一種高對位公差之平面雷射繞射式光學尺之研製

Development of a Planar Laser Diffraction Encoder with High Alignment Tolerance

李博正(Bor-Cheng Lee)

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(2010年)

https://doi.org/10.6342/NTU.2010.10299

摘要

摘要

現今許多奈米加工與量測系統都有賴於奈米位移量測技術；然而，一般具長行程奈米解析度的感測器不僅昂貴還容易受到環境的影響，於是感測器的簡易化、低成本、高解析、不易受環境影響等是量測科技中重要的方向。

目前已發展出許多一維具有奈米解析度的感測器，但二維奈米解析度的感測器仍然稀少而且複雜；傳統的二維量測系統多由兩組一維量測系統組合而成，兩個一維量測系統的組裝對位將造成使用上的障礙，並且造成量測誤差的產生。綜合以上兩點，發展具高解析與準度之二維感測器是當前量測技術的重要課題。

本論文發展一種新的平面雷射繞射式光學尺(PDGI)，以平面光柵同時獲得二維的移動，並克服組裝對位上的問題。其為一種光柵干涉儀，原理是利用都卜勒效應，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，最後將光干涉訊號轉換成電壓訊號，經過解碼得知實際位移至1nm解析度。

光學架構上，本光學尺採用偏極光學元件設計特殊的光路，能大幅提高光柵與光學頭間之對位公差同時簡化光學系統，並獲得四組正交光學干涉訊號。另一方面，使用光柵模擬軟體模擬平面光柵，進而完成平面光柵的製作與驗證。利用光學架構上的特性設計了以平面光柵為轉換基準的高度量測系統。並在光學分析軟體的模擬下，確認了能有效地提高對位公差。在訊號解析上，採用NI DAQ卡配合LabVIEW，訊號修正後以計數與細分計算出位移。

完成之平面雷射繞射式光學尺(PDGI)之尺寸為40×40×45mm3。經德國SIOS NMM-1奈米定位平台校驗後，在25mm×25mm×5mm量測範圍內，兩軸最大誤差值分別在17nm,-20nm以下，量測重複性在15nm,11nm以下；高度軸最大誤差值在-20nm以下，量測重複性在12nm以下。

關鍵字

雷射光學尺 ； 平面光柵 ； 干涉 ； 繞射 ； 細分

並列摘要

Abstract
Nowadays, many nano manufacturing and measuring systems depend on the metrology in the nanometer displacement. However, sensors with long measuring distance and nano-scale resolution are not only expensive, but easily affected by the unstable environment. Thus, to develop sensors that have compact, low cost, high resolution, and low environment effect is becoming more indispensable.
Many 1D sensors with nano-scale resolution was been developed at present, but 2D sensors with nano-scale resolution are still scarce and complicated. Traditional 2D sensor use a pair of 1D sensors in crossed construction. The alignment tolerance among two 1D sensors become adoption barriers, and caused the metrology errors. To sum up, developed a 2D sensors with high resolution and accuracy is important topic of metrology currently.
In this thesis a novel planar diffraction grating interferometer (PDGI) is developed. Obtain 2D displacement with planar grating, and overcome alignment problem. It is a kind of grating interferometer which is based on the principle of light diffraction and Doppler Effect , and take the grating pitch as the length unit, instead of laser wavelength. It can reduce errors caused by the unstable environment. The interference signals are finally converted into voltage signals, and are decoded to the displacement with resolution of 1 nm.
In the optical system, the PDGI adopts polarized optical components to design special optical path that improved the head-to-scale tolerance substantially and simplifies the optical system, and obtain four interference quadrature signals. On the other hand, simulate planar grating by the grating analysis software, and then make one to put to the test. Use the feature of optical system to design Z-axis measure system which is based on the planar grating. And the high head-to-scale alignment tolerance is confirmed by the simulation of optics analysis software. In the signal processing, by combing NI DAQ and LabView, after the signal correction the displacement is calculated by pulse count and waveform interpolation.
The outcome size of PDGI is 40×40×45mm3. The Germany SIOS NMM-1 nano-stage was adopted as the calibration tool. Within the measuring distance of 25mm×25mm×5mm, the three axes measurement accuracy is below 17 nm, -20 nm and -20 nm and the measurement repeatability is below 15 nm, 11 nm and 12 nm.

並列關鍵字

Laser optical encoder ； Planar grating ； Interference ； Diffraction ； Interpolation

參考文獻

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