應用於白光干涉測量之嵌入式抑制線上振動系統開發

Development of an In-Situ Vibration-Resistance System for White-Light Interferometric Measurement

何仁杰(Calvin Ho)

指導教授 ： 曾百由

國立臺北科技大學/機電學院/機電整合研究所/碩士(2011年)

摘要

本研究在發展一套以嵌入式微控制器為基礎的控制單元，作為在自動化光學檢測中普遍需要使用的振動偵測與補償系統。本研究針對使用白光干涉顯微量測系統為目標。由於白光干涉量測技術具有量測微奈米級檢測物與大範圍量測之特性，但相當容易受到環境振動而影響到其量測精度。尤其在進行步階掃描位移取像來進行 3D 形貌辨識的取像時最容易因為振動而造成形貌辨識的精確度下降。所以許多振動補償的技術被開發及討論來完成更精確的白光干涉顯微量測系統。一般的振動補償系統使用以個人電腦為基礎的控制架構，透過影像擷取卡，並搭配雙相機同步取像後經 PC 程式運算以獲得即時的環境振動之位移資訊後，做振動補償並控制白光干涉量測用相機取得正確量測深度的白光干涉圖譜影像，完成垂直掃描後即可利用傳統的白光干涉演算法來得到待測物之三維形貌。
由於 PC Base 的架構並非專用的設計，所以雖然軟硬體設計及架設容易，但因資源利用率的諸多限制，使得振動補償控制的頻率無法提升。再則所需搭配的影像擷取卡價格也高，若要將研究成果商品化可能因價格過高而無法上市。
本系統是藉由性能/價格比極佳的 32-Bit 嵌入式微處理器為控制核心，將振動偵測與補償系統所需的影像擷取硬體、類比至數位轉換器、數位輸出及輸入介面以及通信介面整合為一單板式的嵌入式系統。由開發結果證實可將包括振動偵測之觸發取像與取像後計算補償輸出時間總合在 300us 內完成，大大減少原有 PC Base 系統中需要耗費約 10 ~ 15 ms 的時間。可以有效的提高振動補償頻率及提高白光干涉圖譜影像取得的精確性。

關鍵字

嵌入式微處理器 ； 白光干涉 ； 步階掃描 ； 振動 ； 補償 ； 形貌辨識

並列摘要

In this study, an embedded real-time controller based on ADI Blackfin BF561 was developed to improve the performance of vibration-resistance system used in white-light interferometer. The purpose of this embedded control system is to detect the vibration and compensate it for White Light Interferometer when processing stepping photograph grabbing for surface profile measurement.
The active interferometer has been approved as an effective architecture to increase the precision of surface profile measurement by detecting the movement caused by vibration then stabilized by piezoelectric transducer. However, most of active interferometers were implemented in PC based platform. It’s easy to be setup and modulized but the latency of image grabbing processing , algorithm mathematic and I/O trigger delay is around 10~15ms and the latency is variant if different PCs are used.
A customized embedded control system with a 600MHz high performance microprocessor, Camera Link interface, DAC circuit and UART command port. A completed command set has also been defined to interface with interferometer for close loop control. The latency has been reduced and fixed to 250us as tested for all the procedures from CCD trigger to PZT control signal output. With the advantage of fixing latency, the response of interferometer can accelerated so that the overall accuracy vibration-resistance will be improved in the range of a few nanometer

並列關鍵字

Embedded Microcontroller ； White Light Interferometer ； Steppingphotograph grabbing ； vibration ； Compensate ； surface profile

參考文獻

[2] D. Wu, R.H. Zhu, L. Chen, J.Y. Li, (2002), “Transverse spatial phase-shifting method used invibration compensated interferometer,” Optik 115, No.8.

[3] X. Li, T. Yamauchi, H. Iwai, Y. Yamashita, H. Zhang, and T. Hiruma,(2006), “Full-field quantitative phase imaging by white-light interferometry with active phase stabilization and its application to biological samples,” Opt. Lett. 31, 1830-1832.

[4] T. Yamauchi, H. Iwai, M. Miwa, and Y. Yamashita, (2007), “Measurement of topographic phase image of living cells by white-light phase-shifting microscope with active stabilization of optical path difference,” Proc. SPIE 6429, 64291Q.

[5] J. Schmit and A. G. Olszak and Shawn McDermed, (2002), “White light interferometry with reference signal,” Proc. of SPIE, vol. 4777, pp. 102-109.

[7] C. L. Koliopoulos, “Simultaneous phase shift interferometer, (1991),” SPIE Vol. 1531 Advanced Optical Manufacturing and Testing, pp119-127.