JPH04105004A - Thermal displacement correcting device for glass scale - Google Patents

Abstract

PURPOSE:To correct the amount of movement by forming interferential striations using No.1 reflex laser beam directly reflected by a half mirror and No.2 reflex laser beam which is reflected by a reflex mirror upon passing through the half mirror and which is emitted from the half mirror. CONSTITUTION:Part of a laser beam 8 from a laser source 2 is reflected by a half mirror 5 of a glass scale 1 and becomes a reflex laser beam A to be case onto an interferometer 3. Another part of the laser beam 8 penetrates the half mirror 5 to become a laser beam 8a, which becomes laser beams 8b-8d upon passing through a reflex mirror 6, which become a reflex laser beam B upon passing through the half mirror 5 to be cast onto the interferometer 3. The interferential striations of these laser beams A, B in the condition a scale 1 remains out of thermal displacement are sensed by the interferometer 3 in advance. When the scale 1 makes thermal displacement, the laser beam A remains out of change, but penetrates the scale 1, while laser beams 8b'-8d' reflected by the reflex mirror 6 become a reflex laser beam C, and these laser beams A, C form interferential striations differing from in the condition without thermal displacement. Therefore, the amount of thermal displacement of the scale 1 can be determined by comparing the value of interferential striations.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal displacement correction device for a glass scale, which is suitable for detecting thermal displacement of a glass scale as a reference standard and correcting reading errors.

[Prior Art] In machine tools and the like, a measuring means as shown in FIG. 3 is generally employed as a means for measuring the amount of movement of a moving body. That is, a large number of graduations 4 are engraved with high precision on a glass scale la fixed to a fixed side 7 of a machine tool or the like. On the other hand, on the moving body 9 side, a reading device 12 equipped with a lead bed 10, an electric signal converter 11, etc. is arranged. The read head 10 of the reading device 12 reads the moving scale 4, and the amount of movement is detected based on the number of scale marks. Note that the amount of movement is converted into an electrical signal by an electrical signal converter 11 that engages the read head 10, and sent to the display device side of the scale.

[Problems to be Solved by the Invention] In FIG. 4, it is assumed that the glass scale 1a is in a state without thermal displacement. Assume that the reading device 12 initially confirms the 1 scale at position a, moves to position b, and confirms the 4 scale. In this case, if the l scale is set to t, the amount of movement will be 31. Since there is no thermal displacement in the glass scale 1a, the amount of movement can be detected accurately. FIG. 5 shows the glass scale la' when the glass scale 1a of FIG. 4 is thermally displaced. It is assumed that the intervals between each scale in FIG. 4 have been expanded, and the 1 scale, 2 scale, etc. are 1' scales.

It spreads out like a 2' scale. For convenience of explanation, it is assumed that the displacement of the customer scale is expanded by 1.5 times. Therefore, when the movable body 9 moves from position a to position b, the reading device 12 reads the scale 1' and the scale 3', and the amount of movement is detected as 2. Therefore, actually 3
■Regardless of whether you have moved, it will be detected if you do not move for 2m11 seconds. In other words, a measurement error will occur accordingly.

Since it is impossible to prevent the glass scale 1a from being thermally displaced, it is possible to accurately detect whether or not the glass scale 18 has been thermally displaced beyond a predetermined tolerance range prior to measurement, and to determine how much heat has been generated. If it is possible to detect whether a displacement has occurred, it becomes possible to correct the measured value accordingly.

The present invention was created based on the above requirements,
It is an object of the present invention to provide a thermal displacement correction device for a glass scale that can accurately detect the expansion/contraction degree and strain state of a glass scale as numerical data and correct the measured value (movement amount) based on the numerical data. .

[Means for Solving the Problems] In order to achieve the above objects, the present invention provides an elongated glass scale having graduations engraved on its surface and corner faces at the four corners, and the corner faces of the glass scale. a laser light source that inputs a laser beam into one of the laser beams;

and an interferometer that forms interference fringes by reflected light from the glass scale. The interferometer is formed from a reflecting mirror that reflects light, and the interferometer includes a first reflected laser beam that is directly reflected from the semi-transparent mirror, and a laser beam that has entered the inside of the glass scale through the semi-transparent mirror. The present invention employs a glass scale thermal displacement correction device that is configured to form the interference fringes by sequentially reflecting and re-emitting the second reflected laser beam from the semi-transparent mirror.

[Operation] The laser light from the laser light source is reflected by the semi-transparent mirror of the glass scale, and the first reflected laser light enters the interferometer side.

On the other hand, the laser beam enters the glass scale, is sequentially reflected by three reflecting mirrors, is emitted from the original semi-transparent mirror as a second reflected laser beam, and enters the interferometer.

Since the first and second reflected laser beams have different path lengths until they enter the interferometer, they form interference fringes. The shape of the interference fringes when there is no thermal displacement on the glass scale is different from the shape of the interference fringes when thermal displacement occurs and the value of the difference in path length changes. Therefore, the thermal displacement of the glass scale can be quantitatively determined from the change in the interference fringes.

[Example] Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a plan view showing the overall structure of this embodiment, and FIG.
The figure is an explanatory plan view for explaining the operation of this embodiment.

The apparatus according to this embodiment includes a glass scale 1, a laser light source 2, and an interferometer 3.

The glass scale 1 is fixed to the fixed side 7 and is made of a glass material that undergoes almost the same thermal displacement as the material of the fixed side 7. It is possible to form the glass material from a material that undergoes the same thermal displacement as the material of the fixed side 7 by using existing known techniques by modifying the components of the glass. The glass scale 1a is made of a transparent elongated plate material, has square faces at its four corners, and scales 4 are engraved with high precision on its surface. One of the corner surfaces is formed as a semi-transparent mirror 5, and the remaining three corner surfaces are formed from reflecting mirrors 6, 6, 6. The 6 semi-transparent mirrors 5 transmit a part of the incident light while transmitting the other part of the incident light. It is an optical element formed so as to partially reflect the light.On the other hand, the reflecting mirror 6 is formed so as to reflect the progress of the incident light using light reflection development. It is formed to be internally reflective. Both semi-transparent mirrors and reflective mirrors can be manufactured by depositing a metal such as aluminum on the surface of glass, or by forming a dielectric multilayer film in which dielectric thin films with different refractive indexes are alternately stacked.

In addition, the reflecting mirror 6 directly below the diagram of semi-transparent tIA5 is semi-transparent f
jA5 is formed so as to reflect the light transmitted from the A5 toward the surface, and the reflecting mirror 6 located right next to the reflecting mirror 6 in the drawing is formed so as to reflect the incident light directly upward, and the reflected light 6
The nine reflecting mirrors 6 at the top of the figure are each formed so as to reflect the incident light toward the semi-transparent mirror 5 side.

The laser light source 2 emits a laser beam 8.
is incident on the semi-transparent mirror 5, and a part of it is directly reflected to the interferometer 3.
A portion of the light enters the glass scale 1 as it is, and is arranged so as to be incident on the reflecting mirror 6 located directly below the semi-transparent mirror 5 in the drawing.

A known interferometer 3 is used, and two interferometers with different paths are used.
The laser beam is configured to form interference fringes commensurate with the path difference between the two laser beams.

Next, the operation of this embodiment will be explained in more detail with reference to FIG.

The laser beam 8 from the laser light source 2 hits the semi-transparent @5 of the glass scale 1, and a part of it is directly reflected to become the first reflected laser beam A and enter the interferometer 3. On the other hand, laser beam 8
A part of the light passes through the glass scale 1 and becomes a laser beam 8a, which enters a reflecting mirror 6, is reflected at a right angle, becomes a laser beam 8b, and hits the next reflected beam 6, which is reflected upward in the figure at a right angle, resulting in a laser beam. The light becomes light 8c and enters the next reflection @6. Here, it is further reflected at right angles to become a laser beam 8d, travels again to the semi-transparent mirror 5 side, exits from the semi-transparent mirror 5, becomes a second reflected laser beam B, and enters the interferometer 3.

Interference fringes caused by the first reflected laser beam A and the second reflected laser beam B in a state where the glass scale 1 is not thermally displaced are detected and measured in advance by the interferometer 3. Next, the first
Interference fringes caused by the second reflected laser beams A and B are determined and measured in advance. In Figure 2, glass scale 1
Suppose that it undergoes thermal displacement and expands to the state shown by the two-dot chain line. In this case, the first reflected laser beam A does not change. but,
The laser beam transmitted through the glass scale 1 and reflected by the reflection@6 becomes a laser beam 8b' different from the laser beam 8b and enters the reflecting mirror 6, and the laser beam 80' reflected by the reflecting mirror 6 (
(almost the same as the laser beam 8c) is transmitted to the next reflecting mirror 6 by the laser beam 8d.
' (different from the laser beam 8d) and is reflected toward the semi-transparent mirror 5 side. In other words, the laser beam that enters the glass scale 1 due to the thermal displacement of the glass scale 1 returns to the original semi-transparent #I5 side after passing through a longer path than in the case without thermal displacement and becomes the second reflected laser beam C. The light enters the interferometer 3.

Therefore, the first reflected laser beam A and the second reflected laser beam C
This results in the formation of interference fringes with a shape different from the interference fringes in a state without thermal displacement.

Glass scale 1 by comparing the measured values of interference fringes.
The amount of thermal displacement can be determined quantitatively as numerical data. The correct amount of movement can be determined by correcting the amount of movement each time using this numerical data.

[Effect of the invention] According to the present invention, the following effects can be achieved.

1) When thermal displacement occurs in the glass scale.

Since the shapes of the interference fringes caused by the two laser beams entering the interferometer are different, the amount of thermal displacement of the glass scale can be grasped as numerical data from changes in the interference fringes, and the amount of movement can be corrected accordingly. I can do it.

2) Since the interference fringes can change sensitively even to subtle changes in the glass scale, minute thermal displacements can be detected and no reading errors occur.

3) It is a relatively simple method in which two reflected laser beams are formed by a semi-transparent mirror and a reflecting mirror formed on the glass scale itself, and thermal displacement is detected by changes in the interference fringes.It is easy and inexpensive to implement. I can do it.

8d'...Laser beam, A...First reflected laser beam, B, C...Second reflected laser beam, 9...Moving object, 10...Read head, 11...Electricity Signal converter, 12...reading device.

[Brief explanation of the drawing]

Fig. 1 is a structural plan view showing the overall structure of an embodiment of the present invention, Fig. 2 is an explanatory plan view for explaining the operation of the embodiment, and Fig. 3 is a conventional measurement of the amount of movement. A schematic configuration diagram showing the means, and FIGS. 4 and 5 are partial plan views for explaining a measuring method using a conventional measuring means. 1, la, la...Glass scale, 2...Laser light source, 3...Interferometer, 4...Scale, 5...Semi-transparent mirror, 6...Reflector, 7...Fixed side, 8, 8a, 8
b, 8b', 8c, 8c' 8cl.

Claims (1)

[Claims] an elongated glass scale having graduations engraved on its surface and corner faces at its four corners; and one of the corner faces of the glass scale.
The glass scale is composed of a laser light source that injects a laser beam into the glass scale, and an interferometer that forms interference fringes by reflected light from the glass scale. forming a corner surface from a reflecting mirror that reflects the laser beam only inside the glass scale;
The interferometer includes a first reflected laser beam that is directly reflected from the semi-transparent mirror, and a laser beam that has entered the inside of the glass scale through the semi-transparent mirror, which are sequentially reflected by the reflecting mirror and then emitted from the semi-transparent mirror again. A thermal displacement correction device for a glass scale, characterized in that the device is configured to form the interference fringes with a second reflected laser beam.