FPD OF AN OPTICAL PICKUP WITHOUT A GAIN SELECTION SWITCH, AND AN OPTICAL PICKUP DEVICE AND AN OPTICAL RECORDING/REPRODUCING DEVICE INCLUDING THE FPD, CONCERNED WITH IMPROVING RELIABILITY

摘要

PURPOSE: An FPD(Front Photo Detector) of an optical pickup without a gain selection switch, and an optical pickup device and an optical recording/reproducing device including the FPD are provided to simplify a structure without a gain selection switch, and to move a signal through a physically defined path according to a wavelength of an incident light without a gain selection process, thereby improving reliability. CONSTITUTION: An FPD(300) comprises as follows. A photo diode(310) outputs a current proportioned to an optical power emitted from the first or the second laser diode. A current voltage amplifying circuit(320) converts the current outputted from the photo diode(310) into a voltage. A voltage amplifying circuit(330) amplifies the voltage outputted from the current voltage amplifying circuit(320) into a predetermined gain. The photo diode(310) consists of an optical device(311) for differentiating a direction of the light emitted from the first and second laser diodes.