JPH1123710A - Range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a range finder which can measure the distance to a target by responding to the wide-range distance of the target and the variation of mirror surface reflection, etc. SOLUTION: A range finder measures the light intensity of received optical signals by using an optical system 4 which fetches received light and a plurality of detectors 6 (6a6c). The levels of the light made incident to the detectors 6 are optically changed in several steps of 1/10, 1/100,... by taking the dynamic ranges of the detectors 6 into consideration. An arithmetic section 10 corrects the distance to a target by selecting a correcting value from a pre-prepared table indicating the relation between intensities of light and correcting distances by using the peak value of the detector 6 operating in the dynamic range of the detectors 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a distance measuring device,
In particular, the present invention relates to a distance measuring device that enables highly accurate distance measurement.

[0002]

2. Description of the Related Art A distance measuring apparatus for measuring a distance to a target as a non-measurement object projects a light beam toward the non-measurement object, projects the light beam, and receives reflected light from the target. The distance to the target is measured by measuring the time required to perform the measurement with a counter.

In such a distance measuring device, the level of a received light signal greatly changes due to a change in the distance to the target or the reflectance of the surface of the target, and therefore, the dynamic range of a signal processing circuit for processing the received light must be set large. In some cases, the operation dynamic range of the signal processing circuit cannot be supported, and a measurement error occurs.

Therefore, conventionally, a light attenuating plate having a different transmittance depending on the position on the surface is provided in the reference light path, and the position of the light attenuating plate is adjusted so that the reference signal level matches the received light signal level. A configuration for canceling an error generated between the light receiving signal and the reference signal has been adopted. However, in this configuration, the position of the light attenuating plate must be moved using a balance motor or the like, and there is a limit to performing this movement at a high speed. If it changes, it cannot respond quickly and cannot perform high-speed distance measurement.

In order to solve this problem, Japanese Patent Laid-Open Publication No.
Japanese Patent Application Laid-Open No. 6788 discloses a distance measuring apparatus that changes a light emitting signal level in response to a change in the distance or reflectance of a target object at a high speed, and always maintains a constant light receiving signal level. .

[0006]

In the above distance measuring device,
In order to improve the distance accuracy, the light receiving timing is set at a fixed position (for example, 1/2 of the peak) of the rising edge of the light receiving pulse, and the correction is made according to the light receiving amount. In consideration of this, the dynamic range exceeds 10 5 to 10 6, and the detector for detecting the amount of received light has a limited dynamic range. There is a problem that the light amount of the light receiving signal cannot be detected with respect to the distance.

That is, when the intensity of the incident light is extremely high, the output level of the detector is usually saturated.
The generation timing of the stop pulse in the counting operation by the counter described above is advanced, and a smaller value is obtained as the distance.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a distance measuring apparatus capable of measuring a distance in response to a change in a wide range of a target object and a change in specular reflection at a high speed.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a distance measuring apparatus according to the present invention is provided with a timing for emitting laser light emitted toward a target and a timing for receiving light reflected from the target. A distance measuring device having a distance measuring means for measuring a distance to the target based on the plurality of light amount extracting means for sequentially taking out the amount of reflected light from the target so as to have a small light amount; and the plurality of light amount extracting means A plurality of detector means for detecting each light from and converting it to an electric signal, and peak detection means for detecting the respective peak values of the outputs of the plurality of detector means,
And calculating means for correcting the distance obtained by the distance measuring means based on the peak values of the plurality of detector means obtained by the peak detecting means.

Here, the calculating means corrects a predetermined value determined based on the peak values of the plurality of detector means obtained by the peak detecting means as a distance obtained by the distance measuring means, A distance obtained by the distance measuring means is corrected to a predetermined value determined based on a detector having a peak value equal to or less than a predetermined threshold value for each detector among peak values of the plurality of detectors.

The plurality of detectors and the predetermined value are tabulated, and the light quantity extracting means is a means for optically branching at a plurality of levels in consideration of the dynamic range of the plurality of detectors. is there. This light quantity extracting means is a beam splitter.

[0012]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of a distance measuring apparatus according to an embodiment of the present invention.

A distance measuring apparatus according to one embodiment of the present invention includes a laser generating section 1 for generating a laser beam, a light transmitting optical system 3 for expanding a laser beam emitted from the laser generating section 1 to a desired spread angle, A start detection circuit 2 for detecting the emission of laser light from the laser generator 1 and generating a start pulse; and a light receiving optical system 4 for guiding the reflected light from the target 11 to a light receiving circuit
And a part of the reflected light from the target object 11 in a predetermined dynamic range, for example, M, for example, 1/10 of the incident light,
A plurality of beam splitters 5A to 5C for extracting light having a light amount of 1/100,... 1 / N, and a plurality of beams for respectively detecting reflected light from the target 11 extracted by the beam splitters 5A to 5C. Detectors 6A-6
C and peak detection circuits 7A to 7C for detecting respective peak values of outputs from the plurality of detectors 6A to 6C.
A light receiving circuit 8 for detecting reflected light from the target 11 to generate a stop pulse; and a counter for measuring a time interval between the start pulse output from the start detecting circuit 2 and the stop pulse output from the light receiving circuit 8. Circuit 9, count data from counter circuit 9 and peak detection circuit 7
And a calculation unit 10 that performs distance correction using the peak values of the received light output from A to 7C.

Next, the operation of the embodiment of the present invention will be described. The laser light emitted from the laser generator 1 is
The beam is spread to a desired beam divergence angle through the light transmission optical system 3 and is emitted toward the target 11. Part of the laser light emitted from the laser generator 1 is supplied to the start detector circuit 2.
, And a start pulse is generated at the timing. The start pulse thus generated is sent to the counter circuit 9 to start the counter operation inside the counter circuit.

As described above, normally, when the intensity of incident light is extremely high, the output level of the detector is saturated, the timing of the generation of the stop pulse in the counting operation by the counter is advanced, and the distance is reduced. Value is obtained. In the present embodiment, as described above, 1/10, 1/100,.
A plurality of beam splitters 5A to 5C for extracting light of N light amounts, a plurality of detectors 6A to 6C for detecting reflected light from the target 11 extracted by the beam splitters 5A to 5C, respectively; Detector 6A
6C are provided with peak detection circuits 7A to 7C for detecting the respective peak values of the outputs from.

The laser beam having a predetermined divergence angle from the light transmitting optical system 3 is applied to the target 11, a part of the reflected laser light returns, and a plurality of beam splitters are passed through the light receiving optical system 4. It is led to 5A-5C. The plurality of beam splitters 5A to 5C receive the reflected light, and correspond to the corresponding detectors 6A to 6C with a dynamic range of, for example, 1/10, 1/100,.
Output to The remaining reflected light that has passed through the beam splitters 5A to 5C is guided to the light receiving circuit 8.

More specifically, in the first beam splitter 5A, one of the lights received through the light receiving optical system 4 is received.
The light amount of / 10 is transmitted to the detector 6A. Further, in the next beam splitter 5B, the light amount of 1/100 of the light received by passing through the detector 6B is transmitted to the detector 6B. Further, in the beam splitter 5C, 1 / N of the light received through the preceding beam splitter is transmitted to the detector 6C.

The reflected signals guided to the plurality of detectors 6A to 6C and converted into electric signals are sent to a corresponding plurality of peak detection circuits 7A to 7C, where the peak values are detected. The detected peak value is output to the calculation unit 10.

On the other hand, the light receiving circuit 8 generates a stop pulse in response to the incident reflected light and sends it to the counter section 9. The stop pulse sent to the counter unit 9 is
Stops the counter operation started by the start pulse. The measurement time interval from the start pulse to the stop pulse thus obtained is output to the arithmetic unit 10.

The arithmetic unit 10 includes peak detection circuits 7A to 7C
An appropriate peak value is selected from the peak values output from the control circuit, a correction value is determined based on the selected peak value, and the correction value is added to the data output from the counter circuit and output as distance data.

Specifically, when the incident light level is very high, the operation of the detector 6A is saturated, and the peak detection circuit 7
The output of A also becomes a saturation level. Since this saturation level can be obtained experimentally in advance, if a level slightly lower than the obtained saturation level (for example, 80%) is set as a threshold value. If a peak value less than this threshold value is detected, it can be determined that the detector is operating normally.

Therefore, if a threshold value is set for each of the detectors 6A to 6C, and the detected levels of the actually obtained peak detection circuits 7A to 7C are compared with the threshold values, the detector operates normally. The detector that is operating and the detector that is in a saturated operation state can be distinguished from each other, and the level of incident light can be determined from the detector that is operating normally, so that a predetermined value can be added to the distance value obtained by the counter circuit 9 for correction. .

If the relation between the detector and the value to be added is tabulated in advance, the relation can be easily read and the correction processing can be performed.

[0024]

As described above, since the distance measuring apparatus according to the present invention corrects one laser beam for each laser beam according to the level of the reflected light, it can accurately detect a light receiving signal of any level. Good distance measurement.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a distance measuring apparatus according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser generation unit 2 start detection circuit 3 light transmission optical system 4 light reception optical system 5A to 5C beam splitter 6A to 6C detector 7A to 7C peak detection circuit 8 light reception circuit 9 counter circuit 10 operation unit 11 target

Claims (6)

[Claims] 1. A distance measuring apparatus having distance measuring means for measuring a distance to a target based on an emission timing of a laser beam emitted toward the target and a light receiving timing of receiving reflected light from the target. A plurality of light quantity extraction means for sequentially taking out the light quantity of the reflected light from the target so as to have a small light quantity, and a plurality of detector means for detecting each light from the plurality of light quantity extraction means and converting the light into an electric signal A peak detection unit that detects a peak value of each of the outputs of the plurality of detector units, and a distance obtained by the distance measurement unit based on the peak values of the plurality of detector units obtained by the peak detection unit. And a calculating means for correcting the distance. 2. The apparatus according to claim 1, wherein said calculating means corrects a predetermined value determined based on the peak values of said plurality of detector means obtained by said peak detecting means as a distance obtained by said distance measuring means. The distance measuring device as described. 3. The distance measuring means obtains a predetermined value determined based on a detector having a peak value equal to or less than a predetermined threshold value for each detector among peak values of the plurality of detector means. The distance measuring apparatus according to claim 1, wherein the distance is corrected. 4. The distance measuring apparatus according to claim 1, wherein said plurality of detectors and said predetermined value are tabulated. 5. A distance measuring apparatus according to claim 1, wherein said light quantity extracting means is means for optically branching at a plurality of levels in consideration of a dynamic range of said plurality of detectors. 6. A distance measuring apparatus according to claim 1, wherein said light quantity extracting means is a beam splitter.