Optical pickup apparatus, integrated circuit, and method for controlling laser output of optical pickup apparatus
An optical-pickup apparatus includes: a first laser light source including a first laser diode to emit a laser beam having a first wavelength, and a back-monitor photodetector to receive the laser beam emitted in a backward direction, not being an optical-disc direction, and output a first monitor signal; a second laser-light source including a second laser diode to emit a laser beam having a second wavelength; a light-receiving circuit including a front-monitor photodetector to receive the laser beam emitted in a forward direction, being the optical-disc direction, and output a second monitor signal, and a switch circuit to be inputted with the first and second monitor signals, and output the first or second monitor signal according to a switch signal; and first and second drive circuits to drive the first and second laser diodes according to the first and second monitor signals outputted from the light-receiving circuit, respectively.
1. An optical pickup apparatus comprising:
a first laser light source including
a first laser diode configured to emit a laser beam having a first wavelength, and
a back monitor photodetector configured to receive the laser beam emitted from the first laser diode in a backward direction, which is not a direction of an optical disc, and output a first monitor signal corresponding to a current signal flowing through the back monitor photodetector;
a second laser light source including a second laser diode configured to emit a laser beam having a second wavelength;
a light-receiving circuit including
a front monitor photodetector configured to receive the laser beam emitted from the second laser diode in a forward direction, which is a direction of the optical disc, and output a second monitor signal corresponding to a current signal flowing through the front monitor photodetector,
a switch circuit configured to be inputted with the first and the second monitor signals, and output one of the first and the second monitor signals according to a switch signal,
a current/voltage converter circuit configured to convert into a voltage signal one of the first and the second monitor signals outputted from the switch circuit, and output the voltage signal,
a resistor to which the first monitor signal is supplied, and
a voltage/current converter circuit configured to convert a voltage generated across the resistor into a current signal in the same direction as a direction of the second monitor signal, and input the current signal to the switch circuit;
a first drive circuit configured to drive the first laser diode according to the first monitor signal outputted from the light-receiving circuit; and
a second drive circuit configured to drive the second laser diode according to the second monitor signal outputted from the light-receiving circuit.
2. An integrated circuit comprising:
a terminal configured to be inputted with a first monitor signal outputted from a back monitor photodetector of a first laser light source, the first laser light source including a first laser diode configured to emit a laser beam having a first wavelength and the back monitor photodetector configured to receive the laser beam emitted from the first laser diode in a backward direction, which is not a direction of an optical disc, the first monitor signal corresponding to a current signal flowing through the back monitor photodetector;
a front monitor photodetector configured to receive a laser beam emitted from a second laser diode of a second laser light source in a forward direction, which is a direction of the optical disc, and output a second monitor signal, the second laser light source including the second laser diode configured to emit the laser beam having a second wavelength, the second monitor signal corresponding to a current signal flowing through the front monitor photodetector;
a switch circuit configured to be inputted with the first and the second monitor signals, and output one of the first and the second monitor signals according to a switch signal;
a current/voltage converter circuit configured to convert into a voltage signal one of the first and the second monitor signals outputted from the switch circuit, and output the voltage signal;
a resistor to which the first monitor signal is supplied; and
a voltage/current converter circuit configured to convert a voltage generated across the resistor into a current signal in the same direction as a direction of the second monitor signal, and input the current signal to the switch circuit.
3. A method for controlling laser output of an optical pickup apparatus, comprising:
with respect to the integrated circuit of claim 2 ,
inputting the first monitor signal to the terminal;
causing the front monitor photodetector to receive the laser beam emitted from the second laser diode in the forward direction; and
controlling output of the first laser diode according to the first monitor signal outputted from the integrated circuit and controlling output of the second laser diode according to the second monitor signal outputted from the integrated circuit.