Development of simple configuration of laser diffraction encoder system with high alignment tolerance
Date Issued
2007
Date
2007
Author(s)
Li, Bai-Kun
Abstract
For the development of micro/nano technology, many nano manufacturing and measuring systems depend on the metrology or positioning in the nanometer displacement scale. However, Sensors with long measuring distance and high resolution are expensive and easily affected by the unstable environment. Thus, to development the sensors have compact, low cost, high resolution, and low environment effect is becoming more indispensable. newly simple configuration and compact laser diffraction encoder system with high alignment tolerance was developed in this thesis. It is one type of the grating interferometer which principle used by Doppler Effect, taking the grating pitch instead of laser wavelength, it can reduce errors caused by the unstable environment. Through moving grating, the interference signals are converted into voltage signals, and finally be encoded to the displacement information. n the optical frame, the optical encoder adopts a special design in optical path that simplify the optical configuration and minify structure size. The environmental disturbance and complicated assemble procedure in optical system can be reduced effectively. On the other hand, the feasibility of high alignment tolerance between the optical head and the grating is achieved by the simulation of optics analysis software.n the signal processing frame, A signal correcting procedure is also developed in this thesis. The signal correction of DC drift and amplitude variation can be reached by combing analogical circuit, personal computer, NI DAQ and Labview software interface. The Errors in quadrature signals caused by the oscillating of the grating can be corrected effectively. In addition, the displacement measurement were accomplished with count and interpolation program by Labview software.o verify the theoretical predictions and the overall system specifications of the system, the SIOS MI5000 laser interferometer was adopted as the calibration tool. Within the measuring distance of 15mm, running the test at closed chamber with no temperature, humidity, vibrating calibration in regular laboratory environment, the measurement accuracy is below 20nm and the measurement repeatability is below 14 nm.
Subjects
Laser optical encoder
Grating
Interference
Diffraction
Interpolation
Type
thesis
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