Optical signal detecting circuit and information reproducing device using the same
AssigneeHitachi Consumer Electronics Co., Ltd.
InventorsTakahiro Kurokawa, Hideharu Mikami
Life of this patent
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Abstract
An object of the present invention is to achieve both low noise and fast response in an optical signal detecting circuit capable of providing all of three signals—a focus error signal, a tracking error signal, and an RF signal—with only a single detection system. A single current-to-voltage converter converts a current signal obtained by adding currents flowing through two photodiodes, into a voltage signal. Not only currents flowing into the photodiodes, but also currents flowing out from the photodiodes are taken out as the voltage signals. Moreover, by applying two different reference voltages to the current-to-voltage converters, a reverse bias voltage is applied between the terminals of each photodiode.
Claims6
An optical signal detecting circuit comprising:
- a quadrant photodetector in which a first photodetector, a second photodetector, a third photodetector, and a fourth photodetector are contiguously arranged counterclockwise in the listed order, each of the photodetectors receiving an optical signal and converting the optical signal into a current signal;
- and
- a first current-to-voltage converter, a second current-to-voltage converter, a third current-to-voltage converter, and a fourth current-to-voltage converter, each of which converts the current signal to a voltage signal and outputs the voltage signal, wherein
- the first current-to-voltage converter converts a current signal into a first voltage signal and outputs the first voltage signal, the current signal being obtained by adding current signals flowing respectively into the first photodetector and the second photodetector,
- the second current-to-voltage converter converts a current signal into a second voltage signal and outputs the second voltage signal, the current signal being obtained by adding current signals flowing out respectively from the first photodetector and the third photodetector,
- the third current-to-voltage converter converts a current signal into a third voltage signal and outputs the third voltage signal, the current signal being obtained by adding current signals flowing out respectively from the second photodetector and the fourth photodetector,
- the fourth current-to-voltage converter converts a current signal into a fourth voltage signal and outputs the fourth voltage signal, the current signal being obtained by adding current signals flowing respectively into the third photodetector and the fourth photodetector, and
- by applying a first reference voltage, generated by a first reference voltage source, to the second current-to-voltage converter and the third current-to-voltage converter and applying a second reference voltage, generated by a second reference voltage source, which is higher than the first reference voltage, to the first current-to-voltage converter and the fourth current-to-voltage converter, a reverse bias voltage is applied to the first photodetector, the second photodetector, the third photodetector, and the fourth photodetector, the reverse bias voltage being equal to a difference between the second reference voltage and the first reference voltage.
A detecting circuit comprising:
- a plurality of current-to-voltage converters;
- and
- a plurality of detectors, wherein
- a first reference voltage is applied to a predetermined current-to-voltage converter among the plurality of current-to-voltage converters,
- a second reference voltage is applied to another current-to-voltage converter among the plurality of current-to-voltage converters, the second reference voltage being greater than the first reference voltage, and
- a reverse bias voltage of a magnitude corresponding to the difference between the second reference voltage and the first reference voltage is applied to each of the plurality of detectors.
Dependencies are inferred from the claim text.