JPH0915333A - Optical radar equipment - Google Patents

Abstract

PURPOSE: To provide optical radar equipment of which a scanning mechanism of laser light is simplified, regarding the optical radar equipment wherein the laser light is cast by scanning on a target and detection of the target is executed on the basis of the reflected light. CONSTITUTION: Optical radar equipment having light generating sources 12 and 13, a scanning means 15 which scans the direction of the light generated from the light sources and sends the light into a prescribed coverage and target detecting means 14 and 18 which receive 17 the reflected light returning from the prescribed coverage and detect a target located inside the coverage. The scanning means is equipped with a reflecting member 16 which is fixed rotatably, reflects the light of the light sources and sends it into the prescribed coverage, a rotation drive means 22 which drives a rotating shaft to rotate and a motion converting means 21 which converts a rotational motion of the rotating shaft by the rotation drive means into a swing motion of the reflecting member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical radar device for scanning a laser beam to irradiate a target object, and detecting and measuring the distance based on the reflected light from the target object. The present invention relates to an optical radar device having a simplified mechanism.

[0002]

2. Description of the Related Art In recent years, in vehicles, robots and other moving bodies, a system has been developed for detecting obstacles and measuring distances by mounting an optical radar device in order to improve safety and automate operation. . Representative examples of these systems include a collision prevention system for robots, automobiles, trains, etc., a stop position control system for transport vehicles in a manufacturing line, an approach warning system around construction equipment, and the like.

In these systems, it is necessary to detect an obstacle over a wide range and measure the shape of a large obstacle. Therefore, an optical radar device has been developed that scans a laser beam over a predetermined area. This type of optical radar device is provided with a mechanism for scanning laser light using a reflecting mirror.

That is, a reflecting mirror is rotatably arranged in front of the laser emitting portion of the optical radar device. The laser light emitted from the laser emitting section is once reflected by the reflecting mirror and then sent to the outside. The optical radar device swings the rotary shaft of the reflecting mirror by using a stepping motor or the like. Then, the reflection angle of the laser light fluctuates, and the laser light is scanned left and right within a predetermined coverage area and is sent (actually, the 60th case).
-42982).

A laser beam scanning mechanism using a polygon mirror is also known. That is, a polygon mirror having a polygonal prism-shaped reflecting surface is rotatably arranged in front of the laser emitting portion of the optical radar device. The laser light emitted from the laser emitting section is once reflected on one side of the polygon mirror and then sent to the outside. The optical radar device rotationally drives the rotation axis of this polygon mirror using a motor or the like. Then, with the rotation of the polygon mirror, the reflection angle of the laser light is turned to one side, and the laser light is scanned within a predetermined coverage area and transmitted.

[0006]

By the way, in the conventional example in which the reflecting mirror is driven to swing, it is necessary to reversely drive a stepping motor or the like. Therefore, there is a problem that a complicated control system is required to control the stepping motor and the like. Further, when the stepping motor is driven in reverse, the reflecting mirror is braked and accelerated in the opposite direction, which requires a large amount of torque.

Therefore, it is difficult to increase the swing speed of the reflecting mirror, and it is difficult to shorten the scanning cycle of the laser light. In particular, when the laser beam is scanned at a constant speed, the reflecting mirror needs to be rapidly inverted at the time of scanning inversion, and there is a problem that a stepping motor that generates a larger torque is required.

On the other hand, in the conventional example using the polygon mirror,
A large polygon mirror is used to place multiple reflective surfaces on the polygon mirror. For example, if the scanning angle of the laser beam is 2
If it is 0 degree, the angle formed by the adjacent reflecting surfaces is 170 degrees, and 36 reflecting surfaces are required. A large polygon mirror can be obtained by making the reflecting surface sufficiently wide with respect to the beam diameter of the laser beam and arranging 36 reflecting surfaces. Therefore, when the polygon mirror is used, there is a problem that the laser beam scanning mechanism becomes large.

Further, if the number of faces of the polygon mirror is reduced and the size of the polygon mirror is reduced, the angle at which the laser beam is invalidly irradiated becomes wider. For example, if a three-sided polygon mirror is configured, the scanning angle of the laser light is expanded to 240 degrees. Of these,
Assuming that the scanning angle used for radar distance measurement is 20 degrees, the remaining scanning angle of 220 degrees is invalid.

Therefore, if the size of the polygon mirror is reduced,
There is a problem that the time during which the laser beam is invalidly scanned increases. In order to solve such a problem, an object of the present invention is to provide an optical radar device which simplifies the scanning mechanism and can easily control the scanning mechanism.

In addition to the above object, an object of the present invention is to provide an optical radar device capable of more easily controlling the scanning mechanism. In addition to the above object, an object of the present invention is to provide an optical radar device capable of easily controlling the scanning speed of laser light at a constant speed.

[0012]

According to a first aspect of the present invention, there is provided a light source which emits light, a scanning means which scans the direction of the light emitted from the light source and sends the light within a predetermined coverage area. In the optical radar device provided with the target detection means for receiving the reflected light returning from the inside of the covered area and detecting the target located in the covered area, the scanning means is rotatably fixed and reflects the light from the light source. A reflecting member for transmitting light within a predetermined coverage area, a rotation driving means for driving the rotating shaft to rotate, and a motion converting means for converting the rotational movement of the rotating shaft by the rotating driving means into the swinging movement of the reflecting member. It is characterized by that.

According to a second aspect of the present invention, in the optical radar device according to the first aspect, the motion converting means is rotationally driven by the rotational driving means, and the cam surface is in sliding contact with the sliding contact portion of the reflecting member. The cam member is

According to a third aspect of the present invention, in the optical radar device according to the second aspect, the length of the line segment M connecting the swing center of the reflecting member and the sliding contact portion of the reflecting member is a, and the cam member is a cam member. Is the distance b between the line segment M and the center of rotation of the cam member when the predetermined rotation angle is zero, and the line segment M when the predetermined rotation angle is zero.
Let c be the distance between the point at which the rotation center of the cam member is vertically projected and the swing center of the reflection member, the cam member is
The diameter L from the center of rotation to the sliding contact portion is: L = [{ba−sin (kψ)} ² + {a · cos (kψ)
-C} ² ] ^1/2 (where k is a constant of proportionality).

[0015]

In the optical radar device according to the first aspect, the motion converting means converts the rotational movement of the rotary shaft by the rotational driving means into the swinging movement of the reflecting member. Therefore, since the rotary drive means only needs to rotate in one direction, it is not necessary to reversely drive the motor or the like as compared with the conventional example. Therefore, the rotation driving means can be easily realized including the control system, and the entire scanning mechanism can be simplified.

In the optical radar device of the second aspect, the cam member is used as the motion converting means. Therefore, since the rotation driving means only has to rotate the cam member in one direction, the rotation driving means can be easily realized including the control system, and the entire scanning mechanism can be simplified. Further, since the cam member has a moment of inertia, it acts as a flywheel (flywheel) for the rotary drive means. for that reason,
Fluctuations in the rotation speed of the rotation driving means are suppressed, and the uniform speed of the scanning speed can be improved.

Further, by appropriately accelerating the rotational speed of the cam member, the swinging motion of the reflecting member can be easily increased. In the optical radar device according to claim 3, the diameter L from the rotation center to the sliding contact portion at the rotation angle ψ of the cam member is L = [{ba-sin (kψ)} ² + {a ・ cos (kψ).
-C} ² ] ^1/2 (where k is a proportional constant), the swing angle θ of the reflecting member satisfies θ = k · ψ as shown in FIG.

As described above, since the swing angle θ of the reflecting member changes in proportion to the rotation angle ψ of the cam member, the scanning speed of the laser beam is equalized by controlling the rotation speed of the rotation driving means at a constant speed. The speed can be controlled. In particular, when a DC motor or the like is used as the rotation driving means, by negatively feeding back the counter electromotive force of the DC motor, the rotation speed of the motor can be easily controlled at a constant speed. Therefore, it is not necessary to separately provide means for detecting and controlling the swing angle θ of the reflecting member,
A scanning mechanism that scans laser light at a constant speed can be easily realized.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing an embodiment corresponding to claims 1 to 3. In the figure, the control output of the microprocessor 11 is connected to the laser driving unit 12, and the output of the laser driving unit 12 is connected to the laser emitting unit 13 and the time measuring unit 14.

A reflecting mirror 16 is rotatably arranged on the optical axis of the laser beam emitted from the laser emitting section 13 via a light transmitting optical system 15. A light receiving optical system 17 is arranged adjacent to the light transmitting optical system 15, and a light receiving element 18 is arranged on the optical axis of the light receiving optical system 17. The output of the light receiving element 18 is connected to the time measuring unit 14, and the output of the time measuring unit 14 is connected to the microprocessor 11. Reflector 16
An angle detector 19 is arranged on the swinging axis of the angle detector 1.
The output of 9 is connected to the microprocessor 11. A cam follower 20 is fixed to the end side of the reflecting mirror 16, and the cam follower 20 is in sliding contact with the cam surface of the cam 21.

The rotation center of the cam 21 is meshed with the rotation shaft of the motor 22, and the rotation speed detector 2 is attached to the rotation shaft of the motor 22.
3 are connected. The output of the rotation speed detector 23 is input to the motor drive circuit 24, and the drive output of the motor drive circuit 24 is connected to the motor 22. A spring 25 is provided on the end side of the reflecting mirror 16 and urges a spring force in a direction to bring the cam follower 20 into contact with the cam 21.

Regarding the correspondence relationship between the invention according to claims 1 to 3 and the present embodiment, the light source corresponds to the laser driving section 12 and the laser emitting section 13, and the target detecting means is the light receiving element 18, the time. Corresponding to the measuring unit 14, the reflecting member is the reflecting mirror 1.
6, the rotation driving means corresponds to the motor 22, the rotation speed detector 23 and the motor driving circuit 24, and the motion converting means corresponds to the cam 21.

The operation of this embodiment will be described below. The microprocessor 11 causes the laser emitting section 13 to generate a laser beam via the laser driving section 12. Laser light is
The light passes through the light sending optical system 15, is reflected by the reflecting mirror 16, and is sent to the outside. A part of the laser light thus sent to the outside is reflected by the target and returns to the optical radar device as reflected light. The reflected light is reflected by the reflecting mirror 16 and focused on the light receiving element 18 via the light receiving optical system 17. Light receiving element 18
Photoelectrically converts the reflected light and outputs it to the time measuring unit 14.
The time measuring unit 14 measures the round-trip time from when the laser light is sent to when the reflected light is received, and outputs it to the microprocessor 11. The microprocessor 11 calculates the distance to the target based on this round-trip time.

In such an optical radar device, the motor drive circuit 24 drives the motor 22 to rotate at a constant speed based on the output of the rotation speed detector 23. The cam 21 is rotated at a constant speed by transmitting the rotational movement of the motor 22. The reflecting mirror 16 that is in sliding contact with the cam surface of the cam 21 swings according to the displacement of the cam surface.

Here, as shown in FIG. 3A, the cam 2
When the rotation angle of 1 is zero, the line segment M connecting the roller center O ″ of the cam follower 20 and the swing axis O of the reflecting mirror 16
Let a be the length of. The distance between the rotation center O ′ of the cam 21 and the line segment M is b, and the distance between the swing center O and the point where the rotation center O ′ is projected perpendicularly to the line segment M is c.

When the reflecting mirror 16 having such a positional relationship is swung by the swing angle θ, the diameter L from the rotation center O ′ to the roller center O ″ of the cam follower 20 is L = [{b−a -Sin θ} ² + {a · cos θ-c} ² ] ^1/2 (Equation 1) where the swing angle θ of the reflecting mirror 16 is proportional to the rotation angle ψ of the cam 21. If so, θ = k · ψ (where k is a proportional constant) (Equation 2).

Substituting this equation 2 into the equation 1, L = [{ba-sin (kψ)} ² + {acos (kψ) -c} ² ] ^1/2 (where k is proportional Constant) (Equation 3) is obtained. When the cam surface shape of the cam 21 is determined so as to satisfy the formula 3 within a predetermined rotation angle range, the rotation angle ψ of the cam 21 and the swing angle θ are proportional to each other within the rotation angle range. .

FIG. 4 is a diagram showing an example of the cam surface shape calculated by using the equation (3). In this example, the rotation angle is about 80
It is possible to obtain a linear change of the rocking angle of 12 degrees in the range of 18 to 162 degrees and 198 to 342 degrees, which correspond to%.
In the range of rotation angles 343 to 17 degrees and 162 to 198 degrees, the angle of the cam 21 is rounded so that the reflecting mirror 1 can be rotated.
The shock given to 6 can be buffered.

The microprocessor 11 is the angle detector 1
If the range in which the reflecting mirror 16 swings at a constant speed is detected via 9 and the laser light is transmitted within that range, the effective time is about 80% and the scanning speed is constant. An excellent scan is performed. As described above, in the optical radar device according to the present embodiment, the motor 22 may rotate in one direction,
The motor drive circuit 24 can be easily realized as compared with the conventional example.

Since the cam 21 has a moment of inertia, the cam 21 acts as a flywheel (flywheel) for the motor 22. Therefore, the motor 2
The fluctuation of the rotation speed in 2 is suppressed, and the uniform speed of the rotation speed can be improved. Further, by appropriately accelerating the rotation speed of the cam 21, the swinging motion of the reflecting mirror 16 can be easily increased.

Further, the rotation angle ψ of the cam 21 and the reflecting mirror 16
Is proportional to the swing angle θ of the laser beam, the scanning speed of the laser light can be easily controlled at a constant speed by controlling the rotation speed of the motor 22 at a constant speed. Although the spring 25 urges the cam 21 and the cam follower 20 in the contacting direction in the above-described embodiment, the present invention is not limited to such a configuration, and the cam 21 is formed in the peripheral portion of the cam. The front follower (face cam) is provided with a cam follower 2 in its groove.
The tip portion of 0 may be slidably fitted.

[0032]

As described above, according to the first aspect of the present invention, since the rotary driving means only needs to rotate in one direction, it is not necessary to reversely drive the rotary driving means as compared with the conventional example. Therefore, the rotation driving means can be easily realized including the control system, and the entire scanning mechanism can be simplified.

According to the second aspect of the present invention, since the cam member is used as the motion converting means, the cam member acts as a flywheel (flywheel) with respect to the rotation driving means. Therefore, the fluctuation of the rotation speed in the rotation driving means is suppressed, and the uniform speed of the rotation speed can be improved. Also, by appropriately accelerating the rotation speed of the cam member,
The oscillating motion of the reflecting member can be easily increased in speed, and the scanning cycle of the laser light can be shortened.

Further, in the mechanism using the cam member, the scanning mechanism can be downsized while securing a large area for the reflecting member as compared with the conventional polygon mirror. According to the third aspect of the present invention, since the rotation angle ψ of the cam member and the swing angle θ of the reflection member are proportional to each other, the scanning speed of the laser light can be simplified by controlling the rotation speed of the rotation driving means at a constant speed. It can be controlled at a constant speed. As described above, by applying the present invention, it is possible to realize an optical radar device that can increase the scanning speed while simplifying the laser light scanning mechanism and that is excellent in the uniform speed of the scanning speed.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a cam member according to a third aspect of the invention.

FIG. 2 is a diagram showing an embodiment corresponding to claims 1 to 3;

FIG. 3 is a diagram for explaining the movement of the cam in this embodiment.

FIG. 4 is a diagram showing an example of a cam surface shape of the present embodiment.

[Explanation of symbols]

 11 Microprocessor 12 Laser Driving Section 13 Laser Emitting Section 14 Time Measuring Section 15 Light Transmitting Optical System 16 Reflecting Mirror 17 Light Receiving Optical System 18 Light Receiving Element 19 Angle Detector 20 Cam Follower 21 Cam 22 Motor 23 Rotation Speed Detector 24 Motor Driving Circuit 25 Spring

Claims (3)

[Claims] 1. A light source that generates light, a scanning unit that scans the direction of the light generated from the light source, and sends the light into a predetermined coverage area, and a reflected light that returns from within the predetermined coverage area. In an optical radar device including a target detection unit that detects a target located in the coverage area, the scanning unit is rotatably fixed, reflects the light of the light source, and sends the light to the predetermined coverage area. A reflecting member that emits light; a rotation driving unit that rotationally drives the rotation shaft; and a motion conversion unit that converts the rotational movement of the rotation shaft by the rotation driving unit into the swinging movement of the reflection member. Optical radar device. 2. The optical radar device according to claim 1, wherein the motion conversion means is a cam member which is rotationally driven by the rotational drive means and whose cam surface is in sliding contact with a sliding contact portion of the reflecting member. An optical radar device characterized by being present. 3. The optical radar device according to claim 2, wherein a length of a line segment M connecting a swing center of the reflecting member and a sliding contact portion of the reflecting member is a, and the cam member is predetermined. With a predetermined rotation angle of zero,
The distance between the line segment M and the rotation center of the cam member is b, and the point at which the rotation center of the cam member is vertically projected onto the line segment M and the swing of the reflection member in the state where the predetermined rotation angle is zero. Assuming that the distance from the motion center is c, the diameter L of the cam member from the rotation center at the rotation angle ψ to the sliding contact portion is L = [{ba−sin (kψ)} ² + {a · cos (Kψ)
-C} ² ] ^1/2 (where k is a proportional constant), and an optical radar device having a cam surface shape.