Methods and apparatuses for detecting a modulation transition in an optical storage medium

Circuits, architectures, systems, methods, software, and algorithms for detecting a modulation transition (e.g., a change from a written portion containing RF-modulated data to an unwritten portion containing only a wobble signal modulation) on an optical storage medium. The method generally includes steps of focusing a first spot of light onto an optical storage medium, wherein the first spot is substantially centered on a first track of the optical storage medium, focusing a satellite spot of light onto an optical storage medium, wherein the satellite spot at least partially overlaps a track adjacent to the first track, generating a satellite signal from light reflected from the optical storage medium from the satellite spot, and detecting the modulation transition by detecting a change in a level of the satellite signal. The present invention advantageously provides for detecting a modulation transition between a main (current) track and an adjacent (next) track, so that demodulation of a signal from an optical storage medium can be smoothly switched from one mode to another.