JPH058412U - Laser interferometer - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide a laser interferometer that can prevent the fluctuation of the length measurement value due to environmental changes and improve the stability of the length measurement value. According to the present invention, a laser beam from a light source 25 is split into a reference laser beam and a length measuring laser beam by a beam splitter 26, the reference laser beam is incident on a fixed reflecting surface 23, and the length measuring laser beam is staged. Moving reflection surface 22 provided on 21
To the fixed reflection surface 23 in a laser interferometer that measures the moving distance of the stage 21 by causing the reference laser light and the measurement laser light reflected by the fixed reflection surface 23 and the movable movable reflection surface 22 to interfere with each other. A reflecting member 27 that reflects the reference laser light to be incident to the movable reflecting surface 22 side is provided, and the fixed reflecting surface 23 is slightly deviated from the optical path of the length measuring laser light and the stage 21 is attached to the beam splitter 26. It is arranged in the vicinity of a distance of ½ of the movable range of the stage from the position of the moving reflection surface when it is closest.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a laser interferometer, which measures a moving distance of a moving body such as a stage using laser interference.

[0002]

[Prior Art]

 The configuration of such a laser interferometer will be described with reference to FIG.

FIG. 1 shows a configuration example of a length measuring machine for detecting the movement amount of the XY stage. In the XY stage, an X stage 2 is provided on a base 1 so as to be movable in the X direction, and a Y stage 3 is provided on the X stage 2 so as to be movable in the Y direction.

An X mirror 4 and a Y mirror 5 are provided on outer surfaces of the Y stage 3 in the X direction and the Y direction, respectively, and interferometers 6, 7 are provided to the X mirror 4 and the Y mirror 5 from outside the stage. Are arranged to face each other. The laser light supplied from the laser light source 8 installed outside the stage is branched by the half mirror 9 and enters the interferometers 6 and 7, respectively.

The interferometers 6 and 7 split the incident laser light into a length measuring laser light and a reference laser light by a beam splitter or the like. The length measuring laser light is made incident on the X mirror 4 and the Y mirror 5 which face each other, and the reference laser light is made incident on the reference mirror fixed inside the interferometers 6, 7. The returned measurement laser light and the reference laser light reflected by the X mirror 4, the Y mirror 5, and the reference mirror become the interference laser light combined again by the beam splitter. The interference laser light is incident on detectors 11 and 12 provided for each interferometer 6 and 7. Here, the interference laser light is detected by the detectors 11 and 12 to measure the movement amounts in the X and Y directions.

[0006]

[Problems to be solved by the device]

 However, the above-described laser interferometer has a problem that accurate length measurement cannot be performed if there is a change in the environment between the interferometers 6 and 7 and the X mirror 4 and the Y mirror 5. That is, when air temperature changes between the interferometers 6 and 7 and the X mirror 4 and the Y mirror 5 due to temperature change, humidity change, and atmospheric pressure change, the refractive index of the air changes and the measurement laser This is because the wavelength of light changes, which causes fluctuations in the measured values.

The present invention has been made in view of the above circumstances, and provides a laser interferometer that can greatly reduce the fluctuation of the length measurement value due to environmental changes and improve the stability of the length measurement value. The purpose is to

[0008]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention splits a laser beam from a light source into a reference laser beam and a measuring laser beam, makes the reference laser beam incident on a fixed reflecting surface, and measures the measuring laser beam. A laser for measuring the moving distance of the stage by causing the reference laser light and the length measuring laser light that are incident on the movable reflection surface provided on the stage to be reflected and reflected by the fixed reflection surface and the movable movable reflection surface, respectively. In the interferometer, a reflecting member is provided for reflecting the reference laser light to be incident on the fixed reflecting surface toward the moving reflecting surface side, and the fixed reflecting surface is slightly deviated from the optical path of the length measuring laser light. Therefore, it is arranged in the vicinity of a distance of 1/2 of the movable range of the movable reflecting surface.

[0009]

[Action]

 According to the present invention configured as described above, when the stage is located at the center of the movable range, the environment of the length measurement laser beam and the environment of the reference laser beam are the same. Therefore, even if the wavelength of the length measurement laser beam changes due to environmental changes, the reference laser beam also undergoes the same wavelength change, and fluctuations in the length measurement value due to the wavelength change are removed. However, since the stage is mainly used around the center of the movable range, the environmental difference due to the movement of the moving reflecting surface can be minimized.

[0010]

【Example】

 An embodiment of the present invention will be described below. FIG. 1 shows a schematic configuration of a laser interferometer length measuring machine according to an embodiment of the present invention. The figure shows a stage that is movable in one axis direction.

As for the stage, a movable stage 21 having a U-shaped cross section is placed on a base 20 which is a fixed side. A movable mirror 22 serving as a movable reflection surface is attached to a side surface of the movable stage 21 which is orthogonal to the moving direction. A fixed mirror 23, which serves as a fixed reflection surface, is provided on the base 20. Further, a notch 24 is provided in the lower portion of the side surface of the movable stage 21 to which the moving mirror 22 is attached. The notch 24 prevents the side surface of the movable stage 21 from hitting the fixed mirror 23 when the movable stage 21 moves.

On the other hand, the laser light emitted from the light source including the light source unit and the detection unit and the light source unit of the detection unit 25 is split into the length measurement laser light and the reference laser light by the beam splitter 26, and the length measurement laser light is The reference laser light is made incident on the movable mirror 22, and the reference laser light is made incident on the fixed mirror 23 by a reflection mirror 27 serving as a reflection member. Here, the installation position of the fixed mirror 23 will be described with reference to FIG.

Given that the movable mirror 22 can move from A to B with the movement of the movable stage 21, and the distance is L, the fixed mirror 23 is in the vicinity of the optical path of the length measurement laser beam and is a distance L from A. It is arranged near the position C at a distance of / 2. Note that it is not always necessary to exactly match the position of L / 2. At this position C, when the movable mirror 22 reaches the position C, the environments of the length measurement laser beam and the reference laser beam become substantially equal. Next, the operation of this embodiment configured as described above will be described.

The laser light emitted from the laser light source of the light source / detection unit 25 is split into a length measurement laser light and a reference laser light by the beam splitter 26. The length-measuring laser beam is incident on the moving mirror 22, is reflected there, and is incident on the beam splitter 26 again. On the other hand, the reference laser light is made incident on the fixed mirror 23 arranged at the position C shown in FIG. 2 with its optical path made parallel by the reflection mirror 27, reflected there, and again enters the beam splitter 26. To do.

Here, when the movable mirror 22 is at the position C, the environments of the length measurement laser beam and the reference laser beam are almost equal. In this embodiment, the distance from the moving mirror 22 away from the position C is the environmental difference from the reference laser light. However, the difference in the environment is greatly reduced. Further, since the stage mainly uses the central part of the movable range, by arranging the fixed mirror 23 at the position shown in FIG. 2, the moving mirror 22 is extremely close to the position C, and therefore the reference laser beam is used. It is highly likely that the environment difference with

As described above, the measurement laser light and the reference laser light that have been similarly affected by the environment are combined again by the beam splitter 26 and become interference laser light, which is incident on the light source and the detection portion of the detection portion 25. . In the detection unit, the length measurement is performed by detecting the change in the interference fringes of the interference laser light that changes according to the movement of the moving mirror 22.

As described above, according to this embodiment, the movable mirror 22 for reflecting the length-measuring laser light is attached to one side surface of the movable stage 21, and the most beam of the moving mirror 22 is near the optical path of the length-measuring laser light. Since the fixed mirror 23 on which the reference laser light is incident is arranged in the vicinity of a distance of 1/2 of the stage moving range from the position of the splitter 26, the length measurement laser light and the reference laser light are subject to the same environmental change, and the same Since the wavelength changes, fluctuations in measured values due to environmental changes can be prevented and the stability of measured values can be improved. In addition, since the central part of the moving range of the stage is mainly used, it is extremely effective to dispose the fixed mirror 23 in the vicinity of a half of the moving range of the stage in order to reduce the environmental difference. . Although the above-mentioned one embodiment is directed to the one-axis stage, the principle of the present invention can be easily applied to a two-axis or more stage as shown in FIG.

[0018]

[Effect of the device]

 As described in detail above, according to the present invention, it is possible to provide a laser interferometer that can prevent fluctuations in length measurement values due to environmental changes and improve the stability of length measurement values.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a laser interferometer according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining an arrangement state of fixed mirrors in a laser interferometer according to an embodiment.

FIG. 3 is a diagram showing a configuration of a conventional laser interferometer.

[Explanation of symbols]

21 ... Movable stage, 22 ... Moving mirror, 23 ... Fixed mirror, 25 ... Light source and detector, 26 ... Beam splitter, 27 ... Reflecting mirror.

Claims (1)

[Claims for utility model registration] [Claim 1] A laser beam from a light source is split into a reference laser beam and a length measuring laser beam, the reference laser beam is incident on a fixed reflecting surface, and the length measuring laser beam is measured. The moving distance of the stage is measured by causing the reference laser light and the length-measuring laser light that are incident on the movable reflecting surface provided on the target stage and reflected by the fixed reflecting surface and the movable movable reflecting surface to interfere with each other. In the laser interferometer, a reflecting member for reflecting the reference laser light to be incident on the fixed reflection surface toward the moving reflection surface side is provided, and the fixed reflection surface is slightly deviated from the optical path of the length measurement laser light. 1/2 of the movable range of the movable reflecting surface
A laser interferometer, which is arranged near the distance.