JPH09297014A - Laser radar 3-d form measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser radar 3-D form measurement device which can precisely measure even from a distant place and whose resolution in distance direction is easily raised. SOLUTION: Two laser beams 100 of different wavelengths are generated from a laser generation device 1, and the same point of a sample 10 is irradiated with the two laser beams 100 through an optical branching device 2 and a deflection device 3 at the same time, for scanning of the sample 10, and two reflected laser beams 101 from the sample 10 are made incident to a photodetector 4 for detection of synthesized optical signal. An output signal of the photodetector 4 is processed with a frequency analyzer 5 and a distance information calculator 6 to calculate a distance information, and then, a 3-D form of the sample 10 is, with a 3-D form calculator 8, found from the distance information and an angle information from the two laser beams 100 for the sample 10, which is processed with an angle information processor 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser radar three-dimensional shape measuring apparatus for measuring the three-dimensional shape of an object using laser light.

[0002]

2. Description of the Related Art Conventionally, for example, when measuring the three-dimensional shape of an object such as a hull member or a large steel structure of a bridge, the distance to the object to be measured is optically measured using laser light, A laser radar three-dimensional shape measuring device that detects a three-dimensional shape of a measurement target is used.

In a conventional laser radar three-dimensional shape measuring apparatus, a laser beam is radiated onto the object to be measured, the object to be scanned is scanned, and the reflected laser beam from the object to be measured is detected. The distance to the measurement target is calculated based on the light and the angle is calculated from the direction of the laser light with which the measurement target is irradiated, and the three-dimensional shape of the measurement target is obtained based on the distance and the angle.

Here, the conventional laser radar three-dimensional shape measuring apparatus has a pulse method (for example, Japanese Patent Laid-Open No. 7-13992).
3) and a phase difference method (for example, Japanese Patent Laid-Open No. 7-1).
There are two measurement methods (described in Japanese Patent No. 39925), and each of them has a different method of calculating the distance to the measurement target.

In the pulse method, a pulsed laser beam corresponding to a predetermined clock pulse is irradiated, the time difference between this laser beam and the reflected laser beam from the measurement object is measured, and the distance from this time difference to the measurement object is measured. To calculate.

On the other hand, in the phase difference method, laser light whose intensity is modulated by a predetermined modulation signal is irradiated, the phase difference between this laser light and the reflected laser light from the measuring object is measured, and this phase difference is measured. Calculate the distance from to the measurement target.

[0007]

As described above, the conventional laser radar three-dimensional shape measuring apparatus is roughly classified into two measuring methods, a pulse method and a phase difference method. However, there is a problem that it is difficult to accurately obtain the distance information by any of the pulse method and the phase difference method, and the measurement accuracy is deteriorated.

Further, in order to increase the resolution in the distance direction, it is necessary to use a high-speed clock pulse having a narrow pulse width in the pulse system, and it is necessary to increase the modulation frequency in the phase difference system. There is a problem in that the device becomes complicated and the cost is increased due to the increase in speed and the increase in bandwidth.

An object of the present invention is to provide a laser radar three-dimensional shape measuring apparatus capable of performing precise measurement even from a long distance and easily improving the resolution in the distance direction.

[0010]

In order to solve the above problems, the present invention provides a laser scanning means for scanning a measurement target while simultaneously irradiating a plurality of laser beams having different wavelengths to the same position on the measurement target, and a laser scanning means. And a signal processing unit for processing an output signal of the light detection unit to obtain a three-dimensional shape of a measurement target.

In the laser radar three-dimensional shape measuring apparatus configured as described above, the phase relationship between a plurality of reflected laser beams having different wavelengths differs depending on the distance to the object to be measured, and accordingly, the combined light output from the photodetection means. Since the signal waveform of the signal also changes depending on the distance to the measurement target, the three-dimensional shape of the measurement target can be obtained by analyzing this signal waveform.

Specifically, for example, in the signal processing means, the output signal of the light detecting means is subjected to frequency analysis, the analysis result is converted into distance information of the measurement object, and this distance information and the angle information of a plurality of laser beams are used. If the three-dimensional shape of the measurement target is obtained, the distance information is obtained as a relative change in the distance to the measurement target due to scanning, and this distance information is not affected by the distance to the actual measurement target. Measurement accuracy does not change from a long distance.

Further, when the wavelengths of a plurality of laser beams irradiating the object to be measured are changed, the frequency of the output signal of the light detecting means is changed, and accordingly, the resolution in the distance direction is also changed.

[0014]

1 is a diagram showing a schematic configuration of a laser radar three-dimensional shape measuring apparatus according to an embodiment of the present invention. This laser radar three-dimensional shape measuring apparatus includes a laser generator 1, an optical branching device 2, a deflecting device 3, a photodetector 4,
It is composed of a frequency analyzer 5, a distance information calculator 6, an angle information processor 7, a three-dimensional shape calculator 8, and a display device 9,
The three-dimensional shape of the measurement target 10 is measured.

The laser generator 1 generates two laser lights 100 having wavelengths close to each other. In this embodiment, the laser light having a wavelength of 780.0 nm to 780.18 nm is divided into 1000 equal parts for every 0.00018 nm. Then, for example, laser light of two wavelengths such as wavelengths 780.0 nm and 780.00018 mm, wavelengths 780.0 nm and 780.00036 nm, wavelengths 780.0 nm and 780.00052 nm, ..., Wavelengths 780.0 nm and 780.18 nm. Occurs selectively. The two wavelengths are
It is selected according to the resolution in the distance direction described later.

Laser light 10 generated by the laser generator 1
0 is guided to the deflecting device 3 via the optical branching device 2. The deflecting device 3 is configured by combining a biaxial rotating mechanism such as a motor and a light reflecting member such as a mirror, and deflects the laser light 100 incident through the optical branching device 2 to measure the measurement target 10.
Simultaneously irradiating the same portion of the measurement target 10 with the measurement target 10 in the elevation direction V and the azimuth direction U as shown in FIG. In addition, the deflecting device 3 moves in the elevation angle direction V along with this scanning.
And information indicating the azimuth direction U is output to the angle information processor 7. In the following description, it is assumed that the measurement points A and B are scanned in this order, and the point (here, the measurement point A) where the laser beam 100 is first irradiated on the measurement target 10 is referred to as a reference point.

The laser light 100 deflected by the deflecting device 3 is reflected by the measuring object 10 and two reflected laser lights 101 are generated. Here, the light intensities of the two laser lights 100 at the measurement points A and B of the measurement target 10 are as shown in FIG. The horizontal axis represents the distance that the two laser beams 100 have passed from the laser beam generator 1, the vertical axis represents the light intensity, the thin lines represent the laser beams having the wavelengths of 780.0 nm and 780.00018 nm, and the thick lines represent the wavelengths of 780.17982 nm and 7.
This represents a laser beam of 80.18 nm.

The reflected laser light 101 enters the deflecting device 3 in the opposite direction to the laser light 100, is reflected by the optical splitter 2 and enters the photodetector 5. The photodetector 4 receives the reflected laser light 101 from the measurement target 10, detects the combined light intensity thereof, and outputs an electric signal corresponding to the combined light intensity. Here, the reflected laser light 101 has wavelengths close to each other, and assuming that the light intensities of the laser light 100 reflected by the measurement target 10 are I1 and I2 and the reflectance of the measurement target 10 is R, the reflected laser light 101 is combined. The light intensity I is calculated by the following formula.

I = R (I1 + I2) FIG. 4 shows an example of the time change of the combined light intensity detected in this way. The vertical axis represents time, the horizontal axis represents light intensity, and the reflected laser light 101 from the measurement point A in the measurement target 10 is measured.
Represents the combined light intensity of. Further, FIG. 5 shows the difference in the combined light intensity depending on the measurement points. The vertical axis represents time, the horizontal axis represents the light intensity, and the solid and dotted lines represent the combined light intensity of the reflected laser light 101 from the measurement points A and B, respectively. It represents the change over time. In this way, when the distance to the measurement target 10 is different as in the measurement points A and B, the combined light intensity is displaced.

The frequency analyzer 5 frequency-analyzes the signal corresponding to the combined light intensity output from the photodetector 4, and outputs the analysis result to the distance information calculator 6. Specifically, the frequency analyzer 5 Fourier transforms the output signal of the photodetector 4 to obtain the fundamental frequency. At this time, the frequency analyzer 5 first compares the basic frequency of the signal corresponding to the combined light intensity of the reflected laser light from the reference point (here, the measurement point A) with another measurement point (here, the measurement point B). Then, the difference in the fundamental frequency of the signal corresponding to the combined light intensity of the reflected laser light is obtained. For example, as shown in FIG. 6, the difference in fundamental frequency between the measurement point A and the measurement point B, which are reference points, is indicated by Δν. In FIG. 6, the horizontal axis represents frequency and the vertical axis represents light intensity.

The distance information calculator 6 converts the difference Δν of the fundamental frequencies, which is the analysis result output from the frequency analyzer 5, into distance information on the measurement object 10, and the three-dimensional shape calculator 8
Output to Specifically, the difference ΔR between the distance from the laser generator 1 to the reference point (here, the measurement point A) and the distance from the laser generator 1 to another measurement point (here, the measurement point B) is measured in the measurement target 10. Output as distance information. This distance difference ΔR is the above-mentioned difference in fundamental frequency Δ
When ν and the speed of light are c, ΔR = c / 2Δν calculated by the following equation. The resolution in the distance direction is also determined based on the above equation.
As described above, in the present embodiment, the wavelength is 780.0 nm
Since 780.18 nm is divided into 1000 equal parts and two selected wavelengths of laser light are irradiated, the minimum resolution in the distance direction is 780.0 nm and 780.18 nm.
It becomes 1.69 mm when irradiated with a laser beam of nm,
The dynamic range of the measurement area is 1690 mm.
The difference Δν of the fundamental frequency at this time is 88.74 GH.
z.

On the other hand, the angle information processor 7 has a measuring object 10
The information indicating the elevation angle direction V and the azimuth angle direction U output from the deflection device 3 in accordance with the scanning of 1 is processed, and the angle information with respect to the measurement target 10 is output to the three-dimensional information calculator 8.

The three-dimensional shape calculator 8 is the distance information calculator 6
The three-dimensional shape of the measurement target 10 is calculated based on the distance information of the measurement target 10 output from the angle information and the angle information of the measurement target 10 output from the angle information processor 7, and the result is output to the display device 9. The display device 9 displays the three-dimensional shape of the measurement target 10 as shown in FIG. 7, for example.

As described above, in the laser radar three-dimensional shape measuring apparatus of the present embodiment, the measuring object 10 is scanned while the measuring object 10 is irradiated with the laser beams 100 having different wavelengths, and the measuring object 10 is measured. Reflected laser light from 10 1
01 is detected, and the distance information to the measurement target 10 is obtained based on the fundamental frequency when the signal corresponding to the combined light intensity of the reflected laser light 101 is subjected to frequency analysis.

At this time, the laser beam 1 on the measuring object 10
00 is the reference frequency based on the reflected laser light 101 from the spot (measurement point A in the present embodiment) first, and the reflection laser from the other measurement point (measurement point B in the present embodiment) to this is the reference frequency. By obtaining the difference between the fundamental frequencies based on the combined light intensity of the light 101, the distance information is obtained as a relative change in the distance to the measurement target 10 due to the scanning, and this distance information is obtained from the actual measurement target 10. Since it is not affected by the distance, it is possible to measure even from a long distance without changing the accuracy.

The laser beam 1 for irradiating the object 10 to be measured
By changing the wavelength of 00, the resolution in the distance direction can be easily improved. In the above embodiment, the wavelength of 780.
The case of selectively irradiating laser light of two wavelengths of 0 nm to 780.18 nm has been described, but first, two laser light of wavelengths 780.0 nm and 780.000018 nm are irradiated, and then the wavelength of 780.0 nm. And 780.000036 nm, and the wavelengths of 780.0 nm and 780.005
2 nm, ..., Wavelength 780.0 nm and 780.18
It is also possible to increase the difference between the wavelengths of the two laser beams such as nm to perform the measurement and gradually increase the resolution in the distance direction. In this case, the same portion of the measurement target 10 is scanned.

[0027]

As described above, according to the present invention, a three-dimensional shape of a measurement target is obtained based on a combined optical signal of a plurality of reflected laser lights generated by irradiating the measurement target with a plurality of laser lights. As a result, it is possible to provide a laser radar three-dimensional shape measuring apparatus capable of performing accurate measurement from a long distance and easily increasing the resolution in the distance direction.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a laser radar three-dimensional shape measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining scanning of two laser beams in the same embodiment.

FIG. 3 is a diagram showing light intensities of two laser lights with respect to a distance to a measurement target in the same embodiment.

FIG. 4 is a diagram showing an example of a temporal change of combined light intensity in the same embodiment.

FIG. 5 is a diagram showing a difference in combined light intensity depending on measurement points in the same embodiment.

FIG. 6 is a diagram showing an example of a result of frequency analysis in the same embodiment.

FIG. 7 is a diagram showing an example of a three-dimensional shape measured in the same embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser light generator 2 ... Optical branching device 3 ... Deflection device 4 ... Photodetector 5 ... Frequency analyzer 6 ... Distance information calculator 7 ... Angle information processor 8 ... Three-dimensional shape calculator 9 ... Display device 10 ... Target of measurement

Claims (2)

[Claims] 1. A laser scanning unit that scans a measurement target while simultaneously irradiating the same position of the measurement target with a plurality of laser lights having different wavelengths, and detects a combined optical signal of a plurality of reflected laser lights from the measurement target. A laser radar three-dimensional shape measuring device comprising: a light detecting means; and a signal processing means for processing an output signal of the light detecting means to obtain a three-dimensional shape of the measurement target. 2. The signal processing means frequency-analyzes the output signal of the light detecting means, converts the analysis result into distance information of the measurement object, and the distance information and angle information of the plurality of laser beams. The laser radar three-dimensional shape measuring apparatus according to claim 1, wherein the three-dimensional shape of the measurement target is obtained from the above.