Distance Measuring Device and Distance Measuring Method

• US 20130003038A1
• Filed: 01/28/2011
• Published: 01/03/2013
• Est. Priority Date: 03/26/2010
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Tachizaki, Takehiro, Watanabe, Masahiro, Yoshitake, Yasuhiro, Matsui, Tetsuya, Matsumoto, Hirokazu, Hariyama, Tatsuo, Takamasu, Kiyoshi
• Granted Patent: US 8,982,332 B2
• Time in Patent Office: Days
• US Class Current: 356/3.1
• CPC Class Codes: G01B 9/02003 using beat frequencies
• CPC Class Codes: G01B 9/02007 Two or more frequencies or sources used for interferometric measurement using only beat G01B9/02003
• CPC Class Codes: G01B 9/02008 by using a frequency comb
• CPC Class Codes: G01B 9/0207 Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 7/4815 using multiple transmitters
• CPC Class Codes: G01S 7/4911 Transmitters

Abstract

Disclosed is a distance measuring device using an optical comb. In order for the absolute distance to an object to be measured which has a surface with low reflection ratio or a scattering surface and is approximately 10 m apart, to be easily measured with accuracy of 0.1 mm or more using an optical and contactless method, the distance measuring device which measures the distance to the object to be measured is configured such that the distance to the object to be measured is measured by comparing the phase of the beat signal between a light source and a plurality of CW lasers which are reflected or scattered by the object with the phase of the beat signal between the light source and a plurality of CW lasers prior to being irradiated onto the object.

Claims

1. A distance measuring device measuring a distance to a target object, the distance measuring device comprising:

a light source oscillating light at constant frequency intervals;

a plurality of CW laser oscillators which oscillates a plurality of CW lasers controlled in a manner such as to provide a constant frequency difference from a frequency of the light source;

a unit irradiating the plurality of CW lasers to the target object;

a unit spatially scanning the plurality of CW lasers on a surface of the target object;

a unit observing a beat between the light oscillated from the light source and the plurality of CW lasers reflected or scattered from the target by the irradiating;

a unit generating a beat signal of the observed beat signal between the light oscillated from the light source and the plurality of CW lasers reflected or scattered from the target by the irradiating;

a unit extracting a phase of the generated beat signal of the observed beat signal between the light oscillated from the light source and the plurality of CW lasers reflected or scattered from the target by the irradiating; and

a unit extracting a phase of a beat signal of a beat signal between the light oscillated from the light source and the plurality of CW lasers before irradiating the target object,

wherein the distance to the target object is measured by comparing the phase of the beat signal of the beat signal between the light oscillated from the light source and the plurality of CW lasers reflected or scattered from the target object by the irradiating and the phase of the beat signal of the beat signal between the light oscillated from the light source and the plurality of CW lasers before irradiating the target object.

2. The distance measuring device according to claim 1,

wherein beats between the light oscillated from the source and the plurality of CW lasers are extracted and a beat generated between the extracted beats is extracted to thereby extract the phase of the beat between the plurality of CW lasers.

3. The distance measuring device according to claim 1,

wherein the light source and the plurality of CW lasers are used and a triangulation method and time of flight are used to measure the distance to the target object.

4. The distance measuring device according to claim 1,

wherein the distance to the target object is measured by light emitted from the light source.

5. The distance measuring device according to claim 1,

wherein distance measurement accuracy and a distance measurement range are changed by changing a frequency difference between the plurality of CW lasers controlled in a manner such as to provide a constant frequency difference from the light source.

6. The distance measuring device according to claim 1,

wherein the plurality of CW lasers are spatially scanned on a surface of the target object by a rotating polyhedron having a mirror surface.

7. The distance measuring device according to claim 1,

wherein the plurality of CW lasers are spatially scanned on a surface of the target object by rotating or oscillating a pair of mirrors.

8. The distance measuring device according to claim 1,

wherein the plurality of CW lasers are spatially scanned on a surface of the target object by a rotating polyhedron having a concave mirror and a mirror surface.

9. The distance measuring device according to claim 1,

wherein the plurality of CW lasers are spatially scanned on a surface of the target object by rotating a mirror surface having two rotation axes.

10. A distance measuring device measuring a distance to a target object, the distance measuring device comprising:

a light source oscillating light at constant frequency intervals;

a plurality of CW laser oscillators which oscillates a plurality of CW lasers controlled in a manner such as to provide a constant frequency difference from a frequency of the light source;

a unit irradiating the plurality of CW lasers to the target object;

a unit spatially scanning the plurality of CW lasers on a surface of the target object;

a unit observing a beat between the light oscillated from the light source and the plurality of CW lasers reflected or scattered from the target by the irradiating;

a unit generating a beat signal of the observed beat signal between the light oscillated from the light source and the plurality of CW lasers reflected or scattered from the target by the irradiating;

a unit extracting a phase of the generated beat signal of the observed beat signal between the light oscillated from the light source and the plurality of CW lasers reflected or scattered from the target by the irradiating; and

a unit extracting a phase of the beat signal of the beat signal between the light oscillated from the light source and the plurality of CW lasers before irradiating the target object,

wherein the distance to the target object is measured by comparing the phase of the beat signal of the beat signal between the light oscillated from the light source and the plurality of CW lasers reflected or scattered from the target object by the irradiating and the phase of the beat signal of the beat signal between the light oscillated from the light source and the plurality of CW lasers before irradiating the target object.

11. A distance measuring device measuring a distance to a target object, the distance measuring device comprising:

a plurality of CW laser oscillators which oscillates a plurality of CW lasers whose oscillation frequencies are variable;

a unit acquiring a beat by the plurality of CW lasers;

a frequency stabilizing unit keeping constant a difference between the oscillation frequencies of the plurality of CW lasers;

an optical system irradiating the CW lasers to the target object;

an optical system scanning the plurality of CW lasers on a surface of the target object;

an optical system receiving the plurality of CW lasers reflected or scattered from the target object by the irradiation of the plurality of CW lasers;

a unit extracting a beat between the plurality of CW lasers reflected or scattered from the target object by the irradiation of the plurality of CW lasers;

a unit extracting a phase of the beats between the plurality of CW lasers reflected or scattered from the target object by the irradiation of the plurality of CW lasers; and

a unit calculating the distance to the target object based on the extracted phase,

wherein the distance to the target object is measured based on a difference between the phase of at least either one of the reflected light or the scattering light from the target object and a phase before irradiating the target object.

12. The distance measuring device according to claim 11,

wherein the beat by the plurality of CW lasers is used for stabilizing the frequencies of the plurality of CW lasers oscillated from the plurality of CW laser oscillators.

13. The distance measuring device according to claim 11,

wherein a corrected frequency signal is used as a frequency reference for stabilizing the frequencies of the plurality of CW lasers.

14. The distance measuring device according to claim 11,

wherein a global positioning system (GPS) signal is used as the frequency reference.

15. The distance measuring device according to claim 11,

wherein an atomic clock is used as the frequency reference.

16. The distance measuring device according to claim 11,

wherein a stabilized oscillator is used as the frequency reference.

17. The distance measuring device according to claim 11,

wherein the stabilization of the frequencies of the plurality of CW lasers is realized by keeping constant a difference frequency between the beat by the plurality of CW lasers and the frequency reference.

18. The distance measuring device according to claim 11,

wherein there are a plurality of difference frequencies between the beat by the plurality of CW lasers and the frequency reference.

19. The distance measuring device according to claim 11,

wherein the beat of the plurality of CW lasers is subjected to frequency-division to lower the frequency to perform phase comparison.

20. The distance measuring device according to claim 11,

wherein the beat of the plurality of CW lasers is mixed with a signal with a frequency extremely close to a frequency of the beat to lower the frequency to extract the phase of the beat.

21. The distance measuring device according to claim 11,

wherein frequency-stabilizing CW lasers or outside resonance CW lasers or narrow band oscillation CW lasers are used as the plurality of CW lasers.

22. The distance measuring device according to claim 11,

wherein the distance to the target object is measured by a triangulation method or Time of flight using the plurality of CW lasers.

23. The distance measuring device according to claim 11,

wherein the plurality of CW lasers are spatially scanned on a surface of the target object by a rotating polyhedron having a mirror surface.

24. The distance measuring device according to claim 11,

wherein the plurality of CW lasers are spatially scanned on the surface of the target object by rotating or vibrating a pair of mirrors.

25. The distance measuring device according to claim 11,

wherein the plurality of CW lasers are spatially scanned on a surface of the target object by a rotating polyhedron having a concave mirror and a mirror surface.

26. The distance measuring device according to claim 11,

wherein the CW lasers are spatially scanned on a surface of the target object by rotating a mirror surface having two rotation axes.

27. A distance measuring device measuring a distance to a target object, the distance measuring device using:

a plurality of CW laser oscillators which oscillates a plurality of CW lasers whose oscillation frequencies are variable;

a unit acquiring a beat between the plurality of CW lasers;

a frequency stabilizing unit keeping constant a difference between the oscillation frequencies of the plurality of CW lasers;

an optical system irradiating the CW lasers to the target object;

an optical system scanning the plurality of CW lasers on a surface of the target object;

an optical system receiving the plurality of CW lasers reflected or scattered from the target object;

a unit extracting a beat between the plurality of CW lasers reflected or scattered from the target object;

a unit extracting a phase of the beat between the plurality of CW lasers reflected or scattered from the target object; and

a unit calculating the distance to the target object based on the extracted phase, the distance measuring device measuring the distance to the target object based on a difference between a phase of the plurality of CW lasers at least one of the reflected light or the scattering light from the target object and a phase of the plurality of CW lasers before irradiating the target object.

28. A distance measuring device measuring a distance to a target object, the distance measuring device comprising:

a light source CW laser having a plurality of oscillation frequencies;

a unit acquiring a beat of the light source;

an optical system irradiating the target object with light emitted from the light source;

an optical system scanning on a surface of the target object the light emitted from the light source;

an optical system receiving the light reflected or scattered from the target object by the irradiating;

a unit extracting a beat between the lights emitted from the light source and reflected or scattered from the target object;

a unit extracting a phase of the beat between the lights emitted from the light source and reflected or scattered from the target object; and

a unit calculating the distance to the target object based on the extracted phase,

wherein the distance to the target object is measured based on a difference between the phase of at least one of the reflected light or the scattering light from the target object and a phase of the light emitted from the light source and before irradiating the target object.

29. The distance measuring device according to claim 28,

wherein the light source is realized by combining a plurality of CW lasers oscillating with a single frequency.

30. The distance measuring device according to claim 28,

wherein the light source is realized by dividing the CW laser oscillating with the single frequency and adding mutually different types of frequency modulation to the respective CW lasers.

31. The distance measuring device according to claim 28,

wherein the light source is realized by extracting mutually different frequency components from a light source emitting light in a wide band.

32. A distance measuring method measuring a distance to a target object, the distance measuring method using a distance measuring device which includes:

a light source oscillating a CW laser having a plurality of oscillation frequencies;

a unit acquiring a beat of the light source;

an optical system irradiating a target object with light emitted from the light source;

an optical system scanning on a surface of the target object with the light emitted from the light source;

an optical system receiving light reflected or scattered from the target object by the irradiation of the light;

a unit extracting a beat between the lights emitted from the light source and the light reflected or scattered from the target object;

a unit extracting a phase of the beat between the lights emitted from the light source and the light reflected or scattered from the target object; and

a unit calculating the distance to the target object based on the extracted phase of the beat,

the method comprising the steps of;

calculating a difference between a phase of at least one of the reflected light or the scattering light from the target object and a phase of the light before irradiating the target object; and

measuring the distance to the target object based on the calculated difference of the phases.

33. A distance measuring device measuring a distance to a target object, the distance measuring device comprising:

a light source oscillating light at constant frequency intervals;

a plurality of CW laser oscillators which oscillate a plurality of CW lasers controlled in a manner such as to provide a constant frequency difference from a frequency of the light source;

a light dividing unit dividing light emitted from the plurality of CW lasers into measuring light and reference light;

a first detection unit irradiating a target object with the measuring light obtained by the light dividing unit, and detecting reflected light or scattering light from the target object;

a second detection unit detecting the reference light and the light from the light source; and

a processing unit calculating the distance to the target object by comparing a phase of a beat signal between the light from the light source and the reflected light or the scattering light from the target object by the irradiation of the measuring light, which is calculated based on a signal obtained from the first detection unit, and a phase of a beat signal between the light from the light source and the reference light, which is calculated based on a signal obtained by the second detection unit.