Self-calibration of a variable-line-spacing grating for an absolute optical encoder with a Fizeau interferometer

Xin Xiong, Lue Quan, Yuki Shimizu, Hiraku Matsukuma, Wei Gao

Research output: Contribution to journalArticlepeer-review

Abstract

The principle of the self-calibration method for the evaluation of a planar scale grating having a constant pitch is extended to realize the evaluation of the pitch distribution of a planar scale grating having variable line spacings (VLSs) along the X-and Y-directions. In the conventional self-calibration method, the wavefronts in the zeroth-order diffracted beam and the first-order diffracted beams observed by a Fizeau interferometer arranged in the Littrow configuration were employed to evaluate the pitch deviation of a scale grating. The arithmetic operation with the wavefront data realizes the evaluation of the pitch deviation over a large area in a short time, while cancelling the influence of the out-of-flatness of a scale grating. Meanwhile, theoretical equations in the conventional self-calibration method cannot be directly applied to the evaluation of a VLS grating due to its unique properties of the pitch distribution. In this paper, major modifications are thus made to the conventional theoretical equations for deriving the pitch distribution of a VLS grating. To verify the performance of the newly proposed method, the pitch distribution of a VLS grating employed in a commercial planar absolute encoder is evaluated in experiments.

Original languageEnglish
Article number064005
JournalMeasurement Science and Technology
Volume32
Issue number6
DOIs
Publication statusPublished - 2021 Jun

Keywords

  • absolute optical encoder
  • Fizeau interferometer
  • pitch deviation
  • self-calibration
  • variable-line-spacing grating

ASJC Scopus subject areas

  • Instrumentation
  • Engineering (miscellaneous)
  • Applied Mathematics

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