Koninklijke Philips Corporation N.V.

Chee Kang Thong

Rain Jilin Zhang

Bin Chye Lim

The invention relates to a method for preventing interchange of a first optical information carrier () with a second optical information carrier in an optical drive. Initially, the light () is focused at the first optical information carrier () in the optical apparatus followed by the steps of detecting reflected light () from the first optical information carrier () and generating a plurality of signals (CA, RF, FE) from the detected light (), such as a focus error signal (FE). Upon obtaining an indication of a signal, e.g. the focus error signal (FE), is absent or reduced below a certain level, there is a step of assessing if the first optical information carrier () has been removed from the optical drive. If removed, reproduction of information by the optical drive is made impossible until some pre-determined measures have been taken, e.g. restart of the optical drive or other measures.

Method for preventing interchange of optical information carriers

A method and device are disclosed for improving reliability of reading an optical storage medium, such as an optical disc (). A disc spin speed value () of the optical disc () is provided and an unnormal value of said disc spin speed value (), which differs from a disc spin speed value within a range of nominal disc spin speed values, is detected, indicating normal spinning operation of said optical disc (). By using this method, the spinning loss of an optical disc, e.g. due to insufficient disc clamping force, is detected fastly and reliably, in a manner resulting in a reduced risk of damaging the disc and disc reader during such spinning loss. Further actions may be taken in both cases, including disabling the drive in order to prevent damage of the disc or to thwart such illegal usage.

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Singapore, Singapore

Chee Kang Thong