JP3225659B2 - Laser interferometer alignment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser interferometer used for inspecting the surface condition of a precision optical product such as a parallel plane glass or the like, and a laser for performing alignment between an object and a reference plate. The present invention relates to an alignment device for an interferometer.

[0002]

2. Description of the Related Art A laser interferometer is used to inspect the surface condition of a precision optical product. The laser interferometer has a structure shown in FIG. In the figure, reference numeral 1 denotes a laser light source, and a laser light emitted from the laser light source 1 is diverged by a diverging lens 2,
By passing through the collimator lens 3, the light is converted into parallel light. The laser beam that has passed through the collimator lens 3 is
And a part of the light is reflected by the reference surface 4a. Also,
The light that has passed through the reference plate 4 irradiates the subject 5 and is partially reflected by the test surface 5a. A half mirror 6 is provided between the collimator lens 3 and the diverging lens 2, and the reflected light from the reference surface 4 a of the reference plate 4 and the reflected light from the test surface 5 a of the subject 5 are reflected by the half mirror 6. Then, the light is guided to the interference fringe imaging means 8 via the imaging lens 7, and the interference fringe imaging means 8 forms an interference fringe due to both reflected lights.

[0003] Here, the subject 5 is mounted on a support table 9, and the test surface 5 a of the subject 5 and the reference surface 4
If a is not in a predetermined positional relationship, the interference fringe imaging means 8 cannot form an interference fringe. Therefore,
An alignment mechanism is provided to perform alignment between the subject 5 and the reference plate 4. The alignment mechanism includes a second half mirror 10, a condenser lens 11, and an alignment screen 12. The second half mirror 10 is arranged at a position between the diverging lens 2 and the half mirror 6, and the light from the laser light source 1 passes through the second half mirror 10, but the return light is Is reflected by the half mirror 10. Further, the alignment screen 12 is provided with the condenser lens 1.
1 and a second half mirror 1
The reflected light from 0 is focused on a predetermined position on the alignment screen 12.

When the laser light is emitted from the laser light source 1 with the half mirror 6 displaced out of the optical path, the laser light is partially reflected by the reference surface 4a of the reference plate 4, and the object A part of the test surface 5a is also reflected. Then, these reflected lights are reflected by the second half mirror 10, condensed by the condenser lens 11, and a condensed spot is projected on the alignment screen 12. here,
The optical path between the reference plate 4 and the subject 5 is the collimator lens 3
The two reflected lights are condensed on the surface including the alignment screen 12. The reference plate 4 is assembled integrally with the alignment screen 12, so that the reflected light from the reference plate 4 is focused on a predetermined position on the alignment screen 12. Accordingly, when the support table 9 is tilted in an appropriate direction and angle, the position of the condensing point of the reflected light from the test surface 5a of the subject 5 moves, and the position where this spot overlaps with the condensing point from the reference plate 4 Then, the alignment between the subject 5 and the reference plate 4 has been performed.

[0005]

By the way, in the above-mentioned alignment operation, if the converging point from the subject 5 is projected on the alignment screen 12, this converging point is The operation of adjusting the focal point to coincide with the focal point can be easily performed. However, when the focal point from the subject 5 is out of the range of the alignment screen 12, the support table 9 can be moved in any direction and how much. I don't know what to do. Therefore, in the groping state, the support 9
Must be moved in various directions, and this operation is extremely troublesome, and has a problem that a long time is required.

The present invention has been made in view of the above points, and an object of the present invention is to facilitate alignment between a subject and a reference plate.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a method of tilting a movable table on which a subject is mounted in a non-rotating manner to a supporting member via a universal joint in an arbitrary direction. It is characterized in that it is configured to be connected to the movable table and to be provided with a tilt drive unit that moves up and down and in a circular motion.

[0008]

In order to perform alignment between the subject and the reference plate, it is necessary to tilt the center axis of the subject in any direction at an arbitrary angle. When the center axis is inclined, the center axis must be kept from rotating. In order to satisfy these demands and to enable this alignment operation to be performed automatically by a simple mechanism, the subject is placed on a movable base, and the movable base is adjusted by a universal joint so that the center axis is adjusted. It can be tilted in any direction and at any angle without rotating. In addition, the tilting drive means is engaged with the movable table. When the tilt drive means is moved up and down,
The movable table tilts by an angle corresponding to the height position. Further, when the tilt drive means is moved circularly, the tilt direction of the movable table changes.

Therefore, the subject is placed on the movable table, and the height position of the tilt driving means is adjusted so that the movable table is in a horizontal state. In this state, the tilt driving means is rotated and displaced in the vertical direction. As a result, the center axis of the subject placed on the movable base is tilted and displaced from the vertical direction so as to follow a spiral trajectory. In the middle of this operation, the focal point of the reflected light from the subject is projected on the alignment screen. When this focal point is projected on the alignment screen, the tilt driving means is stopped at that position, and the position of the movable table is finely adjusted, so that the focal point of the reflected light of the subject on the alignment screen is reflected from the reference plate. By displacing the light so as to coincide with the position of the condensing point of the reflected light, a state is achieved in which the central axis of the subject coincides with the central axis of the reference plate.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Since the optical system itself of the laser interferometer is the same as that of the above-described conventional technology, the members constituting the optical system are denoted by the same reference numerals as those shown in FIG. 2 to 4, only a mechanism for displacing the subject 5 when the subject 5 is aligned with the reference plate 4 is shown in FIGS.

As shown in FIG. 2, a movable table 20 is used as a member on which the subject 5 is placed. The movable table 20 can be tilted in any direction and at any angle. For this purpose, as shown in FIGS. 3 and 4, the movable base 20 is configured to be supported on a support post 22 via a universal joint 21. The universal joint 21 includes a ring body 23 and two sets of rotating shafts 24 and 25 orthogonal to each other. Each of the rotating shafts 24 and 25 is provided as a pair, and the first rotating shaft 24 is attached so as to protrude inward from the inner surface side of the ring body 23, and has a spherical end portion. It is rotatable about its axis by engaging with a receiving portion 22a formed on the support post 22 and having a concave spherical shape. Thereby, the ring body 23 can be tilted about the first rotation shaft 24. On the other hand, the second rotation shaft 25 is fixedly provided on a bracket 26 provided on the lower surface of the movable base 20, and extends inward at a position orthogonal to the first rotation shaft 24. ing. The tip of the rotating shaft 25 also has a spherical shape, and is engaged with a concave spherical receiving portion 23a provided on the outer surface of the ring body 23 so as to be rotatable around the axis. The table 20 can be tilted about the second rotating shaft 25 with respect to the ring body 23. Therefore,
The movable table 20 moves in any direction with respect to the support post 22,
It can be tilted at any angle.

A spring support 27 is located below the movable base 20.
Are provided, and the spring receiving base 27 and the ring body 23 are provided.
, A pair of tension springs 28 are stretched at positions shifted by 90 ° from the mounting portion of the first rotating shaft 24, and also between the movable table 20 and the spring receiving table 27. A pair of tension springs 29 are stretched at positions shifted from the second rotation shaft 25 by 90 °. Therefore, when no load is applied to the movable base 20, the two sets of tension springs 28, 2
The movable table 20 is held in a horizontal state by the operation of 9, and can be freely tilted by applying a force to a part of the outer peripheral side in either the upper or lower direction.

In order to tilt the movable table 20, a rotary table 30 is provided at a position below the spring receiving table 27.
2 is inserted. An arm 31 is erected on the rotary table 30, and a roller 32 is mounted on a tip of the arm 31 so as to be in contact with the lower surface of the movable table 20 at a position on the outer peripheral side. Rotary table 30
A ring gear 33 is continuously provided at a lower portion of the rotary table 30.
The drive gear 36 is meshed with a drive gear 36 connected to a motor 35 mounted on an elevating plate 34 that can be moved up and down along the support post 22. When the motor 35 is operated, the rotary table 30 rotates and the rollers 32 move. 20 will roll along the lower surface.

The elevating plate 34 is driven to move up and down by a linear actuator 37, and the rotary table 30 is also moved up and down at the same time to change the height position of the roller 32. For this,
The elevating plate 34 has a connecting ring 3 on its inner peripheral side.
8, the connecting ring portion 38 is inserted through the support post 22, and the turntable 30 is rotatably connected to the connecting ring portion 38 via a bearing 39. When the plate 34 is moved up and down, the rotary table 30 is also moved up and down in conjunction with it. However, the elevating plate 34 is held in a non-rotating state even when the rotary table 30 rotates, and the guide rod 40 is supported to regulate the rotation of the elevating plate 34 and to guide it vertically. The guide rods 40 are erected from a base plate 41 to which the posts 22 are attached.

The present embodiment is configured as described above. The subject 5 is set on the movable base 20 and is opposed to the reference plate 4 mounted on the laser interferometer at a predetermined interval. In this state, the laser light is emitted from the laser light source 1 and a part of the laser light is reflected on the reference surface 4a of the reference plate 4,
In addition, a part of the light passing through the reference plate 4
a, and the interference fringes generated between the two reflected lights are imaged on the interference fringe imaging means 8, so that the inspection of the finish accuracy of the surface 5a of the test surface 5a of the subject 5 can be performed. .

In order to inspect the subject 5 placed on the movable base 20 accurately, the center axis of the subject 5 must exactly coincide with the center axis of the reference plate 4. For this purpose, it is necessary to perform alignment, that is, alignment between the two central axes. In performing this alignment,
First, laser light is emitted from the laser light source 1 with the half mirror 6 displaced outside the optical path. As a result, a part of the light is reflected on the reference surface 4a of the reference plate 4, and a part of the light passing through the reference plate 4 is reflected. This reflected light is reflected by the second half mirror 10 and is projected on the alignment screen 12 via the condenser lens 11. Here, the reference plate 4
Is reflected at a predetermined position on the alignment screen 12. However, since the subject 5 is installed on the movable base 20 and the movable base 20 is provided separately from the laser interferometer, the optical path of the reflected light from the subject 5 is not necessarily from the reference plate 4. The optical path of the reflected light does not always match. Therefore, the position of the movable table 20 is adjusted so that the spots of the two reflected lights coincide with each other. This position adjustment can be performed without particular difficulty if the two reflected spots are projected on the alignment screen 12. However, when no reflected spot is projected from the subject 5 on the alignment screen 12, it is not clear in which direction and how much the position is shifted.

Then, by operating the motor 35 and rotating the rotary table 30, the roller 32 rolls along the lower surface of the movable base 20, and the linear actuator 37 is operated to rotate with the lifting plate 34. The table 30 is raised. Thereby, the universal joint 2
The movable base 20 connected to 1 will tilt,
Moreover, this tilting direction is 360 ° together with the rolling of the roller 32.
Change. As a result, as shown in FIGS. 5 to 8, the center axis A of the subject 5 placed on the movable base 20 is tilted and displaced so as to draw a spiral trajectory from a vertical state. The radius increases as the turntable 30 rises. However, the central axis A is held in a non-rotational state around the axis. When the movable base 20 is tilted to some extent, a spot is projected on the alignment screen 12 in due course. Motor 3 at that position
5 and the linear actuator 37 are stopped. As described above, when both condensed spots appear on the alignment screen 12, it becomes possible to determine in which direction and how much the spot should be moved to determine whether the two spots coincide with each other. By providing a fine adjustment mechanism or the like, the center axis of the subject 5 is
Can be adjusted to coincide with the central axis of.

[0018]

As described above, according to the present invention, a movable table on which a subject is installed is connected to a supporting member via a universal joint so as to be tiltable in any direction in a non-rotating state. Since the tilt drive unit that moves up and down and moves in a circular motion is provided in engagement with the tilt drive unit, even if the center axis of the subject and the reference plate is largely displaced,
The center axis of the subject can be moved along a trajectory that is swirled while holding the center axis of the subject in a non-rotational state around the axis, so that the center axis of the subject is very easily and quickly moved to the center of the reference plate. Alignment can be performed so as to coincide with the axis.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing an optical system of an inspection apparatus for a subject using a laser interferometer.

FIG. 2 is an explanatory diagram of a configuration of an alignment apparatus showing one embodiment of the present invention.

FIG. 3 is an explanatory diagram of a configuration of a universal joint.

FIG. 4 is a cross-sectional view taken along line XX of FIG. 2 with a part omitted.

FIG. 5 is an explanatory diagram showing a tilted state of a subject.

FIG. 6 is an explanatory diagram showing another tilt state of the subject.

FIG. 7 is an explanatory view showing still another tilting state of the subject.

FIG. 8 is an explanatory diagram showing another tilted state of the subject.

[Explanation of symbols]

 Reference Signs List 1 laser light source 4 reference plate 5 subject 10 second half mirror 11 condenser lens 12 alignment screen 20 movable base 21 universal joint 22 support post 23 ring body 24 first rotation axis 25 second rotation axis 27 spring Cradles 28, 29 Tension spring 30 Rotary table 32 Roller 34 Elevating plate 35 Motor 37 Linear actuator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-225305 (JP, A) JP-A-59-24819 (JP, A) Fully open 3-25122 (JP, U) Fully open Showa 63- 86934 (JP, U) US Patent 5,160,112 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 9/00-11/30 102 G12B 1/00-17/08

Claims (2)

(57) [Claims] 1. A light from a laser light source is converted into parallel light by a collimator lens, and a part of the light is reflected by a reference plate.
A laser interferometer that irradiates the subject with the transmitted light of the reference plate and inspects the surface state of the subject based on interference fringes generated between the reflected light and the reflected light from the reference plate, A half mirror is interposed in an optical path from a laser light source to a collimator lens, and reflected light from the half mirror is projected onto an alignment screen to perform alignment between the reference plate and the subject. A movable table on which a sample is placed is connected to a support member via a universal joint so as to be tiltable in an arbitrary direction in a non-rotating state, and the movable table is engaged with a tilt drive unit that moves vertically and circularly. An alignment device for a laser interferometer, wherein the alignment device is provided. 2. The universal joint, wherein the support member surrounds a ring body and is connected to the ring body via a pair of first rotating shafts rotatable about an axis therebetween, and is movable with the ring body. The ring body is formed by being connected to a base via a pair of second rotating shafts provided in a direction orthogonal to the first rotating shaft and rotatable around the axis. First
2. The laser interferometer according to claim 1, wherein a balance spring is mounted at a position orthogonal to the rotation axis of the movable table and at a position orthogonal to the second rotation axis of the movable table. Alignment device.