Laser power monitor device, optical pickup including the...

Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium

Reexamination Certificate

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Reexamination Certificate

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10751647

ABSTRACT:
In order to improve the frequency characteristic of a laser power monitor device and the precision of laser power control when low-speed recording is performed, there is provided a laser power monitor device for an optical recording and/or reproducing apparatus, the laser power monitor device including a photo diode unit to receive part of a light emitted from a laser diode and output a current proportional to optical power, and a monitor circuit to receive the current output from the photo diode unit, convert the received current into a voltage, and outputs the voltage to an automatic laser power control circuit, and the photo diode unit includes a plurality of photo diodes connected to the monitor circuit to supply current to the monitor circuit. The laser power monitor device further includes a switch unit, wherein the switch unit is located between the photo diode unit and the monitor circuit to receive a signal on a current recording speed and switch so that the number of photo diodes supplying current to the monitor circuit is reduced as the recording speed is increased.

REFERENCES:
patent: 4721850 (1988-01-01), Sakai et al.
patent: 5233175 (1993-08-01), Latta et al.
patent: 6061317 (2000-05-01), Shodo
patent: 6445670 (2002-09-01), Oshima
patent: 6734793 (2004-04-01), Nagara
patent: 2001-33629 (2001-04-01), None
Notice of Office Action issued by Korean Patent Office on Nov. 22, 2004 and English translation thereof.
First Office Action dated Aug. 4, 2006 issued in the corresponding Chinese Application No. 200410005092.9.

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