The high accuracy data processing system of laser interferometry signals based on MSP430

Yong-yue Qi; Yu-chi Lin; Mei-rong Zhao

doi:10.1117/12.833406

28 August 2009 The high accuracy data processing system of laser interferometry signals based on MSP430

Yong-yue Qi, Yu-chi Lin, Mei-rong Zhao

Proceedings Volume 7382, International Symposium on Photoelectronic Detection and Imaging 2009: Laser Sensing and Imaging; 73821G (2009) https://doi.org/10.1117/12.833406
Event: International Symposium on Photoelectronic Detection and Imaging 2009, 2009, Beijing, China

Abstract

Generally speaking there are two orthogonal signals used in single-frequency laser interferometer for differentiating direction and electronic subdivision. However there usually exist three errors with the interferential signals: zero offsets error, unequal amplitude error and quadrature phase shift error. These three errors have a serious impact on subdivision precision. Based on Heydemann error compensation algorithm, it is proposed to achieve compensation of the three errors. Due to complicated operation of the Heydemann mode, a improved arithmetic is advanced to decrease the calculating time effectively in accordance with the special characteristic that only one item of data will be changed in each fitting algorithm operation. Then a real-time and dynamic compensatory circuit is designed. Taking microchip MSP430 as the core of hardware system, two input signals with the three errors are turned into digital quantity by the AD7862. After data processing in line with improved arithmetic, two ideal signals without errors are output by the AD7225. At the same time two original signals are turned into relevant square wave and imported to the differentiating direction circuit. The impulse exported from the distinguishing direction circuit is counted by the timer of the microchip. According to the number of the pulse and the soft subdivision the final result is showed by LED. The arithmetic and the circuit are adopted to test the capability of a laser interferometer with 8 times optical path difference and the measuring accuracy of 12-14nm is achieved.

Citation Download Citation

Yong-yue Qi, Yu-chi Lin, and Mei-rong Zhao "The high accuracy data processing system of laser interferometry signals based on MSP430", Proc. SPIE 7382, International Symposium on Photoelectronic Detection and Imaging 2009: Laser Sensing and Imaging, 73821G (28 August 2009); https://doi.org/10.1117/12.833406

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KEYWORDS

Interferometers

Phase shifts

Data processing

Error analysis

Laser interferometry

Laser systems engineering

Computer simulations

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