Focus jump device for reproducing information from a storage medium

A focus jump device which is adapted to be used in an information reproduction apparatus for reproducing information from a storage medium having at least two recording layers or used in an information recording apparatus for recording information onto the storage medium and which moves a focus position of a light beam in a direction perpendicular to the storage medium to the focus position corresponding to a target recording layer so that the light beam is irradiated on the target recording layer, said device comprising:

• a focus position moving unit for moving the focus position of the light beam;
• a focus error signal detector for detecting a focus error signal based on a variation of a returning light from the storage medium, the variation of the returning light being based on a variation of the focus position of the light beam with respect to the recording layer;
• a feedforward controller for supplying a drive signal to the focus position moving unit to move the focus position of the light beam in an acceleration state in an acceleration control mode and to move the focus position of the light beam in a deceleration state in a deceleration control mode;
• a linearizing converter for linearizing the focus error signal, which is detected by the focus error signal detector during an interlayer jump for moving the focus position of the light beam to the target recording layer triggered by the acceleration control;
• a reference position setting unit for setting a reference position indicating the focus position variation according to a passage of time as a target value;
• and
• a position controller for comparing an output value of the linearizing converter with a target value to generate an error, and for outputting the drive signal to the focus position moving unit to reduce the error thereby to control the focus position of the light beam.