# US 5,710,750 A · Optical disc device

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 5,710,750 A
- Document ID: US5710750A
- Status: Granted
- Kind: A
- Application number: 08/717,199
- Filed: 1996-09-18
- Granted: 1998-01-20
- Earliest claimed: 1995-09-22
- Assignees: Sony Corporation
- Inventors: Kaoru Tachibana
- Web page: https://patentgrep.com/patent/US5710750A

## CPC

- G11B 20/10203: {baseline correction (DC correction by choosing codewords of the modulation code G11B20/1426)}
- G11B 7/005: Reproducing (G11B7/0065 takes precedence)
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

An optical disc device is equipped with a high-pass filter for removing a low-frequency noise in a played-back signal, an adder for adding the output signal of the high-pass filter and a correction signal as a low frequency component lost from the played-back data at the noise removal, a first comparator for binarizing the output signal of the adder, and a low-pass filter, having a frequency characteristic complementary to that of the high-pass filter, for suppressing a high frequency component of the output signal of the first comparator to generate the correction signal. In addition, a second comparator for binarizing the output signal of the adder taking a slice level as a reference and outputting played-back data and a controller for varying the slice level and/or a direct current level of the output signal of the adder so that a duty ratio of the played-back data becomes a prescribed value are provided. Thus, the influence of low frequency noise can then be effectively avoided and high-density recorded data can he surely played-back even when the d.c. level of the played-back signal fluctuates due to variations in the laser power.

## Claims

### Claim 1

An optical device for playing back data recorded on a disc-shaped recording medium on the basic of a played-back signal obtained by projecting a light beam onto said disc-shaped recording medium and receiving said light beam returned from said disc-shaped recording medium, comprising:
a high-pass filter for suppressing a low frequency component of said played-back signal and outputting the resulting signal
an adder for adding an output signal of said high-pass filter and a correction signal and outputting the resulting signal;
a first comparator for binarizing an output signal of said adder and outputting the resulting signal;
a low-pass filter, having a frequency characteristic complementary to the frequency characteristic of said high-pass filter, for suppressing a high frequency component of an output signal of said first collator to generate said correction signal;
a second comparator for binarizing said output signal of said adder taking a slice level as a reference and outputting the resulting signal as played-back data; and
a controlling circuit for varying one of said slice level and a direct current level of said output signal of said adder in such a manner that a duty ratio of said played-back data becomes a prescribed value.

### Claim 2

An optical device for playing back data recorded on a disc-shaped recording medium on the basis of a played-back signal obtained by protecting a light beam onto said disc-shaped recording medium and receiving said light beam returned from said disc-shaped recording medium, comprising:
a first high-pass filter for suppressing a low frequency component of said played-back signal and outputting the resulting signal;
an adder for adding an output signal of said first high-pass filter and a correction signal and outputting the resulting signal;
a first comparator for binarizing said an output signal of said adder and outputting the resulting signal;
a low-pass filter, having a frequency characteristic complementary to the frequency characteristic of said first high-pass filter, for suppressing a high frequency component of an output signal of said first comparator to generate said correction signal;
a second high-pass filter for removing a direct current component from said output signal of said adder; and
a second comparator for binarizing said output signal of said adder taking a slice level as a reference and outputting the resulting signal as played-back data.