Optical random access memory having multiple state data spots for

Abstract

An optical memory is disclosed in which data is stored in an optical data layer capable of selectively altering light such as by changeable transmissivity or polarization. The data is illuminated by controllable light sources and an array of multi-surface imaging lenslets project the image onto a common array of light sensors. Data is organized into a plurality of regions or patches (called pages) in which each page contains a field of data spots that encode multiple states or levels of data by the amount of transmissivity or polarization of that spot. By selective illumination of each data page, one of the lenslets images the selected data page onto the light sensors. Light in the data image pattern strikes different ones of the arrayed light sensors, thereby outputting the multiple levels per spot in the form of electrical data signals that are A/D converted to digital. A special sensor array uses charge coupled devices (CCDs) that provide multiple storage buckets or levels for each photo sensor element to store and output reference level data along with signal data to quantify and normalize the sensor elements. By selectively and sequentially illuminating different ones of the data regions (pages) on the data layer, correspondingly different data spot patterns are imaged by the corresponding lenslets onto the common sensor array, thereby enabling many stored data pages to be retrieved by multiplexing at electro-optical speed.