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Abstract

An EET ('eight-to-ten') method has been proposed for two-dimensional spatial encoding of information stored in two- or three-dimensional, in particular fluorescent optical carriers. The method specifically ensures the same writing density as DVD carriers with EFM ('eight-fourteen modulation') modulation code but for 0.8.times.0.4.mu. information pit (fluorescent mark), i.e. as in CD data carriers. The larger--as compared to the DVD format--pit size enables a simpler technology for manufacturing fluorescent multilayer carriers, for instance of ROM type, and a stronger fluorescent signal in reading. The high writing density is ensured through virtually 100% filling of the information layer area with fluorescent marks in a gap-free manner. In addition, this allows application of the parallel data reading procedure and a ten-fold higher reading speed than in DVD systems. Increasing the size of the channel bit to 0.4 .mu.m--which is 1.5 and 3 times higher than for CD and DVD formats, respectively--allows a significant reduction in the frequency band and hence in photoreceiver noises. For equal values of the reading radiation wavelength and numerical aperture of the objective lens used, the proposed ETT ('eight-to-ten') method of two-dimensional encoding in fluorescent carriers enables a significant lower magnitude of reading error probability in contrast to existing optical information carriers of DVD-type. It is also applicable to other write-once and rewritable optical data carriers based on various physical and chemical principles of forming information pits.

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