JPH06265636A - Laser distance measuring apparatus - Google Patents

Abstract

PURPOSE:To suppress the measuring errors caused by the fluctuation of the rising time of a received light pulse in a laser distance measuring apparatus, which performs the distance measurement based on the round trip time of the pulse laser light to a target. CONSTITUTION:The reflected light of the pulse laser light, which is transmitted from a laser generating part 2 through a light transmitting optical system 3, from a target 16 is reflected from a reflector 4 in multiplex times. Each reflected light is received with a light receiving optical system 5. Photoelectric conversion is performed in a photodetector 6. Thus, the output of the detection of the light in the pulse train corresponding to the received light input is obtained. The output pulse train is inputted into an amplifier 7 having a threshold value and the effective level is judged. Only the value, which exceeds a threshold value for judging the effective level is selected and made to be the stop signal. The signals are counted by a stop counter, 8. The operation for dividing the distance data, which are obtained by a distance counter 9 and a latch circuit 10 by utilizing the last of the stop signals, by the counted value (n) is performed in an operation ROM 11. Thus, the actual distance is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser range finder,
In particular, the present invention relates to a laser range finder that measures the distance to a target based on the round-trip time of pulsed laser light emitted toward the target.

[0002]

2. Description of the Related Art Conventionally, a laser range finder of this type measures a distance based on one round trip time until a pulse laser beam irradiated toward a target is reflected from the target and received by a light receiving system. .

In this case, the reflected light fluctuates depending on the distance to the target, the reflectance of the target, the weather conditions in the propagation space, etc., and this appears as fluctuations in the rise time of the received pulse due to the reflected light. The fluctuation of the rising time of the received pulse causes the count value of the counter that counts the round trip time to change using the stop signal normally generated based on the received pulse, and has been a main cause of the distance measurement error.

In order to solve this problem, Japanese Patent Laid-Open No. 2-664
In Japanese Patent Publication No. 84, a plurality of beam splitters are arranged in a light receiving system to divide a light receiving input into a plurality of light receiving inputs, and a plurality of optical attenuators each having a different optical attenuation amount in the branched paths, and a plurality of these optical attenuators. The lowest level of the multiple detection outputs of the multiple received light pulses received by the multiple photoelectric converters and the multiple detector systems equipped with the pulse height discrimination waveform shaping circuit It discloses that the signal is selected as a signal and fluctuations in the rise time of the received pulse due to reflected light are suppressed.

[0005]

In order to suppress the rise time fluctuation of the received pulse in this conventional laser range finder, a plurality of beam splitters are arranged in the light receiving system to divide the light receiving input into a plurality of light receiving inputs. Since an optical attenuator and a detector system including a photoelectric converter and a waveform discriminating waveform shaping circuit are arranged at each of the inputs, there is a problem that the device becomes complicated and the time required for optical and electrical adjustment increases. It was

Further, in the light receiving system, since the light receiving input is branched by a plurality of beam splitters to perform the light receiving processing, the interposition of the beam splitter itself causes the light receiving level to be approximately 1 for each time.
It will be reduced to / 2, and even if there are multiple light receiving optical systems, there is a structural limit, so there is a limit to the number of reception levels that can be selected. There was a problem in that there was a limit to the conversion.

The object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a laser distance measuring device having a simple structure capable of greatly improving a distance measuring error due to a change in rise time of a received pulse, that is, a light receiving pulse.

[0008]

An apparatus of the present invention is a laser which receives reflected light of pulsed laser light emitted toward a target and measures the distance to the target based on the round-trip time of the pulsed laser light. In the distance measuring device, the reflected light is received while being multiple-reflected between the target and the reflector, and a predetermined threshold value that is determined as an effective level among a plurality of reflected lights from the target obtained by the multiple reflection A means for measuring the distance to the target is defined as 1 / n of the multiple round-trip time determined by the light reception timing of the final reflected light of n reflected light beams exceeding n.

According to the apparatus of the present invention, the multiple round-trip time of the pulsed laser light is generated in synchronization with the emission timing of the pulsed laser light, and the n number of the pulsed laser light obtained by multiple reflections of the pulsed laser light. The configuration is such that it is obtained from a count value based on a stop signal generated in synchronization with the last reflected light of the reflected light.

The apparatus of the present invention is a laser range finder that receives reflected light of pulsed laser light emitted toward a target and measures the distance to the target based on the round-trip time of the pulsed laser light. A laser is generated and is output as a transmission pulse laser light through a light transmission optical system, and the reflected light from the target is multiple-reflected between the target and the reflector and is synchronized with the output of the transmission pulse laser light. Laser light transmitting means for outputting a start signal for setting the start timing of distance measurement to the target, and a plurality of reflected lights obtained by multiple reflection of the laser light transmitting means are received as received laser light through a light receiving optical system. The n outputs generated in correspondence with the n reflected lights exceeding the predetermined threshold for determining the effective level are used to measure the distance to the target. Laser light receiving means for outputting as n stop signals for setting a measurement period including end timing, and measurement of multiple round-trip times required for multiple reflection up to the target by the start signal and the n number of stops. And a distance calculating means for measuring the multiple round-trip time set by a signal and calculating 1 / n thereof as the round-trip time to the target in order to visually display the distance to the target.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, FIG.
3 is a timing chart of main signals in FIG.

The laser distance measuring apparatus according to the present embodiment sends out a sending pulsed laser beam 301 and also starts a start signal 201.
And a laser light transmitting section 13 which constitutes a laser light transmitting means for multiply reflecting the transmission pulsed laser light with the target 16, and the laser light transmitting section 13 multiple reflection between the target 16 and the laser light transmitting section 13. The laser light receiving unit 14 that constitutes the laser light receiving unit that receives the received pulsed laser light 501 and outputs n stop signals 701 of a pulse train corresponding to a photoelectric conversion that exceeds a predetermined threshold value. , A start signal 201 and a stop signal 701 are input, and based on these two signals, the transmitted pulsed laser light 301
The number of multiple round trip times to and from the target 16 is calculated, and one round trip time of the pulsed laser light to the target 16 is calculated by using 1 / n of this time to obtain the distance to the target 16. ,
A distance calculation unit 15 that constitutes a distance display unit that visually displays is provided.

The laser light transmitting unit 13 receives the trigger signal 101 generated by the pulse generating unit 1 output from the distance calculating / displaying unit 15, which will be described later, and generates the pulsed laser light. The light-sending optical system 3 for irradiating the target 16 as the sending pulsed laser light 301 and the target 1
The reflector 4 that multiple-reflects the reflected light from the target 16 and the target 16.

The laser light receiving section 14 is arranged in the vicinity of the reflector 4 and receives the reflected wave and the multiple reflected wave from the target 13 as the received pulse laser beam 501 at the same time as the reflector 4, and the light receiving optical system 5. The photodetector 6 that photoelectrically converts the received light input of the optical detector 6 and outputs it, and only the pulse train included in the photodetection output of the optical converter 6 that exceeds a predetermined threshold value for determining the effective level is output as the stop signal 701. And an amplifier 7 with a threshold value.

The distance calculation display unit 15 is reset by the pulse generator 1 that outputs a trigger signal 101 that drives the entire operation and a reset signal 102 that resets the distance calculation operation, and the reset signal 102 that the pulse generator 1 outputs. The stop counter 8 which counts the number of the stop signals 701 and outputs as the stop counter value 801, and the start signal which is reset by the reset signal 102 output by the pulse generator 1 and is output by the laser generator 2 in synchronization with the laser generation. Start counting at 201 and distance data 9
The distance counter 9 that outputs 01, the latch circuit 10 that latches the distance data 901 at the rising timing of the stop signal 201 and outputs the distance data string 1001, and the target 16 up to the target 16 based on the distance data string 1001 and the stop counter value 801 ROM 11 for calculating the distance of
And a distance display unit 12 for visually displaying the calculated distance.

Next, the operation of this embodiment will be described.

The trigger signal 101 output from the pulse generation unit 1 of the distance calculation display unit 15 is input to the laser generation unit 2 to generate pulse laser light, and this pulse laser light is transmitted through the light transmission optical system 3 The target 16 is irradiated with 301 and the start signal 201 is output to the distance counter 9 at a timing synchronized with the generation timing of the pulsed laser light from the laser generator 2. This start signal 201 is shown in FIG.

The palace laser light reflected from the target 16 is repeatedly reflected by the reflector 4 and irradiated on the target 16 repeatedly, and is reflected multiple times between the target 16 and the reflector 4, and the light receiving optical system is reflected each time. 5 is incident as a received pulsed laser beam 501. The reflected light from the target is shown with a double arrow by a dotted line.

The photodetector 6 photoelectrically converts the received light input and outputs it as a photodetection output 601 to the amplifier with threshold value 7. The light detection output 601 is illustrated by P1, P2, ..., P7 in FIG. The photodetection output 601 becomes a pulse train whose peak value decreases due to propagation and reflection loss for each round trip.

The amplifier with threshold value 7 compares the input photodetection output 601 with a predetermined threshold value as shown in FIG. 2B, and the photodetection output exceeding this threshold value, the example of FIG. Then, pulses corresponding to five photodetection outputs P1 to P5 are generated and sent to the stop counter 8 as a stop signal 701. This threshold value is preset as a value for determining the validity of the light detection output level. This stop signal 701 is shown in FIG.

The stop counter 8 is reset by the reset signal 102 output from the pulse generator 1, counts the number of pulses of the input stop signal 701, and sets the count value as a stop counter value 801 in the arithmetic ROM 1
Send to 1. This stop counter value 801 is shown in FIG.
It shows in (d). In the example of FIG. 2D, the stop counter value is "5".

The distance counter 9 is reset by the reset signal 102 output from the pulse generator 1, starts counting by the start signal 201 supplied from the laser generator 2, and has a predetermined distance value corresponding to the count time. The data of the data structure. The latch circuit 10 latches at the rising timing of the stop signal 701 indicated by the arrow in FIG. 2C, and sends it to the arithmetic ROM 11 as the distance data string 1001. This distance data string 1001 is shown as D in FIG.
, D2, ..., D5.

The arithmetic ROM 11 stores the final distance data included in the input distance data string 1001 and the distance data indicated by D5 in the case of FIG. 2 (e) as the stop counter value output from the stop counter 8, that is, the number of multiple reflections. The actual distance as a divided value is obtained, and the actual distance is visually displayed on the distance display unit 12.

As described above, the distance measurement is performed by using the multiple reflection term in which the pulsed laser light is reflected multiple times between the reflector 4 and the target 16, so that the photodetection output used for the distance measurement is previously obtained. Since the value becomes close to the threshold value to be set and the fluctuation is remarkably suppressed, it is possible to remarkably suppress the fluctuation error of the rise time of the received light pulse. Can be compressed into.

Conventionally, the error of this type of laser range finder is
Unless consideration is given to error elimination, the error due to the rise time of the received light pulse is the main factor and is almost constant regardless of the distance. In other words, it is small enough for long distances,
There was a relatively large error at short distances. According to the present invention, when the distance is short, the power of the pulsed laser light is less attenuated, the number of reflections increases, and the distance measurement error can be further improved in inverse proportion to the distance.

In this way, it is possible to remarkably improve the distance measurement error due to the rising fluctuation of the received light pulse with a simple structure.

[0028]

As described above, according to the present invention, the reflected light is multiply reflected between the target and the reflector, and based on the final reflected light of n multiple reflected lights exceeding the threshold value for judging the effective input. By obtaining the distance to the target by setting the measured round-trip time to 1 / n, fluctuations in the rise time of the received light pulse due to the reflected light are significantly suppressed, and the distance measurement error is reduced to 1 / n.
There is an effect that it is possible to realize a laser distance measuring device having a simple structure that can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a timing chart of main signals in FIG.

[Explanation of symbols]

 1 pulse generator 2 laser generator 3 light-transmitting optical system 4 reflector 5 light-receiving optical system 6 photodetector 7 threshold amplifier 8 stop counter 9 distance counter 10 latch circuit 11 arithmetic ROM 12 distance display 13 laser light transmission Part 14 Laser light receiving part 15 Distance calculation part 16 Target

Claims (3)

[Claims] 1. A laser range finder that receives reflected light of pulsed laser light emitted toward a target and measures the distance to the target based on the round-trip time of the pulsed laser light. The n-th reflected light which is received while being multiple-reflected between the target and the reflector and which exceeds a predetermined threshold value which is determined as an effective level among a plurality of reflected lights from the target obtained by the multiple reflection A laser distance measuring device comprising means for measuring the distance to the target by using 1 / n of the multiple round-trip time determined by the reception timing of the reflected light as the round-trip time of the pulsed laser light. 2. The multiple round-trip time of the pulsed laser light is:
Counting based on a start signal generated in synchronization with the emission timing of the pulsed laser light and a stop signal generated in synchronization with the last reflected light of the n reflected lights obtained by multiple reflections of the pulsed laser light The laser distance measuring apparatus according to claim 1, wherein the laser distance measuring apparatus is obtained from a value. 3. A laser range finder that receives reflected light of pulsed laser light emitted toward a target and measures the distance to the target based on the round-trip time of the pulsed laser light generates a pulsed laser. This is output as a transmission pulse laser light through the light transmission optical system, and the reflected light from the target is multiple-reflected between the target and the reflector and the distance to the target is synchronized with the output of the transmission pulse laser light. Laser light transmitting means for outputting a start signal for setting measurement start timing, and a plurality of reflected lights obtained by multiple reflections of the laser light transmitting means are received as received laser light through a light receiving optical system and judged as an effective level. The n outputs generated corresponding to the n reflected lights exceeding the predetermined threshold are set to the end timing of the distance measurement to the target. Laser light receiving means for outputting as n stop signals for setting the measurement period including, and measurement of multiple round-trip times required for multiple reflections to the target by the start signal and set by the n stop signals Distance measuring means for measuring the multiple round-trip time and calculating 1 / n thereof as the round-trip time to the target to visually display the distance to the target. .