| US 7,590,043 B2 | ||
| Optical pickup and optical information recording apparatus using the same | ||
| Kunikazu Ohnishi, Yokosuka (Japan); Tomoto Kawamura, Yokohama (Japan); and Masayuki Inoue, Yokohama (Japan) | ||
| Assigned to Hitachi, Ltd., Tokyo (Japan); and Hitachi Media Electronics Co., Ltd., Iwate-Ken (Japan) | ||
| Filed on Oct. 02, 2007, as Appl. No. 11/905,529. | ||
| Application 11/905529 is a continuation of application No. 10/687910, filed on Oct. 20, 2003, granted, now 7,327,661, filed on Feb. 05, 2008. | ||
| Claims priority of application No. 2002-306471 (JP), filed on Oct. 22, 2002. | ||
| Prior Publication US 2008/0031104 A1, Feb. 07, 2008 | ||
| This patent is subject to a terminal disclaimer. | ||
| Int. Cl. G11B 7/00 (2006.01) | ||
| U.S. Cl. 369—112.03 [369/112.12; 369/112.11; 369/112.07] | 2 Claims |
| 1. A beam separation device for an optical pickup configured to separate a laser light beam emitted by a laser light source
into at least three light beams comprising:
the beam separation device being divided into first, second and third areas, each of which has a prescribed periodic structure,
the first area is placed between the second and third areas,
the second area has periodic structure that is shifted from that of the first area by approximately 90° in the phase of the
periodic structure, and
the third area has periodic structure that is shifted from that of the second area by approximately 180° in the phase of the
periodic structure.
|