JP3203299B2 - 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 a distance measuring apparatus for transmitting a laser beam while scanning it, receiving the light reflected by the reflector, and detecting the distance to the reflector.

[0002]

2. Description of the Related Art FIG.
This is a conventional distance detecting device disclosed in Japanese Patent Application Laid-Open Publication No. H11-209,873. In FIG. 5, reference numeral 101 denotes a laser diode for distance measurement that generates light for distance measurement, 201 denotes a laser diode for scanning position detection that generates light for detecting a scanning position, and 104 denotes an outside by reflecting the light for distance measurement. A rotation mirror 202 for emitting the light for detection and reflecting the light for detection, 202 is a position detection element (PSD) for detecting the incident position of the light for scanning position detection reflected by the rotation mirror, and 102, 203, 302 Each lens system 103 includes a fixed mirror 1 for reflecting light from a laser diode for distance measurement and irradiating the mirror with light.
Reference numeral 05 denotes a motor for driving the rotating mirror 104.

Next, the operation of the above-described conventional distance detecting device will be described. A rotating mirror 104 that reflects light on both sides is rotated by a motor 105 within a required angle range. The distance measuring light of the distance measuring laser diode 101 is reflected by the fixed mirror 103, further reflected by the rotating mirror 104, and emitted to the outside. Light reflected from the object is received by the light receiving element 301. The distance to the object is measured based on the time from emission of the light for distance measurement to reception of the reflected light. Detection light emitted from the scanning position detecting laser diode 201 is reflected by the rotating mirror 104 and enters the position detecting element 202. The position detection element 202 outputs a position signal indicating the incident position. The scanning angle position of the distance measuring light scanned by the rotating mirror 104 is represented by a position signal of the position detecting element 202. Feedback control of the motor 105 is performed using this position signal.

[0004]

In such a conventional distance measuring device, when the distance is not measured, the power supply to the motor is cut off, so that the rotating mirror attached to the motor is mechanically unstable. Therefore, when this device is used for a vehicle, when the distance measurement is not performed, there is a problem that the rotating mirror may be damaged or fall off due to external vibration due to a road surface or the like.

Further, when the distance measurement is restarted, it is necessary to turn on the power to the motor and return to the scanning start position, so that there is a problem that the start of the distance measurement is delayed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a reliable distance measuring apparatus that does not cause a mirror to be damaged or fall off due to vibration.

Another object of the present invention is to make it possible to immediately start scanning when resuming distance measurement.

[0008]

According to a first aspect of the present invention, there is provided a distance measuring apparatus comprising: a light transmitting means for transmitting laser light; a light receiving means for receiving light reflected by a reflector of the transmitted laser light; - a distance calculating means for calculating a distance to the reflector on the basis of the relationship of the light receiving signal, and reflecting the laser beam by a mirror, scanning within a predetermined range by the mirror swings by a cam mechanism and a stepping motor scanning means for distance measurement instrumentation comprising means for detecting the scanning position, the
When the distance is not measured, the mirror is fixed by applying a predetermined excitation to the stepping motor.
However, the fixed position of the mirror is such that the mirror is mechanically stable.
It is characterized by a position. Contract for this invention
The distance measuring device according to claim 2, wherein the light transmitting device transmits a laser beam.
Means for receiving reflected light from the reflector of the transmitted laser light
Based on the relationship between the transmitting and receiving signals
Distance calculating means for calculating the distance to
Reflected by the mirror, stepping the mirror with the cam mechanism
Scan within a predetermined range by oscillating with a motor
Scanning means, and means for detecting a scanning position,
When the distance is not measured by the distance measuring device,
By applying a predetermined excitation to the stepping motor,
The mirror is fixed and the fixed position of the mirror is stepping
The load is light and easy to start in the direction of motor rotation.
It is to be replaced . The distance measurement according to claim 3 of the present invention.
When the distance measuring device is powered on,
By moving the motor slowly, the mirror
It is characterized in that it is moved to a fixed position.

[0009]

[0010]

[0011]

[0012]

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a laser diode 11 for generating pulsed laser light, and the laser diode 1
A light transmitting means 12 comprising a light transmitting lens 12 for condensing the pulse light emitted from 1 and forming a laser beam very narrow in the scanning direction; 2 a mirror 21 for reflecting the laser beam generated from the light transmitting means 1; The scanning means 3 comprises a stepping motor 22 for swingingly driving the mirror 21 via a cam 23 and a spring 24 for pressing the mirror 21 against the cam surface. Mirror 2
A lens 32 for condensing the pulse light reflected again at 1;
A photodiode 31 for converting the received reflected pulse light into an electric signal;
Distance calculation means for measuring the reciprocating time of the reflected pulse light received by the light receiving means 3 from the pulse emission timing of 1 and calculating the distance, and 5 detects a predetermined swing position (scanning position) of the mirror in the scanning means 2. The origin detecting means 6 is a processing device for obtaining distance measurement data for each angle.

Next, the operation of the first embodiment configured as described above will be described. The light transmitting means 1 drives the laser diode 11 in a pulsed manner to emit pulsed light. The laser pulse light generated by the laser diode 11 is generally a beam having weak directivity, but is condensed by the light transmitting lens 12 to be shaped into a beam having a very narrow width in the scanning direction. In the scanning means 2, the light transmitting surface of the mirror 21 is arranged so that the shaped laser beam is incident at an angle of about 45 °. The mirror 21 is pressed against the cam surface of the cam 23 by a spring 24 and is driven by the stepping motor 22 via the cam 23 to scan the incident laser beam toward the object. The laser beam reflected by the light transmission surface of the mirror 21 hits the target object and is reflected, and reenters the mirror 21 as reflected pulse light. The light receiving surface of the mirror 21 is arranged so that the reflected pulse light is incident at an angle of about 45 °, and reflects the reflected pulse light to make it incident on the light receiving means 3. The light receiving means 3 condenses the reflected pulse light by the lens 32, performs photoelectric conversion by the photodiode 31, and inputs the converted light to the distance calculating means 4. The distance calculating means 4 measures the time Δt from the time when the laser diode emits a pulse to the time when the reflected pulse light is received by the light receiving means 3 and is input. The light speed (3 × 108
m / s) to calculate the distance to the object.

FIG. 2 is a diagram for explaining the operation of the scanning means 2.
Number of steps (a) of stepping motor 22 and mirror 2
1 shows the relationship with the swing angle (b) of FIG. 1 and the output (c) of the origin detecting means. The cam 23 is a stepping motor 2
By driving the mirror 2 for 20 steps, the mirror 21 is shaped so that the forward movement of the swing of the mirror 21 is similarly performed in four steps. Therefore, one reciprocation of the swing operation of the mirror 21 is performed in 24 steps of the stepping motor 22. A distance measurement is performed during this forward operation, and the laser beam is scanned during this time.

The rotation angle of one step of the stepping motor 22 is 15 °, the corresponding swing angle of the mirror is 0.3 °, and the scanning angle of the laser beam is 0.6 ° which is twice as large. Therefore, the total scanning angle of the laser beam is 0.6 ° × 20 = 12 °. Further, as shown in the figure, the excited phase of the motor is determined according to the number of steps of the stepping motor. The motor shown in this embodiment has four phases and is driven by one-phase excitation. Also, this motor makes one rotation in six cycles of the excitation pattern. Further, the swing position of the mirror is detected by the origin detecting means 5.

The origin detecting means 5 detects, for example, the end of the oscillating mirror using a photo interrupter or the like, and detects when the oscillating position is displaced to a certain position. Here, it can be seen from the figure that the excitation phase at the position where the distance measurement is started, that is, when the swing angle of the mirror is 0 °, is always the A phase. Therefore, after the origin detecting means 5 detects that the swing angle of the mirror is equal to or less than the predetermined angle, the time when the excitation phase of the stepping motor becomes the A phase is set as the start position of the scanning range for performing distance measurement. After the start position is determined, the swing angle of the mirror is known from the step position of the motor according to the shape of the cam 23, and the light transmission angle is detected. The distance from the distance calculating means 4 and the scanning angle from the scanning means 2 are determined by the processing unit 6
And associate the distance with the angle.

When the distance is not measured, the excitation of the motor 22 is fixed at a predetermined scanning angle, and the cam 23 and the mirror 21 are fixed at that position.

As described above, when the distance is not measured,
Since the mirror is fixed, the mirror is not damaged or dropped due to external vibration or the like.

Embodiment 2 FIG. 3 is a view for explaining the second embodiment, and shows a mirror swing angle (a) corresponding to the number of steps of the stepping motor and a load (b) in the rotation direction of the cam. As shown in the figure, the load in the rotation direction of the cam changes depending on the spring attached to the mirror, the shape of the cam surface, and the like, in accordance with the number of steps of the stepping motor. That is, when this load is 0 (point A in the figure), the cam is most stable and is in a stable position where it does not rotate in either direction. In the first embodiment, when the distance is not measured,
Locking the cam in this stable position makes the mirror more mechanically stable and more vibration resistant.

Embodiment 3 FIG. 4 is a view for explaining the third embodiment, and shows a mirror swing angle (a) corresponding to the number of steps of the stepping motor and a rotation torque (b) required for the motor to rotate. This required torque changes according to the load in the rotation direction of the cam in FIG. When the required rotational torque is negative (part B in the drawing), a force acts in a forward direction with respect to the rotational direction, and thus the motor is easily started. Therefore, in the first embodiment, when the distance is not measured, the mirror can be easily driven when the distance is measured again by fixing the cam to the position B in the figure where the required rotational torque of the motor is negative.

Embodiment 4 In the fourth embodiment, when the distance is not measured, the mirror is fixed at the position of the stepping motor step number 1 in FIG. 2, that is, the scanning start position.
When distance measurement is performed again, measurement can be started immediately. Thus, the distance measurement can be restarted without a time delay.

Embodiment 5 The fifth embodiment is a modification of the first embodiment. When the power of the distance detecting device itself is turned on, the stepping motor is operated at a slow speed in advance, and the mirror is moved to a predetermined position with the motor starting torque increased. Move to the fixed position. For example, a mirror is located at a position where a motor can be easily started. In this state, the motor can be rotated. After that, rotation can be continued by inertia. If it is impossible to start at the normal speed when measuring the mirror, as described above, when turning on the power of the device, move the mirror to a position that is easy to start, and always stop the motor when stopping the motor. If this position is set, this problem is solved.

[0024]

As described above, according to the distance measuring apparatus according to the first aspect of the present invention, even when the distance is not measured, the mirror is fixed by applying a predetermined excitation to the stepping motor, so that the mirror is fixed from the outside. by the vibration of, never as a mirror is damaged or fall off, and reliable device
If you do not measure this distance,
Since it is fixed at a stable position, vibration resistance is improved. Ma
According to the distance measuring device according to claim 2 of the present invention,
If you do not want to measure the distance,
Fixed at a position where the load is light and easy to start in the direction of rotation
Start the stepping motor to measure the distance.
When starting, the load is light in the direction of rotation.
Fewer luxes are required and start-up is easier. This allows
The motor does not need to have a large torque, and may be small.
In addition, it is possible to increase the scanning speed by increasing the rotation speed.
You. Further, according to the distance measuring device according to claim 3 of the present invention.
If the device is powered on,
The motor is operated at a slow speed.
Dynamic torque is increased, and the mirror can be easily moved to a fixed position.
Can move. As a result, even the fixed position of the mirror can be restarted
Motor position, you can increase the motor speed.
You. Therefore, a higher scanning speed can be expected.

[0025]

[0026]

[0027]

[0028]

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an operation of the first embodiment of the present invention.

FIG. 3 is a diagram illustrating the operation of the second embodiment of the present invention.

FIG. 4 is a diagram illustrating an operation of a third embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a conventional device.

[Explanation of symbols]

1 light transmitting means, 2 scanning means, 3 light receiving means, 4 distance calculating means, 5 origin detecting means, 6 processing device.

Claims (3)

(57) [Claims] 1. A light transmitting means for transmitting laser light, a light receiving means for receiving light reflected by a reflector of the transmitted laser light, and a distance for calculating a distance to the reflector based on a relationship between a transmission and reception signal. calculation means, and reflecting the laser beam by the mirror, comprising: a scanning means for scanning a predetermined range by the mirror swings by a cam mechanism and a stepping motor, means for detecting the scanning position, the distance In the measuring device, when the distance is not measured, the mirror is fixed by applying predetermined excitation to the stepping motor, and the fixing position of the mirror is such that the mirror is mechanically stable.
A distance measuring device characterized by a position . 2. A light transmitting means for transmitting laser light, and a light transmitting means.
Receiving means for receiving the reflected light of the reflected laser light by the reflector
And the distance to the reflector based on the relationship between the sending and receiving signals.
Distance calculating means for calculating, and the laser light is reflected by a mirror
Then, the above mirror is moved by a cam mechanism and
Scanning means for scanning within a predetermined range by swinging
And a means for detecting a scanning position
When the distance is not measured,
The above-mentioned mirror is fixed by applying the specified excitation to the motor.
The fixed position of the mirror depends on the rotation of the stepping motor.
Load should be light and easy to start in the direction of rotation.
And a distance measuring device. 3. When the distance measuring device is powered on,
By moving the stepping motor slowly, the mirror is
2. The apparatus according to claim 1, wherein said apparatus is moved to a fixed position.
Or the distance measuring device according to 2.