The Optical Scanning System of the Philips ‘VLP’ Record Player

The main function of the optical scanning system in the Philips ‘VLP’ record player ^[1] is to read out the video information recorded on the surface of the disc. To follow the information track on the record with the aid of a control mechanism it must also deliver a signal that is a measure of the lateral misalignment of the optical system in relation to the track. The video information is stored on the surface of the record in the form of small pits which are 0.8 μm wide, about 0.16 μm deep and of variable length. The pits are inscribed on a spiral track with a pitch of approximately 2 μm. The picture quality and mechanical accuracy of an optical system that can detect each pit individually and track the spiral sufficiently accurately to prevent cross-talk between adjacent turns of the track must meet extremely exacting standards. At the same time the system must be as simple as possible to produce and easy to adjust. Finally, care must be taken to ensure that the signal-to-noise ratio is sufficiently high. The article describes the optical system which we chose for the ‘VLP’ record player to satisfy these various requirements.

Print ISSN

0361-4573

Published

1974-07

Content type

Original Research

DOI

10.5594/J10635