Jitter-free optical storage system with minute sphere disk

We propose a new optical data storage system with minute spheres. To avoid a problem of jitter as instability of rotating disk speed and fluctuation of recording bit formation, we have devised a new process. The process involves the use of dye-doped minute spheres arranged upon a surface-relief structure as recording bits. Alternate laminating recordable sphere layer with sensitivity and buffer layer with insensitivity structurally limits recording bits in three dimensions. We can limit a sensitive region within a sphere diameter. A reflection-type confocal optical microscope can read out both bit signals and shape signals from minute spheres at high resolution. Confocal relection of ~10% was measured before and after recording from a single minute sphere with Spiropyran as a recording dye. Also, the shape signal from each minute sphere is utilized as a clock signal in recording and readout. The clock signal can be produced by separating a high-level signal and a low-level signal on the basis of a threshold. In our minute-sphere optical storage system, a shift between positions of the recording bit and the clock signal does not occur because the clock signal is generated based on the shape signal from a minute sphere as the recording bit. This jitter-free technique proved to be extremely effective for disk recording and readout.