Basic principle of a new measurement system of long measuring range of digital modulation

Zeng-yao Zhang; Qian-min Mao

doi:10.1117/12.716129

13 October 2006 Basic principle of a new measurement system of long measuring range of digital modulation

Zeng-yao Zhang, Qian-min Mao

Proceedings Volume 6280, Third International Symposium on Precision Mechanical Measurements; 62800F (2006) https://doi.org/10.1117/12.716129
Event: Third International Symposium on Precision Mechanical Measurements, 2006, Urumqi, China

Abstract

Usually a capacitive displacement transducer (CDT) is made by printed-circuit-board (PCB) technology, so the reduced pitches of electrodes are limited by PCB technology and lead wire design, and the increase of its resolution, too. If a line array source replaces the transmitting electrodes of the CDT, a scale grating replaces the scale electrodes and a detector replaces the pick-up electrode of the CDT and also increase its number of the subdivision, the solution could be greatly improved on condition that the mathematical model of the CDT is maintained. Grating technology is organically combined with CDT technology. The basic operation principle of the system is as follows: a linear array source has several groups and every group has 8 light cell (organic light-emitting diode (OLED), or Liquid Crystal on Silicon Display (LCoS). (these line array sources are required to determinate speed response). The pitch of the cells is w. Every cell emits a light signal if driven by a digital signal. The pitch of the scale grating is W (=8w). The transmission (or reflection) characteristic function of the scale grating is T_i(x). After I_i(t) passes through the scale grating and is modulated by the displacement x of the scale grating, the total intensity I(x,t) is obtained. The photoelectric detector receives I(x,t) and transforms it into an electric signal. Subsequently the signal is demodulated and filtered, thus the fundamental harmonic of I₁(x,t) is obtained. It is obvious, that the phase of I₁(x,t) has a linear relation with x. After processing the phase demodulation circuit and the MPU, the displacement x of the scale grating is obtained.

Citation Download Citation

Zeng-yao Zhang and Qian-min Mao "Basic principle of a new measurement system of long measuring range of digital modulation", Proc. SPIE 6280, Third International Symposium on Precision Mechanical Measurements, 62800F (13 October 2006); https://doi.org/10.1117/12.716129

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