Optical pickup for 3-d data storage reading from the multilayer

Abstract

An optical pickup providing the 3-D reading of the binary optical information from the multilayer fluorescent disk by means of fluorescent sites excitation, is described. The 2-D information at the separate layer is recorded by chemical transformation of the photosensitive material from one stable molecular form A (non fluorescent) to other stable molecular form B (fluorescent) via UV light illumination. The present invention particularly concerns the methods and apparatus to read the stored memory from the read only 3-D optical memory and includes: (i) only one, focused to the desired layer, reading laser beam, which induces the fluorescence in the whole volume confined within conical surface of focused beam, (ii) active medium which posses the fluorescing properties and is organized in a form of multilayer optical disc, (iii) detection of fluorescence at the wavelength different from the excitation wavelength, (iv) spectral, spatial and electronic filtration of the detected signal in order to extract signal from the noise fluorescence coming from all out-of-focus layers. Utilization of dichroic mirror and/or filter in the optical pickup prevents the photo diode from the reading laser radiation.