Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Panasonic Intellectual Property Management Co., Ltd.

Toshihiro Torii

Junji Nakatsuka

Teruhiko Izumi

Takaaki Sato

Masashi Uchida

Takatomi Sakakibara

Yoshihiro Horii

In a DAC device, a distortion correction function g1(x) of a harmonic obtained from a result of a frequency analysis on an analog output signal of a DAC circuit is obtained. A correction value is determined based on the correction function g1(x) in accordance with an input digital signal, and is previously stored in a memory. A nonlinear correction circuit reads a corresponding correction value from the memory in accordance with the value of a digital signal output from a digital filter, and transmits the correction value to a subtractor. The subtractor subtracts the correction value from the digital signal output from the digital filter.

DAC device and audio system

A white dot out detecting device according to the present invention comprises a recording/reproduction control signal generator for generating a recording/reproduction control signal showing a recording state or a reproducing state of an optical disk, a variable gain amplifier for amplifying and outputting an information signal read from the optical disk and adjusting a gain in the amplification based on the recording/reproduction control signal, an envelope detector for detecting an output envelope of the variable gain amplifier, an integrator for integrating an output of the envelope detector, a slice level setting unit for setting a slice level as a reference for detecting a white dot out based on an output of the integrator, a comparator for detecting the white dot out based on comparison of the output of the envelope detector and the slice level to each other, and a level shifter for temporarily shifting the slice level to a high-level side when a change of the recording/reproduction control signal is detected.

White dot out detecting 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

Growing community of inventors

Uji, Japan

Toshihiro Torii