JP3135630B2 - Laser-based measuring instrument using Doppler effect - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser-based measuring instrument using the Doppler effect for measuring, for example, vibrations of a moving object, and more particularly to an improvement in the adjustment of an irradiation angle of a laser beam on the object. Things.

[0002]

2. Description of the Related Art A conventional laser-based measuring instrument using the Doppler effect of this type has, for example, the apparatus shown in FIG. The apparatus shown in FIG. 1 is also a drawing showing one embodiment of the present invention (with the addition of a laser irradiation angle adjusting means indicated by reference numeral 5). Here, only the equivalent parts of the conventional method will be described. I do.

The apparatus shown in FIG. 1 is a measuring instrument for detecting a physical quantity such as displacement, vibration, and the like of a rotating measuring object 2 in a direction perpendicular to the rotating direction. First, the laser beam from the laser light source 11 is supplied to the first beam splitter (B
S1) It is separated into two by 12. The first beam is applied to the measurement target 2 via the mirror 19, and the second beam is applied to the acousto-optic device (AOM) 14 and the AOM driver 1
5, and is adjusted to a laser beam having a predetermined frequency.

With respect to the above-mentioned first beam, the reflected light from the measuring object 2 is converted into a second beam splitter (BS2) 1
The signal is input to the optical-electrical converter 18 via the mirror 3 and the mirror 16. The second beam acts as reference light, emits the above-described optical frequency shift means, and is input to the optical-electrical converter 18 via the third beam splitter (BS3).

In the optical-electrical converter 18, the above-mentioned reference light (first beam) and the reflected beam (second beam)
Is input. Both of these beams are
Overlap interference occurs in the electric converter 18. When the measurement object 2 is vibrating in a direction (beam irradiation direction) perpendicular to the movement direction, the frequency of the second beam (reflected light of the measurement object 2) is shifted by a predetermined amount due to the Doppler effect. Accordingly, a beat frequency corresponding to the difference in frequency between the second beam and the reference light is generated in the optical-electrical converter 18. Then, the beat frequency is converted into an electric signal, and a frequency signal corresponding to the vibration of the measurement target is obtained.

By outputting this frequency shift signal to the utilization device 4 and performing desired processing in the utilization device 4, various measurements such as vibration, velocity, and displacement can be performed.

[0007]

By the way, in a laser-based measuring instrument using this type of Doppler effect, FIG.
As shown in the left figure, it is desirable that the laser beam irradiated to the measurement target 2 be irradiated so as to coincide with the direction of the vibration to be measured. As shown in the right diagram of FIG. 3, when the irradiation laser light is not perpendicular to the vibration plane, the laser light is affected not only by the vibration to be measured but also by the motion of the measurement target 2, and the vibration to be measured is faithfully captured. It is not possible. That is, in this type of laser-based measuring instrument, it is necessary to adjust the irradiation direction of the laser light so as to match the direction of the displacement or the like to be measured.

[0008] In this type of conventional apparatus, the laser light is radiated only in a predetermined direction, and no means is specifically provided for this adjustment. Therefore, in order to make the measurement result highly accurate, it was necessary to perform the adjustment very precisely. The present invention seeks to improve in this regard.

[0009]

According to the present invention, a laser beam is applied to an object (measurement object) moving in a predetermined direction in order to measure the speed or displacement of the object in a direction intersecting the direction of the movement. Irradiating the object to be measured with a Doppler effect measuring device that analyzes the reflected laser light to which the Doppler effect is applied from the object and measures the speed or displacement of the vibration. Means for detecting the frequency shift amount of the reflected laser light from the measurement object, and means for varying the irradiation angle of the laser light on the measurement object so as to make the detected frequency shift amount zero, It was configured to adjust the irradiation angle of the laser beam.

[0010]

Operation Referring to FIG. In order to measure the speed or displacement of the measurement object 2 moving at a predetermined speed v0 in a direction perpendicular to this direction of motion, as shown in the left diagram of FIG.
It is desirable to irradiate the laser beam from a direction perpendicular to the direction of movement. Now, it is assumed that the measurement target 2 that moves at the speed v0 does not change its position in a direction perpendicular to the direction of the movement. As shown in the left diagram of FIG. 3, when the measurement target 2 is irradiated with laser light from a direction perpendicular to the direction of its movement,
The reflected laser light is not affected at all. That is, the frequency shift due to the Doppler effect related to the moving speed v0 of the measurement target 2 does not occur, and the laser light having the same frequency is reflected.

On the other hand, as shown in the right diagram of FIG. 3, when a laser beam is irradiated on the measurement target 2 at a predetermined angle θ, the reflected laser beam is affected by v0 · cos θ by the Doppler effect and the frequency is changed. shift. The relationship between the laser irradiation angle and the frequency shift amount is as shown in FIG. When the measurement target 2 moving at the speed v0 is irradiated with laser light at right angles to the moving direction, the reflected laser light does not change and has the maximum frequency. Then, each time the irradiation angle deviates from the right angle, the frequency shift amount gradually increases. Therefore, by knowing the frequency shift amount, it is possible to know the irradiation angle of the laser beam to the measurement target 2 and to adjust the angle efficiently.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to one embodiment of the drawings. The embodiment apparatus shown in FIG. 1 detects a frequency shift amount that shifts in accordance with the irradiation angle of the laser light and adjusts the irradiation angle of the laser light.

In the apparatus shown in FIG. 1, the irradiation angle of the laser beam is adjusted before the actual measurement. Optical-electrical converter 1
8 is changed over by the switch 3 to change the irradiation angle adjusting means 5
Connect to The output signal of the optical-electrical converter 18 is converted by the frequency-voltage converter 51 into a voltage signal corresponding to the frequency. This voltage signal becomes one input of the comparing means 53. Further, the other terminal of the comparing means 53 has
A reference voltage signal corresponding to the output frequency signal of the optical-electrical converter 18 when the laser light from the laser light source 11 is irradiated perpendicularly to the measurement target 2 is referred to as a reference voltage generator 5.
2 has been entered.

Accordingly, a signal representing the deviation of the actual irradiation angle of the laser beam from the reference voltage, that is, the vertical irradiation angle, is generated in the comparing means 53. The comparison signal is output to a frequency difference display 54 such as a meter, and visually displays the amount of the deviation.

The user of the apparatus adjusts the irradiation angle of the laser light source 11 with respect to the measurement target 2 while observing the amount of deviation displayed on the display 54. This adjustment is completed when the deviation amount becomes zero. Then, the switch 3 is switched and the output signal of the optical-electrical converter 18 is connected to the utilization device 4 to perform the intended measurement. This measurement operation is as described above.

In this adjustment, the positional relationship between the laser light source 11 and the object to be measured 2 may be changed manually.
Further, a device (for example, a mechanism for automatically adjusting the mirror 19 according to the amount of the deviation) that automatically adjusts the positional relationship between the two may be provided.

FIG. 2 shows a second embodiment of the present invention, in which an amplifier whose output level fluctuates according to an input frequency signal is used. That is, this amplifier corresponds to a frequency signal input from the optical-electrical converter 18 (FIG. 1) when the irradiation angle of the laser light from the laser light source 11 is exactly perpendicular to the measurement target 2. A tuned amplifier with the highest output level can be used.

This tuning amplifier preferably has the characteristics shown in FIG. That is, the input frequency shown in the figure
f0 is equal to the output frequency of the optical-electrical converter 18 corresponding to the state where the laser light from the laser light source 11 is irradiated on the measurement target 2 in a vertical relationship. When the input frequency to this amplifier is f0, the output level is maximum. Therefore, as shown in FIG. 6, the positional relationship between the laser beam of the laser light source 11 and the measurement target 2 may be adjusted so that the output level of the tuning amplifier is at the maximum.

Referring to FIG. FIG. 2 shows a mechanism for adjusting the laser irradiation angle, and has the same function as the adjusting mechanism 5 shown in FIG. Opto-electric converter 1 shown in FIG.
When the adjustment of the laser beam is performed, the output signal of switch 8
Is input to the tuning amplifier 55 of the adjustment mechanism 5 shown in FIG. The tuning amplifier 55 has an output level corresponding to the input frequency signal as shown in FIG. The peak detection circuit 56 holds the maximum value of the output of the tuning amplifier 55. The output value of the peak detection circuit 56 is visually displayed on the level display 57.

The user of the apparatus adjusts the positional relationship between the laser light of the laser light source 11 and the object 2 so as to maximize the display level of the level indicator 57. This adjustment is
Similar to the above-described embodiment, the adjustment may be performed manually, or a mechanism capable of changing the positional relationship between the laser light source and the measurement target 2 may be provided to automatically adjust the positional relationship. In the apparatus of this embodiment, an example in which the measurement operation and the adjustment operation are performed by switching the switch 3 (FIG. 1) has been described. However, the configuration may be such that these operations are performed simultaneously. In this case, the output signal of the optical-electrical converter 18 shown in FIG. 1 may be sent to both the utilization device 4 and the irradiation angle adjusting mechanism.

[0021]

As described above, according to the present invention, the laser light source 1
1 is configured to detect the best condition of the positional relationship between the laser beam and the object to be measured, and furthermore, the two are adjusted based on this, so that reliable and efficient adjustment can be performed. Since the laser beam can be irradiated at a predetermined angle without fail, accurate measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a laser-based measuring instrument having a mechanism for adjusting an irradiation angle of a laser beam according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a configuration of a laser light irradiation angle adjustment mechanism according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating a principle of detecting an irradiation angle of laser light according to the present invention.

FIG. 4 is a graph showing the relationship between the irradiation angle of laser light of a laser-based measuring device using the Doppler effect and the frequency of the reflected laser light, which is the subject of the present invention.

FIG. 5 is a graph showing characteristics of a tuning amplifier according to a second embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating the operation of a tuning amplifier according to a second embodiment of the present invention.

[Explanation of symbols]

 11: Laser light source 2: Measurement target 3: Changeover switch 4: Utilization device 5: Irradiation angle adjustment mechanism

Claims (2)

(57) [Claims] 1. An object moving in a predetermined direction (measurement object)
Vibration in the direction intersecting the direction of motion, to measure physical quantities such as speed, irradiate the object with laser light, analyze the reflected laser light to which the Doppler effect has been added from the object, vibration of the object, the laser utilized measuring device using the Doppler effect to measure the physical quantity such as velocity, means for irradiating laser light to the measurement target, the frequency shift amount of the reflected laser light from the measurement target real
Means for detecting when vibration to be measured direction, a direction corresponding to a physical quantity such as velocity
In the above, when the measurement object is irradiated with the laser light,
Equivalent to the frequency shift of the reflected laser light from the measurement target
Reference frequency shift amount output means that outputs the frequency shift amount
And the frequency shift of the reflected laser light actually detected.
Means for comparing the frequency shift amount of the reflected laser light actually detected.
The frequency shift output from the reference frequency shift amount output means
A laser-based measuring instrument using the Doppler effect, which is configured to variably adjust an irradiation angle of the laser beam to the measurement object so as to match the laser beam. 2. An object moving in a predetermined direction (measurement target)
In order to measure the physical quantity such as vibration and velocity in the direction intersecting with the movement direction, the object is irradiated with laser light, and the reflected laser light from the object to which the Doppler effect has been added is analyzed to determine the vibration, velocity, etc. A laser-based measuring apparatus using the Doppler effect for measuring the physical quantity of the laser beam; An amplifier that generates a maximum output level when a frequency signal that matches the frequency is input, and adjusts an irradiation angle of the laser light to the measurement target to the predetermined angle so as to maximize the output level of the amplifier. And a laser-based measuring device using the Doppler effect.