| 摘要 |
PURPOSE:To detect the secondary distortion of information by providing the titled device with a reading means for reading out information from a medium for alternately recording binary information with the frequency of 50% proposed duty ratio. CONSTITUTION:Signals with bit length 2T and T are alternately recorded in an optical disk 1a. When these signals are reproduced by a head 1, the reproduced signal with the bit length 2T is not almost influenced by the fluctuation of the duty ratio, but the amplitude of the reproduced signal with the bit length is changed at the vertical position of a center level 12, i.e. the upper amplitude is reduced when the rate is <=50%, and increased when the ratio is >=50%. The upper and lower signals are envelope-detected 3a, 3b, respectively extracted through BPFs 4a, 4b (center frequency fc=1/tau) and converted into sine signals and amplitude peak values h1, h2 are detected. A decision logic 6 detects the presence or absence of secondary distortion and deviation from the 50% duty ratio based on the size relation of the peak values h1, h2. When h1=h2, the duty ratio of the reproduced signal are 50% and no generation of secondary distortion can be decided. |
