Optical: systems and elements – Compound lens system – Microscope
Reexamination Certificate
2000-08-21
2002-01-22
Nguyen, Thong (Department: 2872)
Optical: systems and elements
Compound lens system
Microscope
C359S368000, C359S391000
Reexamination Certificate
active
06341037
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a positioning stage. More specifically, it relates to a mechanism for an accurate movement control while resting a workpiece thereon during accurate measurement by microscope inspection, optical measurement etc.
2. Description of Related Art
Conventionally, during microscope inspection etc., a workpiece is put on a cross-travel stage and is moved so that a portion of interest comes within a predetermined measurement area located on an extension of an objective. For measurement, the portion of interest has to be accurately moved little by little.
In view of the above requirement, the portion of the stage for the workpiece to be put on is arranged to be movable in X and Y directions and a driving mechanism capable of accurate feeding movement little by little is provided to control movement thereof.
For such driving mechanism of the stage, a rack-and-pinion mechanism and a feeding mechanism using a rail and a friction gear can be used. However, on account of problem relating to accuracy and movement smoothness, another type of feeding mechanism using a belt and a pulley recently comes into use (see Japanese Patent Publication No. Hei 7-1340, Japanese Patent Laid-Open Publication No. Hei 4-31814 and Japanese Patent Laid-Open Publication No. Hei 9-113814).
The feeding mechanism with a belt and a pulley, for moving a table for a workpiece to be put on relative to a base, has a pair of pulley supported on, for instance, a base side and an endless belt is wound between the pulleys. One table is supported movably relative to the base and is associated with a part of the belt through a joint. Ordinarily, the table is supported by a guide rail for guiding the table in an extension direction of the belt.
A manipulation knob is connected to a shaft of one of the pulleys and the pulley is rotated by rotating the knob, thus circulatingly rotating the endless belt stretched therearound. By thus feeding the belt, the table associated with a joint is also fed, thus feeding the table by the knob.
Incidentally, for quickly feeding the table by directly holding the table in adjusting the portion of interest to the measurement area, a clutch mechanism etc. for releasing the feeding mechanism composed of the belt and the pulley is provided. Ordinarily, the joint of the table relative to the belt is released. Specifically, the joint is fixed and released at any position of the belt.
According to the above-described conventional feeding mechanism by the belt and the pulley, following problems arise.
First, it is difficult to simplify the structure of the feeding mechanism and to reduce a size thereof.
In other words, tension has to be applied to the belt to eliminate a slack of the belt and further strong tension is necessary for driving the belt by the pulley. Specifically, in order to transfer the rotation of the pulley to the belt, a predetermined friction is necessary between the pulley and the belt, and further strong tension is necessary for the belt to satisfy the requirement. Accordingly, a structure and strength enough to endure the strong tension of the belt is necessary for the pulley, rotation shaft thereof, support portion thereof etc.
Second, feed of the table cannot be adjusted finely enough.
In other words, since the conventional feeding mechanism by the belt and pulley rotates the pulley by rotating the manipulation knob to drive the belt wound between the pulleys, relationship between a control input of the manipulation knob (circumference thereof) and a feed displacement of the belt (i.e. feed displacement of the table) depends on a radius of the manipulation knob and the pulley. Accordingly, in order to set the feed of the table, the radius of the pulley has to be made small.
However, when the radius of the pulley is reduced, curvature of the belt wound therearound becomes small. And an allowable minimum bend radius for assuring normal operation is determined in advance in view of material thereof. Accordingly, the radius of the pulley cannot be reduced beyond the allowable minimum bend radius, thus unable to sufficiently set the minute feed of the table.
Third, the components cannot be arranged freely enough.
Specifically, in the conventional feeding mechanism by the belt and the pulley, since the manipulation knob is connected to the shaft of the pulley, the disposition of the components is restricted by the position of the pulley. Operability of the manipulation knob is not so good because the pulley is ordinarily disposed at both ends of the stretched belt (end of the feeding mechanism). However, as described above, since the location is restricted by the position of the pulley, it cannot be easily changed. Though the position can be changed using other transmission means, the mechanism can be so complicated.
Further, the feeding mechanism by the belt and the pulley may be provided in crosswise two directions for moving biaxially, i.e. X and Y-axis directions in the conventional stage drive mechanism. Further, for improving operability, the manipulation knob of respective shafts is formed in coaxial double cylindrical shape. However, as described above, the location of the manipulation knob is restricted by the pulley position at the end of the feeding mechanism, and the respective manipulation knobs have to be adjusted at the same position in order to form the manipulation knob in the double cylindrical form. Accordingly, the feeding mechanism of respective directions is only allowed to cross at the end thereof. More specifically, the feeding mechanism can only be disposed at a periphery of respective tables and the space at central portion cannot be used.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a positioning stage capable of simplifying and size-reducing a structure thereof, improving feeding accuracy of the table and freely arranging respective components.
The present invention is a positioning stage having: a table for a workpiece to be rested; a base for supporting the table; and a feeding mechanism interposed between the table and the base for moving the table relative to the base in a predetermined movement direction along a surface of the table, in which the feeding mechanism has: a pair of pulley supported by either one of the table and the base; a loop-shaped drive force transmission member stretched between the pair of pulley, at least a part of the drive force transmission member extending in the movement direction; a joint for connecting the other one of the table and the base with a part of the drive force transmission member extending in the movement direction; and a pinch mechanism provided to the either one of the table and the base for holding a part of the drive force transmission member to drive the drive force transmission member.
According to the above arrangement, the drive force transmission member is driven not by the pulley portion but by the pinch mechanism separately provided (a combination of a rotation drive capstan and a pinch roller rotating by being pressed). The pinch mechanism holds the drive force transmission member (belt, wire, chain and other flexible elongated member) to secure transmission of the drive force. Accordingly the strong tension of the drive force transmission member necessary for transmitting the rotation of the pulley to the drive force transmission member is not required, thus size-reducing and simplifying the portion adjacent to the pulley.
Further, since the drive force transmission member is not wound to the roller of the pinch mechanism (driving side, capstan), the allowable minimum bend radius does not influence on the pinch mechanism. Accordingly, the feed can be minutely set by reducing the radius of the roller of the pinch mechanism.
Further, since the pinch mechanism can be disposed to any section of the path of the drive force transmission member, the operation knob etc. for controlling feed operation can be more freely disposed. Further, when the feeding mechanism is provided in two direction
Sano Hidekazu
Tanaka Shoichi
Mitutoyo Corporation
Nguyen Thong
LandOfFree
Positioning stage does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Positioning stage, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Positioning stage will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2847752