Abstract: Disclosed is an apparatus for reading information recorded on the track of a data carrier (1). The apparatus comprises rotating means (2) for supporting and rotating the data carrier (1) around an axis of rotation (3). The rotating means (2) comprises a turntable (21) and a motor (23) for rotating the turntable (21). The apparatus according to the invention is able to suppress a wobble introduced by the data carrier (1) when rotated. This is done by a flexible part (24) in the rotating means (2). In an embodiment the supporting surface of the turntable (21) comprises the flexible part (24). This allows the data carrier (1) to tilt in radial and tangential direction. The centrifugal forces, which are present when rotation the data carrier (1), are able to level the data carrier (1), thus reducing the wobble.

Abstract: 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 (IS).

Abstract: A method is described for measuring the thickness of an optical disc and determining whether the disc is a CD or a DVD. The optical lens is caused to move towards the disc with a substantially constant speed, with the optical beam switched on, and the focal error signal (FES) is analyzed. By timing the S-shaped curve (62), the actual value of said speed is determined. By timing different reflections (72, 73) from the disc, taking into account the measured speed, the thickness of the disc is determined. An important advantage is that the outcome of the thickness measurement is substantially independent from the actual value of said speed, and thus independent from the actual sensitivity of the actuator.

Abstract: An optical disc drive (I) comprises an optical pickup (3) with a 4-quadrant photo-detector (20); an objective lens (14) mounted displaceably with respect to the photo-detector (20); an optical displacement actuator (30) for displacing the objective lens (14); and a servo controller (70) for controlling the focus actuator (30). The controller (70) receives respective detector signals (S1, S2, S3, S4) from the photo-detector (20). The controller (70) is adapted to process these detector signals to produce a focal error signal (FE) which is zero if these signals all have identical magnitude. The controller (70) is further adapted to subtract/add an offset parameter (?off) from/to said focal error signal (FE), and to provide the difference/sum as a control output signal.

Abstract: Disclosed is an apparatus for reading information recorded on the track of a data carrier (1). The apparatus comprises rotating means (2) for supporting and rotating the data carrier (1) around an axis of rotation (3). The rotating means (2) comprises a turntable (21) and a motor (23) for rotating the turntable (21). The apparatus according to the invention is able to suppress a wobble introduced by the data carrier (1) when rotated. This is done by a flexible part (24) in the rotating means (2). In an embodiment the supporting surface of the turntable (21) comprises the flexible part (24). This allows the data carrier (1) to tilt in radial and tangential direction. The centrifugal forces, which are present when rotation the data carrier (1), are able to level the data carrier (1), thus reducing the wobble.