Super-resolution in optical data storage

In this paper we summarize how fundamental work on the theory of optical imaging performed by our research group over a number of years has led to experimental developments, using specially calculated image-plane masks, which have confirmed that optical resolution in high-aperture microscopy, both coherent and incoherent (fluorescence microscopy), can reach nearly twice the conventional Rayleigh limit. In particular, we give a detailed treatment of our current work on the application of these ideas to the active area of high-density optical data storage on compact discs (digital versatile discs (DVDs)). A conventional optical disc can be regarded as a coherent-light confocal scanning microscope and our general theories thus show the feasibility of `superdense' optical data-storage systems. The achievement of near twice the Rayleigh limit for DVDs in the entertainment sector is important at the present time since this would enable full-length motion pictures to be read on an uncomplicated reader rather than the two-layer or double-sided reading systems now being promoted. Optical discs which use fluorescent material are also being proposed and our resolution enhancements will also apply to these.