JP2007285967A - Laser length measuring machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser length measuring machine capable of measuring a moving body with a fixed reflector even when adjusting positions in the moving direction and the right angle direction of the moving body. <P>SOLUTION: This laser length measuring machine comprises a beam splitter 2 which divides a laser beams L emitted from a laser light source 1 into a measurement light beam m advancing in the moving direction of the moving body 7 and a reference light beam r advancing in the right angle direction of the measurement light beam, a movable prism 4 which is fixed on the moving body and reflects the measurement light beam to the beam splitter, a fixed prism 10 which reflects the reference light beam r to the beam splitter, and a plane mirror 10 which is vertical to the moving direction of a movable reflector in the vicinity of the beam splitter so as to reflect the measurement light beam reflected by the movable prism in the laser length measuring machine, which measures displacement of the moving body by detecting interference of the measurement light beam and the reference light beam. The machine can further adjust position of the moving body in the right angle direction to the moving direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser length measuring machine used for a stage moving type precision length measuring machine, a precision machine tool, a semiconductor inspection apparatus and the like.

  FIG. 3 shows an optical system of a conventional laser length measuring machine. This laser length measuring machine includes a laser light source 1, a beam splitter 2, a fixed prism 3, a movable prism 4, and a light receiver 6. The movable prism 4 is fixed to a moving body 7 whose displacement is to be measured. The laser beam L emitted from the laser light source 1 is divided into two directions by the beam splitter 2. One laser beam divided in two directions is directed to the movable prism 4 as a measurement beam m, and is reflected by the movable prism 4 toward the beam splitter 2. The other laser beam divided into the two directions is directed to the fixed prism 3 as a reference beam r, and is reflected toward the beam splitter 2 by the fixed prism 3. The measurement light beam m and the reference light beam r that have returned to the beam splitter 2 are reflected or transmitted by the beam splitter 2 and are incident on the light receiver 6.

  Here, when the movable prism 4 moves together with the moving body 7, the interference fringes between the measurement light beam m and the reference light beam r change, and a pulse 5a is generated from the light receiver 6 due to the interference between the light beams m and r with time t. The displacement of the moving body 7 can be measured from the period T of the pulse 5a.

Japanese Utility Model Publication No. 1-107905

  By the way, in the conventional laser length measuring machine as described above, if the position of the movable body 7 is shifted in a direction perpendicular to the measurement axis or the movement direction X, the position of the movable prism 4 is moved accordingly. The measurement light beam m reflected by (1) cannot return to the starting point from the beam splitter 2. Then, there is a problem that the measurement light beam m and the reference light beam r do not return to the same position on the beam splitter 2, and the interference due to both the light beams m and r cannot be observed, making measurement impossible. For this reason, conventionally, it has not been considered at all to adjust the position of the moving body 7 in the direction perpendicular to the moving direction X.

  However, in recent laser length measuring machines, in order to achieve high accuracy, there has been an increasing demand for accurately positioning the measurement object on the measurement axis, but the above problem has been an obstacle.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide a laser length measuring machine that can measure even if the moving body having a reflector fixed thereto is positioned in the direction perpendicular to the moving direction of the moving body. To do.

  In order to achieve the above object, the present invention provides a beam splitter that divides a laser beam emitted from a laser light source into a measurement beam that travels in a moving direction of a moving body and a reference beam that travels in a direction perpendicular to the measurement beam. A movable reflector fixed to the moving body and reflecting the measurement light beam toward the beam splitter, a fixed reflector reflecting the reference light beam toward the beam splitter, and reflected by the movable reflector In a laser length measuring device that measures the displacement of the moving body by detecting interference between the measured measuring beam and the reference beam reflected by the fixed reflector, the measuring beam reflected by the movable reflector is reflected. A plane mirror perpendicular to the moving direction of the movable reflector is provided in the vicinity of the beam splitter, and the moving body is perpendicular to the moving direction. Characterized in that the location adjustable.

  According to the present invention, even if the position of the movable body with the movable reflector fixed is adjusted in the direction perpendicular to the moving direction, the measurement light beam reflected by the movable reflector is reflected by the plane mirror and returns to the original optical path to move the movable body. Since it is reflected again by the reflector and always returns to the starting point from the beam splitter together with the reference beam, the interference between the two beams can be observed. For this reason, the measurement object can be placed on the measurement axis, and high-precision measurement is possible. In addition, since the measurement light beam reciprocates between the beam splitter and the movable reflector and between the plane mirror and the movable reflector, the interference fringe changes with respect to the displacement of the same moving body as compared with the conventional laser length measuring machine. The measurement becomes more accurate by doubling.

  Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an embodiment of a laser length measuring machine according to the present invention.

  In this laser length measuring machine, the movable body 7 is mounted on a base 14 that moves along the measuring axis 12 of the length measuring machine main body so that the position of the moving body 7 can be adjusted in the horizontal direction and the vertical direction with respect to the moving direction X. On the other hand, it is attached by a left and right adjustment screw and a height adjustment screw (not shown). In the vicinity of the beam splitter 2, a plane mirror 10 perpendicular to the moving direction X of the moving body 7 is fixed so as to face a movable prism (corner cube) 4 that is a movable reflector.

  Further, the measurement light beam m and the reference light beam r emitted from the beam splitter 2 pass through the ¼λ plate 8 on the way to and from the back. This is because when light enters the beam splitter 2, the polarized light perpendicular to the incident surface is reflected and the polarized light parallel to the incident surface passes. The polarization plane is rotated by 90 ° so as to be reliably reflected or transmitted by the beam splitter 2 and input to the light receiver 6.

  Since the configuration of the present embodiment other than the above is the same as that of the conventional one, the same parts are designated by the same reference numerals and the description thereof is omitted.

  Now, according to the laser length measuring machine configured as described above, the measurement light beam m separated from the laser light beam L by the beam splitter 2 is reflected by the movable prism 4 and enters the plane mirror 10. The measurement light beam m is reflected by the plane mirror 10, returns along the same optical path, is reflected by the movable prism 4 again, and returns accurately to the starting point on the beam splitter 2. Moreover, even if the movable body 7 is adjusted in the horizontal direction and the vertical direction with respect to the movement direction, the measurement light beam m always returns accurately to the starting point from the beam splitter 2. Thus, since the measurement light beam m and the reference light beam r always return to the same position on the beam splitter 2, the interference between both the light beams m and n can be detected by the light receiver 6 and the displacement of the moving body 7 is measured. Can not be measured.

  Further, as shown in FIG. 2A, in the conventional laser length measuring machine, the measurement light beam m only reciprocates between the movable prism 4 and the beam splitter 2, so that the displacement of the moving body 7 is changed. The change in optical path length due to δ is 2δ. On the other hand, as shown in FIG. 2B, in the laser length measuring machine of this embodiment, the measurement light beam m is between the movable prism 4 and the beam splitter 2 and between the movable prism 4 and the plane mirror 10. Since the light travels back and forth, the change in the optical path length due to the displacement δ of the movable prism 4 is 4δ. As a result, the laser length measuring machine according to the present embodiment can detect even a half of the displacement δ of the conventional one, and can measure with high accuracy.

It is a figure which shows one Example of the optical system of the laser length measuring machine which concerns on this invention. It is a figure explaining the reason which can perform a highly accurate measurement with the laser length measuring machine which concerns on this invention. It is a figure which shows one Example of the optical system of the conventional laser length measuring machine.

Explanation of symbols

1 Laser light source 2 Beam splitter 3 Fixed prism (fixed reflector)
4 Movable prism (movable reflector)
7 Moving object 10 Plane mirror m Measurement beam r Reference beam

Claims (1)

A beam splitter that divides the laser beam emitted from the laser light source into a measuring beam that travels in the moving direction of the moving body, and a reference beam that travels the laser beam in a direction perpendicular to the measuring beam, and is fixed to the moving body and A movable reflector that reflects a measurement beam toward the beam splitter, a fixed reflector that reflects the reference beam toward the beam splitter, a measurement beam reflected by the movable reflector, and a reflection by the fixed reflector In the laser length measuring machine that detects the interference with the reference beam and measures the displacement of the moving body,
A plane mirror perpendicular to the moving direction of the movable reflector is provided in the vicinity of the beam splitter so as to reflect the measurement light beam reflected by the movable reflector,
A laser length measuring machine characterized in that the position of the moving body can be adjusted in a direction perpendicular to the moving direction.

Images