	US 7,518,976 B2
	Optical head with light sources of different wavelength
Kousei Sano, Osaka (Japan); Yoshiaki Komma, Hirakata (Japan); and Toshiyasu Tanaka, Osaka (Japan)
Assigned to Panasonic Corporation, Osaka (Japan)
Appl. No. 10/543,537 PCT Filed Jan. 27, 2004, PCT No. PCT/JP2004/000689 § 371(c)(1), (2), (4) Date Jul. 27, 2005, PCT Pub. No. WO2004/068480, PCT Pub. Date Aug. 12, 2004.
Claims priority of application No. 2003-021839 (JP), filed on Jan. 30, 2003.
Prior Publication US 2006/0077550 A1, Apr. 13, 2006
Int. Cl. G11B 7/13 (2006.01)

U.S. Cl. 369—120 [369/44.41; 369/94]

2 Claims

1. An optical head comprising:

a first light source that emits light of a first wavelength for at least either one of recording and reproducing information of a first information recording medium;

a second light source that emits light of a second wavelength for at least either one of recording and reproducing information of a second information recording medium;

an optical element for diffracting light of the first and the second wavelength; and

a photodetector that is provided with a detection region for detecting light that is reflected by the first information recording medium or the second information recording medium, and that passes through the optical element;

wherein the first information recording medium and the second information recording medium are multi-layer disks having at least two recording layers;

wherein the detection region includes a first diffracted light detection region for detecting one of first and higher order diffracted light of the first wavelength that is diffracted by the optical element, and a second diffracted light detection region for detecting one of first and higher order diffracted light of the second wavelength that is diffracted by the optical element;

wherein the first diffracted light detection region is arranged such that it does not overlap an outline of a spot on the photodetector of zero order light coming from the first information recording medium that comes from a recording layer that differs from the recording layer that is to be recorded or reproduced;

wherein the second diffracted light detection region is arranged such that it does not overlap an outline of a spot on the photodetector of zero order light coming from the second information recording medium that comes from a recording layer that differs from the recording layer that is to be recorded or reproduced;

wherein the spot on the photodetector changes from a minimum range to a maximum range;

wherein each of the first diffracted light detection region and the second diffracted light detection region includes a plurality of diffracted light detection regions;

wherein both of all the first diffracted light detection regions and all the second diffracted light detection regions are arranged inside the smaller range of a first minimum range, which is the minimum range of the spot on the photodetector of zero order light coming from the first information recording medium that comes from a recording layer that differs from the recording layer that is to be recorded or reproduced, and a second minimum range, which is the minimum range of the spot on the photodetector of zero order light coming from the second information recording medium that comes from a recording layer that differs from the recording layer that is to be recorded or reproduced.