| 摘要 |
PURPOSE:To remove zero-order diffracted light from a reflected wave and to improve an SN ratio of an information regenerative signal by preparing a wedge at the incident side of a reference beam of a hologram lens placed on an optical recording medium. CONSTITUTION:A laser beam with P polarization is made incident to a hologram lens 1 via a polarized light beam splitter 7, a lambda/4 plate 8 and a wedge 10 with a wedge angle of 8 deg.. Diffracted light (solid line) is reflected at a recording midium 6, through the hologram lens 1, the wedge 10 and the lambda/4 plate 8, changes to an S polarized light beam and reflected at the beam splitter 7 to be made incident to an optical detector 9. On the other hand, a zero-th diffracted beam emitting from the central part of the hologram lens 1 is made incident to the recording medium 6 at a minute angle of indidence and its reflected light is not made incident to the optical detector 9, therefore, an SN ratio of an information regenerative signal is improved. |
