Form Error Characterization of Reflective-Type Gratings

Abstract:

A form error characterization of a reflective-type scale grating, which is used in three-degree-of-freedom (3-DOF) encoders for position measurement of a planar motion stage, is presented. The scale grating has a micro-structured surface, the pitch of which is 1 µm in both X- and Y- direction. The periodic pattern on the scale grating generates diffracted beams when a laser beam incidents to the grating surface. The ±1st order diffracted beams from the grating contain information about the stage motions of not only X- or Y- directional in-plane displacement but also Z-directional out-of-plane displacement, and are therefore able to be utilized for multi-axis position detection. Accuracies of the position detection are mainly determined by a period deviation and a Z-directional out-of-flatness of the scale grating. The form error characterization of the grating is possible by using Fizeau interferometer, although the form error of a reference mirror in the Fizeau interferometer still remains as a measurement error in the form of the measured scale grating. In this paper, a new method was proposed to evaluate the form error characterization of the scale grating for the 3-DOF encoder, while eliminating the form error of the reference mirror in the Fizeau interferometer.

• Periodical: Key Engineering Materials (Volumes 523-524)
• Pages: 859-864
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.523-524.859
• Online since: November 2012
• Authors: Yuki Shimizu, Woo Jae Kim, So Ito, Wei Gao
• Keywords: Interferometer, Linear Encoder, Out-of-Flatness, Period Deviation, Scale Grating

References

[1] W. Gao, A. Kimura, "A Three-axis Displacement Sensor with Nanometric Resolution", Annals of the CIRP, Vol. 56, No. 1, pp.529-532, (2007).

DOI: 10.1016/j.cirp.2007.05.126

[2] Beers JS, Penzes WB, NIST Length Scale Interferometer Measurement Assurance, NISTIR 4998: (1992), pp.1-28.

[3] Hocken RJ, Trumper DL, Wanga C, Dynamics and Control of the UNCC/MIT Sub-atomic Measuring Machine, Annals of the CIRP, Vol. 50, No. 1(2001), pp.373-376.

DOI: 10.1016/s0007-8506(07)62143-x

[4] Weckenmann A, Hoffmann J, Long Range 3D Scanning Tunnelling Microscopy, Annals of the CIRP, Vol. 56, No. 1 (2007), p.525–528.

DOI: 10.1016/j.cirp.2007.05.125

[5] Fizeau interferometer Catalogue, Zygo Corporation.

[6] W. GAO, A. Kimura, A fast evaluation method for pitch deviation and out-of-flatness of a planar scale grating, Annals of the CIRP, Vol. 59,No.1(2010), pp.509-5.

DOI: 10.1016/j.cirp.2010.03.035

[7] G.Schulz and J.Schwider, Precise Measurement of Planeness, Appl.Opt.，Vol. 6, Issue 6 (1967)，pp.1077-1084.

DOI: 10.1364/ao.6.001077

[8] K.E. Elssner, R.Burow, J.Grzanna and R.Spolaczyk, Absolute sphericity measurement, Appl.Opt.，Vol. 28, Issue 21(1989), pp.4649-4661.

DOI: 10.1364/ao.28.004649

[9] R.Mercier,M.Lamare,P.Picart J.P. Marioge, Two-flat method for bi-dimentional measurement of abusolutedeparture from the besut sphere ,Pure and Appl.Opt.,Vol. 6 (1997), pp.117-126.

DOI: 10.1088/0963-9659/6/1/013