| 摘要 |
<p>A switchable liquid crystal diffractive element (32) for use in an optical drive capable of reading multiple tracks of an optical disk (22) simultaneously, and writing or erasing at least one track of the optical disk is disclosed. When the liquid crystal diffractive element is in an 'on' state, it splits an incident beam into multiple beams suitable for simultaneously reading multiple tracks of an optical disk. When the liquid crystal diffractive element is in an 'off' state, it permits an incident beam to pass through without being split, for writing to an optical disk. Embodiments are disclosed that use multiple electrodes to create switching and non-switching regions of a liquid crystal element to form a switchable phase grating, and that use a switching liquid crystal element and a non-switching grating, or a birefringent non-switching grating, to form a switchable diffractive element.</p> |
