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Image compression technology, applications and their storage size, and high density high capacity technology are discussed. The technology based on the 0.6 mm thick substrate that is similar to the conventional DVD is suitable for the next generation DVD using blueviolet laser from the viewpoint of advantages for users and disk manufactures.

With increased use of smartphones and social networking services, the amount of unstructured image data has been increasing significantly. A high-speed search method is required to use such data for big data analysis. Holographic optical correlation is a promising technique for this purpose. This study introduces a recording method that realizes speedup in an optical correlator. High-density recording is effective for achieving not only speedup, but also high capacity. However, the high-density recording by shortening the shift amount in shift-multiplexed recording results in a large error in the calculated correlation rate owing to crosstalk from adjacent holograms. To suppress this crosstalk, we propose a low-correlation data interleaving method that rearranges the recording order of image data based on the correlation rate with the last recorded image data. We analytically and experimentally confirmed that the proposed method improves the recording density and the correlation speed to 1.33 times.

The performance of a 0.6-mm-thick substrate disk was studied for tilted disk conditions. It was shown by numerical calculation that the reduction in the peak intensity of the optical spot was 0.5 dB under a disk tilt of 7 mrad when the numerical aperture (NA) of an objective lens was 0.6. The tilt angle dependence of the reading/writing performance was measured for a double-sided disk with a wavelength of 690 nm. Excellent signal quality was obtained, such as carrier-to-noise ratio of over 50 dB, erasability of more than 27 dB, crosstalk of under -27 dB, and jitter of under 30% of the window width for a tilt angle of 7 mrad.

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