ABSTRACT
The rapid growth in digital information throughout the world has demanded storage with a high capacity and high transfer rate. Holographic data storage (HDS) is one promising candidate for next-generation data storage because of its high potential in capacity and transfer rate. However, high-volume HDS usually suffers from inter-signal interference (ISI). Here, we first develop volume recording and reproduction models for HDS. We reveal through optical simulations based on the developed models that ISI differs not only between pages but also between areas on the same page. Then, we develop an advanced equalization technique called segmented adaptive equalization (SAE) that takes into account inter-area ISI difference. We can improve signal quality much more than conventional equalization techniques by using SAE. We are confident that SAE can enhance the realization of HDS.
ABSTRACT
We propose a new type of lensless camera enabling light-field imaging for focusing after image capture and show its feasibilities with some prototyping. The camera basically consists only of an image sensor and Fresnel zone aperture (FZA). Point sources making up the subjects to be captured cast overlapping shadows of the FZA on the sensor, which result in overlapping straight moiré fringes due to multiplication of another virtual FZA in the computer. The fringes generate a captured image by two-dimensional fast Fourier transform. Refocusing is possible by adjusting the size of the virtual FZA. We found this imaging principle is quite analogous to a coherent hologram. Not only the functions of still cameras but also of video cameras are confirmed experimentally by using the prototyped cameras.
