Development of an optical sound reproduction system for negative phonograph cylinders

最近在德国柏林发现了许多底片留声机圆筒。由于在负圆柱体中，声音信息被编码在圆柱体内壁的凸部分，因此传统的留声机不适用于声音再现。在本研究中，我们开发了一种用于负极圆柱的光学声音再现系统。紧凑型光学头通过检测声道在负极内壁上的高度变化来恢复声音信息。为此，使用激光二极管、小透镜、反射镜、分束器和PSD设计并制造了一个插入圆柱体的紧凑型光学头。在检测光学器件中插入由透镜和针孔组成的中继光学器件，有效地抑制杂散光，提高再现声音的信噪比。驱动单元在驱动单元中，通过将负极插入更大的保持缸中，并通过六个螺钉将其固定在保持缸中来保持负极。所述保持筒由直流电机旋转，所述保持筒和电机均安装在平移台上，平移台上由脉冲电机驱动，以保持激光束的跟踪。整个系统和声音再现上述组件组合成一个系统，由一个控制单元控制，并对系统的最终性能进行了检查和验证。声音成功地从一些旧的负片圆筒中复制出来，其中包括由川上大二郎领导的日本老牌戏剧表演公司演奏和录制的koto和三味线圆筒。

It was found recently that many negative phonograph cylinders have been preserved in Berlin, Germany. Since, in the negative cylinder, sound information is encoded in convex portions of the inside wall of the cylinder, a conventional phonograph is inapplicable to the sound reproduction. In the present study, we have developed an optical sound reproduction system for the negative cylinders.1. Compact optical headSound information is recovered by detecting height variations of the sound track on the inside wall of the negative, To this end, a compact optical head to be inserted into the cylinder was designed and constructed using a laser diode, small lenses, mirrors, a beam splitter and a PSD.A relay optics consisting of a lens and a pinhole was inserted in the detection optics to reject stray light effectively and to improve an SNR of reproduced sounds.2. Driving unitIn the driving unit, the negative is held by inserting it into a larger holding cylinder and by fixing it to the holding cylinder with six screws. The holding cylinder is rotated by a DC motor, and the cylinders and motor are mounded on the translation stage, which is driven by a pulse motor to keep a tracking by the laser beam.3. Entire system and sound reproductionAbove components were combined into a system and controlled by a control unit, and the final performance of the system was examined and verified. Sounds were reproduced successfully from some old negative cylinders, in which cylinders of koto and shamisen played and recorded by a Japanese old company of drama shows, led by Otojiro Kawakami, are included.