| 摘要 |
PURPOSE:To make it possible to discriminate the absolute position of a tone arm to a record disc by detecting and operating incident light quantities onto plural slits formed on a sensor plate which is moved according to rotation of the arm axis. CONSTITUTION:When film plate 29 on sensor plate 21 moved according to rotation of the tone arm axis is placed on plural photo couplers 25 and 27, position information 1 and 0 are obtained in case of the transparent part of film 29 placed on them and the non-transparent part of film 29 placed on them respectively. Thus, approximate arm position information of 000000-111111 in the binary scale can be obtained by using, for example, 6 photo couplers. By photo couplers 26 and 28, analogue signals obtained by detecting the transmission light of reference slit hole 45 and detailed position detection slit 46 consisting of transparent and non-transparent parts are subjected to A/D conversion to obtain minute position information. Further, a photo coupler is fixed to the lower part of the arm, and the reflection quantity from the record disc surface is detected to obtain inter-tune information. |
