title: An Auto-Focusing Method in a Microscopic Testbed for Optical Discs.
abstract: An auto-focusing method in a digital image system is demonstrated that uses a standard deviation of pixel gray levels as a feedback signal. In this system, an optical microscope and a charge coupled device (CCD) camera are used to create clear pit images of optical discs. A dynamic focusing scheme is designed in the system-control software, which is able to eliminate environmental disturbances and other noises so that a fast and stable focus can be achieved. The method shows an excellent focusing accuracy. The performance and possible applications of this method are discussed. The test results for optical discs are given in this paper.
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-0001.
authors.forename: X
authors.initials: X
authors.lastname: Tang
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-0001.
authors.forename: P
authors.initials: P
authors.lastname: L'Hostis
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, MD 20899-0001.
authors.forename: Y
authors.initials: Y
authors.lastname: Xiao
keywords: auto-focus; disc testbed; optical discs; standard deviation