Lsi Logic Corporation

Philip J Armitage

David I Boddy

Brian E Merrigan

A method of determining interrupts in data on an optical disc, the data supported in a signal envelope subject to variation by mirror modulation and said interrupts. The method comprises the steps of (A) filtering the signal envelope to generate a first signal; (B) re-biasing the first signal to produce an intermediate signal having voltage swings attributable to the mirror modulation; (C) defining a slice level below a reference level to sample the mirror modulation to produce a mirror signal; (D) slicing the intermediate signal to generate the mirror signal containing a pulse resulting from a level transition through the slice level associated with re-biasing of the positive transition component; and (E) registering the presence of the pulse during the on-track mode of operation to identify the interrupt in data on the optical disc.

Apparatus and method of interrupt detection in an optical disc environment

In the context of mirror modulation ( ) extraction during track seek or jump modes of an optical disc reading device ( ), such as a DVD ROM, a mirror averaged level (i.e. the dc level ( ) of the RF envelope ( )) is held so that the mirror modulation ( ) is seen as a swing below a set mirror rebias level ( ) at an output of a mirror amplifier ( ), as shown in FIG. . With the holding of the dc level ( ) by a ground-referred capacitor ( ) during seek operation of the device ( ), a first input (n ) to the mirror amplifier varies with the mirror modulation, whereas a second input (p ) to the mirror amplifier ( ) does not vary. This phenomenon enables the top level of a RFRP signal ( ) to be defined by the mirror rebias level ( ) and the mirror component swing (during seek operation) to be optimized and always to occur below the mirror rebias level ( ). During on-track operation, the first input (n ) and the second input (p ) are essentially equal and so the RFRP signal ( ) sits at the dc level ( ). Being able both to define the mirror rebias level ( ) and to vary a gain ( ) of the mirror amplifier ( ) allows a swing, arising from the mirror modulation, in the RFRP signal ( ) to be optimally positioned in relation to top and bottom hold circuits ( ) used for definition of a slice level ( ) for mirror recovery purposes.

Apparatus and method providing a mirror averaging function to generate a mirror signal from optical data on an optical disc

An mixer includes a differential signal input, a differential local oscillator input, a gain control input and a differential signal output. The mixer has a stepped signal gain from the differential signal input to the differential signal output which is variable from a first gain to a second, different gain as a function of the gain control input and has a substantially constant DC common mode output bias voltage at the differential signal output.

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Oldham, United Kingdom

Philip J Armitage