| 摘要 |
The invention relates to optical memories.
<??>A focusing mechanism for an optical head comprises a light source 103A, 103B which is moved by an actuator 105 on the optical axis of a lens 101, one face of which carries a diffraction grating constituted by a Fresnel microlens 102. The movement of the light source enables the image point 104A, 104B to move while keeping the lens in a fixed position.
<??>Application to optical-disc readers.
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