| 摘要 |
1387304 Optical recording and playback PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 8 March 1972 [11 March 1971] 10791/72 Heading G5R A disc 1 of transparent non-diffusing material carries optically-readable recordings 3, 4, 5 lying substantially in two or more mutually parallel planes at different depths in the disc. A playback beam 22, Fig. 4, is selectively focused on a chosen recording plane, e.g. by the insertion of one of alternative plates 20, 20a rotatable about a spindle 21. Recording tracks may differ in colour, being selectively played back with the aid of filters. |
