Optical head and device and system provided with this

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;
• a first photodetector that is provided with a first detection region for detecting light that is reflected by the first information recording medium, and that passes through the optical element;
• and
• a second photodetector that is provided with a second detection region for detecting light that is reflected by 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 first 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,
• wherein the second detection region includes 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 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
• wherein the second diffracted light detection region is arranged such that it does not overlap an outline of 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.