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Proceedings Paper

Angle measurement by moire interference technique
Author(s): Brahm Pal Singh; Vijay Trimbak Chitnis
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Paper Abstract

A new approach for small angle measurement by moiré interference technique is reported. Moiré signal is obtained by a pair of parallel Ronchi ruling gratings in the reflection mode. A relative rotation between the two gratings gives rise to- the intensity variation known as the moiré signal. The present approach for small angle measurement utilizes the region of higher slope of the moiré signal to get very high accuracy. The moiré signal is amplified and its inversion is obtained electronically. The difference of the moiré and its inverted signal with suitable dc shift is obtained by differencial amplifier and used for the small angle measurement. The present technique is successfully used for small angle measurement with the accuracy of the order of 10−7 radian with a time constant 0.1 sec. The accuracy is found to be dependent on the pitch of the grating, signal to noise ratio of the system and the response time. The experiments are carried out using a pair of 25μm pitch gratings. Piezo-electric transducer (PZT) is used to drive one of the gratings and the angular sensitivity of the order of 500 mV/ micro radian is observed.

Paper Details

Date Published: 1 December 1991
Proc. SPIE 1554, Second International Conference on Photomechanics and Speckle Metrology, (1 December 1991); doi: 10.1117/12.57416
Show Author Affiliations
Brahm Pal Singh, National Physical Lab. (Japan)
Vijay Trimbak Chitnis, National Physical Lab. (India)

Published in SPIE Proceedings Vol. 1554:
Second International Conference on Photomechanics and Speckle Metrology
Fu-Pen Chiang; Fu-Pen Chiang, Editor(s)

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