JPH07198329A - Laser-position orienting apparatus - Google Patents

Abstract

PURPOSE:To provide a measuring instrument, which can perform simultaneous measurement with a plurality of measuring resolutions and can perform the distance measurement and the measurement of minute displacement at the same time. CONSTITUTION:Laser light is split into three beams with a half-mirror group 2. The beat modulated light is formed of two laser light beams among the split laser beams. Frequency shifting is performed for the other one laser light beam. The modulated light is cast on an orientation target 9. The frequency- shifted laser light is made to interfere with the returned beat modulated light. The position information of the orientation target 9 is obtained based on the interference light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser position locator for measuring position and the like.

[0002]

2. Description of the Related Art The prior art will be described with reference to FIGS. The laser position locator is roughly classified into two methods. The first is a conventional laser position locator using modulated laser light shown in FIG. The laser light emitted from the laser light source 1 is split into two by the half mirror 8a. Half mirror 8a
The laser light reflected at is f ₁ Hz by the frequency shifter 3.
And the other laser beam that has been transmitted through the half mirror 8a and reflected by the reflection mirror 7c.
Interference at b produces beat modulated light at f ₁ Hz. The modulated light is split into two by the half mirror 8c, and one of the modulated lights enters the photodetector 10a as reference light. The other modulated light is applied to the orientation target 9 as measurement light,
The measurement light reflected by the orientation target 9 and returned returns to the photodetector 10b. The measurement light and the reference light taken into the photodetector are converted into current signals I _M and I _R. The optical path difference L between the measurement light and the reference light is obtained by measuring the phase difference between the current signals I _M and I _R with the phase measuring device 14a. With the optical path difference L, it is possible to obtain position information up to the orientation target at the wavelength level of the modulated light.

The second is a laser position locator utilizing the interference shown in FIG. The laser light emitted from the laser light source 1 is split into signal light and local light by the half mirror 8a. The signal light undergoes a frequency shift of f ₁ Hz by the frequency shifter 3 and is then split into two by the half mirror 8b to become measurement light and reference light. Immediately before being taken into the photodetector, both lights interfere with the local light by the half mirrors 8c and 8d and are converted into modulated light of frequency f ₁ Hz. The respective lights modulated to f ₁ Hz enter the photodetectors 10a and 10b and are converted into current signals I _R and I _M. This current signal I
_R, by measuring the phase meter 14a the phase difference of I _M, the optical path difference L of the reference light and the measurement light is obtained. Position information up to the orientation target can be obtained at the wavelength level of the laser light by L.

[0004]

Since the principle of laser position locating is phase measurement, the resolution is determined by the wavelength of the measuring light in the conventional position locating device described above. Therefore, the laser position locator using the modulated laser beam has a low resolution and is suitable for locating an object at a long distance, but is not suitable for locating at a short distance. In addition, since the laser position locator using interference has high resolution,
It is suitable for measuring short distances and small displacements, but not suitable for locating long distances. As described above, the conventional laser position locating device is limited in its use, and there is a problem that the locating device lacks versatility. It is an object of the present invention to provide a device that can solve the above problems.

[0005]

A laser position locating apparatus according to the present invention includes a laser light source 1, a half mirror group 2 for dividing a laser beam emitted from the laser source into three, and a divided laser beam. First and second frequency shifters for frequency-shifting two laser lights, laser light frequency-shifted by the first frequency shifter 3, and frequency shift of the laser lights divided by the half mirror group 2. Equipped with an optical system that makes beat-modulated light by interfering laser light that has not been received, irradiates the measured object with the beat-modulated light made by the optical system as length-measuring light, and returns after being reflected. By interfering the beat-modulated light with the laser light that has been frequency-shifted by the second frequency shifter 4,
The feature is that high-resolution distance information and low-resolution distance information from the modulated light to the object to be measured are obtained at the same time.

[0006]

Since the laser position locator of the present invention is constructed as described above, beat modulated light is produced by the interference of two lasers having different frequencies. Therefore, the beat-modulated light returning from the orientation target contains the low-resolution information of the beat-modulated light wavelength level and the high-resolution information of the laser light wavelength level. Even if it is detected, due to the responsivity of the photodetector, beat-modulated light can only obtain low-resolution information at a long level. However, by interfering the beat-modulated light and the laser light that has undergone a frequency shift different from the beat-modulated frequency, new beat-modulated light containing high-resolution information of the beat-modulated light appears. As a result, high resolution information at the laser wavelength level can be obtained, and low-resolution position determination and high-resolution position determination can be performed at once.

[0007]

Embodiment FIG. 1 shows an embodiment of the laser position locating device of the present invention.
~ It demonstrates concretely by FIG. FIG. 1 is a block diagram of a laser position locating device according to the present invention. The laser light emitted from the laser light source 1 is divided into three by the half mirror group 2.
One laser beam is a frequency shifter a driven by an oscillator a.
, At a frequency shift of f ₁ Hz. Further, another laser beam passes through the reflection mirror 7a, undergoes a frequency shift of f ₂ Hz in the frequency shifter b driven by the oscillator b, and becomes a local light. The laser light that has undergone the frequency shift of f ₁ Hz passes through the reflection mirror 7b and the half mirror 8
to a. The remaining one laser beam reaches the half mirror 8a via the reflection mirror 7c. The two lights interfere with each other in the half mirror 8a to form beat modulated light. The beat-modulated light is split into two by the half mirror 8b, one of which serves as a reference light, and the other of which is irradiated as a measurement light onto the orientation target 9. The measurement light returning from the orientation target 9 via the reference light and the reflection mirror 7d interferes with the local light subjected to the frequency shift of f ₂ Hz in the half mirrors 8c and 8d, respectively, and then the photodetectors 10a and 10b. Is converted into a current signal at.

Current signals I _m and I _{r of the} measurement signal and the reference signal
Is expressed by the following equations (1) and (2). ^{_{I m = 3A 2/2 +}} aA 2 cos (2πf 1 t + θ m1) + bA 2 cos [2π (f 1 -f 2) t + θ m2] + cA 2 cos (2πf 2 t + θ m3) (1) Formula ^{_{I r = 3A 2/2 +}} aA ² cos (2πf ₁ t + θ _r1 ) + bA ² cos [2π (f ₁ −f ₂ ) t + θ _r2 ] + cA ² cos (2πf ₂ t + θ _r3 ) (2) Expression where θ _m1 = 2πf ₁ L _m / C θ _r1 = 2πf ₁ L _r / C θ _m2 = [2π (f + f ₁ ) L _m −2π (f + f ₂ ) L
_loc ] / C θ _r2 = [2π (f + f ₁ ) L _r −2π (f + f ₂ ) L
_loc ] / C θ _m3 = [2π (f + f ₂ ) L _loc −2πfL _m ] / C θ _r3 = [2π (f + f ₂ ) L _loc −2πfL _r ] / C L _m : optical path length L _{r of} measurement light: reference Optical path length of light L _loc : Optical path length of local light C: Speed of light The phase component of the second term of equations (1) and (2) contains the orientation information of the beat-modulated light, and the third term includes the laser wavelength. Includes level orientation information. The electric signals are the dividers 11a, 11
It is divided into two by b, and each is a low-pass filter (LP
F) 12a, 12b, high-pass filter (HPF) 13
a, 13b.

The component of the second term passes through the dividers 11a and 11b, the component of the third term passes through the HPFs 13a and 13b, and their phases are measured by the phase measuring devices 14a and 14b, respectively. Here, the high cutoff frequency f ₁ of the LPF is set to f
₁ <f _2, the low-frequency cut-off frequency f _h of the HPF f _h>
The component of the fourth term of the equations (1) and (2) is removed as f ₂ .

FIG. 2 shows the principle of obtaining the position information of the orientation target 9 from the obtained phases θ _m and θ _r . Figure 2
As shown in, the measurement light and the reference light have an optical path length difference of L ₁ + 2L ₂ + L ₃ . L ₁ and L ₃ are known, and L ₂ is position information of the orientation target 9 to be obtained. There is a time delay ΔT between the measurement light and the reference light. When the period T of the measuring light is used, the following formula is established.

Θ _m −θ _r = (ΔT / T) * 360 deg Expression (3) Therefore, the optical path difference ΔL between the measurement light and the reference light is ΔL = ΔT * C = T (θ _m −θ _r ) C / 360 ( Equation 4) is obtained. According to FIG. 2, ΔL = L ₁ + 2L ₂ + L ₃ , and since L ₁ and L ₃ are known, L ₂ can be obtained.

L ₂ = [T (θ _m −θ _r ) / 360− (L ₁ + L ₃ )] / 2 (5) Formula Even when the local light is used, the optical path length of the local light is known, and the same applies. . For a signal that has passed through the LPF, T = 1 / (f ₁
-F ₂ ), and T = 1 / f for components that have passed through the HPF
Becomes ₁ . Here, there is a relation of 1 / (f ₁ −f ₂ )> 1 / f ₁ . That is, it shows that the low resolution position information and the high resolution position information of the orientation target 9 are measured at the same time. Therefore, one laser position locator can perform a plurality of measurements at the same time.

[0013]

Since the present invention is constructed as described above, it has the following effects. (1) The laser position locator of the present invention is capable of simultaneous measurement with a plurality of measurement resolutions. (2) Therefore, it is possible to realize a measuring device capable of simultaneously performing distance measurement and minute displacement measurement. Therefore, the industrial use effect is great.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a laser position locating device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a measurement principle according to an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional laser position locating device (modulated laser light type).

FIG. 4 is a diagram showing a configuration of a conventional laser position locating device (interference laser light type).

[Description of Reference Signs] 1 ... Laser light source, 2 ... Half mirror group, 3 ... Frequency shifter a, 4 ... Frequency shifter b, 5 ... Oscillator a, 6 ... Oscillator b, 7a, 7b, 7c, 7d ... Reflection mirror, 8a , 8
b, 8c, 8d ... Half mirror, 9 ... Oriented target,
10a, 10b ... Optical modulator, 11a, 11b ... Divider, 12a, 12b ... Low pass filter, 13a, 13
b ... High-pass filter, 14a, 14b ... Phase measuring device.

Claims (1)

[Claims] 1. A laser light source (1), a half mirror group (2) that divides a laser beam emitted from the laser light source into three, and two laser beams among the divided laser beams are frequency-shifted. A laser that is not frequency-shifted among the first and second frequency shifters, the laser light frequency-shifted by the first frequency shifter (3) and the laser light split by the half mirror group (2). An optical system is provided which makes beat-modulated light by interfering light, and the beat-modulated light produced by the optical system is irradiated as a length-measuring light on the object to be measured, and the beat-modulated light reflected and returned and Second
Laser position locating characterized by simultaneously obtaining high-resolution distance information and low-resolution distance information from the modulated light to the object to be measured by interfering the laser light frequency-shifted by the frequency shifter (4) of apparatus.