Optical head, optical disc drive, computer, optical discplayer and optical disc recorder

An optical head for reading and/or writing information from/on multiple types of storage media, including a first storage medium and a second storage medium, by irradiating a given one of the storage media with a laser beam,

• the first and second storage media including a protective substrate with a thickness t1 and a protective substrate with a thickness t2 (where t1≠t2), respectively, the thicknesses t1 and t2 being the depth of the information storage layer of the storage media as measured from their surface irradiated with the laser beam,
• the optical head comprising:
• a light source that emits the laser beam;
• a diffraction element that diffracts the laser beam to produce diffracted light of multiple orders;
• an objective lens for converging, among the multiple orders of the diffracted light, an nth order (where n is an integer) one of the diffracted light of the multiple orders on the information storage layer of the first storage medium and an mth order (where m is an integer and m≠n) one of the diffracted light on the information storage layer of the second storage medium, respectively;
• a condenser lens for condensing the laser beam that has been reflected from the first or second storage medium;
• a photodetector that receives the condensed laser beam;
• and
• a light shielding portion for preventing a portion of the laser beam that has been reflected from the information storage layer of the second storage medium and that includes its optical axis, from reaching the photodetector, the light shielding portion being arranged so as to reduce loss to be caused by cutting off the portion of the laser beam to a predetermined value or less.