| 摘要 |
PURPOSE:To correct an error to a signal in a minimum inverted width with the addition of a small size hardware among errors due to a data slice level or noise in an analog system reading the data from an optical disk. CONSTITUTION:A pattern other than a wavelength specified by the modulation system is considered to be caused by error. The error detection of the short wavelength is easy and when the shortest wavelength is 3T at a channel bit interval T, the pattern of 3T and preceding and succeeding intervals 3T in total 9T of patterns are looked into and the case that the pattern of middle 3T is not consecutive 3T is to be detected. That is, the erroneous middle bit caused at a higher probability than the probability of which 2 bits at both ends in the pattern of 3T is in error, is detected and the correction is applied. Then the data is inputted to a shift register of 9-stage or over, outputs of each register are decoded as the patterns above and the polarity of the bit data considered to be in error is inverted. Thus, the error rate is reduced to as little as possible.
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