光學顯微鏡高速自動對焦演算法

A High Speed Auto-focusing Algorithm for Optical Microscope

曾志濤(Chin-Tao Tseng)

指導教授 ： 章明

中原大學/工學院/機械工程學系/碩士(2009年)

https://doi.org/10.6840/cycu200900404

摘要

在自動化生醫觀測與光學檢測領域中，顯微鏡為一基本常用的設備，其自動對焦功能為一基本的需求，可靠的自動對焦技術能夠快速、有效率的找到最佳的對焦位置，簡化使用者反覆的操作，提高工作效率，以應付龐大的樣本檢測與觀察的需要。
在顯微鏡自動對焦的技術中，清晰度為一常用辨別對焦的方法，但現有文獻中的清晰度演算法常有其特定限制而無法有效的應用在不同顯微鏡系統上，且運算速度無法符合高速對焦的需求，因此本文提出一種新的清晰度演算法，結合一維Hilbert轉換以及Pearson相關性，在各種不同顯微鏡的環境下，都能夠快速、準確的對焦到清晰的影像。
本研究根據文獻所提出的四種指標與計算時間來評比本演算法與另七種常用的清晰度演算法的效能，實驗結果顯示本演算法不僅能夠在各種顯微鏡環境下都有良好的對焦效果，在運算速度、準確度、一致性及抗雜訊能力上也都有極佳的表現。

關鍵字

光學顯微鏡 ； 自動對焦 ； Hilbert轉換 ； Pearson相關性

並列摘要

Microscope is a fundamental instrument for automated biomedical observation and optical inspection. The auto-focusing function of the microscope is a basic demand. Reliable auto-focusing technology can find the best focus position quickly and efficiently. This simplifies user involvement in the examination of a number of specimens as repeatability is better with auto-focusing.
Sharpness is commonly used method to find focus position in microscope auto-focusing technology. The existing algorithms are often restricted to their specific target and can not be effectively applied at different microscope systems. Furthermore, execution speed is unable to provide the demand of high-speed focus. This paper presents a new sharpness algorithm, combining one-dimensional Hilbert transform and Pearson correlation. It can focus the distinct image with high speed and accurately at versatile microscopes.
This study has considered four criterions, accuracy, range, number of false maxima, FWHM, and execution time to estimate the performance of the proposed algorithm. Experimental results show that the developed algorithm provides a good performance in focusing with high speed, accuracy, consistency and the ability of anti-noise in comparison to adoption of other seven algorithms.

並列關鍵字

Optical microscope ； Auto-focusing ； Hilbert transform ； Pearson correlation

參考文獻

[23] 陳培榮，“白光干涉儀高速低成本自動對焦系統，” 中原大學機械工程學系碩士論文，pp.10~14，2008年。

[2] J. F. Brenner, B. S. Dew, J. B. Horton, J. B. King, P. W. Neirath, and W. D. Sellers “An automated microscope for cytologic research a preliminary evaluation,” Journal of Histochemistry and Cytochemistry, Vol.24, No.1, pp.100~111, 1976.

[5] S. K. Nayar and Y. Nakagawa, “Shape from focus,” Proceedings of the IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol.4, No.8, pp.824~831, 1994.

[6] M. L. Mendelsohn and B. H. Mayall, “Computer-oriented analysis of human chromosomes–Ⅲ focus,” Comput. Biol. Med., Vol.2, pp.137, 1972.

[7] F. Groen, I. T. Young, and G. Ligthart, “A Comparison of different focus functions for use in autofocus algorithms,” Cytometry, Vol.12, pp.81~91, 1985.