Information reproducing apparatus with a DC level correcting capability
AssigneesHitachi, Ltd., Hitachi Video & Information System, Inc.
InventorsSeiichi Mita, Toru Kawashima, Masanori Matsuzaki, Toshimitsu Kaku, Hiroyuki Tsuchinaga
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Abstract
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.
Claims12
An information reproducing apparatus for reproducing recorded information from a recording medium in which each sector of the recording medium has at least one area bearing a specific pattern expressive of a synchronizing signal for phase-locking a clock signal for demodulating data, comprising:
- reproduction means for deriving a reproduced signal including said specific pattern from said recording medium;
- DC (direct current) level correction means for correcting a DC level of said reproduced signal so that a DC level of a part of said reproduced signal corresponding to said specific pattern as derived by said reproduction means agrees with a predetermined reference level;
- means for receiving a read gate signal indicative of a first time period during which said reproduced signal derived by said reproduction means is to be demodulated;
- AC (alternating current) signal generation means for generating an AC signal whose average potential is equal to said predetermined reference level;
- and
- signal replacement means for substituting said AC signal for said reproduced signal in a second time period other than said first time period indicated by said read gate signal.
A method for reproducing recorded information from a recording medium in which each sector has at least one area bearing a specific pattern expressive of a synchronizing signal for phase-locking a clock signal for demodulating data, comprising the steps of:
- deriving a reproduced signal including said specific pattern from said recording medium;
- correcting a DC (direct current) level of said reproduced signal so that a DC level of a part of said reproduced signal corresponding to said specific pattern agrees with a predetermined reference level;
- and
- replacing a part of the DC corrected reproduced signal by a predetermined AC (alternating current) signal whose average potential is equal to said predetermined reference level, in a time period other than a time period during which the reproduced signal is to be demodulated.
An information reproducing apparatus for reproducing recorded information from a recording medium in which each sector has at least one area bearing a specific pattern expressive of a synchronizing signal for phase-locking a clock signal for demodulating data, comprising:
- reproduction means for deriving a reproduced signal which contains a fluctuation of a low frequency component, from said recording medium;
- detection means for detecting said low frequency component from within said reproduced signal delivered from said reproduction means;
- subtraction means for subtracting said low frequency component detected by said detection means, from said reproduced signal;
- and
- binarization means for converting an output of said subtraction means into a bi-level signal:
- wherein said detection means includes a non-recording level detecting circuit which detects said low frequency component from within a part of said reproduced signal as derived from an unrecorded part of said recording medium, and wherein said information reproducing apparatus further comprises memory means for storing therein a low frequency component which is to be afforded to said binarization means;
- wherein said memory means includes a first memory which stores therein the low frequency component of the reproduced signal part as detected by said detection means from the unrecorded part at an outer peripheral edge of a disk being said recording medium, and a second memory which stores therein the low frequency component of the reproduced signal part as detected by said detection means from the unrecorded part at an inner peripheral edge of said disk;
- and
- wherein said information reproducing apparatus further comprises arithmetic means for executing predetermined operations for the data stored in the first and second memories, thereby to generate said low frequency component which is to be afforded to said binarization means.
An information reproducing apparatus for reproducing recorded information from a recording medium in which each sector of the recording medium has at least one area bearing a specific pattern expressive of a synchronizing signal for phase-locking a clock signal for demodulating data, comprising:
- means for receiving a signal, including said specific pattern, reproduced from said recording medium;
- means for correcting a DC level of the reproduced signal so that a DC level of a part of said reproduced signal corresponding to said specific pattern agrees with a predetermined reference level;
- means for providing an interpolation signal whose average potential is equal to said predetermined reference level;
- means for modifying the corrected reproduced signal by replacing the corrected reproduced signal with said interpolation signal in a time period other than a time period during which the reproduced signal is to be demodulated;
- and
- means for demodulating said corrected reproduced signal which has been modified by said interpolation signal.
A method for reproducing recorded information from a recording medium in which each sector has at least one area bearing a specific pattern expressive of a synchronizing signal for phase-locking a clock signal for demodulating data, comprising the steps of:
- deriving a reproduced signal including said specific pattern from said recording medium;
- correcting a DC (direct current) level of said reproduced signal so that a DC level of a part of said reproduced signal corresponding to said specific pattern agrees with a predetermined reference level;
- and
- replacing a part of the DC corrected reproduced signal by a predetermined signal whose average potential is equal to said predetermined reference level, in a time period other than a time period during which the reproduced signal is to be demodulated.
Dependencies are inferred from the claim text.