MEDIUM FOR RECORDING OPTICALLY READABLE DATA, METHOD FOR MAKING SAME AND OPTICAL SYSTEM REPRODUCING SAID DATA

摘要

The invention concerns a recording medium for optically readable data of the multilayer type, a method for making same and an optical system for reproducing said data for reading the medium. The medium (Sb) comprises a stack of layers (C1 to CN) whereof the interfaces constitute planes (P1 to PN) bearing slightly phase-shifting information elements. Said planes generate a relatively significant disturbance of the transmitted beam while diffracting only a very small part of the light passing through them. The reading beam (FI) is focused on the bearing plane and reading is performed by transmission. The disturbances caused by the neighbouring defocused layers are eliminated by far field detection of only the low spatial frequencies in the transmitted beam. The invention is particularly useful for very high capacity data optical storage.