US 7,558,184 B2
	Optical pickup device
Kenji Nagatomi, Gifu (Japan); Seiji Kajiyama, Gifu (Japan); and Tetsuhisa Hosokawa, Yokohama (Japan)
Assigned to Sanyo Electric Co., Ltd., Osaka (Japan)
Filed on Sep. 06, 2005, as Appl. No. 11/218,783.
Claims priority of application No. 2004-303989 (JP), filed on Oct. 19, 2004.
Prior Publication US 2006/0083147 A1, Apr. 20, 2006
Int. Cl. G11B 7/00 (2006.01)

U.S. Cl. 369—121  [369/112.03]

8 Claims

1. An optical pickup device, comprising: a semiconductor laser that houses three emission elements, respectively emitting reference, first, and second laser beams having different emission wavelengths and optical axes, in a single package; and a diffraction grating for matching by a diffraction effect, the optical axis of the first laser beam with the optical axis of the reference laser beam, wherein a numerical aperture of the first laser beam incident on an objective lens is greater than a numerical aperture of the second laser beam on the objective lens, and the diffraction grating is disposed in an optical path between the semiconductor laser and the objective lens, wherein the three emission elements are housed in the single package such that a distance between the emission element emitting the first laser beam and the emission element emitting the reference laser beam in a direction perpendicular to the optical axis of the reference laser beam is greater than a distance between the emission element emitting the second laser beam and the emission element emitting the reference laser beam in a direction perpendicular to the optical axis of the reference laser beam.