| US 7,468,942 B2 | ||
| Optical pickup, optical element, and information reproducing apparatus configured for use with any of plural types of recording media | ||
| Katsuhiro Koike, Tsurugashima (Japan); Koichi Maruyama, Tokyo (Japan); and Shuichi Takeuchi, Saitama (Japan) | ||
| Assigned to Pioneer Corporation, Tokyo-to (Japan); and Hoya Corporation, Tokyo (Japan) | ||
| Filed on May 07, 2004, as Appl. No. 10/840,479. | ||
| Claims priority of application No. P2003-131262 (JP), filed on May 09, 2003; and application No. P2004-012270 (JP), filed on Jan. 20, 2004. | ||
| Prior Publication US 2004/0223442 A1, Nov. 11, 2004 | ||
| Int. Cl. G11B 7/135 (2006.01) | ||
| U.S. Cl. 369—112.07 [359/569] | 19 Claims |
| 1. An optical pickup comprising:
a light source for emitting a plurality of laser beams with different wavelengths; and
an objective lens for focusing the laser beams emitted from said light source on recording surfaces of plural types of information
recording media, wherein
a diffractive lens structure is provided in a light path of said laser beam, said structure including ring zone areas divided
by a plurality of phase steps for correcting a wavefront aberration of said laser beam,
a diameter of an outermost phase step of said diffractive lens structure is smaller than a second largest effective diameter
of effective diameters required for reproduction of said plural types of information recording media,
wherein a focused point of a reproducing laser beam which passes through said diffractive lens structure during reproducing
at least one of those of said plural types of information recording media that are other than an information recording medium
requiring a largest effective diameter for reproduction, resides between (i) a position at which an optical axis meets said
laser beam passing through a height corresponding to an effective diameter required for reproduction of said information recording
media, and (ii) a position at which the optical axis meets said laser beam passing through an innermost of an area outside
said outermost phase step, and
wherein the edge angles of all the phase steps are obtuse angles more than 90 degrees.
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