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Proceedings Paper

A High-Resolution Laser Scale Interferometer
Author(s): Hideto Iwaoka; Koji Akiyama
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Paper Abstract

This paper describes a compact, high-resolution laser scale interferometer measuring only 40 x 68 x 28 mm, with a scale -- a holographically-produced diffraction grating --of pitch 0.83 μm and 108 mm long. A collimated vertical light beam from a diode laser is diffracted from the horizontal diffraction grating and split into two beams; the beams are reflected so that they impinge symmetrically on opposite sides of a half-silvered mirror which acts as both interferometer and optical phase shifter. Scale movement generates sinusoidal quadrature optical signals. A zero-crossing detector circuit generates four pulses per cycle (one pulse per 0.1 μm movement) from the quadrature outputs, and an A/D converter and microprocessor are used for precision analog interpolation and linearization. To normalize the quadrature optical signals (to eliminate the effects of light amplitude variation) ±√ ((sin)2 + (cos)2) --the square root of the sum of the squares of the quadrature signals -- is used as the A/D converter reference signal. Linearity of ±0.1 μm and 1 nm resolution were obtained.

Paper Details

Date Published: 12 December 1984
PDF: 5 pages
Proc. SPIE 0503, Application, Theory, and Fabrication of Periodic Structures, DiffractionGratings, and Moire Phenomena II, (12 December 1984); doi: 10.1117/12.944824
Show Author Affiliations
Hideto Iwaoka, Yokogawa Hokushin Electric Corporation (Japan)
Koji Akiyama, Yokogawa Hokushin Electric Corporation (Japan)


Published in SPIE Proceedings Vol. 0503:
Application, Theory, and Fabrication of Periodic Structures, DiffractionGratings, and Moire Phenomena II
Jeremy M. Lerner, Editor(s)

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