from each other so that a measurement object such as a preceding vehicle is An object of the present invention is to provide a small-sized, space-saving optical distance measuring device capable of estimating the existing direction and capturing an object to be measured by automatically operating the optical system in that direction.

[0007]

In order to achieve the above object, the present invention comprises a light emitting element and a light receiving element, and is based on a propagation delay time from light emission by the light emitting element to light reception by the light receiving element. In a distance measuring device for measuring a distance to a reflector such as a car, one light emitting element and a plurality of light receiving elements are mounted on a turntable, and the light receiving areas of the plurality of light receiving elements are partially adjacent to each other. The reflectors are always captured within the overlapping area of the light receiving areas based on the combination of the driving means for rotating the turntable and the size relationship of the distance measurement values for each light receiving element, which are set in different ranges so that they overlap. And a control means for controlling the drive means.

In the present invention, the control means for controlling the driving means always captures the reflector in the overlapping area of the light receiving areas based on the combination of the magnitude relations of the light receiving intensities of the respective light receiving elements. It may be an operating control means.

[0009]

[Function] When there is no reflected light from a preceding vehicle or the like and the light receiving element does not receive this, the distance measurement value for the light receiving element system becomes "maximum distance". There is a distance measurement value of, that is, "small distance"
Becomes Therefore, based on the combination of the magnitude relations of the distance measurement values for each light receiving element, it can be estimated whether the preceding vehicle is in the left or right direction. If the preceding vehicle or the like is deviated to the left or right based on this judgment, the control means
The direction of the light receiving area is deflected by driving the driving means to rotate the turntable, and the turntable is stopped when the reflector is captured in the overlapping area of the light receiving areas.

The left-right direction of the preceding vehicle or the like can be estimated based on the combination of the magnitude relations of the received light intensities of the respective light-receiving elements. It can always be captured in the overlapping area of the light receiving area.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings.

FIG. 1 shows the system configuration of the optical distance measuring device. In the case of this embodiment, this distance measuring device is assumed to be mounted on a vehicle.

In FIG. 1, the distance measuring device is divided into three parts: a laser radar head 1, a time measuring unit 20, and a signal processing unit 30.

The laser radar head 1 has one light emitting element 2 composed of an LD (laser diode) and two light receiving elements 3 and 4 composed of a PD (pin photodiode). A light-emitting lens (condensing lens) 5 is arranged, and light-receiving lenses (condensing lenses) 6 and 7 having lattice-shaped mechanical filters 8 are arranged in front of the respective light-receiving elements 3 and 4. Reference numeral 9 is an LD drive circuit, and 10 is a light receiving circuit.

The one light emitting element 2 and the two light receiving elements 3 and 4 are mounted on the turntable 14 as shown in FIG. 2, and the lenses 5, 6, and the mechanical filter 8 belonging to them are also included in the turntable 14. Mounted on.
As can be seen from FIG. 2, the light emitting element 2 and its lens 5 are
Although it is drawn on one side of the laser radar head 1 in FIG. 1, it is actually located between the two light receiving elements 3 and 4 and the lenses 6 and 7 thereof as shown in FIG.

The time measuring unit 20 includes a pulse generator 21 for generating a start pulse for the LD drive circuit.
And the light-receiving circuit 10 starts timing by the start pulse.
Time measuring unit 22 that finishes time measurement with a stop pulse from
And a power supply unit 23. In addition, the signal processing unit 3
Reference numeral 0 includes a rangefinder side unit 31 that calculates a distance based on the time data obtained by the time measuring unit 22, and a display unit 32 that displays the result.

Further, the laser radar head 1 rotates the turntable 14 so that the light receiving areas 43 and 44 of the light receiving elements 3 and 4 and the light emitting area (not shown) of the light emitting element 2 are shown in FIG. 2A to 2B, a servo mechanism 11 for deflecting and a drive motor 12 thereof are provided. The current rotation angle of the servo mechanism 11 is detected by the potentiometer 13 that works in conjunction with the drive motor 12.

In the signal processing unit 30, the reflector 40 of the preceding vehicle is always provided with the two light receiving elements 3 as shown in FIG.
As a control means for rotating the turntable 14 so as to capture it in the overlapping area of the four light receiving areas 43 and 44,
A servo operation unit 33 that gives an appropriate command to the drive motor 12 of the servo mechanism 11 is provided. Specifically, the servo operating unit 33 rotates the drive motor 12 relative to the servo mechanism 11 based on the combination of the magnitudes of the measured values of the light receiving elements 3 and 4 measured by the distance meter side unit 31. It gives a command about the presence or absence of and the direction of rotation.

Next, the operation of the above configuration will be described.

In FIG. 1, a pulse generator 21 of the time measuring unit 20 outputs a start pulse to the LD drive circuit 9 of the laser radar head 1. LD drive circuit 9
Drives the LD which is the light emitting element 2 by the trigger of this start pulse to generate a laser pulse. Also,
The start pulse is given to the time measuring unit 22 and the time measuring unit 22 starts counting time. The laser pulse reflected by the reflector 40 (FIG. 2) of the preceding vehicle is received by one or both of the light receiving elements 3 and 4 to generate a current, and the light receiving circuit 10
After being amplified by, the stop pulse is output to the time measuring unit 22. The time measuring unit 22 measures the time interval between the start pulse from the pulse generating unit 21 and the stop pulse from the light receiving circuit 10, and outputs it as time data to the distance meter side unit 31. The distance meter side unit 31 calculates the distance to the preceding vehicle from the time data and outputs it as distance data to the vehicle control unit (ASC ECU).

Here, when the light receiving element does not receive the reflected light, the distance measurement value in the corresponding light receiving element system in the distance meter side portion 31 becomes "maximum", and the distance data indicates "no preceding vehicle". Treated as a signal. However, if there is some distance measurement value, it is determined that there is a preceding vehicle, and it is treated as a signal to that effect.

Next, the relationship with the operation of the optical system will be described.

FIG. 2A shows the case where the reflector 40 of the preceding vehicle is located only within the light receiving area 44 of the left light receiving element 4,
Further, FIG. 2B shows a case where the reflector 40 is located in the light receiving areas 43 and 44 of the left and right light receiving elements 3 and 4, respectively.

For convenience of description, the reflector 40 of the preceding vehicle is first shown.
However, as shown in FIG. 2 (A), it is supposed to be located only within the light receiving area 44 of the light receiving element 4. In this case, the reflected light from the reflector 40 of the preceding vehicle is received only by the light receiving element 4, and the output states of the light receiving elements 3 and 4 are as shown in FIG. At this time, the distance measurement value on the distance meter side portion 31 has a relationship of “maximum distance” for the light receiving element 3 and “small distance” for the light receiving element 4. The servo control unit 33 of the signal processing unit 30 estimates that the preceding vehicle is in the left direction from the magnitude relationship of the signals of the distance measurement values, and causes the servo mechanism 11 to rotate the turntable 14 counterclockwise "left". "Move command" is given. As a result, the drive motor 12 rotates forward, the turntable 14 rotates in the direction of the arrow in FIG. 2B, and the light receiving areas 43 and 44 move to the left. As shown in FIG. 2B, the reflector 40 of the preceding vehicle receives the light receiving area 4
When the light receiving elements 3 and 4 enter the overlapping area, the output states of the light receiving elements 3 and 4 are as shown in FIG. 3B, and the measured distance values are in the “small distance” relationship for both the light receiving elements 3 and 4. Become.
Here, the servo control unit 33 stops the "left movement command".

Contrary to the above, when the reflected light is received only by the light receiving element 3, the distance measurement values have a relationship of "small distance" for the light receiving element 3 and "maximum distance" for the light receiving element 4, and The control unit 33 determines that the preceding vehicle is in the right direction and gives the servo mechanism 11 a “right movement command” for moving the turntable 14 in the clockwise direction. As a result, the drive motor 12 rotates in the reverse direction, the turntable 14 rotates in the clockwise direction from FIG.
3,44 moves to the right. The reflector 40 of the preceding vehicle
When entering the overlapping area of the light receiving areas 43 and 44, the distance measurement values for both the light receiving elements 3 and 4 have a "small distance" relationship, and at that time, the servo control unit 33 stops the "right movement command". When the distance measurement values are “maximum distance” for the light receiving elements 3 and 4, the servo control unit 33 does not give any instruction to the servo mechanism 11.

As described above, in the system of the two light receiving elements 3 and 4, the turntable 14 is rotationally displaced until a certain distance measurement value is obtained, that is, the above "small distance" is obtained. The preceding vehicle can always be captured directly in front of the optical system of the laserator head 1. Therefore, it is possible to widen the distance measurement area without unnecessarily widening the light emission field and without performing unnecessary data processing by scanning a wide range.

In the above embodiment, an instruction is given to the servo mechanism 11 based on the magnitude relationship of the distance measurement values, but the light receiving signal level difference between the two light receiving elements is measured, and proportional rotation control is performed based on the signal. You can also In this case, instead of the servo operating unit 33, the light receiving areas 43 and 44 are always in the overlapping region based on the combination of the magnitude relations of the light receiving intensities of the two light receiving elements 3 and 4 observed by the time measuring unit 22. A control means for controlling the drive motor 12 so as to capture the reflector 40 will be provided.

Further, in the above embodiment, the case of capturing in the horizontal direction has been described. However, in actuality, it is necessary to capture in the vertical direction depending on the road condition. It is practical to install.

[0029]

As described above, according to the present invention, the following excellent effects can be obtained under either structure of claim 1 or 2.

1) Since a desired wide sensing area can be secured by providing a plurality of light receiving elements having a low unit price, it is not necessary to scan a narrow emission beam at a wide angle as in the conventional case, so that signal processing becomes easy. Moreover, since it is not necessary to increase the number of light emitting means, an inexpensive system can be constructed. 2) Since the light receiving areas of the respective light receiving elements are different, the direction in which the measurement target such as a preceding vehicle exists can be estimated, and the measurement target can be captured by automatically operating the optical system in that direction.
This capture control requires only a simple automatic control system, and the system can be provided at low cost. Further, since the capturing operation has a simple structure by rotating the turntable, a compact and space-saving optical distance measuring device is provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the relationship between the rotational position of the laser radar head in FIG. 1 and the direction of a light receiving area.

FIG. 3 is a timing chart showing light emitting / light receiving operations of a light emitting element and a light receiving element in FIG.

FIG. 4 is a diagram showing a conventional optical distance measuring device.

[Explanation of symbols]

 1 Laser Radar Head 2 Light-Emitting Element (Laser Diode) 3,4 Light-Receiving Element (Pin Photodiode) 5 Light-Emitting Lens (Condensing Lens) 6,7 Light-Receiving Lens (Condensing Lens) 8 Mechanical Filter 9 LD Drive Circuit 10 Light receiving circuit 11 Servo mechanism 12 Drive motor 13 Potentiometer 14 Turntable 20 Time measuring unit 21 Pulse generator 22 Time measuring unit 30 Signal processing unit 31 Distance meter side 33 Servo operation unit 40 Reflector 43,44 Light receiving area of preceding vehicle

Claims (2)

[Claims] 1. A distance measuring device comprising a light emitting element and a light receiving element, for measuring a distance to a reflector such as a preceding vehicle based on a propagation delay time from light emission by the light emitting element to light reception by the light receiving element, One light emitting element and a plurality of light receiving elements are mounted on a turntable, and the light receiving areas of the plurality of light receiving elements are set to different ranges so that they partially overlap each other, and the turntable is driven to rotate. And a control means for controlling the driving means so as to always capture the reflector in the overlapping area of the light receiving areas based on a combination of the magnitude relationship of the distance measurement values for each light receiving element. Optical distance measuring device characterized by. 2. The control means for controlling the driving means operates so as to always capture the reflector in the overlapping area of the light receiving areas based on the combination of the magnitude relations of the light receiving intensities of the respective light receiving elements. The optical distance measuring device according to claim 1, which is a control means.