International Business Machines Corporation

Hiroshi Matsushita

Koichiro Nanke

Edwin Ralph Childers

David P McReynolds

Henry E Aviles

Tetsuya Kokubo

Kouji Takahashi

The invention is an optical disk drive which controls mechanical feedback to a focus servo actuator by shifting the phase of the feedback along its path back to the servo an additional 180 degrees to eliminate the degradation of the phase margin and prevent servo instability. The phase shift may be induced at any practical location along the feedback path. The phase shift is preferably induced by creating a slit or opening in the base of the optical disk drive. The opening must be positioned properly, shaped appropriately, and large enough to create a new base resonant frequency which prevents the opposite sides thereof from vibrating in phase. Alternatively, the phase shift may be induced by altering other components in the feedback path. For example, the phase shift can be induced by modifying the spindle motor assembly to create a new spindle resonant frequency.

Phase shifting feedback control in an optical disk drive

The invention is an information reproduction apparatus provided with supporting means for supporting a recording medium, a drive source for moving the recording medium between the initial insertion position and the reproduction position by driving said supporting means, transmission means for transmitting the driving force of said drive source to said supporting means, retraction means operable to force a transmission element to retract from said transmission means, said transmission element being a part of said transmission means, and motion means operable to force the recording medium to move from the reproduction position to the initial insertion position under the condition that said transmission element is not engaged in said transmission means. In forcibly moving said supporting means, when the drive is out of operation, said supporting means are released from the drive force by means of said retraction means, freeing the supporting means from the resistance force of the drive force.

Recording medium emergency release mechanism

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Atsugi, Japan

Hiroshi Matsushita