| 摘要 |
A photo detecting device and a reproducing apparatus for a multilayered holographic information storage medium using the same are provided to focus a signal beam to a first focus and to focus a reference beam to a second focus, using a lens unit, so as to reproduce data at high speed and to prevent optical detectors from moving in an axial direction. A holographic information storing/reproducing device comprises an information recording device(100) and an information reproducing device(500). The information recording device has a light source(110), a lens unit(200), and a driving part(220). The lens unit sorts the light from the light source into a reference beam(R) passing through a first area(I) and a signal beam(S) passing through second areas(II). The lens unit includes a first lens(210) which focuses the signal beam to a first focus(F1) and a second lens(230) which focuses the reference beam to a second focus(F2). The area of the second lens has a first flat area(210A) having no refractive force and first lens areas(210B) having refractive force. First beam cutoff parts(250) are placed on the optical path between the second lens and a holographic information storage medium(300).
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