Micro motor, a typical equipment to adjust the zoom lens, together with a position feedback sensor constitute the closed position loop, which is the key factor to perform successfully accurate lens focusing. Traditionally, the incremental grating ruler tends to be adopted as the position sensor, which continues counting the number of grating pitches on a dynamic one-dimensional moving platform. Instead of incremental counting, this paper proposes a dual-frequency-moiré based absolute position sensing method for reading immediate position at static environment. According to the relative positions of two kind of moiré, the absolute position of the measurement point can be retrieve at nano-meters level through look-up table. By the way, the measurement range can be expanded to millimeters level satisfying the demands of lens focusing, and furthermore the measurement efficiency is improved greatly without dynamic moving. In order to verify the performances of proposed method, a model of dual-frequency-moiré is built, and theological principles are deduced. Finally, the simulation results indicate that, with established configurations, dual-frequency-moiré could measure position within 0~5000μm. At the same time, the measurement accuracy achieves nano-meters level.

Date Published: 8 October 2015
PDF: 6 pages
Proc. SPIE 9677, AOPC 2015: Optical Test, Measurement, and Equipment, 96770C (8 October 2015); doi: 10.1117/12.2197026

Published in SPIE Proceedings Vol. 9677:
AOPC 2015: Optical Test, Measurement, and Equipment
Sen Han; Jonathan D. Ellis; Junpeng Guo; Yongcai Guo, Editor(s)