Improved Measurement Accuracy of a Laser Interferometer: Extended Kalman Filter Approach

Wooram LEE  Dongkyun KIM  Kwanho YOU  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E93-A   No.10   pp.1820-1823
Publication Date: 2010/10/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E93.A.1820
Print ISSN: 0916-8508
Type of Manuscript: LETTER
Category: Systems and Control
heterodyne interferometer,  extended Kalman filter,  measurement accuracy,  nonlinearity,  error compensation,  

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In this paper a nonlinearity compensation algorithm based on the extended Kalman filter is proposed to improve the measurement accuracy of a heterodyne laser interferometer. The heterodyne laser interferometer is used for ultra-precision measurements such as those used in semiconductor manufacturing. However the periodical nonlinearity property caused by frequency-mixing restricts the accuracy of the nanometric measurements. In order to minimize the effect of the nonlinearity, the measurement process of the laser interferometer is modeled as a state equation and the extended Kalman filtering approach is applied to the process. The effectiveness of our proposed algorithm is demonstrated by comparing the results of the algorithm with experimental results for the laser system.