Back to results
US 5,428,455 AGranted
Apparatus for reducing noise in high-frequency band
AssigneeSanyo Electric Co., Ltd.
InventorsNobukazu Hosoya, Tooru Sasaki
Life of this patent
Estimating the term…
Abstract
An apparatus for reducing noise in the high-frequency band is provided in the preceding stage of a limiter (8) with a high-frequency band correcting filter (12) for reducing a high-frequency band component of a reproduced RF signal from an optical disc. The reproduced RF signal has its high-frequency component lowered before entered into the limiter (18), reducing noise and beat components. As a result, a signal which is less influenced by the noise and beat and has good S/N can be obtained.
Claims5
An apparatus for reducing noise of a reproduced FM signal in a high-frequency band, comprising:
- high-frequency band correcting means for lowering a high-frequency band component of said reproduced FM signal so that a level of an upper side band component is suppressed in comparison with a level of a lower side band component in said reproduced FM signal;
- limiter means for limiting an output signal of said high-frequency band correcting means in amplitude;
- first and second band-pass filter means provided between said high-frequency band correcting means and said limiter means in parallel, said first band-pass filter means having a first pass-band, and said second band-pass filter means having a second pass-band wider than said first pass-band;
- and
- switch means for selecting one of said first and second band-pass filter means, applying an output signal of said high-frequency band correcting means to the selected band-pass filter means, and applying an output signal of the selected band-pass filter means to said limiter means.
2 more elements
An apparatus for reducing noise of a reproduced FM signal in a high-frequency band, comprising:
- high-frequency band correcting means for lowering a high-frequency band component of said reproduced FM signal so that a level of an upper side band component is suppressed in comparison with a level of a lower side band component in said reproduced FM signal;
- limiter means for limiting an output signal of said high-frequency band correcting means in amplitude;
- converting means for converting a light beam from an optical record medium, which has signals recorded thereon in pits constituting a track, into an electrical signal, said converting means comprising first photoelectrical converting means provided on a preceding side with respect to a reproducing direction of said track, and second photoelectrical converting means provided on a succeeding side;
- delaying means for delaying an output signal of said first photoelectrical converting means, delay time of said delaying means being variable;
- time difference detecting means for detecting time difference between an output signal of said second photoelectrical means and an output signal of said delaying means to output a signal corresponding to the detected time difference;
- said delaying means being responsive to said signal outputted from said time difference detecting means for having said delay time changed;
- FM-detecting means for detecting an FM output signal of said limiter means;
- low-pass filter means for passing a low-frequency band component of an output signal of said FM-detecting means;
- deemphasis means for attenuating a high-frequency band component of an output signal of said low-pass filter means;
- and
- control means responsive to said signal outputted from said time difference detecting means for controlling an amount of attenuation of the high-frequency band component by said deemphasis means.
8 more elements
A reproducing apparatus for reproducing an optical record medium which has signals recorded thereon in pits constituting a track, comprising:
- converting means for converting a light beam from said optical record medium into an electrical signal, said converting means comprising first photoelectrical converting means provided on a preceding side with respect to a reproducing direction of said track, and second photoelectrical converting means provided on a succeeding side;
- delaying means for delaying an output signal of said first photoelectrical converting means, delay time of said delaying means being variable;
- time difference detecting means for detecting time difference between an output signal of said second photoelectrical means and an output signal of said delaying means to output a signal corresponding to said detected time difference;
- said delaying means being responsive to said output signal of said time difference detecting means for having said delay time changed;
- adding means for adding the output signal of said delaying means and the output signal of said second photoelectrical converting means;
- high-frequency band correcting means for lowering a high-frequency band component of an output signal of said adding means;
- limiter means for limiting an output signal of said high-frequency band correcting means in amplitude;
- FM-detecting means for detecting an FM output signal of said limiter means;
- low-pass filter means for passing a low-frequency band component of an output signal of said FM-detecting means;
- deemphasis means for attenuating a high-frequency band component of an output signal of said low-pass filter means;
- and
- control means responsive to said output signal of said time difference detecting means for controlling amount of attenuation of a high-frequency band component by said deemphasis means.
9 more elements
A reproducing apparatus for reproducing an optical record medium which has signals recorded thereon in pits constituting a track, comprising:
- converting means for converting a light beam from said optical record medium into an electrical signal, said converting means comprising first photoelectrical converting means provided on a preceding side with respect to a reproducing direction of said track, and second photoelectrical converting means provided on a succeeding side;
- delaying means for delaying an output signal of said first photoelectrical converting means, delay time of said delaying means being variable;
- time difference detecting means for detecting time difference between an output signal of said second photoelectrical means and an output signal of said delaying means to output a signal corresponding to said detected time difference;
- said delaying means being responsive to said output signal of said time difference detecting means for having said delay time changed;
- adding means for adding the output signal of said delaying means and the output signal of said second photoelectrical converting means;
- high-frequency band correcting means for lowering high-frequency band component of an output signal of said adding means;
- limiter means for limiting an output signal of said high-frequency band correcting means in amplitude;
- FM-detecting means for detecting an FM output signal of said limiter means;
- low-pass filter means for passing a low-frequency band component of an output signal of said FM-detecting means;
- deemphasis means for attenuating a high-frequency band component of an output signal of said low-pass filter means;
- and
- control means responsive to said output signal of said time difference detecting means for controlling amount of attenuation of a high-frequency band component by said deemphasis means;
- first and second band-pass filter means provided between said high-frequency band correcting means and said limiter means in parallel, said first band-pass filter means having a first pass-band, and said second band-pass filter means having a second pass-band wider than said first pass-band;
- and
- switch means for selecting one of said first and second band-pass filter means, applying an output signal of said high-frequency band correcting means to the selected band-pass filter means, and applying an output signal of the selected band-pass filter means to said limiter means.
12 more elements
Dependencies are inferred from the claim text.