| 摘要 |
<p>PURPOSE:To eliminate a zero-point control, by obtaining a sum of the positive and negative side envelope signals of the analog signal waveform to be binary coded and carrying out a subtraction to the analog signal. CONSTITUTION:The output of a photodetector 1 is amplified by an amplifier 2 and supplied to positive and negative side envelope circuits 3 and 4 plus an arithmetic part 8. At the part 8, an operation is performed as shown by the equation (1) on the basis of the outputs Va, Vp and Vn of the amplifier 2 plus the envelope circuits 3 and 4, respectively. However, the offset control is incomplete for the amplifier 2 plus the circuits 3 and 4. As a result, the output of the part 8 becomes as shown by the equation (2) in case when the fluctuations Va, Vp and Vn are caused to the reference levels, respectively. Accordingly a control has only to be given to the output level of a reference power source 10 so as to give an offset to -(Vp+Vn)/2.</p> |
