JPH0921871A - Semiconductor laser distance measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct rough measurement and accurate measurement at the same time, and make measurement of long distance possible with high accuracy and in a short time in a distance measuring device using a semiconductor laser. SOLUTION: A reference pulse 15 sent from a clock generating part 1 and a pulse signal 16 sent from a pulse producing part 2 are inputted to an AND computing element 3, a light projection signal 17 is outputted, projected to an object in a laser driving part 4 and a semiconductor laser 5, its reflection is received with a light-receiving element 8 and an amplifier 8, then inputted to a phase detecting device 11 and a light-receiving timing detection part 10. In accurate measurement, phase difference to the reference pulse 15 is measured with the phase detecting device 11, and in rough measurement, time difference to a pulse signal 16 is measured with a time measuring part at the same time, both outputs 20, 21 are operated with an operation part 13 to calculate distance, then the distance obtained is displayed in a display part 14. Long distance can be measured with a semiconductor laser, with high accuracy, in a short time, and in large output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to distance measurement using a semiconductor laser, and more particularly to a semiconductor laser distance measuring device capable of measuring a long distance with a distance measuring range of 10 cm or more with high accuracy.

[0002]

2. Description of the Related Art As a conventional distance measuring method using a semiconductor laser, (a) a method of measuring the flight time from the emission of light to the reflection and return of an object using a single pulsed light (Time-of-flight measurement method), (b) A method (phase difference detection method) of detecting the phase difference between the light emission and the reflection and return to the object using the modulated light of a single frequency is used. There is.

FIG. 8 is a diagram showing the configuration of a distance measuring system using such a conventional semiconductor laser.
The driver 42 is driven by to emit a laser beam from the semiconductor laser 43, and the laser beam is emitted to the object 37 at the distance L through the optical system 44. The laser light reflected from the object 37 receives the light receiving system 45.
And the light is received by the light receiving element 46 and amplified by the amplifier 47 to become the light receiving signal 48.

FIG. 9 (a) shows the measurement principle of the above-mentioned flight time measurement method as one of such distance measuring methods. The light emission signal 40 and the light reception signal 48 are reflected from the object 37 and returned. Measure the time Δt to arrive and measure the distance;
It is calculated as L = (C / 2) × Δt. However, C is the speed of light.

FIG. 9B shows the principle of the above-mentioned phase difference detection method. The light emission signal 40 is a pulse train of frequency f ₁ , and the light reception signal 48 is returned when this pulse train is reflected by the object 37. Since the phase difference θ is generated, the distance is; L =
It is determined as (C / 2f ₁ ) × (θ / 2π). Where C
Is the speed of light.

[0006]

The above-mentioned prior art FIG.
In the time-of-flight measurement method shown in (a), high output is obtained by using a pulse semiconductor laser, and long-distance measurement is possible. However, a time resolution of several hundred ps is required to obtain an accuracy of 1 cm, but the high resolution time measurement counter and the feasibility of generating a short light emission pulse and the error in the light reception timing detection time difference due to the change in the light reception level cause a high error. Precision is difficult. Currently, the portable type has been commercialized with an accuracy of about 5 cm.

In the phase difference detection method described with reference to FIG. 9B,
High accuracy distance measurement is possible by using the phase detector. Currently, products with an accuracy of about 5 mm have been commercialized for surveying. However, since the CW semiconductor laser is used, the output is low, and it is difficult to measure a long distance.
The target is often a reflector.

In this phase difference detection method, the phase is 2π.
When they are deviated, they have the same phase, so only distances corresponding to 0 to 2π can be measured, and in order to measure a long distance, it is necessary to detect and calculate phase differences for two or more types of frequencies. There is a problem that several measurements are required for one distance output and it takes time.

[0009]

In order to solve such a problem, the present invention provides a clock generator, a pulse generator,
Drive unit, pulse semiconductor laser device, light receiving unit, phase detection unit that outputs a precise measurement phase signal from the signal from the light receiving unit, time measurement unit that also outputs a rough measurement time signal from the signal from the light receiving unit, these precise measurement phases Input the signal and the rough measurement time signal,
It is characterized by comprising a calculation unit for calculating the distance and a display unit.

That is, according to the present invention, a clock generator for generating a clock pulse as a reference signal, a pulse generator for generating an output pulse, and the clock pulse output between the output pulses from the pulse generator. And a pulse semiconductor laser device that emits a pulse laser beam toward an object by a light emission signal from the drive unit, and a pulse laser beam that is emitted from the pulse semiconductor laser device and reflected from the object A light receiving part for receiving the light receiving signal and a light receiving signal from the same light receiving part are input, a phase detection part for detecting a phase difference with the clock pulse and outputting a precise phase signal, and a light receiving signal from the light receiving part are input. Then, comparing with the output pulse signal from the output pulse generation unit, to obtain the time difference from it, a time measuring unit for outputting a rough measurement time signal, and a precise measurement phase signal from the phase detection unit and The rough measurement time signal from the time measurement unit is input, the precise measurement distance and the rough measurement distance are calculated, and the calculation unit that calculates the distance to the object based on these values and the output of the calculation unit are received. The present invention provides a semiconductor laser distance measuring device comprising a display section for displaying the same.

The present invention has the following operations by such means. A clock pulse serving as a reference signal is emitted from the clock generation unit. First, when the pulse generation unit issues an output pulse, the drive unit outputs a light projecting signal for outputting the clock pulse within the output pulse width. The pulsed semiconductor laser device receives the light projection signal from the drive unit and emits pulsed laser light to the object.

The pulsed laser light reflected from the object and returning is received by the light receiving section and outputs a light receiving signal to the phase detecting section and the time measuring section. The phase detection unit compares the received light signal with the clock pulse by the received light signal and measures the phase to output a precise measurement phase signal, which enables distance measurement with the same accuracy as the phase difference detection method. At the same time, the time measuring unit compares the light receiving signal with the output pulse signal and outputs the rough measurement time signal by measuring the time, which enables rough distance measurement.

These precise measurement phase signal and rough measurement time signal are input to a calculation unit, and the calculation unit calculates a precise measurement distance and a rough measurement distance according to the speed of light and frequency, and the result of the precise measurement distance and the rough measurement distance are calculated. By calculating the result of the distance, the distance of the object can be measured with the same accuracy as the phase difference detection method without being limited to the distance. These pieces of distance information are displayed on the display unit as needed.

Further, since the rough measurement and the precise measurement can be simultaneously processed by one light emission, the measuring time is short. It is possible to measure a long distance by using a pulsed semiconductor laser device of high output.

[0015]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a semiconductor laser distance measuring device according to an embodiment of the present invention. In the figure, 1 is a clock generator that generates a clock pulse, 2 is a pulse generator that receives a reference signal 15 from the clock generator 1, and generates a pulse signal 16, and 3 is a reference signal 15 and a pulse generator 2. AN for inputting the pulse signal 16 and outputting a light projecting signal 17
D arithmetic unit, 4 is a laser drive unit for driving the pulse semiconductor laser 5 by the light projection signal 17, 5 is a pulse semiconductor laser for emitting the above-mentioned pulse laser light, and 6 is a projection optical system for projecting the laser light on an object. Is.

Reference numeral 7 is a light receiving optical system for receiving the pulsed laser light reflected back from the object, 8 is a light receiving element, 9 is an amplifier, 10 is a light receiving timing detecting section, and 11 is a light receiving signal 18 amplified by the amplifier 9. A phase detection unit that receives the reference signal 15 and detects a phase difference, and a time 12 that receives the light reception timing signal 19 from the light reception timing detection unit 10 and the pulse signal 16 from the pulse generation unit 2 and measures the time difference. The measuring unit 13 is the precise measurement phase output 20 from the phase detecting unit 11.
And the rough measurement time output 21 from the time measuring unit 12,
A calculation unit for calculating the distance, and 14 is a display unit for receiving the distance measurement output 22 from the calculation unit 13 and displaying it.

FIG. 2 is a waveform diagram showing signals and their timings in the distance measuring device shown in FIG.
Is the reference signal 15 generated by the clock generator 1, (b)
Is a pulse signal 16 generated by the pulse generator 2 and having a pulse width 24. (c) is a reference signal 15 and a pulse signal 16
And the light emission signal 17 output from the AND calculator 3 is
(D) shows the phase difference θ between the light receiving signal 18 received by the light receiving element 8 and amplified by the amplifier 9 and the reference signal 15, and (e) shows the pulse with the light receiving timing signal 19 detected by the light receiving timing detecting section 10. The time delay Δt 26 from the signal 16 is shown.

In such a distance measuring device, the clock generator 1 outputs the reference signal 15 having the frequency f ₁ .
The reference signal 15 and the pulse signal 16 output from the pulse generator 2 are input to the AND operator 3, where the AND signal is output.
The calculation is performed and the light projection signal 17 is generated. This light projection signal 17 is a reference signal 15 as shown in FIGS.
The pulse is generated only during the pulse width 24 of the pulse signal 16 of the pulse of. The laser drive unit 4 is driven by the light projecting signal 17, and laser light is emitted from the pulse semiconductor laser 5.

The light from the pulse semiconductor laser 5 is reflected by an object through a light projecting optical system 6, condensed by a light receiving optical system 7 and made incident on a light receiving element 8, and then a light receiving signal 18 is produced by an amplifier 9.

In the case of receiving the light receiving signal 18 and obtaining the distance, the precise measuring method will be described first. Light reception signal 18
Is compared in phase with the reference signal 15 by the phase detector 11. FIG. 3 shows the internal configuration of the phase detector 11.

In FIG. 3, the reference signal 15 is set to sin (2
When expressed as πf ₁ t), the received light signal 18 is sin (2π
f ₁ −θ). The output of the multiplier 27 to which these signals 15 and 18 are input is cos (4πf ₁ t−θ) and c
It consists of a component of osθ. When this output is integrated by the integrator 28, cos θ is output as the precise measurement phase output 20. This is inversely transformed in the arithmetic unit 13 to obtain θ
Then, the precise measurement distance R ₁ is obtained from the relationship between the phase difference θ and the distance R ₁ shown in the following equation (1).

[0022]

[Equation 1]

Here, d ₁ is a distance correction value for the phase delay in the optical system and the circuit, and is obtained by measuring an object whose distance is known in advance or directly receiving the light projected by a mirror or the like.

Next, the rough measuring method will be described. The light reception signal 18 is input to the light reception timing detection unit 10 and the light reception timing is detected. 4, 5 and 6 show typical configurations of the light reception timing detection unit 10.

FIG. 4 shows the comparator 2 as shown in FIG.
9, the rise time of the light receiving signal 18 is measured by the latch 30 and the reset signal 33, and the light receiving timing signal 19 is output as shown in (b) (method 1).

FIG. 5 shows, as shown in FIG.
Is detected by the wave detector 31, a detection signal 32 is output, and this is compared by the comparator 29. When the latch 30 and the reset signal 33 exceed the threshold value, the light reception timing signal 19 is output. In this method, as shown in (b), the received light signal 1
The detection signal 32 of No. 8 is compared with a predetermined threshold value 35 to obtain a time delay Δt ′ 36, and the light reception timing signal 19 is output at this time Δt ′ (method 2).

As shown in FIG. 6A, the received light signal 18 is detected by the wave detector 31, the wave detection signal 32 is output, and this is differentiated by the differentiator 33, and the differentiated signal 34 is input to the comparator 29. The peak of the detection signal 32 is obtained, and the latch 30 and the reset signal 33 are used to detect the light reception timing signal 1 at this peak.
9 is output. In this method, as shown in (b), a differential signal 34 obtained by finely detecting a detection signal 32 obtained by detecting the light reception signal 18 is obtained.
Then, the time at which the peak of the detection signal 32 is reached by this signal is set as a time delay Δt ′ 36, and the light reception timing signal 19 is output at this Δt ′.

Here, in the case of the method of FIGS. 5 and 6, the time delay Δt'36 in the light receiving timing detection unit 10 is shown in FIG.
Time delay Δt26 of the light receiving timing signal shown in (e)
include. Returning to FIG. 1, there is a time delay Δt from the rise of the pulse signal 16 to the rise of the light receiving timing signal 19.
26 is measured by the time measuring unit 12, and the rough measurement time output 2
Output as 1. The rough distance R ₂ is calculated from the relationship between the time delay Δt 26 and the distance R _{2 in} the calculation unit 13 by the following equation (2).

[0029]

[Equation 2]

Here, d ₂ is a distance correction value for the time delay in the optical system and the circuit (including the time delay Δt'36 in the light receiving timing detection unit), and is obtained by the same method as d ₁ in the precise measurement distance. .

Next, a method of obtaining the object distance R from the precise measurement distance R ₁ and the rough measurement distance R ₂ will be described. Here, the precision distance error is ± ΔR ₁ and the rough distance error is ± ΔR ₂ .
In the precise measurement, when the phase shifts by 2π, there is a repetition of the distance due to the same phase, and the distance R of the object is expressed by the following equation (3).

[0032]

(Equation 3)

FIG. 7 shows the relationship between the precise / coarse measurement distance and the object distance. In this equation (3), the distance R of the object 37 is obtained by finding n that minimizes the difference from the rough measurement distance R ₂ . However, the frequency f ₁ is selected so as to satisfy the following expression (4). The distance accuracy under this condition is ±
It becomes ΔR ₁ .

[0034]

(Equation 4)

In FIG. 1, the position R of the object obtained as described above is passed to the display unit 14 as a distance measurement output 22 and displayed or output to the outside. Further, in such a distance measuring device, precise measurement and rough measurement are processed at the same time.
Distance can be measured with one flash.

According to the embodiment described above, pulses are generated by the clock generator 1, the pulse generator 2, the AND operator 3, the laser driver 4, and the pulse semiconductor laser 5, and the light receiving element 8, the amplifier 9, A rough distance measurement (coarse measurement) is possible by measuring the time required for the light reception timing detection unit 10 and the time measurement unit 12 to reflect the object and return it, and the phase of the modulation signal in the reference pulse 15 can be calculated. By measuring with the phase detection unit 11, it is possible to perform distance measurement (precision measurement) with accuracy equivalent to that of the phase difference detection method. By calculating the rough measurement result and the precise measurement result by the calculation unit 13, the distance R of the object can be measured with the same accuracy as the phase difference detection method without limiting the distance.

Further, since the rough measurement and the precise measurement can be simultaneously processed by one light emission, the measuring time is short. Furthermore, by using the high-power pulse semiconductor laser 5, it is possible to measure a long distance.

[0038]

As described above in detail, according to the present invention, the precise phase signal is output by the signals from the clock generator, the pulse generator, the driver, the pulse semiconductor laser device, the light receiver, and the light receiver. A phase detection unit, a time measurement unit that also outputs a rough measurement time signal from a signal from the light receiving unit, a calculation unit that inputs the precise measurement phase signal and the rough measurement time signal, and a display unit Since it is characterized by a semiconductor laser distance measuring device, pulse delay time measurement (coarse measurement) and phase difference detection (precision measurement) enable measurement in a short time with the same accuracy as the phase difference detection method regardless of distance. It will be possible. In addition, it is possible to measure a long distance by using a pulse semiconductor laser.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a semiconductor laser distance measuring device according to an embodiment of the present invention.

FIG. 2 is a signal timing and waveform diagram in the semiconductor laser distance measuring apparatus according to the embodiment of the present invention.

FIG. 3 is a detailed block diagram of the inside of the phase detection unit in FIG.

4A is a detailed block diagram (method 1) of the inside of a light receiving timing detection unit in FIG. 1A and FIG. 4B is a waveform diagram thereof.

5 (a) is a detailed block diagram (method 2) inside the light receiving timing detection unit in FIG. 1 and (b) is a waveform diagram thereof.

6A is a detailed block diagram (method 3) inside the light receiving timing detection unit in FIG. 1A, and FIG. 6B is a waveform diagram thereof.

FIG. 7 is a diagram showing a relationship between an accurate distance and a rough distance and an object distance in the semiconductor laser distance measuring device according to the embodiment of the present invention.

FIG. 8 is a configuration diagram of a conventional distance measuring method.

9A and 9B are diagrams showing the principle of a conventional distance measuring method, FIG. 9A showing a flight time measuring method, and FIG. 9B showing a phase difference detecting method.

[Explanation of symbols]

 1 Clock Generation Section 2 Pulse Generation Section 3 AND Operation Unit 4 Laser Driving Section 5 Pulse Semiconductor Laser 8 Light-Receiving Element 9 Amplifier 10 Light-Reception Timing Detector 11 Phase Detection Section 12 Time Measurement Section 13 Calculation Section 14 Display Section 15 Reference Signal 16 Pulse Signal 17 Light emitting signal 18 Light receiving signal 19 Light receiving timing signal 20 Precise measurement phase output 21 Coarse measurement time output 22 Distance measurement output

Claims (1)

[Claims] 1. A light emitting signal which outputs a clock pulse between a clock generating section for generating a clock pulse serving as a reference signal, a pulse generating section for generating an output pulse, and an output pulse from the pulse generating section. And a pulse semiconductor laser device that emits a pulse laser beam toward an object by a light emission signal from the drive unit, and a light receiving device that receives the pulse laser beam emitted from the pulse semiconductor laser device and reflected from the object Section and the light receiving signal from the same light receiving section,
The phase difference with the clock pulse is detected, the phase detection unit that outputs a precise measurement phase signal, and the light reception signal from the light reception unit are input, and compared with the output pulse signal from the output pulse generation unit. The time difference is obtained, and the time measurement unit that outputs the rough measurement time signal, the precise measurement phase signal from the phase detection unit, and the coarse measurement time signal from the time measurement unit are input, and the precise measurement distance and the coarse measurement distance are obtained. In addition, the semiconductor laser distance measuring device is provided with a calculation unit that calculates the distance to the object based on these values, and a display unit that receives the output of the calculation unit and displays it. .