Development of an optical sound reproduction system for negative phonograph cylinders

最近在德国的柏林发现了许多留声机底片筒。由于在负圆筒中，声音信息被编码在圆筒内壁的凸起部分中，所以传统的留声机不适用于声音再现。在本研究中，我们开发了一个负圆柱的光学声音再现系统。紧凑型光学头通过检测底片内壁上声道的高度变化来恢复声音信息。为此，设计并构造了一种插入圆筒中的紧凑型光学头，其使用激光二极管、小透镜、反射镜，在检测光学系统中插入由透镜和针孔组成的中继光学系统，以有效地抑制杂散光，改善再现声音SNR。驱动单元在驱动单元中，通过将底片插入较大的固定圆筒中并使用六个螺钉将其固定在固定圆筒上来固定底片。该系统采用直流电机带动夹持气缸旋转，气缸和电机安装在平移台上，平移台由脉冲电机驱动，通过激光束保持跟踪.整个系统和声音再现将上述部件组合成一个系统，并由控制单元控制，并对系统的最终性能进行了检查和验证。声音是从一些旧的负圆柱成功地复制，其中包括由川上音次郎领导的日本老剧团演奏和录制的古筝和三味线圆柱。

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.