| 摘要 |
PURPOSE:To execute read/write at a precise timing by removing a low frequency component from a laser beam passing through an encoder plate having a slit-like pattern and then shaping the waveform to obtain a clock signal. CONSTITUTION:A band pass filter 20 passes a laser beam by the signal change corresponding to the slit-like pattern of the encoder plate 16, an amplifier 21 amplifies the passed signal and then a waveform shaping circuit 22 outputs a pusle signal with 50% duty ratio. The pulse signal is applied to monostable multivibrators 23, 24. The monostable multivibrator 23 outputs a pulse with the pulse width of 1/2 the period of an input pulse at the rise of an input pulse and the monostable multivibrator 24 outputs a pulse signal with a period of 1/2 that of an input pulse at the fall of the input pulse. Both the outputs are added by an OR circuit 25, which outputs a precise write and read clock signal with the frequency twice that of the input signal. |
