Optical Audio Reproduction for Stereo Phonograph Records by Using White-light Interferometry and Image Processing.

摘要

This dissertation presents an optical approach for reproducing stereo audio from the stereo disc phonograph records (LPs). Since the late nineteenth century, as one of the most influential recording technologies, the phonograph recording has enjoyed its popularity and produced numerous cylinders and discs that carry speeches, music, and all kinds of audio cultural heritage. The preservation of phonograph sound recordings is thus of world-wide concern. This research provides an alternative approach to digitizing the stereo disc phonograph records, potentially for long-term preservation, by optically acquiring the 3D disc record surface profile and extracting the audio signals from the record surface profile images by using software algorithms.;The dissertation contains three main parts. The first include an introduction to the general background of the optical audio reproduction for the stereo disc phonograph records and the review of the phonograph recording technology, the previous efforts in optically reproducing audio from the cylinder and disc phonograph records, and the relevant optical techniques including the white-light interferometry. The second part focuses on our complete workflow for optically reproducing the stereo audio from the stereo disc phonograph records. This is followed by the evaluation of our workflow and the output audio quality. The dissertation concludes by introducing the challenges and the possible directions in the future development of our optical audio reproduction workflow.;The dissertation discusses the workflow of optically reproducing stereo audio from the stereo disc phonograph records by using the white-light interferometry technique. This workflow includes the acquisition of the 3D disc record surface profile by using a commercial white-light interferometry microscope, the extraction of the record groove undulations, which encodes the stereo audio information, by using our custom image processing algorithms, and finally the reproduction of the stereo audio signal from the groove undulations through signal processing. The workflow is evaluated with a test stereo record containing standard sinusoid signals and a musical record. The quality of the optically-reproduced audio is quantitatively evaluated and compared with that of the audio digitized by a turntable.