WO2010131338A1

WO2010131338A1 - Laser ranging method and laser ranging device

Info

Publication number: WO2010131338A1
Application number: PCT/JP2009/058895
Authority: WO
Inventors: 直行古山
Original assignee: Koyama Naoyuki
Priority date: 2009-05-13
Filing date: 2009-05-13
Publication date: 2010-11-18

Abstract

Provided are a laser ranging method and a laser ranging device for simultaneously irradiating two measurement points with measurement light beams, respectively, without using a mechanical movement mechanism for an optical path system and measuring the distance between the measurement points with high precision by using interference light between the measurement light beams. According to the laser ranging method and the laser ranging device, the frequency of laser light emitted from a laser irradiation means (10) is changed within a predetermined range, and a first measurement point (S1) of an object to be measured (6) and a second measurement point (S2) of the object to be measured (6) are simultaneously irradiated with a first measurement light beam and a second measurement light beam, respectively. A distance (L) from the first measurement point (S1) to the second measurement point (S2) is calculated on the basis of the period of interference fringes of interference light between the first measurement light beam and the second measurement light beam. Consequently, the distance (L) between the first measurement point (S1) and the second measurement point (S2) can be measured with high precision without using the mechanical movement mechanism for the optical path system.

Description

Laser distance measuring method and laser distance measuring apparatus

The present invention relates to a laser distance measuring method and a laser distance measuring apparatus that perform distance measurement between measurement points of an object to be measured using interference of laser light.

In a conventional laser distance measuring method using laser light, for example, the laser light is divided into reference light and measurement light, and the optical path difference between the reference light and measurement light reflected by the object to be measured is obtained. Measure the distance to the object to be measured. In the conventional laser distance measuring method that performs distance measurement based on the time difference between the reference light and the measurement light, the distance measurement accuracy is far from the wavelength level of the laser light, that is, the order of nm (nanometer).

Therefore, as shown in [Patent Document 1] below, the inventor of the present application uses a plurality of laser beams having different wavelengths, and further changes the optical path difference so as to utilize the coherence characteristic of the laser beams. Inventions related to a laser distance measuring method and a laser distance measuring apparatus for performing the laser distance measuring method have been made.

International Publication No. 2008/099788 Pamphlet

According to the invention disclosed in [Patent Document 1], the distance to the object to be measured can be measured with high accuracy, but the object to be measured is more practical than the distance to the object to be measured in practical use. It is often useful to measure the distance between these two measurement points, and further improvements are desired in this regard. Also, when measuring the distance between two measurement points of the object to be measured, it is better to measure the distance to the two measurement points at the same time than measuring the two measurement points of the object to be measured individually. It is preferable in terms of measurement accuracy. Furthermore, the invention disclosed in [Patent Document 1] requires a mechanism for mechanically changing the optical path difference of the reference light or the measurement light, and the apparatus scale is relatively large. desired.

The present invention has been made in view of the above circumstances, and without using a mechanical movement mechanism for the optical path system, the measurement light is simultaneously irradiated to each of the two measurement points, and interference light between the measurement lights is used. It is an object of the present invention to provide a laser distance measuring method and a laser distance measuring apparatus that measure the distance between measurement points with high accuracy.

The present invention
(1) In a laser distance measuring method in which laser light is reflected at a measurement point of the object to be measured 6 and a distance to the measurement point is measured,
Laser irradiation is performed while continuously changing the frequency of the laser beam, and the laser beam is divided into a first measurement beam and a second measurement beam, and then the first measurement beam is subjected to the first measurement of the object 6 to be measured. The second measurement light is reflected at the point S1 at the second measurement point S2 of the object 6 to be measured, and the first measurement light reflected at the first measurement point S1 and the second measurement light reflected at the second measurement point S2 are used. An acquisition step of acquiring the intensity data of the generated interference light in correspondence with the amount of change in the frequency of the laser beam;
A conversion step of Fourier-transforming the intensity data obtained in the acquisition step to acquire a period of interference fringes of interference light generated by the first measurement light and the second measurement light;
A calculation step for calculating a distance L from the first measurement point S1 to the second measurement point S2 based on the period of the interference fringes of the predetermined interference light obtained in the conversion step;
The above problem is solved by providing a laser distance measuring method characterized by comprising:
(2) Laser irradiation means 10 having a function of varying the frequency of the laser light to be output, laser light information acquisition means 26 for acquiring the amount of change in the frequency of the laser light emitted from the laser irradiation means 10, and the laser irradiation means The measurement light dividing unit 15 that divides the laser light emitted from 10 into a first measurement light and a second measurement light, and the first measurement light and the measurement object 6 reflected at the first measurement point S1 of the measurement object 6 Receiving the second measurement light reflected at the second measurement point S2 and outputting a signal according to the intensity of the received light, the amount of change in frequency from the laser light information acquisition means 26, and A calculation unit 20 that receives a signal from the light receiving unit 18;
Based on the amount of change in the frequency of the laser beam from the laser beam information acquisition unit 26 and the signal from the light receiving unit 18, the calculation unit 20 causes the laser irradiation unit 10 to change the laser beam frequency continuously. The intensity data of the interference light generated by the first measurement light reflected at the first measurement point S1 and the second measurement light reflected at the second measurement point S2 when irradiation is performed corresponds to the amount of change in the frequency of the laser light. An acquisition step to acquire,
A conversion step of Fourier-transforming the intensity data obtained in the acquisition step to acquire a period of interference fringes of interference light generated by the first measurement light and the second measurement light;
A laser ranging, wherein a calculation step of calculating a distance L from the first measurement point S1 to the second measurement point S2 based on an interference fringe period of the predetermined interference light obtained in the conversion step is performed. The above problems are solved by providing the

devices

50 and 50a to 50e.
(3) The laser irradiation unit 10 emits a laser beam having a specific frequency, and an optical comb generator that uses the laser beam emitted from the laser irradiation unit 10a as a plurality of laser beams having a predetermined frequency interval. 10b and an optical frequency modulator 10c for modulating the frequency interval of the optical comb generator 10b within a predetermined range. By providing, the above-mentioned problems are solved.
(4) The optical bandpass filters BPF1 to BPF5 that transmit only the laser light within a predetermined frequency range of the laser light emitted from the laser irradiation means 10 are provided on the optical path of the laser light (3) The above-mentioned problems are solved by providing the laser distance measuring devices 50b to 50e.
(5) By providing the laser distance measuring device 50c according to the above (2), the optical path length of the first measurement light and the optical path length of the second measurement light inside the apparatus are equalized. To solve.
(6) By providing the laser distance measuring device 50c according to the above (3), the optical path length of the first measurement light and the optical path length of the second measurement light in the apparatus are equalized. To solve.
(7) By providing the laser distance measuring device 50c according to the above (4), the optical path length of the first measurement light and the optical path length of the second measurement light in the apparatus are equal to each other. To solve.

According to the laser distance measuring method and the laser distance measuring apparatus according to the present invention, the distance between two measurement points can be measured with high accuracy without using a mechanical movement mechanism for the optical path system.

It is a figure which shows schematic structure of the laser ranging apparatus of the 1st form which concerns on this invention. It is a figure which shows schematic structure of the laser ranging apparatus of the 2nd form which concerns on this invention. It is a figure which shows the optical path of the modification of the laser distance measuring device which concerns on this invention. It is a figure which shows schematic structure of the laser ranging apparatus of the 3rd form which concerns on this invention. It is a figure which shows schematic structure of the laser ranging apparatus of the 4th form which concerns on this invention. It is a figure which shows the example which provided the reference mirror in the laser ranging apparatus which concerns on this invention. It is a figure which shows the optical path of the laser ranging apparatus of the 5th form which concerns on this invention. It is a figure which shows the optical path of the laser range finder of the 6th form which concerns on this invention.

Embodiments of a laser distance measuring method and a laser distance measuring apparatus according to the present invention will be described with reference to the drawings.

A laser distance measuring device 50 according to the first embodiment of the present invention shown in FIG. 1 includes a laser irradiation means 10 capable of changing the frequency of emitted laser light within a predetermined range, and the laser irradiation means 10 emits light. A laser beam information acquisition unit 26 that acquires the amount of change in the frequency of the laser beam to be output and outputs it to the calculation unit 20, and a measurement that divides the laser beam emitted from the laser irradiation unit 10 into a first measurement beam and a second measurement beam The light splitting unit 15, the first measurement light reflected at the first measurement point S 1 of the object to be measured 6 and the second measurement light reflected at the second measurement point S 2 of the object to be measured 6 are received and received. Based on the light receiving unit 18 that outputs a signal corresponding to the intensity to the arithmetic unit 20, the amount of change in the frequency of the laser light from the laser light information acquisition unit 26, and the signal from the light receiving unit 18, Calculation unit 2 for calculating the distance L between the measurement point S2 And, the has. In addition, the broken line in FIG. 1 shows the optical path of a laser beam.

As the laser irradiation means 10 of the laser range finder 50 of the first embodiment, a well-known wavelength tunable laser can be used.

First, a method for obtaining the optical path difference in the apparatus between the first measurement light and the second measurement light will be described with reference to FIG. The optical path difference acquisition method described below is basically the same as the laser distance measuring method according to the present invention and the operation of the laser distance measuring apparatus 50 of the first embodiment. The following optical path difference acquisition method is suitable for the laser distance measuring apparatus according to the present invention, but this method is not necessarily used. Further, the optical path difference need not be acquired for each measurement, and may be recorded at the time of shipment of the laser distance measuring device and recorded in a memory or the like.

First, as shown in FIG. 1a, a flat plate 7 having a smooth surface is installed so that the first measurement light and the second measurement light are vertically irradiated on the smooth surface.

Next, the laser irradiation means 10 emits laser light. As described above, the laser irradiation means 10 can change the wavelength of the emitted laser light within a predetermined range. At this time, the wavelength of the laser light changes continuously within the predetermined range. Do as follows. The laser light emitted from the laser irradiation means 10 is divided into two by the beam splitter 4 provided on the optical path of the laser light, one is irradiated to the laser light information acquisition means 26, and the other is the measurement light dividing section 15. Irradiated to the side.

The laser beam information acquisition unit 26 acquires the frequency of the laser beam emitted from the laser irradiation unit 10 and outputs it to the calculation unit 20. As the laser light information acquisition means 26, a known wavelength meter or frequency meter can be used. In the case where the laser beam information acquisition unit 26 measures the wavelength of the laser beam, the measured wavelength is converted into a frequency and output to the computing unit 20. The laser beam information acquisition unit 26 acquires a wavelength control signal from a wavelength control controller that controls the wavelength of the laser beam emitted from the laser irradiation unit 10, and acquires the frequency of the laser beam based on the wavelength control signal. However, it may be output to the calculation unit 20. In this case, it is not necessary to irradiate the laser beam information acquisition means 26 with the laser beam using the beam splitter 4. Further, when a frequency meter is used for the laser beam information acquisition unit 26, a known frequency counter that acquires the frequency of the laser beam by causing the laser beam incident on the laser beam information acquisition unit 26 to interfere with the optical comb laser is used. preferable.

The laser light irradiated to the measurement light splitting unit 15 side passes through the beam splitter 12 and travels to the measurement light splitting unit 15. The laser beam directed to the measurement light splitting unit 15 is divided into two by the measurement light splitting unit 15, and one is irradiated as the first measurement light to the first measurement point S <b> 1 of the flat plate 7 from the emission port 16 a. On the other hand, the other is reflected by the mirror 8 as the second measurement light and is irradiated to the second measurement point S2 of the flat plate 7 from the emission port 16b. As the measurement light splitting unit 15, a half mirror having a spectral ratio of 50:50 may be used, or a beam splitter having a different spectral ratio, for example, 60:40, 70:30, 80:20, or the like may be used. .

The first measurement light applied to the first measurement point S1 is reflected at the first measurement point S1, passes through the measurement light splitting unit 15, is reflected by the beam splitter 12, and reaches the light receiving unit 18. The second measurement light applied to the second measurement point S2 is reflected by the second measurement point S2, and then reflected by the mirror 8, the measurement light splitting unit 15, and the beam splitter 12, and reaches the light receiving unit 18. Therefore, the light received by the light receiving unit 18 becomes interference light between the first measurement light and the second measurement light. Then, the light receiving unit 18 converts the intensity of the interference light into an electric signal and outputs it to the calculation unit 20 as intensity data.

As the acquisition step, the calculation unit 20 acquires the intensity data of the interference light from the light receiving unit 18 in correspondence with the amount of change in frequency from the laser light information acquisition unit 26.

Next, as a conversion step, the calculation unit 20 performs a Fourier transform based on the amount of change in frequency on the acquired intensity data. Thereby, the amplitude I _S12 , period T _S12 , and phase φ _S12 of the interference light are acquired.

Here, if the distance Ld from the dividing point of the measuring beam dividing unit 15 to the reflecting point of the mirror 8 in the laser distance measuring device 50 is Ld = 0.5 m, at this stage, the first measuring point S1 and the second measuring point are used. Since S2 is equidistant, the optical path difference between the first measurement light and the second measurement light is 2 × Ld = 1 m. Assuming that the frequency f of the laser beam is f = 300 MHz (the frequency f = 300 MHz is no longer called light, but here f = 300 MHz is used for convenience in explaining the principle of the present invention). The wavelength λ of the laser light is λ = c / f (c: speed of light 3 × 10 ⁸ m / s).
λ = (3 × 10 ⁸ ) / (300 × 10 ⁶ ) = 1 m
The wavelength λ becomes equal to the optical path difference (2 × Ld) between the first measurement light and the second measurement light inside the apparatus. Accordingly, at this time, the first measurement light and the second measurement light are intensified, and the interference light has a bright peak.

Also, when the frequency f of the laser light changes and f = 600 MHz,
λ = (3 × 10 ⁸ ) / (600 × 10 ⁶ ) = 0.5 m
The wavelength λ is equal to ½ of the optical path difference (2 × Ld) between the first measurement light and the second measurement light. Accordingly, at this time also, the first measurement light and the second measurement light of the laser light are intensified, and the interference light has a bright peak. Similarly, when the frequency f of the laser light becomes 900 MHz and 1.2 GHz, the first measurement light and the second measurement light of the laser light are intensified and the interference light takes a bright peak. Therefore, in this case, the interference light has a bright peak every 300 MHz, and the interference fringe spacing is 300 MHz. The fringe spacing of the interference fringes corresponds to the interference light period T _S12 obtained by Fourier transform.

Therefore, the distance Ld that is ½ of the optical path difference between the first measurement light and the second measurement light can be expressed by the following calculation formula.
2 × Ld = c / T _S12
Ld = c / T _S12 / 2 (1)
Note that since the period T _S12 is obtained by Fourier transform, the period T _S12 can be obtained without actually changing the frequency f of the laser light from 300 MHz to 600 MHz.

Therefore, the calculation unit 20 selects a predetermined period T _S12 of the interference light (in this example, the interference light itself) from the period of the interference fringes of the interference light obtained in the conversion step, and the expression (1) above. A distance Ld that is ½ of the optical path difference between the first measurement light and the second measurement light inside the apparatus is calculated. Then, the value of the distance Ld is recorded in a memory or the like in the calculation unit 20 (not shown).

Next, the laser distance measuring method according to the present invention and the operation at the time of distance measurement for the object 6 of the laser distance measuring apparatus 50 of the first embodiment will be described. As described above, the laser distance measuring method according to the present invention and the operation of the laser distance measuring device 50 according to the first embodiment during distance measurement with respect to the measurement object 6 are the optical paths of the first measurement light and the second measurement light. Since it is equivalent to the method of acquiring the difference, a part of the description is omitted for the overlapping part.

First, as shown in FIG. 1b, the DUT 6 is placed at a predetermined position. At this time, the first measurement light emitted from the laser distance measuring device 50 is applied to the first measurement surface of the device under test 6 and the second measurement light is applied to the second measurement surface of the device under test 6.

Next, the laser irradiation means 10 emits laser light so that its wavelength continuously changes within a predetermined range. And the calculating part 20 performs an acquisition step and a conversion step similarly.

Next, as a calculation step, the calculation unit 20 calculates 1 / of the optical path difference inside the apparatus by the following calculation formula (2) similar to the calculation formula (1) for the interference light period T _S12 obtained in the conversion step. A value (distance L ′) that is ½ of the optical path difference between the first measurement light and the second measurement light after including the value of 2 (distance Ld) is calculated.
L ′ = c / T _S12 / 2 (2)
The distance L ′ here is, as shown in FIG. 1A, when the second measurement point S2 is farther from the laser distance measuring device 50 than the first measurement point S1.
L ′ = Ld + L
When the second measurement point S2 is closer to the laser distance measuring device 50 than the first measurement point S1,
L ′ = Ld−L.
The distance L is the distance from the first measurement point S1 to the second measurement point S2.

Therefore, the calculation unit 20 calculates the distance L from the first measurement point S1 to the second measurement point S2 by subtracting the distance Ld acquired in advance from the distance L ′ and taking the absolute value thereof. Thereby, the distance L between the first measurement point S1 and the second measurement point S2 can be calculated with high accuracy.

Next, a second embodiment of the laser range finder according to the present invention will be described with reference to FIG. The laser distance measuring device 50a of the second embodiment according to the present invention is mainly different from the laser distance measuring device 50 of the first embodiment in the configuration of the laser irradiation means 10 and the laser light information acquisition means 26. .

The laser irradiating means 10 of the laser distance measuring device 50a according to the second embodiment of the present invention shown in FIG. 2 includes a laser irradiating device 10a that emits a laser beam having a specific frequency, and a laser beam emitted from the laser irradiating device 10a. The optical comb generator 10b generates a plurality of laser beams having a predetermined frequency interval, and the optical frequency modulator 10c modulates the frequency interval of the optical comb generator 10b within a predetermined range.

The laser beam information acquisition unit 26 of the laser range finder 50a according to the second embodiment acquires the amount of change in the frequency of the laser beam emitted from the laser irradiation unit 10 from the value of the modulation frequency from the optical frequency modulator 10c. The result is output to the calculation unit 20.

Next, a method for obtaining the optical path difference in the apparatus between the first measurement light and the second measurement light will be described with reference to FIG. The optical path difference acquisition method described below is basically the same as the laser distance measuring method according to the present invention and the operation of the laser distance measuring device 50a of the second embodiment. The following optical path difference acquisition method is suitable for the laser distance measuring apparatus according to the present invention, but this method is not necessarily used. Further, the optical path difference need not be acquired for each measurement, and may be recorded at the time of shipment of the laser distance measuring device and recorded in a memory or the like.

First, as shown in FIG. 2a, a flat plate 7 having a smooth surface is installed so that the first measurement light and the second measurement light are vertically irradiated on the smooth surface.

Next, the laser irradiation device 10a constituting the laser irradiation unit 10 emits a laser beam of a specific frequency f ₀ to the optical comb generator 10b. Optical comb generator 10b in response to the modulation frequency input from the optical frequency modulator 10c, in terms of generating the plurality of light Komureza light equal frequency intervals above and below the center frequency f _0, the laser light of frequency f ₀ At the same time, the measurement light splitting unit 15 is irradiated. For example, if the optical frequency modulator 10c outputs a modulation frequency of DHz, laser light emitted from the optical comb generator 10b includes a laser beam LZ ₀ frequency _{f 0,} as a light Komureza light, the frequency _f 0 + d ( the frequency _{f 1.} a laser beam LZ ₁ in), and the laser beam LZ ₂ frequency _f 0 + 2d (. to frequency _{f 2),} · · ·, the frequency _f 0 + nd of (. to frequency _{f n)} a laser beam LZ _n, and the laser beam _{LZ -1} frequency _f 0 -d (. to frequency _{f -1),} and the laser beam _{LZ -2} frequency _f 0 -2d (. to frequency _{f -2),} ..., laser light LZ- _{n of} frequency f ₀ -nd (referred to as frequency f _-n ). At this time, the intensity of each laser beam is almost
LZ ₁ = LZ ₋₁ , LZ ₂ = LZ ₋₂ ,..., LZ _n = LZ _−n , and
LZ ₀ > LZ ₁ > LZ ₂ >...> LZ _n ,
LZ ₀ > LZ ₋₁ > LZ ₋₂ >...> LZ _−n .

At this time, the optical frequency modulator 10c changes the modulation frequency for the optical comb generator 10b to change the frequency interval within a predetermined range. Accordingly, the frequencies of all the laser beams LZ ₁ , LZ ₂ ,..., LZ _n , LZ ₋₁ , LZ ₋₂ ,..., LZ _−n except for the laser beam LZ ₀ change within a predetermined range. To do. That is, when the modulation frequency output from the optical frequency modulator 10c is changed from dHz to (d + α) Hz, the frequency f ₁ of the laser beam LZ ₁ changes to f ₁ = f ₀ + (d + α), and the laser beam LZ _2. The frequency f ₂ of the laser beam L f changes to f ₂ = f ₀ + 2 × (d + α), the frequency f _n of the laser beam LZ _n changes to f _n = f ₀ + n × (d + α), and the frequency f of the laser beam LZ ₋₁ . ₋₁ changes to f ₋₁ = f ₀ − (d + α), and the frequency f ₋₂ of the laser beam LZ ₋₂ changes to f ₋₂ = f ₀ −2 × (d + α), and the laser beam LZ _−n The frequency f _−n changes to f _−n = f ₀ −n × (d + α). Then, the optical frequency modulator 10 c outputs the value of the modulation frequency to the laser light information acquisition unit 26. For convenience, the laser beams LZ _−n to LZ ₀ to LZ _n emitted from the optical comb generator 10b are collectively referred to as laser light LZ, and the optical comb laser light and laser light LZ _−n emitted from the optical comb generator 10b. To LZ ₋₁ and laser beams LZ ₁ to LZ _n are collectively referred to as laser beam LZ (n).

The laser beam information acquisition unit 26 determines the amount of change in the frequency of the first-stage optical comb laser beam (laser beams LZ ₁ , LZ ₋₁ ) from the modulation frequency value from the optical frequency modulator 10 c, that is, the value of α described above. Is output to the calculation unit 20.

The laser light LZ emitted from the laser irradiation means 10 passes through the beam splitter 12 and travels toward the measurement light splitting unit 15. The laser beam LZ directed to the measurement beam splitting unit 15 is divided into two by the measurement beam splitting unit 15 and one is irradiated as the first measurement beam to the first measurement point S1 of the flat plate 7 from the emission port 16a. On the other hand, the other is reflected by the mirror 8 as the second measurement light and is irradiated to the second measurement point S2 of the flat plate 7 from the emission port 16b.

The first measurement light is reflected at the first measurement point S1, and then reaches the light receiving unit 18 along the same optical path as described above. Further, after the second measurement light is reflected at the second measurement point S2, it reaches the light receiving unit 18 along the same optical path as described above. Therefore, the light received by the light receiving unit 18 is an interference light in which a plurality of interference lights generated by interference between the first measurement light of the laser light LZ and the second measurement light of the laser light LZ are combined. Then, the light receiving unit 18 converts the intensity of the interference light into an electric signal and outputs it to the arithmetic unit 20 as intensity data. The intensity data of the interference light includes the intensity of the interference light between the first measurement light and the second measurement light of optical comb laser lights (for example, laser light LZ ₁ and laser light LZ ₂ ) having different numbers of stages. The intensity of the interference light of the optical comb laser beams having different numbers of stages becomes a beat (beat) and appears in the interference light, and this beat is averaged within the measurement time, and finally becomes background noise with a constant intensity.

As the acquisition step, the calculation unit 20 acquires the intensity data of the interference light from the light receiving unit 18 corresponding to the amount of change in the frequency from the laser light information acquisition unit 26.

Next, as a conversion step, the arithmetic unit 20 performs Fourier transform on the intensity data of the interference light corresponding to the frequency change amount. Thus, the amplitude of the interference light, the period, as a phase, the interference light of the first measuring light of the laser beam LZ ₁ and the second measuring light of the laser beam LZ ₁ amplitude _{I S12 (1),} the period _{T S12 (1)} , Phase φ _{S12 (1)} is acquired. Further, the interference light amplitude _{I S12} of the first measuring light of the laser beam LZ ₂ and the second measuring light of the laser beam LZ ₂ _(2), the period _{T S12 (2),} the phase phi _{S12 (2)} is obtained . The first measuring beam and the interference light amplitude _{I S12} of the second measuring light of the laser beam LZ _n _(n), the period _{T S12 (n),} the phase phi _{S12 (n)} is obtained for the laser beam LZ _n . The amplitude _{I S12 (-1)} of the first measuring beam and the interference light of the second measuring light of the laser beam _{LZ -1} laser beam _{LZ -1,} period _{T S12 (-1),} the phase phi _{S12 (-1 )} Is acquired. The first measuring beam and the amplitude _{I S12} of the second measurement light and the interference light of the laser beam _{LZ -2} of the laser beam _{LZ -2} _(-2), the period _{T S12 (-2),} the phase phi _{S12 (-2 )} Is acquired. The amplitude of the interference light of the first measuring beam and the second measuring light of the laser beam _{LZ -n} of the laser beam _{LZ _-n} _{I S12 _(-n),} the period _{T S12 (-n),} the phase phi _{S12 (-n )} Is acquired.

Note that the background noise due to the interference light of the optical comb laser beams having different numbers of stages is a constant intensity averaged within the measurement time, and thus becomes a constant by Fourier transform. Further, since the frequency of the laser beam LZ ₀ is constant without affecting the modulation frequency of the optical frequency modulator 10c, which also becomes constant by the Fourier transform.

The frequency of the laser beam LZ _n in the positive direction of the number of light Komureza light changes in the increasing direction by the modulation frequency of the optical frequency modulator 10c, the frequency of the laser beam LZ _-n negative direction of the number of stages of optical Komureza light It changes in a decreasing direction depending on the modulation frequency of the optical frequency modulator 10c. However, the fringe intervals (cycles) of the interference light of the optical comb laser beams (laser beam LZ _n and laser beam LZ _−n ) having the same number of positive and negative stages obtained by the Fourier transform are equal. In other words, the interference light of the period _{T S12} of the laser beam LZ ₁ _(1), and the period _{T S12} of the interference light laser beam _{LZ -1} _(-1), the period _{T S12 (1)} = period _{T S12 (-1 ),} and similarly to the period _{T S12} of the interference light laser beam LZ _n _(n), the period _{T S12} of the interference light of the laser beam _{LZ -n} _(-n), the period _{T S12 (n)} = period T _{S12 (-n)} .

Here, assuming that the distance Ld from the dividing point of the measuring light dividing unit 15 to the reflecting point of the mirror 8 in the laser distance measuring device 50a is Ld = 0.5 m and the frequency f of the laser light is f = 300 MHz, the laser light The period T _{S12 (1)} (= period T _{S12 (−1)} ) of the interference light of LZ ₁ and LZ ₋₁ is 300 MHz.

In addition, since the Fourier transform is performed by the amount of change in the frequency of the laser beams LZ ₁ and LZ ₋₁ that does not consider the number n of the optical comb laser beam, in the case of the above example, the laser beam LZ _n , LZ _−n interference light period T _{S12 (n)} (= period T _{S12 (−n)} ) is 300 MHz / (| n |). However, multiplication by the number of stages of optical comb laser light | n | That is, the period T _{S12 (1)} (= T _{S12 (−1)} ), the period T _{S12 (2)} (= T _{S12 (−2)} ),..., The period T _{S12 (n)} (= T _{S12 (−n)} ) is represented by T _{S12 (1)} , T _{S12 (1)} / 2,..., T _{S12 (1)} / n (n = 1, 2, 3,... N). It becomes a series.

Next, the computing unit 20 selects a period T _{S12 (n)} of interference light by a predetermined laser beam LZ _n from the period of interference fringes of interference light constituting the interference light obtained in the conversion step. Note that the interference light cycle T _{S12 (n)} is preferably selected from the interference light of the laser light LZ ₁ or the laser light LZ ₋₁ . As described above, the cycle T _{S12 (n)} of the interference light of each laser beam LZ (n) obtained in the conversion step is a series of cycle T _{S12 (1)} / n. If the maximum cycle T _{S12 (n)} is selected in the sequence of cycle T _{S12 (1)} / n, that is, the cycle T _{S12 (1)} ( ₁₎ of the interference light caused by the laser beam LZ ₁ or the laser beam LZ _−1. = Period T _{S12 (−1)} ). Thus, the period T _{S12 (1)} (= period T _{S12 (−1)} ) of the interference light by the laser light LZ ₁ (laser light LZ ₋₁ ) is selected from the plurality of periods of the interference light constituting the interference light. be able to. If the n-th largest cycle T _{S12 (n)} is selected in the sequence of cycle T _{S12 (1)} / n, that is, the cycle of the interference light by the laser beam LZ _n (laser beam LZ _−n ) having _n stages. T _{S12 (n)} (= period T _{S12 (−n)} ).

Then, the calculation unit 20 is selected when the maximum period T, that is, the period T _{S12 (1)} (= period T _{S12 (−1)} ) of the interference light of the laser light LZ ₁ or the laser light LZ ₋₁ is selected. For the period T _{S12 (1)} , a distance Ld, which is a half value of the optical path difference between the first measurement light and the second measurement light in the apparatus, is calculated by the same equation as the above (1).

Further, when the calculation unit 20 selects the period T _{S12 (n)} (= period T _{S12 (−n)} ) of the interference light by the n-stage optical comb laser light, the distance is calculated using the following equation (1) ′. Ld is calculated.
Ld = c / ( _{TS12 (n)} × | n |) / 2 (1) ′
Then, the calculation unit 20 records the value of the distance Ld in a memory or the like in the calculation unit 20 (not shown).

Next, the operation of the laser distance measuring method according to the present invention and the distance measuring operation of the laser distance measuring apparatus 50a of the second embodiment with respect to the object 6 to be measured will be described. As described above, the laser distance measuring method according to the present invention and the laser distance measuring device 50a of the second embodiment at the time of distance measurement with respect to the object to be measured 6 are the same as the first measuring light and the second light inside the device. Since this method is equivalent to the method for obtaining the optical path difference of the measurement light, a part of the description is omitted for the overlapping portions.

First, as shown in FIG. 2b, the DUT 6 is placed at a predetermined position. At this time, the first measurement light emitted from the laser distance measuring device 50 a is applied to the first measurement surface of the device under test 6 and the second measurement light is applied to the second measurement surface of the device under test 6.

Next, the laser irradiation means 10 emits laser light so that its wavelength continuously changes within a predetermined range. And the calculating part 20 performs an acquisition step and a conversion step similarly. At this time, the first measurement light is reflected at the first measurement point S1 of the device under test 6 and the second measurement light is reflected at the second measurement point S2 of the device under test 6. The light receiving unit 18 receives the first measurement light reflected at the first measurement point S1 of the object 6 to be measured and the second measurement light reflected at the second measurement point S2 of the object 6 to be measured.

Next, the calculation unit 20 selects, as a calculation step, a period T _{S12 (n)} of interference light by a predetermined laser beam LZ _n from the period of interference fringes of interference light constituting the interference light obtained in the conversion step. . Then, when the laser beam LZ ₁ or the laser beam LZ ₋₁ is selected, the value (distance) of a half of the optical path difference between the first measurement light and the second measurement light by the same formula as the above (2). L ′) is calculated. Further, the calculation formula in the case of selected ones of the laser beam LZ _n or laser beam LZ _-n is (2) as well as the following calculation formula (2) ', optical paths of the first measuring beam and the second measuring beam A half value of the difference (distance L ′) is calculated.
L ′ = c / ( _{TS12 (n)} × | n |) / 2 (2) ′
The distance L ′ obtained here includes a value (distance Ld) that is ½ of the optical path difference inside the apparatus.

Next, the calculation unit 20 calculates the distance L from the first measurement point S1 to the second measurement point S2 by subtracting the distance Ld acquired in advance from the distance L ′ and taking the absolute value thereof. Thereby, the distance L between the first measurement point S1 and the second measurement point S2 can be calculated with high accuracy.

Note that the optical paths of the first measurement light and the second measurement light in the laser

distance measuring devices

50 and 50a according to the present invention may be as shown in FIG. In FIG. 3, only the optical paths of the first measurement light and the second measurement light are shown in a simplified manner. A modification of the laser

distance measuring devices

50 and 50a shown in FIG. 3A is an example in which the reflected light of the beam splitter 12 is used as measurement light. 3 (b) and 3 (c), the laser

distance measuring devices

50 and 50a have the first measurement light and the second measurement light by the measurement light dividing unit 15 and the mirror 8 without using the beam splitter 12. It is the example which comprised the optical path with light.

As shown in FIG. 4, the laser distance measuring device 50 a according to the second embodiment of the present invention transmits only laser light within a predetermined frequency range on the optical path of laser light emitted from the laser irradiation means 10. A third embodiment of the laser range finder 50b may be provided with a known optical bandpass filter.

When using the one that transmits only the laser beam in the frequency range of variation of the frequency f ₁ of the optical band-pass filter, for example, laser beam LZ ₁ be installed in a laser distance measuring device 50b, the optical bandpass filter and the laser irradiation means 10 On the optical path between the beam splitter 12 (optical bandpass filter BPF1 in FIG. 4) or on the optical path between the beam splitter 12 and the light receiving unit 18 (optical bandpass filter BPF2 in FIG. 4), or the beam splitter It is provided on the optical path (optical bandpass filter BPF3 in FIG. 4) between the 12 and the measuring light splitting unit 15, the light receiving portion 18 for receiving only the interference light by the laser beam LZ _1, the optical comb generator The load on the processing of the calculation unit 20 can be reduced while using the stable laser beam by 10b.

Also, if installing the optical bandpass filter to the first measuring light optical path (optical bandpass filter BPF4 in FIG. 4), a first measuring light receiving unit 18 receives the to those of only the laser beam LZ ₁ Therefore, similarly, it is possible to reduce the load on the processing of the arithmetic unit 20 while using the stable laser light from the optical comb generator 10b.

Furthermore, if installing the optical band pass filter to the second measuring light optical path (optical bandpass filter BPF5 in FIG. 4), the second measuring light received in the light receiving portion 18 includes only the laser beam LZ ₁ Similarly, it is possible to reduce the load on the processing of the arithmetic unit 20 while using stable laser light from the optical comb generator 10b.

Even when the optical bandpass filter transmits a plurality of optical comb laser beams, the number of laser beams received by the light receiving unit 18 is significantly reduced compared to when no optical bandpass filter is installed. The load on the processing of the unit 20 is greatly reduced.

The configuration of the laser distance measuring device 50b can be applied to a modification of the laser distance measuring device 50a shown in FIG.

Further, the laser

distance measuring devices

50, 50a, 50b of the first to third embodiments according to the present invention are on the optical path of the first measuring light as shown in the laser distance measuring device 50c of the fourth embodiment in FIG. The mirror 8a and the mirror 8b may be installed on the mirror 8a, and the distance from the reflection point of the mirror 8a to the reflection point of the mirror 8b may be equal to the distance Ld from the division point of the measurement light dividing unit 15 to the reflection point of the mirror 8. . 5 shows an example in which the configuration of the fourth embodiment is applied to the laser distance measuring device 50a of the second embodiment. However, the configuration can be applied to a modification of the laser

distance measuring devices

50 and 50a shown in FIG. Is possible.

According to the configuration of the laser distance measuring device 50c of the fourth embodiment, the optical path difference between the first measurement light and the second measurement light in the device is eliminated, and the optical path length of the first measurement light in the device and the second The optical path length of the measurement light can be made equal. Therefore, in the laser range finder 50c of the fourth embodiment, there is no need to obtain the optical path difference inside the device between the first measurement light and the second measurement light and to perform the subtraction process of the distance Ld from the distance L ′. The distance measurement procedure for the distance L can be simplified.

Further, the laser

distance measuring devices

50, 50a, 50b, and 50c according to the present invention can also be applied to a laser distance measuring device including a reference mirror 14 as shown in FIG. In FIG. 6, only the optical path of the laser beam is shown in a simplified manner.

The laser

distance measuring devices

50, 50a, 50b, and 50c shown in FIG. In the case of the laser distance measuring device 50 using a known wavelength tunable laser as the laser irradiation means 10, the light received by the light receiving unit 18 is a reference mirror in addition to the interference light between the first measurement light and the second measurement light. The first interference light between the reference light reflected by 14 and the first measurement light, and the second interference light between the reference light reflected by the reference mirror 14 and the second measurement light. Then, the light receiving unit 18 converts the intensity of the interference light, which is the combination of the three interference lights, into an electrical signal, and outputs the electrical signal to the calculation unit 20.

Next, the calculation unit 20 performs an acquisition step and a conversion step, and performs a Fourier transform based on the amount of change in frequency on the acquired intensity data. Thereby, in addition to the amplitude I _S12 , period T _S12 , and phase φ _S12 of the interference light between the first measurement light and the second measurement light, the amplitude I _S1 , period T _S1 , phase φ _{S1 of} the first interference light, The amplitude I _S2 , period T _S2 , and phase φ _{S2 of} the second interference light are acquired.

Here, since the first measurement light and the second measurement light are obtained by further dividing the laser light split by the beam splitter 12 by the measurement light splitting unit 15, the spectral ratio of the beam splitter 12 and the measurement light splitting unit 15. Is 50:50, that is, a half mirror, the intensity (amplitude) I _S12 is smaller than the amplitude I _S1 of the first interference light and the amplitude I _S2 of the second interference light.

Therefore, the calculation unit 20 calculates, as calculation steps, the amplitude I _S12 of the interference light between the first measurement light and the second measurement light obtained in the conversion step, the amplitude I _S1 of the first interference light, and the amplitude I of the second interference light. The period T _S12 of the interference light between the first measurement light and the second measurement light is discriminated by comparing with _S2 and selecting the period having the minimum amplitude, and based on this period T _S12 , the formula (2) To calculate the distance L ′. Next, the calculation unit 20 calculates the distance L from the first measurement point S1 to the second measurement point S2 by subtracting the distance Ld acquired in advance from the distance L ′ and taking the absolute value thereof.

In addition, when the spectral ratio of the beam splitter 12 and the measurement light splitting unit 15 is other than 50:50, the amplitude I _S12 , the amplitude I _S1 , and the amplitude I _S2 differ depending on the spectral ratio. If the amplitude I _S12 of the interference light with the light, the amplitude I _S1 of the first interference light, and the amplitude I _S2 of the second interference light are acquired in advance, the first measurement light and the second light are obtained from the value of the amplitude I _S12 . The period T _S12 of the interference light with the measurement light can be directly selected.

Further, a rough value of the distance L (distance L ″) and the positional relationship between the first measurement point S1 and the second measurement point S2 are acquired in advance, and a rough distance Ld + distance L ″ is obtained from these values. After calculating the value of (the distance L ″ is negative when the second measurement point S2 is closer to the laser distance measuring device 50 than the first measurement point S1), the period T _S12 and the period T obtained in the conversion step are calculated. _The distance L ′ is calculated by the expression (2) for each of _S1 and the period T _S2, the distance L ′ that approximates the value of the rough distance Ld + distance L ″ is selected, and the selected distance L ′ The distance L from the first measurement point S1 to the second measurement point S2 may be calculated by subtracting the distance Ld from the absolute value and taking the absolute value thereof.

In addition, it is preferable to acquire the value (distance Ld) of ½ of the optical path difference between the first measurement light and the second measurement light inside the apparatus using the flat plate 7 in the same procedure as described above.

Next, when the laser irradiation means 10 shown in FIG. 6 is a laser distance measuring device 50a including a laser irradiation device 10a, an optical comb generator 10b, and an optical frequency modulator 10c, the light received by the light receiving unit 18 is In addition to the interference light in which a plurality of interference lights generated by the interference of the first measurement light of the laser light LZ and the second measurement light of the laser light LZ are combined, the reference light of the laser light LZ The first interference light in which a plurality of interference lights generated by interference with the respective first measurement lights of the laser light LZ are combined, the respective reference light of the laser light LZ, and the respective second measurement light of the laser light LZ. Are combined with the second interference light in which a plurality of interference lights generated by interference with each other are combined. Then, the light receiving unit 18 converts the intensity of the interference light into an electric signal and outputs it to the calculation unit 20 as intensity data. The intensity data of the interference light includes optical comb lasers having different levels of the interference light between the reference light and the first measurement light of the optical comb laser light having different stages (for example, the laser light LZ ₁ and the laser light LZ ₂ ). The intensity of the interference light between the reference light of the light and the second measurement light, the intensity of the interference light between the first measurement light and the second measurement light of the optical comb laser light having a different number of stages, and the first measurement light of the optical comb laser light having a different number of stages The intensity of the interference light between the second and the second measurement lights, and the intensity of the interference light between the reference lights of the optical comb laser lights having different numbers of stages are also included. The intensity of the interference light of the optical comb laser beams having different stages becomes a beat and appears in the interference light, and this beat is averaged within the measurement time and finally becomes a background noise with a constant intensity.

Next, the calculation unit 20 performs an acquisition step and a conversion step, and performs a Fourier transform based on the amount of change in frequency on the acquired intensity data. Thus, the amplitude of the interference light of the first measuring beam and the second measuring beam, periodically, as a phase, the interference light of the first measuring light of the laser beam LZ ₁ and the second measuring light of the laser beam LZ ₁ amplitude I _{S12 (1)} , period T _{S12 (1)} , and phase φ _{S12 (1)} are acquired. Further, the interference light amplitude _{I S12} of the first measuring light of the laser beam LZ ₂ and the second measuring light of the laser beam LZ ₂ _(2), the period _{T S12 (2),} the phase phi _{S12 (2)} is obtained . The first measuring beam and the interference light amplitude _{I S12} of the second measuring light of the laser beam LZ _n _(n), the period _{T S12 (n),} the phase phi _{S12 (n)} is obtained for the laser beam LZ _n . The amplitude _{I S12 (-1)} of the first measuring beam and the interference light of the second measuring light of the laser beam _{LZ -1} laser beam _{LZ -1,} period _{T S12 (-1),} the phase phi _{S12 (-1 )} Is acquired. The first measuring beam and the amplitude _{I S12} of the second measurement light and the interference light of the laser beam _{LZ -2} of the laser beam _{LZ -2} _(-2), the period _{T S12 (-2),} the phase phi _{S12 (-2 )} Is acquired. The amplitude of the interference light of the first measuring beam and the second measuring light of the laser beam _{LZ -n} of the laser beam _{LZ _-n} _{I S12 _(-n),} the period _{T S12 (-n),} the phase phi _{S12 (-n )} Is acquired.

The amplitude of the first interference light, periodically, as phase, amplitude _{I S1} of the interference light of the reference light laser beam LZ ₁ and the first measuring beam of the laser beam LZ ₁ _(1), the period _{T S1 (1),} The phase φ _{S1 (1)} is acquired. The amplitude _{I S1} of the interference light of the first measuring beam of the reference beam laser beam LZ ₂ and the laser beam LZ ₂ _(2), the period _{T S1 (2),} the phase φ _{S1 (2)} is obtained. The amplitude _{I S1} of the interference light of the first measuring beam of the reference beam and the laser beam LZ _n of the laser beam LZ _n _(n), the period _{T S1 (n),} the phase φ _{S1 (n)} is obtained. The amplitude _{I S1} of the first measurement light and the interference light of the reference beam and the laser beam _{LZ -1} of the laser beam _{LZ -1} _(-1), the period _{T S1 (-1),} the phase phi _S1 is _(-1) To be acquired. The amplitude _{I S1} of the reference light and the interference light of the laser beam first measuring light _{LZ -2} laser beam _{LZ -2} _(-2), the period _{T S1 (-2),} the phase phi _S1 is _(-2) To be acquired. Further, the interference light amplitude _{I S1} of the first measuring light of the laser beam _{LZ -n} of the reference beam and the laser beam _{LZ -n} _(-n), the period _{T S1 (-n),} the phase phi _S1 is _(-n) To be acquired.

Furthermore, the amplitude of the second interference light, the period, as a phase, an amplitude _{I S2 (1)} of the interference light of the reference light laser beam LZ ₁ and the second measuring light of the laser beam LZ _1, period _{T S2 (1),} The phase φ _{S2 (1)} is acquired. The amplitude _{I S2} of the interference light of the reference light laser beam LZ ₂ and the second measuring light of the laser beam LZ ₂ _(2), the period _{T S2 (2),} the phase phi _{S2 (2)} is obtained. The amplitude _{I S2} of the second measurement light and the interference light of the reference beam and the laser beam LZ _n of the laser beam LZ _n _(n), the period _{T S2 (n),} the phase φ _{S2 (n)} is obtained. The amplitude _{I S2} of the second measurement light and the interference light and the reference light and the laser beam _{LZ -1} of the laser beam _{LZ -1} _(-1), the period _{T S2 (-1),} the phase phi _S2 is _(-1) To be acquired. The amplitude _{I S2} of the reference light and the interference light of the second measuring light of the laser beam _{LZ -2} laser beam _{LZ -2} _(-2), the period _{T S2 (-2),} the phase phi _S2 is _(-2) To be acquired. The amplitude _{I S2} of the interference light of the second measuring light of the laser beam _{LZ -n} of the reference beam and the laser beam _{LZ -n} _(-n), the period _{T S2 (-n),} the phase φ _{S2 (-n)} is To be acquired.

Then, the period T _{S12 (1)} (= T _{S12 (−1)} ), the period T _{S12 (2)} (= T _{S12 (−2)} ) of the interference light between the first measurement light and the second measurement light,. The period T _{S12 (n)} (= T _{S12 (−n)} ) is a sequence represented by T _{S12 (1)} , T _{S12 (1)} / 2,..., T _{S12 (1)} / n , Period T _{S1 (1)} (= T _{S1 (−1)} ), period T _{S1 (2)} (= T _{S1 (−2)} ),..., Period T _{S1 (n)} (= T _{S1 (−n)} ) is a sequence represented by T _{S1 (1)} , T _{S1 (1)} / 2,..., T _{S1 (1)} / n, and the period T _{S2 ( 1)} (= T _{S2 (−1)} ), period T _{S2 (2)} (= T _{S2 (−2)} ),..., Period T _{S2 (n)} (= T _{S2 (−n)} ) _{S2 (1),} _{T S (1)} / 2, and · · _{·, T S2 (1)} / n sequence represented by.

As described above, the first measurement light and the second measurement light are obtained by further dividing the laser light divided by the beam splitter 12 by the measurement light dividing unit 15. When the spectral ratio is 50:50, that is, a half mirror, the amplitude I _{S12 (1)} (≈amplitude I _{S12 (−1)} ) and amplitude I _{S1 (1)} ( ≒ Amplitude I _{S1 (-1)} ), Amplitude I _{S2 (1)} (≒ Amplitude I _{S2 (-1)} ) are those of amplitude I _{S12 (1)} (≒ Amplitude I _{S12 (-1)} ) as the first interference It becomes smaller than the amplitudes I _{S1 (1)} (≈amplitude I _{S1 (−1)} ) and the amplitude I _{S2 (1)} (≈amplitude I _{S2 (−1)} ) of the light and the second interference light.

Therefore, the calculation unit 20 calculates, as calculation steps, the amplitude I _{S12 (1)} (≈amplitude I _{S12 (−1)} ) of the interference light obtained in the conversion step and the amplitude I _{S1 (1)} (≈amplitude of the first interference light. I _{S1 (−1)} ) and the amplitude I _{S2 (1)} (≈amplitude I _{S2 (−1)} ) of the second interference light are compared, and the series of the period T having the minimum amplitude is selected. The sequence of the period T _{S12 (n)} of the interference light between the first measurement light and the second measurement light ₍ sequence of the period T _{S12 (1)} / n) is determined. Then, select the predetermined period _{T S12 (n)} of the sequence of the period _{T S12 (n),} calculates the 'distance L' by the calculation formula (2) or (2). And the calculating part 20 calculates distance L from 1st measurement point S1 to 2nd measurement point S2 by subtracting distance Ld acquired beforehand from distance L ', and taking the absolute value.

When the spectral ratio between the beam splitter 12 and the measurement light splitting unit 15 is other than 50:50, the amplitude I _{S12 (1)} (≈amplitude I _{S12 (−1)} ) and amplitude I _{S1 (1)} are determined depending on the spectral ratio. Since (≈amplitude I _{S1 (−1)} ) and amplitude I _{S2 (1)} (≈amplitude I _{S2 (−1)} ) are different, the amplitude I _{S12 (1} of the interference light between the first measurement light and the second measurement light is different. ₎ , The amplitude I _{S1 (1)} of the first interference light, and the amplitude I _{S2 (1) of} the second interference light are obtained in advance, the first measurement light and the first interference light from the value of this amplitude I _{S12 (1)} . The period T _{S12 (n)} of the interference light with the two measurement lights can be directly selected.

Further, a rough value of the distance L (distance L ″) and the positional relationship between the first measurement point S1 and the second measurement point S2 are acquired in advance, and a rough distance Ld + distance L ″ is obtained from these values. After calculating the value of (the distance L ″ is negative when the second measurement point S2 is closer to the laser distance measuring device 50 than the first measurement point S1), the period T _{S12 (n)} obtained in the conversion step is calculated. , The distance L ′ is calculated by the expression (2) or (2) ′ for each of the periods T _{S1 (n)} and T _{S2 (n)} , and approximates the value of the rough distance Ld + distance L ″. The distance L ′ from the first measurement point S1 to the second measurement point S2 is calculated by subtracting the distance Ld from the selected distance L ′ and taking the absolute value thereof. good.

Next, a laser range finder 50d according to a fifth embodiment of the present invention will be described with reference to FIG. In FIG. 7, only the optical path of the laser beam is shown in a simplified manner. A laser distance measuring device 50d according to the fifth embodiment of the present invention shown in FIG. 7 includes a beam splitter 12a instead of the mirror 8 of the laser

distance measuring devices

50 and 50a. A beam splitter 12 b is installed on the optical path between the beam splitter 12 and the light receiving unit 18. Then, the distance from the dividing point of the beam splitter 12 to the reflecting point of the beam splitter 12b is made equal to the distance Ld from the dividing point of the measuring beam dividing unit 15 to the reflecting point of the beam splitter 12a.

In this case, the light received by the light receiving unit 18 follows the optical path 1 of the beam splitter 12 → the measurement light dividing unit 15 → the first measurement point S 1 → the measurement light dividing unit 15 → the beam splitter 12 → the beam splitter 12 b → the light receiving unit 18. The first measurement light, the beam splitter 12 → the measurement light splitting unit 15 → the beam splitter 12a → the second measurement point S2, the beam splitter 12a → the beam splitter 12b → the second measurement light that follows the optical path 2 of the light receiving unit 18, and the beam splitter 12 → measurement beam splitting unit 15 → beam splitter 12a → second measurement point S2 → beam splitter 12a → measurement beam splitting unit 15 → beam splitter 12 → beam splitter 12b → second measurement light ′ following the optical path 3 of the light receiving unit 18 ,Become.

Then, the distance from the beam splitter 12 to the measurement beam splitting unit 15 (= the distance from the beam splitter 12a to the beam splitter 12b) is set as the distance La, and the distance from the beam splitter 12b to the light receiving unit 18 is set as the distance Lb. A distance from the unit 15 to the beam splitter 12a (= a distance from the beam splitter 12 to the beam splitter 12b) is a distance Ld, and a distance from the measurement light dividing unit 15 to the first measurement point S1 is a distance L1, and from the beam splitter 12a When the distance to the second measurement point S2 is a distance L2, the optical path length of the optical path 1 that is the first measurement light is
2La + 2L1 + Ld + Lb
The optical path length of the optical path 2 that is the second measurement light is
2La + Ld + 2L2 + Lb
In addition, the optical path length of the optical path 3 which is the second measurement light ′ is
2La + 3Ld + 2L2 + Lb

Therefore, the optical path difference between the optical path 1 as the first measurement light and the optical path 2 as the second measurement light is
2 | L1-L2 |, and | L1-L2 | is equal to the distance L from the first measurement point S1 to the second measurement point S2. Therefore, the optical path difference between the optical path 1 and the optical path 2 is twice the distance L. It becomes.

The light receiving unit 18 receives the first measurement light in the optical path 1, the second measurement light in the optical path 2, and the second measurement light ′ in the optical path 3, and interference light between the first measurement light and the second measurement light. Then, the intensity of the interference light of the interference light between the first measurement light and the second measurement light ′ and the interference light between the second measurement light and the second measurement light ′ is converted into an electric signal as intensity data. The result is output to the calculation unit 20.

Next, the calculation unit 20 performs an acquisition step and a conversion step, and performs a Fourier transform based on the amount of change in frequency on the acquired intensity data. Thereby, when a known wavelength tunable laser is used for the laser irradiation means 10, the amplitude I _S12 , the period T _S12 , the phase φ _S12 of the interference light between the first measurement light and the second measurement light, and the first measurement light Interference light amplitude I _S12 ′ with second measurement light ′, period T _S12 ′, phase φ _S12 ′, interference light amplitude I _S22 ′ between second measurement light and second measurement light ′, period T _S22 ′ , Phase φ _S22 ′ is acquired.

Here, since the second measurement light ′ passes through the

beam splitters

12, 12a, 12b and the measurement light splitting unit 15 more times than the first measurement light and the second measurement light, the

beam splitters

12, 12a, 12b, measurement In the case where the light splitting unit 15 has a spectral ratio of 50:50, the intensity is lower than that of the first measurement light and the second measurement light. Therefore, the amplitude I _S12 ′ of the interference light between the first measurement light and the second measurement light ′ and the amplitude I _S22 ′ of the interference light between the second measurement light and the second measurement light ′ are the first measurement light and the second measurement light. This is smaller than the amplitude _IS12 of the interference light with the measurement light.

Therefore, the calculation unit 20 calculates, as the calculation step, the amplitude _IS12 of the interference light between the first measurement light and the second measurement light obtained in the conversion step and the amplitude of the interference light between the first measurement light and the second measurement light ′. The first measurement light and the second measurement light are selected by comparing the amplitude I _S22 ′ of the interference light between the I _S12 ′ and the second measurement light and the second measurement light ′, and selecting the period having the maximum amplitude. The interference light period T _S12 is discriminated, and the distance L ′ is calculated by the expression (2) with _respect to the period T _S12 . Since this distance L ′ is 2L, which is the optical path difference between the first measurement light and the second measurement light, the calculation unit 20 takes the half of the distance L ′ to obtain the second from the first measurement point S1. A distance L to the measurement point S2 is calculated.

When the spectral ratios of the

beam splitters

12, 12a, 12b, and the measurement light splitting unit 15 are other than 50:50, the amplitude I _S12 , the amplitude I _S12 ′, and the amplitude I _S22 ′ differ depending on the spectral ratio. If the values of _S12 , amplitude I _S12 ′, and amplitude I _S22 ′ are acquired in advance, the amplitude I _S12 can be discriminated, and the period T _S12 of the interference light between the first measurement light and the second measurement light is directly selected. Can do.

Further, a rough value (distance L ″) of the distance L is acquired in advance, and the expression (2) is obtained for each of the period T _S12 , the period T _S12 ′, and the period T _S22 ′ obtained in the conversion step. To calculate the distance L ′, select a distance L ′ that approximates the approximate distance L ″, and take 1/2 of the selected distance L ′ to perform the second measurement from the first measurement point S1. The distance L to the point S2 may be calculated.

Next, in the case where the laser irradiation means 10 shown in FIG. 6 includes a laser irradiation apparatus 10a, an optical comb generator 10b, and an optical frequency modulator 10c, the period of the interference light obtained in the conversion step is the first measurement. A series of interference light periods T _{S12 (1)} / n between the light and the second measurement light, and a series of interference light periods T _{S12 (1)} '/ n between the first measurement light and the second measurement light ′. , A series of interference light period T _{S22 (1)} ′ / n between the second measurement light and the second measurement light ′.

As described above, when the

beam splitters

12, 12a, 12b, and the measurement light splitting unit 15 have a spectral ratio of 50:50, the first measurement light and the second measurement light corresponding to the maximum period T of each series. amplitude I _S12 of interference light of the ₍₁₎ and the first measuring beam and the second 'of the interference light between the amplitude I _{S12 (1)'} measurement light and second measurement light and the interference light and the second measuring beam ' The amplitude I _{S22 (1)} ′ is the maximum of the amplitude I _{S12 (1)} of the interference light between the first measurement light and the second measurement light.

Therefore, the calculation unit 20 determines the cycle T _{S12 (n)} of the interference light between the first measurement light and the second measurement light by selecting the sequence of the cycle T having the maximum amplitude as the calculation step, and the cycle T _After selecting a predetermined cycle T _{S12 (n)} from the sequence of _{S12 (n) (} sequence of cycle T _{S12 (1)} / n), the distance L ′ is calculated by the above formula (2) or (2) ′. calculate. And the calculating part 20 calculates the distance L from 1st measurement point S1 to 2nd measurement point S2 by taking 1/2 of distance L '.

When the spectral ratios of the

beam splitters

12, 12 a, 12 b and the measurement light dividing unit 15 are other than 50:50, the amplitude I _{S12 (1)} , the amplitude I _{S12 (1)} ′, and the amplitude I _{S22 ( 1) Since} 'is different, if the values of the amplitude I _{S12 (1)} , the amplitude I _{S12 (1)} ', and the amplitude I _{S22 (1)} 'are acquired in advance, the first value is calculated from the value of the amplitude I _{S12 (1)} . The period T _{S12 (n)} of the interference light between the measurement light and the second measurement light can be directly selected.

In addition, a rough value (distance L ″) of the distance L is acquired in advance, the sequence of the period T _{S12 (1)} / n obtained in the conversion step, the first measurement light, and the second measurement light ′. A predetermined period T _{S12 (} from the series of interference light periods T _{S12 (1)} '/ n and the interference light period T _{S22 (1)} ' / n between the second measurement light and the second measurement light ' _n) , cycle T _{S12 (n)} ', cycle T _{S22 (n)} ' are selected, and distance L 'is calculated by the formula (2) or (2)' for each of the selected cycles T. The distance L ′ closest to the value of the distance L ″ is selected, and the distance L from the first measurement point S1 to the second measurement point S2 is calculated by taking 1/2 of the selected distance L ′. May be.

According to the laser distance measuring device 50d of the fifth embodiment, the term of the optical path difference (distance Ld) inside the device between the first measurement light and the second measurement light is canceled, so that the laser of the fourth embodiment Similar to the configuration of the distance measuring device 50c, it is not necessary to obtain the optical path difference between the first measurement light and the second measurement light inside the device and to subtract the distance Ld from the distance L ′. The distance procedure can be simplified. Further, since the distance Ld is canceled, the influence of the “swing” of the vibration frequency of the laser beam in the laser irradiation means 10 can be reduced.

Next, a laser range finder 50e according to a sixth embodiment of the present invention will be described with reference to FIG. In FIG. 8, only the optical path of the laser beam is shown in a simplified manner. In the laser range finder 50e according to the sixth embodiment of the present invention shown in FIG. 8, the measurement beam splitting unit 15 is installed at the position of the beam splitter 12 of the

laser range finders

50 and 50a. Further, the mirror 8 is installed on the reflected light side of the measurement light splitting unit 15. Further, a beam splitter 12c is installed on the optical path of the first measurement light reflected by the mirror 8. Furthermore, the beam splitter 12 a is installed at a position equal to the distance from the reflection point of the mirror 8 to the beam splitter 12 c on the optical path of the transmitted light of the measurement light splitting unit 15.

In this case, the light received by the light receiving unit 18 is the optical path 1 of the measurement light dividing unit 15 → mirror 8 → beam splitter 12 c → first measurement point S 1 → beam splitter 12 c → mirror 8 → measurement light dividing unit 15 → light receiving unit 18. And the first measurement light that follows the optical path 2 of the measurement light dividing unit 15 → the beam splitter 12a → the second measurement point S2 → the beam splitter 12a → the beam splitter 12c → the mirror 8 → the measurement light dividing unit 15 → the light receiving unit 18. 2 measurement light 'and the second measurement following the optical path 3 of the measurement light splitting unit 15 → mirror 8 → beam splitter 12c → beam splitter 12a → second measurement point S2 → beam splitter 12a → measurement light splitting unit 15 → light receiving unit 18 Light ”and the optical path 4 of the measurement light splitting unit 15 → beam splitter 12a → second measurement point S2 → beam splitter 12a → measurement light splitting unit 15 → light receiving unit 18 Second measurement light '' 'and measurement light splitting unit 15 → mirror 8 → beam splitter 12c → beam splitter 12a → second measurement point S2 → beam splitter 12a → beam splitter 12c → mirror 8 → measurement light splitting unit 15 → The second measurement light ″ ″ follows the optical path 5 of the light receiving unit 18.

Then, the distance from the mirror 8 to the beam splitter 12c (= the distance from the measuring beam splitting unit 15 to the beam splitter 12a) is the distance La, and the distance from the measuring beam splitting unit 15 to the mirror 8 (= the beam splitter 12a to the beam splitter). The distance from the beam splitter 12a to the second measurement point S1 is the distance Ld, the distance from the beam splitter 12c to the first measurement point S1 is the distance L1, When the distance to the measurement point S2 is a distance L2, the optical path length of the optical path 1 that is the first measurement light is
2Ld + 2La + 2L1 + Lb
Further, the optical path length of the optical path 2 which is the second measurement light ′ is
2La + 2L2 + 2Ld + Lb.
Further, the optical path length of the optical path 3 which is the second measurement light ″ is
2Ld + 2La + 2L2 + Lb
Further, the optical path length of the optical path 4 which is the second measurement light '''is
2La + 2L2 + Lb
Further, the optical path length of the optical path 5 which is the second measurement light '''' is
4Ld + 2La + 2L2 + Lb

The light receiving unit 18 includes the first measurement light in the optical path 1, the second measurement light ′ in the optical path 2, the second measurement light ″ in the optical path 3, the second measurement light ′ ″ in the optical path 4, and the optical path 5. The second measurement light '' '' is received. At this time, since the second measurement light 'on the optical path 2 and the second measurement light' on the optical path 3 have the same optical path length, their periods and phases are also equal. Therefore, the second measurement light 'on the optical path 2 and the second measurement light' on the optical path 3 can be combined and regarded as one second measurement light. The intensity of the second measurement light is the sum of the intensity of the second measurement light ′ and the intensity of the second measurement light ″.

Therefore, the interference light received by the light receiving unit 18 is interference light between the first measurement light and the second measurement light, interference light between the first measurement light and the second measurement light '' ', the first measurement light and the second measurement light. Interference light with measurement light ″ ″, interference light between second measurement light and second measurement light ″ ″, interference light between second measurement light and second measurement light ″ ″, second measurement light Interference light between '' 'and the second measurement light' '' '. Then, the light receiving unit 18 converts the intensity of the interference light combined with the interference light into an electrical signal and outputs the electrical signal to the arithmetic unit 20 as intensity data.

Next, the calculation unit 20 performs an acquisition step and a conversion step, and performs a Fourier transform based on the amount of change in frequency on the acquired intensity data. Thereby, each amplitude, period, and phase of the interference light received by the light receiving unit 18 are acquired. Here, a case where a known wavelength tunable laser is used as the laser irradiation means 10 will be described. However, even when the laser irradiation means 10 includes a laser irradiation apparatus 10a, an optical comb generator 10b, and an optical frequency modulator 10c. The basic operation is equivalent.

Since each period T corresponds to each optical path difference, when the distance L ′ is calculated by the expression (2) for each period T, the following is obtained.
Distance L ′ by period T _S12 of the interference light between the first measurement light and the second measurement light
L ′ = 2 | L1-L2 | = 2L
Distance L ′ by the period T _S12 ″ of the interference light between the first measurement light and the second measurement light ″ ″
L ′ = 2 | Ld + L1-L2 |
Distance L ′ by the period T _S12 ″ ″ of the interference light between the first measurement light and the second measurement light ″ ″
L ′ = 2 | Ld−L1 + L2 |
Distance L ′ by the period T _S22 ″ of the interference light between the second measurement light and the second measurement light ″ ″
L ′ = 2Ld
Distance L ′ by period T _S22 ″ ″ of the interference light between the second measurement light and the second measurement light ″ ″
L ′ = 2Ld
Distance L ′ by the period T _S2 ″ ″ ₂ ″ ″ of the interference light between the second measurement light ″ ″ and the second measurement light ″ ″
L ′ = 4Ld
It becomes.

However, at this stage, it is not known which period T is caused by which interference light. However, the period _{T S22 ''} 'distance obtained from L' (= 2Ld) the period _{T S22 ''''} distance obtained from L '(= 2Ld) equally, the period _{_{T S2''' 2 ''}} '' The distance L ′ (= 4Ld) obtained from the above is twice the distance L ′ (= 2Ld) of the cycle T _S22 ″ ″ and the distance L ′ (= 2Ld) of the cycle T _S22 ″ ″. 20 can specify a value of 2Ld from the values of these three distances L ′. Then, when the arithmetic unit 20 subtracts the 2Ld value from the remaining three distances L ′ to obtain an absolute value, the obtained values are | 2L−2Ld |, 2L, and 2L, and two 2L values are obtained. It is done. Therefore, the arithmetic unit 20 can specify a value of 2L. And the calculating part 20 calculates the distance L from 1st measurement point S1 to 2nd measurement point S2 by taking 1/2 of this 2L value.

If the spectral ratio of the measurement beam splitting unit 15 and the

beam splitters

12a and 12c is other than 50:50, the amplitude I of each interference light differs depending on the spectral ratio. Then, based on the amplitude, the period T _S12 of the interference light of the first measurement light and the second measurement light is selected, and the distance L ′ is obtained by the expression (2), and then the distance L ′ is taken to obtain the distance L. You may ask.

In addition, a rough value (distance L ″) of the distance L is acquired in advance, the distance L ′ closest to the value twice the distance L ″ is selected, and 1/2 of the distance L ′ is taken. Thus, the distance L from the first measurement point S1 to the second measurement point S2 may be calculated.

Similarly to the laser ranging device 50d of the fifth embodiment, the laser ranging device 50e of the sixth embodiment obtains the optical path difference inside the device between the first measuring light and the second measuring light, and from the distance L ′. The distance Ld subtraction process need not be performed, and the distance L distance measurement procedure can be simplified. Further, since the distance Ld is canceled, the influence of the “swing” of the vibration frequency of the laser beam in the laser irradiation means 10 can be reduced.

When the laser irradiation device 10a, the optical comb generator 10b, and the optical frequency modulator 10c are used as the laser irradiation means 10 of the laser ranging device 50d of the fifth embodiment and the laser ranging device 50e of the sixth embodiment, By providing a known optical bandpass filter that transmits only laser light within a predetermined frequency range on the optical path of the laser light, as with the laser distance measuring device 50b of the third embodiment, the optical comb generator 10b can stabilize the operation. It is possible to reduce the load on the processing of the arithmetic unit 20 while using laser light.

As described above, according to the laser distance measuring method and the laser distance measuring device according to the present invention, the first laser light is changed after changing the frequency of the laser light emitted from the laser irradiation means 10 within a predetermined range. The measurement light and the second measurement light are divided, and the first measurement light is irradiated to the first measurement point S1 of the object 6 to be measured and the second measurement light is simultaneously irradiated to the second measurement point S2 of the object 6 to be measured. Then, a distance L from the first measurement point S1 to the second measurement point S2 is calculated based on the period of the interference fringes of the interference light between the first measurement light and the second measurement light. Accordingly, the distance L between the first measurement point S1 and the second measurement point S2 can be measured with high accuracy without using a mechanical movement mechanism for the optical path system. Therefore, the apparatus scale of the laser distance measuring device can be made relatively small, and the first measurement point S1 is more practical than the distance L1 to the first measurement point S1 or the distance L2 to the second measurement point S2. The distance L between the second measurement points S2 can be measured with high accuracy.

Since the laser

distance measuring devices

50 and 50a to 50e described above are examples suitable for the present invention, the configuration of each part of the laser light information acquisition means 26 and the laser distance measuring device, and each optical path in the laser distance measuring device. These can be implemented with modifications without departing from the scope of the present invention.

6 Object to be measured 10 Laser irradiation means 10a Laser irradiation apparatus 10b Optical comb generator 10c Optical frequency modulator 15 Measurement light splitting section 18 Light receiving section 20 Calculation section 26 Laser light information acquisition means 50, 50a to 50e Laser ranging apparatus BPF1 to BPF5 optical bandpass filter S1 first measurement point S2 second measurement point L1 distance (to the first measurement point) L2 distance (to the second measurement point) distance L (between the first and second measurement points)

Claims

In the laser distance measuring method for measuring the distance to the measurement point by reflecting the laser beam at the measurement point of the object to be measured,
Laser irradiation is performed while continuously changing the frequency of the laser beam, and the laser beam is divided into a first measurement beam and a second measurement beam, and then the first measurement beam is a first measurement point of the object to be measured. Then, the second measurement light is reflected at the second measurement point of the object to be measured, and the intensity data of the interference light generated by the first measurement light reflected at the first measurement point and the second measurement light reflected at the second measurement point Obtaining step corresponding to the amount of change in the frequency of the laser beam;
A conversion step of Fourier-transforming the intensity data obtained in the acquisition step to acquire a period of interference fringes of interference light generated by the first measurement light and the second measurement light;
A calculation step for calculating a distance from the first measurement point to the second measurement point based on the period of the interference fringes of the predetermined interference light obtained in the conversion step;
A laser ranging method characterized by comprising:
Laser irradiation means having a frequency variable function for the laser beam to be output;
Laser light information acquisition means for acquiring the amount of change in the frequency of the laser light emitted from the laser irradiation means;
A measuring beam splitting unit that splits the laser beam emitted from the laser irradiation unit into a first measuring beam and a second measuring beam;
A light receiving unit that receives the first measurement light reflected from the first measurement point of the object to be measured and the second measurement light reflected from the second measurement point of the object to be measured and outputs a signal corresponding to the intensity of the received light. When,
A calculation unit that receives the amount of change in frequency from the laser light information acquisition unit and a signal from the light receiving unit;
The calculation unit is
Based on the amount of change in the frequency of the laser light from the laser light information acquisition means and the signal from the light receiving unit, the first measurement is performed when the laser irradiation means performs laser irradiation while continuously changing the frequency of the laser light. An acquisition step of acquiring intensity data of interference light generated by the first measurement light reflected by the point and the second measurement light reflected by the second measurement point in correspondence with the amount of change in the frequency of the laser light;
A conversion step of Fourier-transforming the intensity data obtained in the acquisition step to acquire a period of interference fringes of interference light generated by the first measurement light and the second measurement light;
And a calculation step of calculating a distance from the first measurement point to the second measurement point based on the period of the interference fringes of the predetermined interference light obtained in the conversion step.
A laser irradiation device that emits laser light of a specific frequency, an optical comb generator that converts the laser light emitted from the laser irradiation device into a plurality of laser beams having a predetermined frequency interval, and generation of the optical comb; 3. The laser distance measuring device according to claim 2, further comprising: an optical frequency modulator that modulates a frequency interval of the detector within a predetermined range.
4. The laser distance measuring device according to claim 3, wherein an optical band-pass filter that transmits only laser light within a predetermined frequency range of laser light emitted from the laser irradiation means is provided on the optical path of the laser light.
3. The laser distance measuring device according to claim 2, wherein the optical path length of the first measurement light and the optical path length of the second measurement light inside the device are equalized.
4. The laser distance measuring device according to claim 3, wherein the optical path length of the first measurement light and the optical path length of the second measurement light inside the device are equalized.
The laser distance measuring device according to claim 4, wherein the optical path length of the first measurement light and the optical path length of the second measurement light in the device are equal.