| 摘要 |
PURPOSE:To eliminate a complex optical system and to enable easy differential detection by providing a polarizing means whose polarizing direction is perpendicular to the front surfaces of two photoelectric converting means arrayed in the moving direction of image re-formation of recording pits. CONSTITUTION:Light emitted by a light source 1 is transmitted through a beam splitter (BS) 2, and polarized and image-formed to form an irradiation beam spots 20 on a recording track on a recording medium 73. Reflected light which is varied in angle of polarization by a recording pit travels backward and is reflected by the BS 2 and passed through mutually orthogonal polarizing plates 4 and 5 to form signal beam spots 22 on the photoelectric converting elements 6 and 7. The elements 6 and 7 are so arranged that the spot 22 moves from the element 6 to the element 7 according to the movement of the recording pit. The output signal of the element 6 is passed through a delay element 8, the output of the element 7 is inputted directly to a subtracting circuit 9, and the differential output from which the influence of light quantity variation is removed appears at an output terminal 10.
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