Switchable filter for modulating laser intensity and reducing la

Details Switchable filter for modulating laser intensity and reducing la Switchable filter for modulating laser intensity and reducing la

1992-11-13

1997-02-25

Hindi, Nabil Z.

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369121, 369110, G11B 700

Patent

active

056065418

ABSTRACT:
This invention provides an optical disk device with a switchable filter for reducing the light intensity from a write level to a read level or an erase level. The filter can further be used to modulate the light intensity between a write level and a gap level for the process of recording data. For semiconductor laser sources, this filter reduces laser feedback noise by allowing the laser to operate at a higher, more stable power level during data sensing, and by reducing the amount of light reflected from the storage disk back to the laser cavity. Because the filter transmission can be high during the write process, the power requirements of the semiconductor laser are not increased in the device of this invention. In one embodiment, the switchable filter of this invention includes a variable retarder with means to select light on the basis of its phase or polarization, for example, with polarizers. This retarder can comprise a liquid crystal cell wherein either the optical orientation or retardance is electro-optically tunable.

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