| 摘要 |
An optical pickup apparatus includes a light source for generating a coherent beam, a spatial light modulator having a central region arranged on an optical axis of the coherent beam and an annular region arranged in a manner surrounding the central region, to spatially separate a transmission component of the coherent beam through the central region and a transmission component through the annular region thereby producing a reference beam and a signal beam and propagating those coaxially in a same direction, an objective lens optical system arranged on the optical axis and for illuminating the signal beam and the reference beam coaxially toward the hologram record layer and causing the reference beam and the signal beam to focus on focal points different from each other, image detecting means arranged on the optical axis and for receiving a beam returning from the hologram record layer through the objective lens optical system when the reference beam is illuminated to the hologram record layer; and a polarization-plane rotating device having a central polarizing region arranged on the optical axis and an annular polarizing region arranged in a manner surrounding the central polarizing region and for making transmission components through the central and annular polarizing regions different in rotation angle on the polarization plane from each other.
|
