Time localisation of surface defects on optical discs

Odgaard, Peter Fogh; Wickerhauser, Mladen Victor

doi:10.1109/cca.2004.1387196

Cited by 7 publications

(10 citation statements)

References 4 publications

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“…Other reasons for fast common channel parameter variations are: dust, fingerprints, scratches on the disc, dropouts, etc. [20], [22]. These observations lend support to the assumed parameter model, not just for TwoDOS but also for other 2-D storage systems.…”

Section: Minimum-latency Adaptationsupporting

confidence: 52%

Minimum-Latency Tracking of Rapid Variations in Two-Dimensional Storage Systems

et al. 2007

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The trend of increasing storage densities results in growing sensitivity of system performance to variations of storage channel parameters. To counteract these variations, more adaptivity is needed in the data receiver. Accurate tracking of rapid variations is limited by latencies in the adaptation loops. These latencies are largely governed by delays of the bit detector. In two-dimensional storage systems, data are packaged in a group of adjacent tracks or rows, and for some of the rows the detection delays can increase dramatically with respect to one-dimensional systems. As a result, the effective latencies in the adaptation loops preclude the tracking of rapid variations and really limit the performance of the system. In this paper, a scheme is proposed that overcomes this problem and that can be used for timing recovery, automatic gain control, and other adaptive circuits. Rapid variations for all the rows are tracked using control information from rows for which detector latency is smallest. This works properly if rapid variations are common across the rows as is the case, for example, for the two-dimensional optical storage (TwoDOS) system. Experimental results for TwoDOS confirm that the scheme yields improved performance with respect to conventional adaptation schemes.

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Section: Minimum-latency Adaptationsupporting

confidence: 52%

Minimum-Latency Tracking of Rapid Variations in Two-Dimensional Storage Systems

et al. 2007

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“…The results using the new residuals show an improvement by 6 samples in the beginning and 3 samples in the end. In [26] an extention of the threshold method used on the new residuals is presented, using this method results in an avarage improvement of the fault localization of 6-8 samples in both the begining and the end of the fault. This improvement can seem less significant compared to duration of the scratch which is 441 samples, but many practical experiments with fault tolerant control in CD players have shown that an improvement of a few samples of the fault detection means a lot in the achieved controller performance.…”

Section: Discussion On the Estimated Signalsmentioning

confidence: 97%

“…The intersection between this tangent plane and is consequently an approximation of (26). Finding the intersection, gives a and at a given iteration this gives an update in which is denoted This approximation can again be used as a starting point for a new tangent plane and a new intersection is computed.…”

Section: A the Scaling Projection Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Detection of surface defects and servo signal restoration for a compact disc player

Odgaard

Stoustrup

Andersen

et al. 2006

IEEE Trans. Contr. Syst. Technol.

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Compact disc (CD) players have been on the market for more than two decades, and the involved technologies, including control are very mature. Some problems, however, still remain with respect to playing CDs having to surface defects like scratches and fingerprints. Two servo control loops are used to keep the optical pick-up unit (OPU) focused and radially locked to the information track of the CD. The problem is to design servo controllers which are well suited for both handling surface defects and disturbances like mechanical shocks. The handling of surface defects requires a low-controller bandwidth which is in conflict with the requirement for the handling of disturbances. This control problem can be solved by the use of a fault tolerant control strategy, where the fault detection is very important. The OPU feeds the controllers with detector signals. Based on these, focus and radial distances can be estimated and a pair of residuals can be computed. This paper introduces a model-based method to estimate focus and radial distances as well as residuals, which have the potential to improve the control of a CD player in case of a surface defect. The methods are applied to experimental data of a scratch. The results of this experimental work show the potential of the method.

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“…From the focus and radial residuals, α f [n] and α r [n], faults are extracted based on the algorithm described in (Odgaard and Wickerhauser 2004). From a large number of CDs, with scratches, sequences with detected scratches are extracted into a column vector with the length of 256=2 8 samples.…”

Section: Training Datamentioning

confidence: 99%