Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Teruhiko Izumi

Masayoshi Abe

Toshihiko Takahashi

Shinichi Konishi

Youichi Ogura

Katsumi Morita

Hironori Deguchi

Yasuhiro Tai

Dai Ichiryu

Toshihiro Torii

Hiroaki Hayashi

Takamasa Sakai

Kouju Konno

The dropout detection circuit of the invention includes: a high-speed envelope detection circuit for detecting an envelope of a reflection signal of a light beam with a first time constant; a low-speed envelope detection circuit for detecting an envelope of the reflection signal with a second time constant larger than the first time constant; a differential circuit for generating a difference signal indicating the difference between the envelopes detected by the envelope detection circuits; and a comparator for converting the difference signal to a binary value according to a predetermined binary criterion. The high-speed envelope detection circuit makes the first time constant larger during recording than during reproduction, to enable stable dropout detection irrespective of during reproduction or during recording.

Dropout detection circuit and optical disc apparatus

An optical disc recording/playback apparatus is provided with a first AD converterfor shaping a push-pull signaldetected from an optical disc mediumby a light difference signal shaping circuit, and converting the signal into a digital sampling signalusing a sampling clocksynchronized with a channel frequency; a series of means for detecting wobble amplitude informationduring recording from the digital sampling signal; a series of means for detecting address polarity informationand address position information during playback; and a recording laser power control circuitfor controlling a recording laser power to a power suited for recording on the basis of the wobble amplitude information.

Optical disc recording/playback apparatus

An optical disk device is provided with a first analog-to-digital converter for converting a push-pull signal detected from an optical disc medium into a digital sampling signal according to a sampling clock in the vicinity of a channel frequency. The optical disk device also includes an address polarity information detection circuit for detecting address polarity information from the digital sampling signal, and an address position information detection circuit for detecting address position information from the digital sampling signal while maintaining continuity.

Optical disk device

During a predetermined period of time after the operation of an optical disc drive has changed from recording to playback or from playback to recording, a first monomulti circuit outputs a pulse signal according to the operation change of the optical disc drive. On receipt of the pulse signal, a capacitor included in an integration circuit is short-circuited at a predetermined reference voltage to fix the output value of the integration circuit at the reference voltage. After the period has passed, on receipt of a pulse signal outputted from a second monomulti circuit, a resistor included in the integration circuit is short-circuited, and an envelope signal is integrated with a time constant being reduced, whereby detection of a false defect signal is avoided, and defect detection can be speedily restarted.

Defect detection apparatus

An optical disk control device comprises a playback signal detection unit for detecting data recorded on a disk by irradiating the disk with a converged light beam; a signal switching unit for successively selecting plural data signals obtained by the playback signal detection unit, and performing time-division-multiplexing on the selected signals; an A/D conversion unit for converting an analog signal which has been time-division-multiplexed by the signal switching unit, into a digital signal; an A/D conversion command unit for generating an A/D conversion command of the A/D conversion unit; a serial transfer unit for serial-transferring the command signal generated by the A/D conversion command unit; a serial reception unit for receiving the signal from the serial transfer unit, and controlling the signal selection operation of the signal switching unit on the basis of the received signal; and an arithmetic unit for generating an optical disk drive controlling signal by performing arithmetic processing on the digital signal outputted from the A/D control unit. Therefore, the number of signal lines required for connection between the playback signal detection unit and the A/D conversion unit can be significantly reduced.

Optical disk control device for time-division-multiplexing and A/D conversion

The defect detection device includes: an amplification section for amplifying a reflection signal corresponding to the intensity of light reflected from an optical disc according to a control signal indicating recording or playback; an envelope detection section for outputting an envelope of the amplified signal; a first pulse generation section for outputting a pulse when the level of the control signal changes; an integration section for integrating the envelope; a differential signal generation section for receiving the envelope as a first input signal and the integrated results as a second input signal and outputting a differential signal corresponding to the difference between these signals; and a comparison section for comparing the differential signal with a predetermined value and outputting the results as a defect detection signal. The second input signal is changed so as to reduce the possibility that the defect detection signal may indicate the presence of a defect over the duration of the pulse.

Growing community of inventors

Hirakata, Japan

Teruhiko Izumi