Reduction in Cross-Talk Errors in a Six-Degree-of-Freedom Surface Encoder

Hiraku Matsukuma, Ryo Ishizuka, Masaya Furuta, Xinghui Li, Yuki Shimizu, Wei Gao

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


This paper presents the reduction in cross-talk errors in the angular outputs existing in the previously designed six-degree-of-freedom (DOF) surface encoder for nanopositioning and nanometrology. The six-DOF surface encoder is composed of a planar scale grating and an optical sensor head with a reference grating, a displacement assembly and an angle assembly. The diffracted beams from both the scale and the reference gratings are received by the displacement assembly for measurement of the primary XYZ translational motions. The angle assembly only receives the diffracted beams from the scale grating for measurement of the secondary θXθYθZ angular motions. In this paper, at first, the cross-talk errors in the angular measurement results of the previous surface encoder are identified to be caused by the diffracted beams from the reference grating leaking into the angle assembly due to the imperfection of the polarization components of the sensor head. An improved design of the sensor head is then carried out to reduce the cross-talk errors by changing the position of the angle assembly in the sensor head. The sensor head is further optimized by replacing the beam splitter located in front of the angle assembly from a cube type to a plate type. Experimental results have demonstrated that the cross-talk errors were reduced from 3.2 arc-seconds to 0.02 arc-second.

Original languageEnglish
Pages (from-to)111-123
Number of pages13
JournalNanomanufacturing and Metrology
Issue number2
Publication statusPublished - 2019 Jun 1


  • Cross-talk errors
  • Six-DOF surface encoder


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