| 摘要 |
PURPOSE:To eliminate the need for an objective lens and objective lens driving device, and a tracking focus error signal detector by providing lens-shaped projections for condensing collimated beams of light on a transparent plastic substrate surface. CONSTITUTION:The lens-shaped projections 4 for condensing the collimated beams of light from the optical pickup are provided by every pit or every recording track on the surface of the transparent plastic substrate. The lens- shaped projections formed on the disk surface is irradiated with the luminous flux transmitted through an aperture. Since the lens-shaped projections are provided to be focused so as to condense the light to the recording track surface, there is no need for focus servo. On the other hand, the light with which the recessed parts of the projections is irradiated is condensed to the two points A, B, but the value of d is taken as large as about 50mum in order to prevent the failure in obtaining reproduced signals by the deficiency of the light quantity at this time. The need for the objective lens and the objective lens driving device and tracking focus error signal detector is eliminated and the thickness of the optical pickup is reduced. |
