DISC DRIVE APPARATUS

摘要

A method for controlling an axial position of an objective lens in an optical system of an optical disc drive apparatus, the method comprising the steps of: generating a reference signal (SREF) representing a desired amount of focal error; generating a focal error signal (SFE) representing the actual focal error; generating a focal offset error signal (Sfo) representing the actual focal offset error (FOE); adding the focal offset error signal (SFo) to said reference signal (SREF), and subtracting said focal error signal (SFE), to obtain a result signal (SRES); generating an focal actuator control signal (ScF) on the basis of said result signal (SREs = SREF + SFO. The actual focal offset error (FOE); may be calculated from a lens shift (LS) representing signal on the basis of a predetermined relationship between focal offset error (FOE) and lens shift (lS).