Hitachi, Ltd.

Hitachi Video and Information System, Inc.

Masanori Matsuzaki

Hisataka Sugiyama

Toru Kawashima

Hiroyuki Hori

Toshimitsu Kaku

Seiichi Mita

Hiroyuki Tsuchinaga

Takuya Mizokami

Masahiro Takasago

Masataka Ota

Noritaka Narita

Akira Takagishi

Toshiharu Kon

When the data is reproduced by irradiating a laser beam onto the optical disk, an amount-of-irradiation-beam detection signal is produced according to the amount of the laser beam irradiated onto the optical disk, and the defect on the optical disk is detected on the basis of this amount-of-irradiation-beam detection signal. In addition, when the data is reproduced by irradiating the laser beam onto the optical disk, the amount-of-irradiation-beam detection signal is produced according to the amount of the laser beam irradiated onto the optical disk, an amount-of-reflected-beam detection signal is produced in accordance with the amount of the laser beam reflected from the optical disk, and the defect on the optical disk is detected on the basis of the amount-of-irradiation-beam detection signal and the amount-of-reflected-beam detection signal. Even when the optical disk has a defect, the laser beam is continuously irradiated onto the optical disk.

Optical disk apparatus and data reproducing method

A means for measuring the temperature in the surroundings of a semiconductor laser is provided and, if the temperature is not above a certain level, power correction is performed at high speed by linearly approximating the I-H characteristic according to one item out of reproduction power and multi-pulse recording power, or if the temperature is higher, accurate power correction of the semiconductor laser is accomplished by detecting a plurality of items out of reproduction power and multi-pulse recording power.

Optical disk device and luminescent power control method for semiconductor laser

An information reproducing apparatus is capable of stably and correctly binarizing a signal reproduced from a recording medium, such as an optical disk, even if the reproduced signal contains a fluctuation of its low frequency component. The reproduced signal is replaced by an AC signal in a period other than a period during which the reproduced signal is to be demodulated so that DC fluctuation of the reproduced signal is reduced to thereby stably and correctly binarize the reproduced signal.

Information reproducing apparatus with a DC level correcting capability

A PLL circuit produces a synchronous signal by utilizing a regenerative clock signal in a VFO portion in a regenerative signal which was read out from a recording medium in sections. When a defective portion is present in a regenerative clock signal, the same sector is read out again from the recording medium to obtain the regenerative signal. A loop gain of the PLL circuit is made to be low in the defective portion of the regenerative signal which was read out again, thereby to prevent the synchronous fault of the PLL circuit due to the defective portion.

Apparatus for reproducing data from a regenerative signal using a PLH

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Mito, Japan

Masanori Matsuzaki