PURPOSE: To obtain an optical signal with high sensitivity from a recording medium, by providing a series resonance circuit consisting of an optical semiconductor element having an S-shaped negative resistance characteristic, an inductance element, and a capacity element for executing a charge/discharge operation, on a light receiving part.
CONSTITUTION: A light beam which is emitted from a semiconductor laser 13 being a light emitting part passes through a half mirror 17 and irradiates the surface of a recording medium 15. The light beam which is reflected by the surface of the recording medium 15 is led to a light receiving part 63. This light receiving part 63 is provided with a series resonance circuit consisting of an optical semiconductor element 40 having such an S-shaped negative resistance characteristic as a turnover voltage value drops as a received light quantity increases, an inductance element, and a capacity element for executing a charge/discharge operation in relation to ON and OFF of this optical semiconductor element 40, and outputs a read-out signal. In such a way, an optical signal can be obtained with high sensitivity from the recording medium 15, and also, an optical head for an optical disk, provided with the light receiving part 63 of a simple constitution can be obtained.
FURUKAWA RYOZO
WATANABE NOZOMI
