高對位公差之微小化雷射繞射式光學尺系統的研製

Fabrication of Compact Laser Diffraction Encoder System with High Alignment Tolerance

沈欣懋(Hsin-Mao Shen)

指導教授 ： 范光照

國立臺灣大學/工學院/機械工程學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.01099

摘要

隨著微/奈米技術的蓬勃發展，許多微/奈米加工或量測系統的開發都有賴於奈米等級之位移量測或定位技術；然而現今具長行程量測範圍及奈米解析度之感測器大多易受環境之干擾，且價格昂貴，於是如何開發同時具有微小化、高解析、低成本、易使用等優點之感測器，即是量測科技中一個重要的課題。
本文提出一種具高對位公差之微小化雷射繞射式光學尺系統，係為一光柵干涉儀，其原理是利用都卜勒效應，透過光柵尺將位移資訊轉換成干涉訊號，於是將量測之基準由雷射波長轉換為光柵節距，使環境所造成之量測誤差減小。
光學架構上，本光學尺利用分光系統以及偏極光學元件，能大幅提高光柵與光學頭間之對位公差，並獲得四正交之光學干涉訊號。在光學分析軟體之模擬下，印證了光路架構對於提高對位公差之可行性。文中也探討各光學元件在系統中之位置及角度公差，以作為光學頭機構及調校、組裝上之參考。
本文也同時開發出一套訊號解析流程。經由訊號處理電路，可有效補償因光學元件對位不良或光柵之偏擺造成之不完美正交訊號；此外，本研究以NI DAQ卡配合LabVIEW人機介面實現了訊號之計數與細分割，並建立起完整的量測程式與介面。
整合本論文創新之光學架構、光學量測原理與公差分析、訊號處理流程與量測程式之建立等成果，最後提出一簡易流程進行光學頭之調校與組裝，在光學桌上完成微小化雷射繞射式光學尺系統。經SIOS MI5000雷射干涉儀校驗後，在一般具有環境擾動的實驗室條件下，本光學尺系統在全行程10mm量測範圍內，誤差最大值為53nm，重複性在29.9nm以下。

關鍵字

光柵干涉儀 ； 雷射光學尺 ； 對位公差 ； 正交訊號

並列摘要

For the development of micro/nano technology, many nano manufacturing and measuring systems depend on the methodologies associated with metrology or positioning in the nanometer displacement scale. Sensors with long measuring distance and high resolution, however, are expensive and easily affected by the unstable environment. Thus, the need to have compact, high resolution, low cost and easy-to-use displacement sensors or sensing systems is becoming even more indispensable.
A newly developed compact laser diffraction encoder system with high alignment tolerance was developed during the course in this thesis. It is one type of the grating interferometer using grating to code the displacement information to the grating pitch by Doppler effect such that the measurement scale takes the place of grating pitch instead of laser wavelength and the errors caused by the unstable environment are reduced.
On the optical frame, the use of light division system and polarized optical components improve the head-to-scale tolerance substantially and produce four interference quadrature signals. The feasibility study to high alignment tolerance is achieved by the simulation of optics analysis software. The position and angle tolerances of each optical component are discussed in order to design the mechanism and furthermore calibrate and fabricate the optical head.
A series of signal processing procedure is also developed in this thesis. Errors in quadrature signals caused by misalignment of optical components or the oscillating of the grating can be compensated through the signal processing circuits. In addition, the count and interpolation methodology and the whole measurement program were accomplished with NI DAQ card and LabVIEW interface.
After the novel optical design, measurement principles, tolerance analysis, signal processing and measurement program were integrated, the compact laser diffraction encoder system was accomplished through several simple and easy adjustment and fabrication steps in an optical table. To 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 10mm, even running the calibration at regular laboratory environment, the maximum error is 53nm and the repeatability is below 29.9 nm.

並列關鍵字

grating interferometer ； laser encoder ； alignment tolerance ； quadrature signal

參考文獻

【3】 Ishizuka, K. and Nishimura, T. “Encoder with high resolving power and accuracy,” U.S. Patent No. 5,4164,085, 1992.

【4】 Dobosz, M. “Application of a divergent laser beam in a grating interferometer for high-resolution displacement measurements,” Opt. Eng., 33(3), 897-901, 1994.

【5】 Dobosz, M. (1994b), “New style probe with interferometric transducer for surface roughness and form profiling,” Opt. Eng., 33(3), 902-907, 1994.

【7】 D. H. Mollenhauer, P. G. Ifju, B. Han, “A compact, robust and versatile Moire interferometer,” Optics and Lasers in Engineering, 23(1), 29-40, 1995.

【10】 Sawada, R., Higurashi, E., Ito, T., Ohguchi, O. and Tsubamoto, M., “Monolithic-integrated microlaser encoder,” Appl. Opt., 38(33), 6866-6872, 1999.