JPH11101872A - Laser range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser range finder which can accurately detect the peak position of the waveform of received signals without saturating the waveform of the received signals even when the quantity of received light is large. SOLUTION: The reflected light of a laser beam emitted to an object from a laser range finder is made incident on a light receiving optical system 4 and condensed through a focusing lens 5. A light receiving device 6 converts the quantity of the condensed light into a received signal 15. A level detecting circuit 8 for received signal detects the level of the received signal 15 and, when the level reaches a saturated level, outputs a control signal 16 for moving the focusing lens 5. A driving section 9 moves the lens 5 in accordance with the control signal 16. Consequently, the lens 5 is moved and the saturation of the light receiving device 6 is prevented. A control section 3 receives the pulse waveform of the received signal 15 which is converted when the light receiving device 6 does not reach the saturated level, detects the peak position of the waveform and the receiving time of the reflected light from the object based on the detected peak position, and measures the distance to the object from the receiving time of the reflected light and emitting time of the laser beam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser distance measuring apparatus, and more particularly to a laser distance measuring apparatus which emits a pulse laser.

[0002]

2. Description of the Related Art Conventionally, this type of laser distance measuring device emits pulsed laser light (hereinafter, referred to as laser light), receives reflected light from an object by a light receiving device, and emits the laser light at the time of emission. It is used to measure the distance to the object based on the time of reception of the reflected light.

[0003] Generally, the fluctuation range of the amount of reflected light from an object received by the light receiving device is a dynamic range of a light receiving device in the light receiving device which converts the received light amount into a reception signal which is an electric signal. As shown in FIG. 4, which is a diagram showing the received signal waveform obtained from the light receiver, the peak position of the received signal waveform for determining the reception time of the reflected light is detected. Since it cannot be performed, the distance measurement accuracy is deteriorated. For this reason, in order to improve the deterioration of the distance measurement accuracy when the received signal waveform is saturated, for example, in the technique disclosed in Japanese Patent Application Laid-Open No. 7-191143, the reflected light generated due to the saturated received signal waveform is used. Is corrected according to the degree of saturation. At this time, the process of correcting the detection error of the light receiving time is performed using the signal level of the received signal waveform which is an electric signal. In order to perform the correction process, the received signal waveform must be within a range where a change in the signal level is detected, and the electric signal becomes a saturated waveform when exceeding the dynamic range of the processing circuit. Will not change. Therefore, the range of the signal waveform that can be used for the correction process must be lower than the level where the saturation waveform is obtained. For this reason, in general,
The range that can be corrected is limited to about 60 dB.

[0004]

In the above-described conventional laser distance measuring apparatus, the detection error of the light receiving time is corrected using the received signal waveform which is an electric signal in accordance with the degree of saturation. The possible range is limited to about 60 dB. On the other hand, in general, in a laser distance measuring apparatus using a pulse laser, the variation range of the received light amount is 10
0 dB or more. Therefore, there is a problem that the correction range cannot be covered by the correction processing performed by the conventional laser distance measuring apparatus.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such disadvantages of the prior art and to accurately detect the peak position of a received signal waveform without saturating the received signal waveform even when the amount of received light is large. It is an object of the present invention to provide a laser distance measuring apparatus which does not need to correct the light receiving time.

[0006]

A laser distance measuring apparatus according to the present invention emits laser light, receives reflected light from an object by a light receiving device, emits the laser light, and emits the laser light. In a laser distance measuring device for measuring the distance to the object based on the light receiving time when the light is received, the light receiving device includes a lens that collects the reflected light and a light amount of the collected light converted into an electric signal. And a light receiver for conversion,
The position of the lens is moved to adjust the amount of light entering the light receiver so that the light receiver is not saturated.

Further, the laser distance measuring apparatus of the present invention emits laser light, receives reflected light from an object by a light receiving device, emits the laser light, and emits the reflected light. In the laser distance measuring device for measuring the distance to the object by the light receiving time, the light receiving device has a focusing lens which can be moved to move a focal position, and receives and receives the reflected light. A light receiving optical system for condensing the reflected light by the focusing lens, and a light receiver arranged on a light receiving optical axis indicating an optical axis of the light receiving optical system and receiving the collected reflected light and outputting a reception signal And a focus position moving unit that receives the reception signal output by the light receiver and moves the focus position of the light receiving optical system according to the magnitude of the reception signal.

Further, the focus position moving section of the laser distance measuring apparatus according to the present invention receives the reception signal output by the photodetector, detects a reception signal level indicating the magnitude of the reception signal, and outputs a control signal. A reception signal level detection circuit, and receives the control signal output by the reception signal level detection circuit and moves the focusing lens along the light receiving optical axis to move the focal position of the light receiving optical system according to the control signal. And a drive unit for moving.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of a laser distance measuring apparatus according to the present invention.

In the embodiment shown in FIG. 1, a pulse laser beam (hereinafter referred to as a laser beam) is emitted by a light emitting device 2.
, The reflected light from the object is received by the light receiving device 1, and the control unit 3 measures the distance to the object based on the firing time when the laser light is emitted and the light receiving time when the reflected light is received. In a laser distance measuring device, a light receiving device 1 has a focusing lens 5 which can be moved to move a focal position, receives a reflected light, and condenses the received reflected light by the focusing lens 5. A system 4, a light receiver 6 which is arranged on a light receiving optical axis indicating an optical axis of the light receiving optical system 4 and receives a condensed reflected light and outputs a reception signal 15, and a receiver signal 15 output by the light receiver 6 The focal position moving unit 7 moves the focal position of the light receiving optical system 4 according to the magnitude of the received signal 15.

The focus position moving unit 7 receives a reception signal 15 output from the light receiver 6, detects a reception signal level indicating the magnitude of the reception signal 15, and outputs a control signal 16; A drive unit 9 that receives the control signal 16 output from the reception signal level detection circuit 8 and moves the focusing lens 5 along the light receiving optical axis to move the focal position of the light receiving optical system 4 according to the control signal 16 It is configured.

FIG. 1 also shows an objective lens which is a part of a light receiving optical system 4 for taking reflected light into the light receiving device 1.

Next, the operation of the laser distance measuring apparatus according to this embodiment will be described in detail with reference to FIGS.

FIG. 2 is a diagram showing an example of the principle of adjusting the amount of light incident on the light-receiving device. The light-receiving optical system 4 when the focusing lens 5 in the light-receiving optical system 4 is at the focusing lens position a is shown. Is the focal position a, and when the light to be collected is incident on the light receiving device 6 arranged at the focal position a, the reflected light from the object becomes the light collecting area a and the detection surface 10 of the light receiving device 6 , And that the condensed light amount enters the photodetector 6 at 100%. When the focus position of the light receiving optical system 4 when the focusing lens 5 is moved to be located at the focusing lens position b is the focusing position b, the reflected light from the object is collected at the focusing position b. The spot diameter of the reflected light on the detection surface 10 of the detector 6 becomes large, and the reflected light becomes a condensing area b so as not to enter the detection surface 10.
This indicates that only the light amount corresponding to the area ratio of 0 enters the light receiver 6 and, for example, the light receiver 6 is not saturated. Therefore, by moving the focusing lens 5, the focal position of the light receiving optical system 4 moves, and the spot diameter of the reflected light collected on the detection surface 10 of the light receiver 6 can be changed. It is shown that the light receiver 6 can be prevented from being saturated by adjusting the amount of light incident on the light receiver 6. For example, when the maximum spot diameter on the detection surface 10 due to the movement of the focusing lens 5 is φ3 mm and the effective diameter of the detection surface 10 of the light receiver 6 is φ0.1 mm, the increase / decrease of the light amount is proportional to the area ratio. The amount of received light can be adjusted in the range of 60 dB, which means that the dynamic range of the light receiver 6 is increased by 60 dB.

FIG. 3 is a diagram showing an example of the waveform of a reception signal output from the light receiver. When an amount of light exceeding the dynamic range of the light receiver 6 is incident on the light receiver 6, the reception signal output by the light receiver 6 is shown. Since the signal 15 exceeds the saturation level 33, there is no information on the peak position like the pulse waveform 32 of the laser light originally like the saturation waveform 31, and the peak position of the reception signal waveform for determining the reception time of the reflected light is changed. Indicates that it cannot be detected.

In FIG. 1, the reflected light from the object of the laser light emitted from the light emitting device 2 is incident on the objective lens of the light receiving optical system 4 and is received through the focusing lens 5 constituting a part of the light receiving optical system 4. The light is focused on the vessel 6. The light receiver 6 converts the collected light amount into a reception signal 15 which is an electric signal and outputs the signal. The reception signal level detection circuit 8 receives the reception signal 15 output from the light receiver 6, detects the level of the reception signal 15, and when the detected level reaches the saturation level 33 shown in FIG. For example, focusing lens position b
, A control signal 16 for moving the focusing lens 5 is output. The drive unit 9 moves the focusing lens 5 to the focusing lens position b according to the control signal 16 output from the reception signal level detection circuit 8. When the focusing lens 5 moves, the light receiver 6 does not saturate as shown in FIG. On the other hand, when the level of the reception signal 15 detected by the reception signal level detection circuit 8 has not reached the saturation level 33 shown in FIG. 3, the control signal 16 for moving the focusing lens 5 is not output. At this time, the light receiver 6 outputs, for example, the reception signal 15 having the pulse waveform 32 shown in FIG. The control unit 3 receives the pulse waveform 32, detects the peak position of the pulse waveform 32, sets the peak position as the detection position 34 of the received signal waveform shown in FIG. The time is detected, and the distance from the laser distance measuring device to the object is measured based on the light receiving time and the time when the laser light is emitted from the light emitting device 2.

[0018]

As described above, according to the laser distance measuring apparatus of the present invention, the reflected light from the object incident by the focusing lens is condensed, and the amount of light condensed by the light receiver is converted into the received signal. The received signal level is detected by the received signal level detection circuit, and when this level has reached the saturation level, a control signal for moving the focusing lens is output, and the driving unit moves the focusing lens to receive light. In order to prevent the detector from saturating, the controller can receive the converted received signal pulse waveform when the receiver has not reached the saturation level and detect the peak position of this waveform. The peak position of the received signal waveform can be accurately detected without saturating the signal waveform, and there is no need to correct the light receiving time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a laser distance measuring apparatus according to the present invention.

FIG. 2 is a diagram illustrating an example of the principle of adjusting the amount of light incident on a light receiver.

FIG. 3 is a diagram illustrating an example of a waveform of a reception signal output from a light receiver.

FIG. 4 is a diagram showing a reception signal waveform obtained from a light receiver.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light receiving device 2 light emitting device 3 control unit 4 light receiving optical system 5 focusing lens 6 light receiving device 7 focal position moving unit 8 reception signal level detection circuit 9 drive unit 10 detection surface 15 reception signal 16 control signal 31 saturation waveform 32 pulse waveform 33 Saturation level 34 Received signal waveform detection position

Claims (4)

[Claims] 1. An object, which emits laser light and receives reflected light from an object by a light receiving device and emits the laser light and emits the laser light to the object based on a light receiving time when the reflected light is received. In a laser distance measuring apparatus for measuring the distance of the light receiving device, the light receiving device has a lens for collecting the reflected light and a light receiving device for converting the amount of the collected light into an electric signal, and the position of the lens And adjusting the amount of light entering the photodetector so as not to saturate the photodetector. 2. An object which emits laser light and receives reflected light from an object by a light-receiving device and emits the laser light to the object based on a firing time when the laser light is emitted and a light receiving time when the reflected light is received. In the laser distance measuring apparatus for measuring a distance, the light receiving device has a focusing lens which can be moved to move a focal position, receives the reflected light, and collects the received reflected light by the focusing lens. A light-receiving optical system that emits light, a light-receiving device that is arranged on a light-receiving optical axis indicating an optical axis of the light-receiving optical system, receives the collected reflected light, and outputs a reception signal, and the light output by the light receiver A focus position moving unit that receives a received signal and moves the focal position of the light receiving optical system according to the magnitude of the received signal. A reception signal level detection circuit that receives the reception signal output by the photodetector, detects a reception signal level indicating a magnitude of the reception signal, and outputs a control signal; A drive unit that receives the control signal output by the reception signal level detection circuit and moves the focusing lens along the light receiving optical axis to move the focal position of the light receiving optical system according to the control signal. 3. The laser distance measuring apparatus according to claim 2, wherein: 4. The apparatus according to claim 1, wherein the focus position moving unit includes:
4. The laser distance measuring apparatus according to claim 2, wherein the focus position of the light receiving optical system is moved so as not to be saturated by the received light amount.