JP3253137B2 - Optical distance measuring device - Google Patents

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, in an optical distance measuring device for detecting a preceding vehicle or an obstacle in a traveling direction of a vehicle and measuring a distance to the preceding vehicle or an obstacle, it is necessary to increase a sensing area. is there.

[0003] In response to the above demand, the light emission area is widened by devising an optical system, which makes it difficult to receive light due to a decrease in light emission power density. It has been known. However, in this beam scanning method, it is necessary to process the position (direction) of the emitted light beam and the received light information at the speed of light, and the signal processing system becomes large-scale. Therefore, a method of providing a plurality of light-emitting elements and obtaining a wide-angle light-emitting region (multiple-beam method) is being studied.

FIG. 9 shows an optical distance measuring device of a multiple beam system (Japanese Patent Laid-Open No. 61-259185). In this device, a plurality of light emitting elements a, b, and c including a laser diode or the like are provided in a light transmitter 50, and light beams A, B, and C from light emitting elements a, b, and c driven by a drive circuit 51 are provided. C is radiated through the condenser lens 52. On the light receiver 53 side, the light beams A, B, C
Is reflected by a reflector 53 such as a preceding vehicle or an obstacle,
The 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. The distance measuring circuit reaches the reflector 53 based on the propagation delay time from light emission to light reception. Is measured.
According to the configuration of the light transmitter 50, measurement in a wide range can be performed, and the condenser lens system 52 includes the light emitting elements a, b, and c.
Therefore, the entire apparatus can be downsized.

[0005]

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

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and uses a plurality of light-receiving elements having a low unit price and estimates the direction in which a measuring object such as a preceding vehicle exists by differentiating the light-receiving areas. Another object of the present invention is to provide an optical distance measuring device capable of automatically operating an optical system and capturing an object to be measured.

[0007]

In order to achieve the above object, the present invention comprises a light emitting element and a light receiving element, wherein the light emitting element and the light receiving element are arranged based on a propagation delay time from emission of light 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, a light emitting element and a plurality of light receiving elements are arranged in a horizontal direction, and a condenser lens is arranged in front of each of these elements. A mechanism for displacing the light-receiving area of each light-receiving element by displacing the relative position of the light-receiving element and its condensing lens in the horizontal direction, such that the light-receiving area of the light-receiving element faces the reflector. Operating means for operating the light receiving area of the plurality of light receiving elements.
If you set different ranges so that the neighbors partially overlap
Both are sets of the magnitude relationship of the distance measurement values for each light receiving element.
Position is always within the overlapping area of the light receiving area.
Control for controlling the driving means so as to capture the reflector
This is a configuration provided with means (claim 1).

In the present invention, there is provided means for displacing the light emitting element in synchronization with the displacement of the relative position of the plurality of light receiving elements and the condensing lens in the lateral direction. The area can be oriented (claim 2).

[0009]

[0010]

As shown in FIG. 4, the light receiving area of the light receiving element and its direction (light receiving angles θ1, θ2) are determined by the positional relationship between the condenser lens 6 and the light receiving element 3. The direction of the light receiving area can be deflected by relatively shifting the light receiving lens 6 or the light receiving element 3 in the horizontal direction. The same can be said for the light emitting element.

Since the mechanism for deflecting the light receiving area / light emitting area of each light receiving element may be merely a mechanism for shifting the relative position of the lens or the light emitting / light receiving element to the side, the structure is extremely simple and the installation space is reduced. It is possible to construct a system that is resistant to vibration.

Further, since a plurality of light receiving elements are used, the approximate direction in which the preceding vehicle exists can be recognized, and this determination is made by combining the magnitude relationship of the distance measurement values for each light receiving element.
The reflector can always be captured in the overlapping area of the light receiving areas.

[0013]

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

FIG. 1 shows a system configuration of an optical distance measuring device. In the case of the present embodiment, it is assumed that this distance measuring device is 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 disposed, and light receiving lenses (condensing lenses) 6 and 7 each having a lattice-shaped mechanical filter 8 are disposed in front of the light receiving elements 3 and 4, respectively. 9 is LD
Is a light receiving circuit.

The time measuring unit 20 includes a pulse generator 21 for generating a start pulse for the LD drive circuit.
And the time is started by the start pulse, and the light receiving circuit 10
Time measurement unit 22 to stop timing with stop pulse from
And a power supply unit 23. In addition, the signal processing unit 3
Numeral 0 includes a rangefinder side unit 31 for calculating a distance based on the time data obtained by the time measuring unit 22, and a display unit 32 for displaying the result.

Further, in the laser radar head 1, the light receiving lenses 6, 7 and the mechanical filter 8 are displaced laterally relative to the light receiving elements 3, 4, whereby the light receiving areas 43, 4 of the light receiving elements 3, 4 are moved. 44, for example, as shown in FIG.
Mechanism 11 for deflecting as shown in FIG. 2 (B)
It has.

The signal processing unit 30 always connects the reflector 40 of the preceding vehicle to the two light receiving elements 3 as shown in FIG.
As a control means for controlling the servo mechanism 11 so that the servo mechanism 11 is captured in the overlapping area of the light receiving areas 43 and 44 of No. 4, a servo operation unit 33 for giving an appropriate command to the drive motor 12 of the servo mechanism 11 is provided. This servo operation unit 33
Specifically, from the combination of the magnitude relation of the measured values of the light receiving elements 3 and 4 measured by the distance meter side unit 31, the presence or absence of rotation of the drive motor 12 and the rotational direction Give instructions about. Note that the current displacement amount of the servo mechanism 11 is detected by a potentiometer 13 interlocked with the drive motor 12.

The principle of the mechanism for deflecting the light receiving areas 43 and 44 is as follows. That is, when the positions of the light receiving elements 3 and 4 are on the right side of the optical axis as shown in FIG. 4A, the light receiving angle θ1 is directed to the left region of the light receiving angle θ of the mechanical filter 8. However, as shown in FIG. 4B, when the position of the light receiving elements 3 and 4 moves to the left from the optical axis, the light receiving angle θ
Reference numeral 2 points to the right region of the light receiving angle θ of the mechanical filter 8. This relationship holds even when the mechanical filter 8 is not provided. Therefore, the light receiving areas 43 and 44 can be deflected by relatively laterally displacing any of the light receiving lenses 6 and 7 and the mechanical filter 8 and the light receiving elements 3 and 4.

Incidentally, when the length of the mechanical filter 8 is L ₀ and the grating slit width is a, the light receiving angle θ of the mechanical filter 8 is θ = 2 tan ⁻¹ (a / L ₀ ).
Given by Also, the light receiving angles θ1 and θ of the light receiving elements 3 and 4
2 is given by θ1 = θ2 = tan ⁻¹ (x / S), where S is the focal length of the lens and x is the light receiving element diameter. The light receiving center axis spread angle α is determined by setting the light receiving lens pitch to L
1, when the light receiving element pitch is L2, α = 2 tan ⁻¹
{(L1-L2) / 2S)}.

In this embodiment, the light receiving areas of the light receiving elements 3 and 4 are changed by laterally moving the light receiving lenses 6 and 7 and the mechanical filter 8. That is,
5 and 6, the light emitting lens 5, the light receiving lens 6 and the light receiving lens 7 are arranged side by side in the frame 14 in this order, and the frame 1 is moved by the slider 17 (FIG. 7).
4 is supported so as to be able to move laterally. Light emitting lens 5
A cam 15 is provided between the lens 6 and the light receiving lens 6, and the cam is rotated by a drive motor 12. Further, the light emitting lens 5, the light receiving lens 7, and the frame 1
An elastic body 16 is provided between the two. As a result, the light emitting lens 5, the light receiving lenses 6, 7 and the mechanical filter 8 can be displaced relative to the light emitting element 2 and the light receiving elements 3, 4 by rotating the cam 15 by the drive motor 12. Become. Therefore, the cam 15 and the driving motor 12 constitute a driving means for operating the mechanism 11 so that the light receiving areas 43 and 44 of the light receiving element face the direction of the reflector 40.

Here, the lateral movement of the light emitting lens 5 is also achieved by slightly shifting the optical axis of the LD with respect to the optical axis of the light emitting lens 5 as in the case of the light receiving element. This is because the projection direction can be changed. However, since the focal length and the distance between the element and the lens differ between light reception and light emission, if the same lateral movement amount is used, there occurs a problem that the movement amount in the light emission / light reception direction differs. Accordingly, the lens 15 is driven by the cam 15 so that the movement amount of each lens is different from the rotation angle of the drive motor 12, as shown in FIG. . In the case of the example shown in FIG. 8, the cam 15 is formed as an outer ring in which the light emitting lens 5 is slightly displaced more than the light receiving lenses 6 and 7.

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

In FIG. 1, a start pulse is output from the pulse generation section 21 of the time measurement unit 20 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 the start pulse to generate a laser pulse. Also,
The start pulse is given to the time measuring unit 22 to start measuring 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 that, a stop pulse is output to the time measuring unit 22. The time measuring section 22 measures a time interval between the start pulse from the pulse generating section 21 and the stop pulse from the light receiving circuit 10 and outputs the time interval to the distance meter side section 31 as time data. The rangefinder side unit 31 calculates the distance to the preceding vehicle from the time data and outputs the 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 of the corresponding light receiving element system in the distance meter side section 31 is "maximum", and the distance data is "no preceding vehicle". Treated as a signal. However, if there is any distance measurement value, it is determined that there is a preceding vehicle, and the signal is treated as a signal to that effect.

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

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

For convenience of explanation, the reflector 40 of the preceding vehicle is first used.
Are located only in the light receiving area 44 of the light receiving element 4 as shown in FIG. 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 state of the light receiving elements 3 and 4 is as shown in FIG. At this time, the distance measurement value in the distance meter side unit 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 based on the magnitude relationship between the signals of the distance measurement values, and gives a “left movement command” of the lens system to the servo mechanism 11. As a result, the drive motor 12 rotates forward, and the lens systems 5, 6, 7, 8 move to the left relative to the light receiving elements 3, 4, and the light receiving area 4
3 and 44 move to the left. The reflector 40 of the preceding vehicle is
When entering the overlapping area of the light receiving areas 43 and 44 as shown in FIG. 2B, the output state of the light receiving elements 3 and 4 becomes as shown in FIG. Also has a relationship of “small distance”. Here, the servo control unit 3
3 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 value has a relationship of "small distance" for the light receiving element 3 and "maximum distance" for the light receiving element 4, and the The control unit 33 determines that the preceding vehicle is in the right direction, and gives a “right movement command” of the lens system to the servo mechanism 11. As a result, the drive motor 12 rotates in the reverse direction, and the lens systems 5, 6, 7, 8 move rightward relative to the light receiving elements 3, 4. When the reflector 40 of the preceding vehicle enters the overlapping area of the light receiving areas 43 and 44, the distance measurement values have a relationship of “small distance” for the light receiving elements 3 and 4, and at that time, the servo control unit 33 sets “ Right movement command ”is stopped. When the distance measurement value is “maximum distance” for each of 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, with respect to the two light receiving elements 3 and 4, the light receiving systems 6, 7 and 8 are moved sideways until some distance measurement value is obtained, that is, until the above “small distance” is obtained. By displacing, the preceding vehicle can always be captured in front of the optical system of the laser head 1. Therefore, the distance measurement area can be expanded without unnecessarily expanding the light emission field of view and without performing unnecessary data processing by performing wide-area scanning.

As a means for automatically operating the optical system, a method of rotating the entire optical system on a turntable is conceivable. However, if the rotating object is too large and a rotary drive source (motor or the like) is included, the installation space is large. And there is a problem that the vehicle is easily affected by vibration of the vehicle. However, according to the above configuration,
Since it is only necessary to shift the relative position of the lens or the light emitting / receiving element, a system having a simple structure, reduced installation space, and strong vibration can be configured.

In the above embodiment, the instruction to the servo mechanism 11 is given from the magnitude relation of the distance measurement values. However, the difference in the light receiving signal levels of the two light receiving elements is measured, and the proportional rotation control is performed based on the signals. Can also. In this case, instead of the servo operation unit 33, 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, the light receiving areas 43 and 44 always stay within the overlapping area. Control means for controlling the drive motor 12 so as to capture the reflector 40 will be provided.

In the above embodiment, the case of capturing in the horizontal direction has been described. However, in actuality, capturing in the vertical direction is also required depending on the road conditions. Therefore, one more light receiving element having a different light receiving area in the vertical direction is required. It is practical to install. In this case, if necessary, the optical axis of the lens can be tilted to change the lens angle in the vertical direction.

[0035]

As described above, according to the present invention, the following excellent effects can be obtained.

1) According to the first aspect of the present invention, since a plurality of light receiving elements are provided, it is possible to estimate the position of a measuring object such as a preceding vehicle. Since the light receiving element is less expensive than the light emitting element, the device can be configured at a lower cost. Further, the light receiving area is deflected simply by shifting the relative position of the light receiving lens and the light receiving element to the side, so that a measuring object such as a preceding vehicle can be captured in the light receiving area. This mechanism has a simple structure, requires no installation space, and can be configured as a measurement device that is strong against vibration. In addition, this capture control requires only a simple automatic control system, and the system can be provided at low cost. Also, the outline of the location of the preceding vehicle
Direction recognition is based on the size of the distance measurement for each light receiving element.
Can be determined based on the combination of
An object to be measured, such as a preceding vehicle, is captured in the overlapping area of the light area.
Can be captured.

2) Since the light emitting area of the light emitting element is deflected in synchronization with the light receiving area of each light receiving element, the object to be measured such as a preceding vehicle is more reliably and effectively captured in the light receiving area. it can.

[0038]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a system configuration according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a relative position of a light receiving lens and a light receiving element in FIG. 1 and a direction of a light receiving area.

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

FIG. 4 is a diagram for explaining a principle of deflecting a light receiving area by a lateral movement of a relative position between a light receiving lens and a light receiving element.

FIG. 5 is a front view showing a mechanism for relatively laterally moving the light emitting / receiving lens and the light emitting / receiving element.

FIG. 6 is a plan view of the mechanism of FIG. 5;

FIG. 7 is a side view showing a slide portion of FIG. 6;

FIG. 8 is an explanatory diagram illustrating a relationship between a rotation angle of a drive motor and a lateral movement amount of a light emitting / receiving lens.

FIG. 9 is a diagram showing a conventional optical distance measuring device.

[Explanation of symbols]

 DESCRIPTION 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 Frame 15 Cam 16 Elastic body 17 Slider 20 Time measurement unit 21 Pulse generation unit 22 Time measurement unit 30 Signal processing unit 31 Distance meter side unit 33 Servo operation unit 40 Reflection of preceding vehicle Body 43, 44 Light receiving area

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-143187 (JP, A) JP-A-2-156185 (JP, A) JP-A-58-24876 (JP, A) JP-A-58- 131577 (JP, A) JP-A-6-109847 (JP, A) JP-A-1-263585 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S 7/48 G01S 17 / 00-17/88

Claims (2)

(57) [Claims] 1. A distance measuring device comprising a light emitting element and a light receiving element, wherein the distance measuring apparatus measures a distance to a reflector such as a preceding vehicle based on a propagation delay time from emission of light 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 arranged in the horizontal direction, and a condenser lens is arranged in front of these elements, and the relative positions of the plurality of light-receiving elements and the condenser lens in the horizontal direction are arranged. a mechanism by displacing deflect the light receiving area of the light receiving element, and driving means for the mechanism receiving area of the light receiving element to operate so as to face the direction of the reflector is provided, reception of the plurality of light receiving elements The area
If you set different ranges so that the neighbors partially overlap
Both are sets of the magnitude relationship of the distance measurement values for each light receiving element.
Position is always within the overlapping area of the light receiving area.
Control for controlling the driving means so as to capture the reflector
Optical distance measuring apparatus characterized in that a means. 2. A means for displacing said plurality of light-receiving elements and said light-emitting element in synchronization with a displacement of a relative position of said condensing lens in a lateral direction, wherein said light-emitting area and said light-receiving area are oriented in a direction of a measurement object. 2. The optical distance measuring device according to claim 1, wherein: