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An Auto-Focusing Method in a Microscopic Testbed for Optical Discs

By Xiao Tang, Pierre L&apos and Yu Xiao


this paper. Key words: auto-focus; disc testbed; optical discs; standard deviation. Accepted: July 20, 2000 Available online: 1. Introduction In an optical vision system, an autofocusing element plays an important role. An objective lens collects light from the object and makes a clear image at the focal plane if the distance between the object and the objective lens is perfectly controlled to meet the focusing condition. A feedback signal is always needed for the controlling system. There are many kinds of feedback signal that can be used for this purpose in different systems. For example, an astigmatic field lens and a quad-detector (hardware) are used to create a focusing feedback signal in Compact Disc (CD) drives [1]. For digital image signals grabbed via a CCD camera, the feedback signal for autofocusing can be extracted from the image itself by software using Fourier transforms [2]. A

Year: 2000
DOI identifier: 10.6028/jres.105.046
OAI identifier: oai:CiteSeerX.psu:
Provided by: CiteSeerX
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