| 摘要 |
PURPOSE:To reproduce record on a record disk with simple constitution without contact by arranging long sides of a photodetector in parallel with the record disk and by dividing its photodetection surface into two with its diagonal line. CONSTITUTION:Beam focused via condenser lenses 5 and 5' are slantingly incident to record modulated-groove walls 6 and 6'. Reflected light beams from record modulated-groove walls 6 and 6' never return to condenser lenses 5 and 5', but are incident directly to photodetectors 7 and 7'. Their light spots move on two separate photodetectors according to changes in direction of reflected beams based upon modulated-groove wall surfaces. In this case, two outputs of photodetectors divided into two with the diagonal line are applied to subtracter 8 to obtain a difference signal, which corresponds to a difference in the quantity of light resulting from the movement of light spots on photodetectors. In other words, changes in angle of record modulated-groove wall surfaces can be detected and a sound signal is obtained. This constitution provides the contactless reproduction of a record disk with simple structure. |
