JPS6255501A - Laser length measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to measure the displacement quantities of a plurality of articles to be measured by the same apparatus, by changing over a plurality of light paths by a PLZT element and a reflective mirror. CONSTITUTION:A PLZT element 9 is set to a beam blocking state and a PLZT element 9a is set to a beam transmitting state. Whereupon, the beam A emitted from laser 1 enters an interferrometer 2 and is separated into two directions by a half mirror 3. The beam A1 enters a beam receiving apparatus 5 through a route consisting of a half mirror 3a, the element 9a, a corner cube 4, the element 9a and mirrors 3a, 3 while the beam A2 enters an apparatus 5 through a route consisting of a lambda/4 plate 6, a flat mirror 8, a plate 6, the mirror 3, a corner cube 4a, the mirror 3, the plate 6, the mirror 8, the plate 6 and the mirror 3. The apparatus 5 counts the interference due to the beams A1, A2 to make it possible to measure the displacement quantity of an article 7 to be measured. Next, the element 9 is set to a beam transmitting state and the element 9a to a beam blocking state. Whereupon, the beam A is separated into beams A1, A2 to enter the apparatus 5 through the predetermined routes. In this case, the relative displacement quantity of articles 7, 7a to be measured can be measured from the number of interference fringes counted by the apparatus 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a length measuring device, and particularly to a laser length measuring device that measures the amount of displacement of an object to be measured using optical interference.

(Prior Art) Conventionally, as this type of device, a laser length measuring device having a configuration shown in FIG. 5 is known. Here, 1 is a laser that emits a coherent beam, 2 is an interferometer, and 3 is a half mirror 1.
4, 4& is a corner cube, 5 is a light receiving device, 6 is 174
Wave plate (hereinafter referred to as λ/4 plate), 7 is the object to be measured, 8 is a plane mirror, A 1 person.

A2 indicates a laser beam. The laser beam emitted from the laser 1 enters an interferometer 2, and is separated into two directions by a half mirror 3 installed approximately at the center of the interferometer 2 at an angle of about 45 degrees with respect to the laser beam A. Ru. The laser beam A1 reflected upward from the plane of the paper by the half mirror 3 is reflected by the corner cube 4 attached to the top surface of the interferometer 2, and is emitted in the opposite direction to the direction of incidence and is reflected again by the half mirror 3. The light is reflected by the beam and enters the light receiving device 5. On the other hand, the laser beam A8 transmitted through the nof mirror 3 and emitted in the right direction in the drawing is incident on the plane mirror 8 attached to the object to be measured 7 via the λ/4 plate 6.

The laser beam A reflected here passes through the λ/4 plate 6 again, enters the interferometer 2, is reflected by the No.-7 mirror 3, and then hits the corner cube 4a attached to the bottom surface of the interferometer 2. The light is reflected by the beam, exits in a direction opposite to the direction of incidence, and enters the interferometer 2. This laser beam A is reflected by a half mirror 3 in the interferometer 2 (to the right in the drawing), passes through a λ/4 plate 6, and enters a plane mirror 8 attached to an object to be measured 7 again. The laser beam A reflected here passes through the λ/4 plate 6 again, enters the interferometer 2, passes through the half mirror 3, and reaches the light receiving device 5. That is, interference occurs when the laser beams A□ and A2 that have passed through two different paths overlap. Here, the laser beam A is a beam that depends on the displacement of the object to be measured 7 in the horizontal direction on the plane of the drawing.

Due to the puller effect, a slight change in the wavelength of the laser beam A2 occurs. Therefore, the light beam A1 incident on the light receiving device 5
By counting the interference fringes caused by the interference of A and A, the amount of displacement of the object to be measured 7 can be measured.

(Problems to be Solved by the Invention) However, in the conventional length measuring device as described above, the interferometer 2, the half mirror 3, the corner cube 4°4apλ/4
It was only possible to measure a single object to be measured using an optical system consisting of optical elements such as the plate 6, and it was impossible to measure multiple objects to be measured with the same device.

The present invention was made for the purpose of solving the above conventional problems,
The present invention aims to provide a laser length measuring device that is capable of measuring displacement amounts of a plurality of objects to be measured using the same device.

(Means for Solving the Problems) As a means for solving the problems, a laser length measuring device according to the present invention includes a coherent light source and a laser beam emitted from the light source.
an optical system that irradiates the object to be measured with a beam of light from the center of the object and causes interference between the beam reflected by the object and the beam that is emitted from the light source and passes through a different optical path, and detects the interference beam obtained through the optical system. A plurality of optical paths corresponding to each of the plurality of objects to be measured, and an optical path converting means for selecting an arbitrary optical path among the plurality of optical paths.

(Example) Hereinafter, the present invention will be explained in detail using Examples.

Incidentally, the same members as those in the conventional example shown in FIG. 5 are given the same reference numerals, and their explanations will be omitted.

FIG. 1 is a schematic diagram of a laser length measuring device showing an embodiment of the present invention. Here, 3a is a half mirror, 14b is a corner cube, 7m is a second object to be measured, 9 and 9a are PLZT elements, and 1o is a reflecting mirror. On the coaxial line of the laser beam A emitted from the laser 1, there is a 45° angle with the polarizer 11.
Interferometer 2 with built-in half mirror 3 tilted to λ/
A measured object 7 to which four plates 6 and a plane mirror 8 are attached is arranged.

A half mirror 3a arranged at an angle of 45 DEG is attached to the upper surface of the interferometer 2, and a corner key 4a is attached to the lower surface of the interferometer 2 to reflect the laser beam in a direction opposite to the direction of incidence. The PLZT elements 9 and 9a are elements that have the function of transmitting or blocking light by turning on or off an applied voltage, and are arranged above and on the left side of the half mirror 3&.

Furthermore, the corner cube 4 is placed so as to face the PLZT element 9a.
is located. Further, the reflecting mirror 10 is arranged above the PLZT element 9 at an angle of 45° with respect to the optical path, and a second corner cube 4b is attached to the right side of the reflecting mirror 10.
Objects to be measured 7a are arranged.

This laser length measurement device is configured as described above.
When measuring the amount of displacement of the object to be measured 7, the PLZT element 9 is set to a light blocking state, and the PLZT element 9a is set to a light transmitting state. At this time, the laser beam emitted from the laser 1 enters the interferometer 2, and is separated into two directions by a half mirror 3 installed within the interferometer 2 at an angle of 45 degrees. The laser beam A□ reflected upward by the half mirror 3 is reflected by the half mirror 3a attached to the top surface of the interferometer 2.
The light is reflected by the beam, passes through the PLZT element 9, and enters the corner cube 4. Here, the laser beam A1 has an optical path of 18
Bent 0 degrees and P again! , passes through the ZT element 9&, is reflected by the half mirrors 3m and 3, and enters the light receiving device 5.

On the other hand, the laser beam A2 transmitted through the half mirror 3 is transmitted through the λ/4 plate 6, the plane mirror 8, the λ/4 plate 6, the corner cube 4a, the 1-7 mirror 3, the λ/4 plate 6, the plane mirror 8, the λ/4 plate 6, the corner cube 4a, the 1-7 mirror 3, and the λ/4 plate 6, as in the conventional example.
The light enters the light receiving device 5 through the path of the 4th plate 6, the plane mirror 8, the λ/4 plate 6, and the no-7 Missy 3. Therefore, 1 interferometer 2, No.-7 Mira-3m3m) Corner keep 4#4a, λ/
The amount of displacement of the object to be measured 7 can be measured by counting the interference fringes caused by the interference of the laser beams A1 and A generated by the optical system consisting of the four plates 6 and the PLZT cable 9a using the light receiving device 5. .

Next, the PLZT element 9 is set to a light transmitting state, and the PLZT element 9 is
Set the T element 9& to a light blocking state. At this time, the laser beam emitted from the laser 1 enters the interferometer 2, and is mounted in the interferometer 2 at an angle of 45° and separated into two directions by the nine-point 1-7 mirror 3. The laser beam A1 reflected upward by the half mirror 3 passes through the half mirror 3, passes through the PLZT cable 9, and is reflected by the reflecting mirror 10 arranged at an angle of 45 degrees with respect to the optical path of the laser beam A1. The light enters the corner tube 4b attached to the object 7a. The laser beam fsA whose 180' optical path is bent by this corner cube 4b and travels in the opposite direction along the optical path of the light is reflected again by the reflecting mirror 10, passes through the PLZT element 9), passes through the half mirror 3a, and then returns to the half mirror 3. The light is reflected by the beam and enters the light receiving device 5. On the other hand, the laser beam A transmitted through the half mirror 3 passes through the λ/4 plate, the plane mirror 8, and the λ
The light enters the light receiving device 5 through a path of /4 plate 6, half mirror 3, corner cube 4m, half mirror 3, λ/4 plate 6, plane mirror 8, λ/4 plate 6, and half mirror 3. Therefore, in this case, the amount of relative displacement between the objects to be measured 7 and 7a can be measured from the number of interference fringes counted by the receiver 5.

FIG. 2 shows another embodiment of the present invention, in which 10a is a reflecting mirror. In the embodiment shown in FIG. 1, the interferometer 2, half mirror 3, 3m,
It had a configuration in which the optical path of the laser beam mAt incident on an optical system consisting of corner cubes 4, 4 m and a λ/4 plate 6 was changed to measure the amount of relative displacement of the objects to be measured 7, 7a.

However, in this embodiment, as shown in FIG. 2, the optical path of the laser beam A1 can be switched by replacing the half mirror 3a with a reflecting mirror tOa and by making the reflecting mirror 10 movable. Note that the other configurations are the same as the embodiment shown in FIG. That is, when the reflecting mirror 10m is tilted at 45 degrees (indicated by a solid line), the displacement amount of the object 7 to be measured can be measured;
, 7 & can be measured.

FIG. 3 shows a further embodiment of the invention. In this embodiment, in a laser length measuring device configured almost the same as the conventional example shown in FIG. A half mirror 3b and a PLZT element 9a are arranged.

A PLZT element 9 and a reflecting mirror 10 inclined at 45 degrees with respect to the optical path are arranged above the half mirror 3b. Further, to the right of the reflecting mirror 10, a measurement object 7& to which a plane mirror 8a is attached is arranged. Therefore, when the PLZT element 9 is set to the light blocking state and the PLZT element 9a is set to the light transmitting state, the configuration is exactly the same as the conventional example shown in FIG. By counting , the amount of displacement of the object to be measured 7 can be measured.

Next, set the PK and ZT elements 9& to the light blocking state, and
When the LZT element 9 is set to a light transmitting state, part of the laser beam A emitted from the solid laser 1 is reflected by the half mirror 3 in the interferometer 2. Similar to the conventional example shown in FIG. 5, the light enters the light receiving device 5 via the corner cue f4 and the half mirror 3. On the other hand, the laser beam A that has passed through the half mirror 3 passes through λ/4 and is reflected by the half mirror 31. The light then passes through the PLZT element 9, is reflected by the reflecting mirror 10, and enters the plane mirror 8a attached to the object to be measured 7m. The laser beam A2 reflected in the opposite direction by the plane mirror 8& is reflected again by the reflecting mirror 10, passes through the PLZT element 9, is reflected by the half mirror 3&, passes through the λ/4 plate 6, and passes through the Zino-7 mirror. It is reflected at 3. The laser beam A reflected by the half mirror 3 bends its optical path by 180 degrees at the corner cube 4, is reflected again by the half mirror 3, passes through the λ/4 plate 6, and returns to the half mirror.
3a and passes through the PLZT element 9. Thereafter, the laser beam is reflected by the reflecting mirror 0, and is again incident on the plane mirror 8a attached to the object to be measured 7a.
The light passes through the PLZT element 9, is reflected by the No'-7 mirror 3a, and enters the light receiving device 5 via the λ/4 plate 6 and the half mirror 3 in the interferometer 2. Therefore, interferometer 2, half mirrors 3 and 3m, corner cues f4 and 4&, λ/4 plate 6
, the amount of displacement of the object to be measured 7 is measured by counting the interference fringes caused by the interference between the laser beam person □ and the laser beam person through an optical system consisting of a reflecting mirror 10 and a PLZT element 9°9a. can do.

In this embodiment, a half mirror 3a is placed between a measured object 70 to which a λ/4 plate 6 and a plane mirror 8 are attached.

It had a configuration in which the optical path of the laser beam A was switched using the PLZT element 9 m + 9 and the reflecting mirror 10 to measure the absolute displacement amount of the objects to be measured 7 and 7a. Here, as shown in Fig. 4, a plurality of (three in Fig. 4) measurement objects 7 =
7 a t 7 b... can be implemented by the same means. That is, between the λ/4 plate 6 and the plane mirror 8 attached to the object to be measured 7, the structure is similar to that of the embodiment shown in FIG.
PLZT elements 9a and 9 are arranged. Similarly, half mirrors 3b, 3c and PLZT element 9 are placed above them.
b e 9 e , 9 d , 9 e as the object to be measured 711
It is configured to face plane mirrors 8a and 3b attached to mirror 7b. And each PLZT element 9, 9a.

9b, 9e, 9d, and 9. are set to transmit light or block light as appropriate to switch the optical path of laser beam A, and the absolute displacement of each treasure 7, 7m, and 7b to be measured can be measured. .

In addition, in the embodiments shown in FIGS. 1 to 4 above, PLZ
T elements 9 to 9 or movable reflecting mirror 10a are laser beams A,
, A, but it is also possible to change the optical path of the laser beam by transmitting or blocking the laser beam A1eA* using a mechanical shutter or a shutter using a liquid crystal. be.

The configuration shown in the above embodiment is one form of the present invention.
There are various configurations of the optical system and optical path converting means for interfering the light beams, and it is possible to obtain various types of devices based on the idea of the present invention.

(Effects of the Invention) As explained above, the laser length measuring device according to the present invention can switch a plurality of optical paths corresponding to a plurality of objects to be measured using a PLZT element, a movable reflecting mirror, etc. It is possible to measure the absolute displacement amount of a plurality of objects to be measured or the relative displacement amount between each object to be measured with one device.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a laser length measuring device according to an embodiment of the present invention, and FIGS. 2 to 4 are schematic diagrams of a laser length measuring device according to another embodiment of the present invention. FIG. 5 is a configuration diagram of a conventional laser length measuring device. 1...Laser, 2-...Interferometer, 3.3m, 3b. 3c... Half mirror 14, 4a, 4b... Corner cube, 5... Light receiving device, 6... λ/4 plate, 7
p7' r7 b--Object to be measured, B, f3
m, 8 b--plane mirror, 9°9m, 9b*9et
9d, 9s=PLZT element, 10°10a=reflector, 11-...polarizer, A, A1+12...laser beam. Agent Patent Attorney Seki Taira Yamashita Figure 1 Part 3 q Figure 5

Claims (3)

[Claims] (1) A coherent light source and an optical system that irradiates a part of the light beam emitted from the light source onto an object to be measured, and causes interference between the light beam reflected by the object and the light beam that is emitted from the light source and passes through a different optical path. and a means for detecting an interference light beam obtained through the optical system, the apparatus having a plurality of optical paths corresponding to each of the plurality of objects to be measured, and selecting an arbitrary optical path among the plurality of optical paths. A laser length measuring device having an optical path changing means. (2) The laser length measuring device according to claim (1), wherein the optical path converting means has at least two light modulation elements. (3) The laser length measuring device according to claim (1), wherein the optical path changing means comprises at least one movable mirror.