Patent ID: 7457217

Claim:
Method of measuring the tilt of an optical disc ( 2 ) in an optical disc drive ( 1 ), said method comprising: a step of directing to the optical disc during a normal phase (T OFF ), a first laser beam ( 32 ) having a first optical characteristic for writing/reading information into/from the optical disc, a step of deriving a first intermediate value (RES(OFF)) from a first normalized error signal obtained after reflection of said first laser beam ( 32 ) on the optical disc, a step of directing to the optical disc during a tilt-measuring phase (T ON ), said first laser beam ( 32 ) and a second laser beam ( 42 ) having a second optical characteristic, a step of deriving a second intermediate value (RES(ON)) from a second normalized error signal obtained after reflection of said first and second laser beams ( 32 , 42 ) on the optical disc, a calculation step of deriving a tilt-indicative signal (S TILT ) from the difference between said second and first intermediate values.