| 摘要 |
PURPOSE: A method for compensating the distortion of an optical axis is provided to adjust a focus lens in a horizontal direction, when a beam spot emitted from a light emitting element such as a laser diode and reflected by a recording surface of an optical disk is formed in a position out of an X-Y axis from a center of a light collecting element such as a photo diode. CONSTITUTION: When an optical disk is stably mounted(S10), a microcomputer moves a focus lens to the optical disk from an initial set position(S12) and detects a signal level and a waveform of an FE(Focus Error) signal(S14). Whether the signal levels and waveform in a high section and in a low section of the FE signal are symmetric each other is decided(S16). If so, a normal state is decided(S30). If not symmetric, whether the signal level and waveform of the FE signal in the high section is smaller is decided(S18). If so, the beam spot is decided to be improperly formed in a B or D area of a 4-divided light collecting element, out of X-Y axis(S20). A track offset voltage is supplied to an actuator to move the beam spot formed in the B area to a central position(S22). Whether the signal level and waveform in a high section and in a low section of the FE signal are symmetric each other is decided(S24). If not symmetric, the track offset voltage is variably supplied to move the beam spot formed in a D area to a central position(S26). And normal focusing and tracking operations are performed(S28).
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