JPH0481602A - Polar coordinate type apparatus for noncontact measurement of distance - Google Patents

Abstract

PURPOSE:To use an optical heterodyne method for measurement of the amount of movement in the radial direction of an arm moving in a polar coordinate fashion and thereby to enable execution of highly precise measurement by using an optical fiber having a polarization maintaining property. CONSTITUTION:A laser beam generated in a two-frequency helium-neon laser oscillator 11 and condensed by a condenser lens 12 is led to a stator 23 on the base 22 of a polar coordinate type arm 21 by an optical fiber 13 having a polarization maintaining property. On the occasion of employment, a noncontact type measurer 19 is so regulated as to follow the surface of an object of measurement by the rotation of the base 22 of the polar coordinate type arm in the direction of an arrow U by the rotation of a motor 15 and by the adjustment of the amounts of projection and withdrawal of first and second extension parts 22a and 22b. As the result, distances to an interference system 17 and a reflector 18 are varied and a distance from the base 22 to the reflector 18 is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a non-contact distance measuring device, and particularly to a non-contact ranging device using an optical heterogain method.

(Prior Art) In the conventional optical heterodyne method, the direction of a measurement laser is changed by a mirror, and then the object to be measured is irradiated with the laser. For this reason, it is only applied to orthogonal coordinate type operation installation where the polarization plane of the laser, which is important for precision measurement, can maintain the required direction.

In devices operating in polar coordinates, the plane of polarization is distorted when the direction is changed by a mirror. Therefore, in the case of this type, the only option was to use mechanical measurements (measuring the amount of rotation of the motor, etc.).

(Problem to be solved by the invention) Currently, the measurement accuracy required for inspection is at the 10,000 level or submicron level, and according to the laser light heterodyne method, this is possible because it uses an extremely small wavelength. It can be easily achieved. However, since this optical heterodyne method uses the polarization of light, it was impossible to supply a laser with the correct plane of polarization to a polar coordinate arm with a rotating part using methods such as simple reflection from a mirror. .

In view of these circumstances, an object of the present invention is to provide a polar coordinate type arm that rotates around the base without using a reflector.
An object of the present invention is to provide a non-contact distance measuring device using an optical heterodyne method, which is configured to guide a laser beam without distortion.

(Means for Solving the Problems) A polar coordinate type non-contact ranging device according to the present invention has a laser reception result output signal transmitter to a measurement circuit using an optical heterogain method, and a stator for laser irradiation. A two-frequency laser light source and the stator are connected by a polarization-maintaining optical fiber, and the polar coordinate type arm that can be rotated and telescopically extended and retracted is juxtaposed to the base of the polar coordinate type arm. A laser beam path is formed along the arm, consisting of an outgoing path to a reflecting mirror provided near the tip of the arm and a returning path from the reflecting mirror to the transmitter.

An interferometer, through which the outgoing path and the return path pass, is interposed between the reflecting mirror in the laser optical path, the stator, and the transmitter, and the distance from the base remains unchanged, and from the back side of the reflecting mirror, It is desirable that a non-contact type measuring element is provided protruding from the tip of the arm.

More specifically, the interferometer is fixed to a support plate extending from the base, and the arm body is provided so as to move relative to the support plate, that is, to expand and contract telescopically as described above.

(Function) Since a two-frequency laser beam is guided from a light source through a flexible glass fiber to the laser beam irradiation stator fixed to the base of the polar coordinate type arm, it is possible to control how the arm rotates. However, the plane of polarization of the laser beam does not change. Note that since the mode of reflection at the pair of reflecting mirrors near the tip of the arm, that is, the angle of reflection, is constant regardless of the rotation, expansion and contraction of the arm, there is no possibility that the laser polarization plane will be twisted in the optical path.

When the distance between the fixed central axis of the arm and the object to be measured changes, the arm expands and contracts like a telescopic tube, and the reflector at the tip of the arm changes the distance from the fixed central axis. .

On the other hand, since the distance of the interferometer from the fixed central axis is always constant, the optical path length between the interferometer and the reflecting mirror ultimately changes depending on the distance of the object to be measured. As a result, the state of interference between the outbound laser beam passing through the interferometer and the return laser beam passing through the interferometer also changes as the distance changes. Therefore, by detecting a change in this interference state, the object distance can be measured.

The principle of distance measurement using the optical heterodyne method is shown in FIG.

That is, by shifting the frequencies of the measurement light f1 and the reference light f2, the beat frequency f2-f and the reflected light from the object to be measured f1+Δ
The value f2 (r+ +Δf) obtained by subtracting f from the reference light,
The displacement of the object to be measured is measured by counting the difference Δf.

The object to be measured is the light beam X. The measurement light f1 and the reference light f2 here are polarized waves orthogonal to each other, and the - laser beams A and B are collectively irradiated.

Specifically, for example, polarized laser beams of frequencies f1 and f2 that are emitted from the two-frequency helium-neon laser oscillator 1 and passed through the reference beam splinter 2 are reflected by the mirror 3.4 and reach the receiver 5. At this time, for example, assume that the frequency of the laser beam with frequency f is f7 minus Δf, and the difference between this and frequency f2 is f2f1±
Δf is converted into an electrical signal corresponding to the difference by the receiver 5, and is supplied as a measurement signal S to an output circuit 6 including, for example, a differential circuit.

On the other hand, the laser beam reflected from the reference beam splinter 2 passes from the polarizing beam splitter 7 to the mirror 8, is converted into an electrical signal by the photoelectric conversion element 9, passes through the amplifier 10, and is converted into an electrical signal corresponding to the difference fz f+ between the two frequencies f1 and f2. The reference signal R is supplied to the output circuit 6 as a reference signal R.

In the output circuit 6, the difference ±Δf between the two signals is determined and sent as an output signal T to a reversible counter (not shown), for example. is required.

On the other hand, the measuring stylus is equipped with a means for easily determining the distance y from the object to be measured in a non-contact manner, such as a non-contact measuring stylus with a V-shaped tip using a laser triangulation method. Therefore, by calculating x + y (where x:>y), the distance from the rotation center axis of the arm to the object to be measured can be measured in polar coordinates using a polarized laser beam.

(Example) Next, a specific example of the present invention will be described with reference to the drawings. As shown in FIG. 1, a dual-frequency helium-neon laser oscillator 11 configured to oscillate two polarized laser beams with different frequencies is installed on the support base 20.

A laser beam generated by this laser oscillator 11 and condensed by a condensing lens 12 is guided to a stator 23 on a base 22 of a polar coordinate arm 21 by a polarization-maintaining optical fiber 13. The base 22 has a motor 1 on a coaxial core.
5 is attached, and the arm is pivotally connected to the pedestal 14 via the motor 15.

The polar coordinate type arm 21 has a telescopic structure,
a first extension 22a that is fitted into the base 22 and whose sliding protrusion and retraction from the base 22 is controlled;
The second extension part 22b is fitted into the second extension part 2a and whose sliding protrusion and retraction from the first extension part 22a is controlled. The fixed protrusion 22c has a length corresponding to almost the entire length of the first and second extensions 22a and 22b when they are retracted.
2, and an interferometer 17 is attached near the end on the side remote from the base 22. On the other hand, a reflecting mirror 18 and a non-contact type probe 19 protruding further forward than the reflecting mirror 18 are attached to the distal end side of the second extension part 22b.

Juxtaposed with the stator 23 in the base 22 is a receiver 16 and thus the polar arm 2
1, a reflecting mirror 18 passes from the stator 23 to the interferometer 17.
An optical path is formed, consisting of an outgoing path (dotted chain line) 30 leading to the reflector 18, and a return path (double chain line) 31 returning from the reflecting mirror 18 to the receiver 16 as an output signal transmitter via the interferometer 17. corresponds to the component inside the dashed-dotted line frame at the upper right of FIG.

In use, the arrow U due to the rotation of the motor 15
By rotating the polar coordinate arm base 22 in the direction and adjusting the amount of protrusion and retraction of the first and second extensions 22a and 22b, non-contact measurement can be performed to follow the surface of the object to be measured (not shown). Child 19 is matched.

As a result, the distance between the interferometer 17 and the reflecting mirror 18 changes, and as shown in FIG. 3, the distance X between the base 22 and the reflecting mirror 18 is measured according to the principle shown in FIG. 2. Become. At that time, an output signal is sent from the receiver 16 to the control device 32 through a cable (not shown), and an output signal is also sent from the laser oscillator 11 and each part shown within the two-dot chain line in FIG. 2 through a cable (not shown). Various signals sent to the control device 32 are used to calculate the distance.

The above embodiment can be modified as follows. For example, a probe 19 is attached to the tip of the arm to measure the distance from the tip of the arm to the object W without contact, and the distance y is determined from the center of the arm to the tip of the arm, which is determined by a polar coordinate distance measuring device. By adding up the straight line distance gl x, we get this x-5y
indicates a highly accurate distance from the center of the arm to the object W to be measured.

If this is used, it can be applied to three-dimensional non-contact measuring machines for inspection and measurement.

In addition, if the arm base 22 connected to the pedestal 14 via the motor 15 is configured to be similar to an X-Y moving type so that it can move parallel to the pedestal 14,
It is convenient because the drawing to be measured is enlarged.

(Effects of the Invention) According to the present invention, by using a polarization-maintaining optical fiber, it has become possible to use the optical heterogain method to measure the amount of movement in the radial direction of an arm that moves in polar coordinates. This enables much more accurate measurement (resolution: 0.1582n using a helium-neon laser) than conventional mechanical measurement (in which the amount of movement of the arm tip is determined by the rotation of a motor, etc.).

[Brief explanation of the drawing]

Fig. 1 is a perspective explanatory diagram of an apparatus according to an embodiment of the present invention, Fig. 2 is an optical path/circuit diagram showing the measurement principle, and Fig. 3 is an enlarged perspective view of the main part and a diagram showing an application example. be. 1...2 frequency helium neon laser oscillator 2
...Reference beam splitter-3, 4, 8...
...Mirror 5...Receiver 6...Output circuit 7...A light beam sub-tube 9...
Photoelectric conversion element 10...Amplifier 11...Two-frequency helium neon laser oscillator 12...Condensing lens 13...Optical fiber 14... Frame Base 15...Motor 16...Receiver 17...Interferometer 18...Reflector 19...Non-contact probe 20. ... Support stand 21 ... Polar coordinate arm 22 ... Base 23 ... Stator 30 ... Outward path 31 ... Return route 32... Control device

Claims (1)

[Scope of Claims] 1. A signal transmitter for outputting laser reception results to a measurement circuit using the optical heterodyne method and a stator for laser irradiation are arranged in a polar coordinate type arm that can rotate around the base and telescopically expand and contract. A two-frequency laser light source and the stator are juxtaposed at the base, and are connected to each other by a polarization-maintaining optical fiber, and an outgoing path from the stator to a reflecting mirror provided near the tip of the polar coordinate arm is connected to the stator. A polar coordinate type non-contact ranging device characterized in that a laser optical path consisting of a return path from a reflecting mirror to the transmitter is formed along the arm. 2. An interferometer, through which the outgoing path and the return path pass, is interposed between the reflecting mirror in the laser optical path, the stator, and the transmitter, and the distance from the base remains unchanged, and a 2. The polar coordinate type non-contact distance measuring device according to claim 1, wherein a contact type measuring element is provided protruding from the tip of the arm.