| 摘要 |
PURPOSE:To enlarge a dynamic range, to reduce external-fitting parts, to simplify a circuit constitution and to make a constitution into monolithic by logarithm- compressing a detection current from an optical detection element and that of the light quantity of total reflection and executing division. CONSTITUTION:If laser beams are irradiated on an optical disk and the spot 4 of the reflected light beams irradiate a four-division optical detector 1, detection currents IA-ID are inputted to a current mirror matrix circuit 2 and addition currents IA+B-IB+D are outputted to a logarithm compression circuit 5. The circuit 5 outputs the logarithm compression outputs VA+B-VB+D of the addition currents IA+B-IB+D. On the other hand, light quantity sum detection current is inputted to a logarithm compression circuit 6 and the logarithm compression output VSUM is outputted. The logarithm compression outputs are impedance-converted through a voltage buffer circuit 7, are subtracted (divided) in an expanding and I-V circuit 8 so as to be I-V converted, and are operation-processed in an arithmetic circuit 9, whereby track error and focus error signals are outputted.
|
