Non Contact Phonographic Disks Digitisation Using Structured Colour Illumination
We propose an innovative contactless optical playing device for 78rpm and 33rpm lateral modulation phonographic disks, using structured colour illumination. An area of the disk is illuminated by a beam of rays, with colour depending on the direction of incidence, that are reflected by the groove wall towards a camera image. In contrast with standard methods, that measure the velocity of the groove at a single location, direct access to the audio signal value is obtained here directly from pictures through colour decoding, and the whole height of the groove wall is exploited. This colour coding allows for the detection of occluding dust, and automated interpolation of missing audio signal. Results on distortion, S/N ratio, and bandwidth are presented.
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