Journal of Control Science and Engineering
Volume 2007 (2007), Article ID 36319, 10 pages
doi:10.1155/2007/36319
Research Article
Detection of Surface Defects on Compact Discs
1KK-Electronic a/s, Jens Juuls Vej 40, Viby J 8260, Denmark
2Section of Automation and Control, Department of Electronic Systems, Aalborg University, Fredrik Bajers Vej 7C, Aalborg 9220, Denmark
Received 15 November 2006; Revised 23 April 2007; Accepted 13 August 2007
Recommended by Tomas McKelvey
Abstract
Online detection of surface defects on optical discs is of high importance for the accommodation schemes handling these defects. These surface defects introduce defect components to the position measurements of focus and radial tracking positions. The respective controllers will accordingly try to suppress these defect components resulting in a wrong positioning of the optical disc drive. In this paper, two novel schemes for detecting these surface defects are introduced and compared. Both methods, which are an extended threshold scheme and a wavelet packet-based scheme, improve the detection compared with a standard threshold scheme. The extended threshold scheme detects the four tested defects with a maximal detection delay of 3 samples while the wavelet packet-based scheme has a maximal detection delay of 6 samples. Simulations of focus and radial positions in the presence of a surface defect are performed in order to inspect the importance and consequences of the size of the detection delay, from which it can be seen that focus and radial position errors increase significantly due to the defect as the detection delay increases.