Abstract
An interferometric self-calibration method for the evaluation of the pitch deviation of scale grating has been extended to evaluate the pitch deviation of the long-range type linear scale by utilizing the stitching interferometry technique. Following the previous work, in which the interferometric self-calibration method was proposed to assess the pitch deviation of the scale grating by combing the first-order diffracted beams from the grating, a stitching calibration method is proposed to enlarge the measurement range. Theoretical analysis is performed to realize the X-directional pitch deviation calibration of the long-range linear scale while reducing the second-order accumulation effect by canceling the influence of the reference flat error in the sub-apertures’ measurements. In this paper, the stitching interferometry theory is briefly reviewed, and theoretical equations of the X-directional pitch deviation stitching are derived for evaluation of the pitch deviation of the long-range linear scale. Followed by the simulation verification, some experiments with a linear scale of 105 mm length from a commercial interferential scanning-type optical encoder are conducted to verify the feasibility of the self-calibration stitching method for the calibration of the X-directional pitch deviation of the linear scale over its whole area.
Highlights
Due to their low cost, high resolution, and robustness, optical linear encoders are widely employed for precision positioning applications, such as semiconductor manufacturing, precision machine tools, and coordinate measuring machines (CMMs) [1,2,3,4]
A self-calibration stitching method based on the Fizeau interferometer, in which the pitch deviation of the linear scale can be evaluated while removing the influence from the reference flat error, has been proposed to evaluate the pitch deviation of a long-range linear scale
The stitching interferometry method has never been applied to evaluate the X-directional pitch deviation of the scale grating while eliminating the accumulative second-order effect of the systematic error of the interferometer
Summary
Due to their low cost, high resolution, and robustness, optical linear encoders are widely employed for precision positioning applications, such as semiconductor manufacturing, precision machine tools, and coordinate measuring machines (CMMs) [1,2,3,4]. A Fizeau form interferometer is used to evaluate the X-directional pitch deviation of a reflective-type long-range linear scale with a self-calibration stitching method. The X-directional pitch deviation of a long-range linear scale over its whole area can be self-calibrated in a short time with high throughput. The self-calibrated stitching method for the long-range type linear scale pitch deviation evaluation is proposed by considering the additional phase shift errors introduced in the stitching measurement, which is verified through a simulation. According to Equation (3), by using the stitched positive and negative first-order phase outputs, the pitch deviation of the long-range linear scale over its whole area can be evaluated.
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