JPH02184704A - Length measuring instrument - Google Patents

Abstract

PURPOSE:To reduce the error of an XY stage depending upon a mechanism by forming scale patterns on a scale plate while extending the scale patterns by specific length at orthogonal direction to a moving direction as a length measurement direction. CONSTITUTION:The top and reverse surfaces of the scale plate 210 are varied in refractive index periodically to form the scale patterns (length: about 40mm, period: about several mum) which accurately cross orthogonally each other. As one method for assembling the scale plate on the XY stage, the plate 201 is moved in two dimensions and X-axisl and Y-axisl position sensors (a light emitting element and a light receiving element are incorporated.) 204 and 205 are fixed. When the XY stage moves in a Y-axial moving direction 206, positioning servocontrol is used with the signal of the sensor 205 and then the XY stage moves in the direction 206 accurately along the pattern 203. Movement in an X-axial movement direction is the same. Namely, the total positioning accuracy is determined only by the manufacture accuracy of the plate 201 without being affected by the mechanism elements of the XY stages.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a length measuring device used to control the position of a stage, and particularly to a position measuring device for a two-dimensional moving body such as an XY stage.

[Conventional technology]

Conventionally, rotary encoders and linear encoders have been mainly used as sub-length devices for controlling the position of the xY stage. Among these, the linear encoder can directly change the moving length of the stage, so it has been used in relatively high-precision devices. The configuration of this linear encoder is shown in FIG. In the figure, a linear encoder is composed of a linear scale 401 and a position sensor 402. This linear scale 401 is formed of a glass or metal substrate on which a scale pattern 403 whose reflectance or transmittance changes at regular intervals is drawn. Light emitted from the light emitting element in the position sensor 402 with respect to the linear scale 401 is transmitted or reflected by the IJW American scale 401 and then detected by the light receiving element. At this time, when the linear scale #401 moves relative to the position sensor 402 in the length measurement direction 404 in the periodic direction of the scale pattern 4030, the light receiving element outputs a signal synchronized with the pattern period. In order to count this signal change,
The relative movement distance between linear scale 401 and position sensor 402 is determined.

Next, FIG. 5 shows an example in which a linear encoder is applied to an xY stage. This example has a configuration in which the X stage is mounted on the Y stage. In the same figure, the X stage is
It is placed on a shaft guide rail 501 and moved in the direction of the ye force by a motor 502 and a ball screw 503. Detection of the position in the Y-axis direction is performed by a Y-movement linear scale 504 fixed to the X stage and a Y-axis circumferential position sensor 505 fixed to the Y stage. Similarly, the stage 506 is placed on the X-axis guide rail 507 on the X stage,
It moves in the 6x-axis direction by an X-axis drive motor 508 and an X-axis drive ball screw 509. The position in the X-axis direction is detected using an X-motion linear scale 510 fixed on the stage 506.
and an X-axis circumferential position sensor 511I fixed to the X stage.

[Problems to be Solved by the Invention] The above-mentioned conventional XY stage using a linear scale has the following problems. That is, one of them is
The orthogonality of the Y stage is determined by linear scales 504 and 509.
The point is that it depends on the assembly accuracy of the xy stage mechanism regardless of the above. That is, in order to improve the orthogonality accuracy, a precise orthogonality measuring device and sufficient adjustment time are required. Another point is that the straightness of the stage is largely dependent on the guide and its assembly accuracy. That is, positional errors due to nonlinearity of the guide cannot be detected by a linear encoder. Therefore, if you want to obtain sufficient accuracy, use carefully selected guide parts,
It needed to be assembled by a skilled worker. Furthermore, there is a problem that deterioration of accuracy over time due to abrasion, etc. due to hooks that are not a non-contact guide such as an air slider cannot be avoided.

[! Means for Solving Problem 1] FIG. 1 shows a linear encoder as a length measuring device according to the present invention. In the figure, in the present invention, a scale pattern 102 on a scale plate 101 is extended in a direction perpendicular to a movement direction 103 as a length measurement direction, that is, a movement direction 104, with respect to the movement direction which is the original length measurement direction. The length of the scale plate 101 in the moving direction 104 is necessary to cover the moving distance of the orthogonal axes when an XY stage is assembled using the scale plate 101 according to the present invention.

[Effect]

In the figure, position sensor 10! i is the moving direction 104
If the scale pattern 102 is not completely parallel to the scale pattern 102, the position sensor 105 will also detect a positional deviation signal in the moving direction 103. If this signal is used as a positioning servo signal, when the XY stage moves in the movement direction 104, it is possible to accurately follow the scale pattern 102. Therefore, in the XY stage using the linear scale plate 101 according to the present invention, the accuracy of the scale plate 101 determines the orthogonality and straightness of the xyX stage, and errors depending on the mechanism are significantly reduced.

〔Example〕

Next, a configuration in which a linear encoder is applied to an xY stage as an embodiment of the length measuring device according to the present invention will be described with reference to the drawings.

(Example 1) Figures 2(a) and 2(b) show a plan view from above and a plan view from the side when linear scales according to the present invention are configured on the front and back surfaces of one substrate. It is.

In the figure, scale patterns 202 and 203 whose reflectances are periodically changed are shown on the front and back surfaces of a scale plate 2010.
are drawn on these scale patterns 2 on the front and back sides.
02 and 203 are formed to be exactly orthogonal to each other. The scale plate 201 of this embodiment is used as a reflective scale. Therefore, the scale plate 201 can be made by depositing a highly reflective metal on a metal plate in a grid pattern to form a scale pattern, and then aligning two metal plates υ on the front and back sides. In addition, this scale plate 201
Y-axis position sensor 204 arranged opposite to the upper and lower surfaces of
The X-axis position sensor 205 has a light-emitting element and a light-receiving element incorporated therein, and the distance traveled can be determined by changes in reflected light from the surface of the scale plate 201.

There are two ways to incorporate the linear encoder of this embodiment into an xY stage. One method is to move the scale plate 201 two-dimensionally and fix the Y-axis position sensor 204 and the X-axis position sensor 205. The other method is to move the scale plate 201 two-dimensionally and fix the Y-axis position sensor 204 and In the case of an xY stage configured such that the X-axis stage is mounted on the stage, the Y-axis position sensor 204 is fixed to the X-axis stage, and the
Fixed at 6. Monolithic IC as XY stage
When considering the beam positioner of a laser trimmer for
Stage movable range is 20x20mnz position resolution l-i
The force is about 0.1 μm. Therefore, the scale plate 201 according to the present invention in this case has a scale length of about 40 x 40 mm, and the period of the drawn pattern is several μm.
Position detection within one period can be determined by dividing the intensity of the received light signal to a position resolution of 0.1 μm.

In this configuration, when the xY stage moves in the Y-axis movement direction 206, if the positioning servo is used based on the signal from the along the Y-axis movement direction 208. The same holds true for the opposite X-axis movement direction 20F. Therefore, scale plate 2
01, the overall positioning accuracy is determined only by the manufacturing accuracy of the scale plate 201 without being affected by the mechanical table elements of the xY stage, which simplifies the assembly and adjustment of the XY stage and reduces mechanical wear. It becomes possible to mass-produce homogeneous xY stages without long-term deterioration in accuracy due to deterioration.

(Embodiment 2) FIG. 3 is a plan view showing another embodiment of a linear scale as a length measuring device according to the present invention. In the same figure, the KXX scale pattern 0 on the same plane of the scale plate 301 is shown.
2 and Yllllll pattern 303 are drawn perpendicular to each other. Therefore, the Y-axis position sensor 304
As the X-axis position sensor 305, in addition to a reflective sensor in which the light emitting element and the light receiving element are on the same side, a transmission type sensor in which the scale plate 301 is inserted between the light emitting element and the light receiving element can also be used. Therefore, the scale plate 301 can be manufactured by depositing a scale pattern on a glass substrate instead of a metal plate as in the first embodiment.

Note that 306 is the Y-axis movement direction, and 307 is the X-axis movement direction.

According to such a configuration, when a reflection type sensor is used, the X-axis position sensor 305 and the X-axis position sensor 304 are on the same side with respect to the scale plate 301, which makes it easier to use than the first embodiment. It becomes easier to attach a linear scale to the XY beauty mechanism.

〔Effect of the invention〕

As explained above, in the present invention, since the scale pattern is extended in the direction perpendicular to the length measurement direction, the scale pattern is orthogonal to the movement of the scale in the axial direction perpendicular to the axis to be measured. and can be used as a standard for straightness.

Therefore, the orthogonality and straightness, which were problems with conventional xY stages etc. in which two sets of linear encoders were attached to each axis for positioning, depended on the parts and assembly accuracy of the XY aesthetics mechanism, and the linear encoder corrected them. This completely eliminates problems such as accuracy deterioration due to wear of mechanical parts after long-term use, and the need for skill and man-hours for assembly.

It is equipped with a linear encoder according to the invention ft) CY
This is because the accuracy of the stage, including its straightness and orthogonality, is determined only by the manufacturing accuracy of the linear scale plate, and does not depend on the assembly accuracy of the mechanical parts or changes over time.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a linear encoder explaining the basic configuration of a length measuring device according to the present invention, and FIGS. FIG. 3 is a plan view of a linear encoder seen from above, illustrating another embodiment of the length measuring device according to the present invention, and FIG. 4 is a plan view of a conventional linear encoder. 1IS5 is a plan view showing the structure of an XY stage using a conventional linear encoder. 101--Scale plate, 102--Scale pattern, 103--Movement direction (length measurement direction), 104
ψ...Movement direction, 105...-Position sensor, 20
1-@・Bite scale plate, 2021203 ・-Fist・Scale pattern, 204...Y-axis position sensor, 2Q
S-...X-axis position sensor, 206 - Fist...Y-axis movement direction, 207...X-axis movement direction, 301...
Scale plate, 302゜303...φ scale pattern, 3041I conflict...Y-axis position sensor, 305-...
・X-axis position sensor, 306 ...Y-axis movement direction, 3
01...X-axis movement direction.

Claims (1)

[Claims] A scale substrate on which a scale pattern with changing reflectance or transmittance is drawn at a constant period, a light emitting element that emits light to the scale substrate, and a light receiving element that detects the light reflected or transmitted to the scale pattern. and a position sensor, which determines the relative movement distance between the scale substrate and the position sensor from a change in the output signal of the light receiving element, the scale pattern of the scale substrate being moved in a direction orthogonal to the length measurement direction. A length measuring device characterized by being extended by a predetermined length.