Patent ID: 7486606

Claim:
An optical head, comprising: a light source for emitting a beam of light; a light-concentrating element arranged to concentrate the beam of light on an information recording medium that includes a track in a recording area; a transfer mechanism for transferring the light-concentrating element at least between an outermost circumference and an innermost circumference of the recording area along the information recording medium; a splitting element arranged to split a beam of light that returns from the information recording medium into a plurality of beams of light; and a detector arranged to detect the plurality of beams of light that is obtained by the splitting element, wherein, the splitting element includes a plurality of areas which are divided by a division line, the division line is set parallel to tangential directions of the track in a middle in radius directions of the recording area on a transfer line of the light-concentrating element between the outermost circumference and the innermost circumference of the recording area, and the division line is set in directions which halve an angle at which the tangential directions of the track at the outermost circumference of the recording area on the transfer line meet the tangential directions of the track at the innermost circumference of the recording area on the transfer line.