A Basic Concept for Next Generation DVD: 0.6 mm Substrate Disk Technology using Blue-Violet Laser

Abstract

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.

Compact description of substrate-related aberrations in high numerical-aperture optical disk readout

“…The low NA formula for the rms aberration underestimates the true aberration for NA ϭ 0.50 (CD) with a factor 1.24, for NA ϭ 0.65 (DVD) with a factor 1.48, and, for NA ϭ 0.85 (BD) even with a factor 2.20. Apparently, spherical aberration increases significantly more rapidly with NA than with the well-known NA 4 law.…”

“…3. Ratio of the exact rms aberration and the paraxial NA 4 estimate for spherical aberration from thickness mismatch (solid curve, left axis) and the ratio of the exact focal shift and the paraxial focal shift for spherical aberration from thickness mismatch (dashed curve, right axis) for n 1 ϭ 1.0 and n 2 ϭ 1.6.…”

“…This may be achieved by a decrease in wavelength and an increase in the numerical aperture (NA) of the scanning objective lens, as the size of the focal spot scales as ͞NA. The compact disk (CD) operates at a wavelength ϭ 0.785 m and a numerical aperture NA ϭ 0.45-0.50, the digital versatile disk (DVD) operates at a wavelength ϭ 0.660 m and a numerical aperture NA ϭ 0.50-0.65, and the recently proposed Blu-ray disk [1][2][3] (BD) and advanced optical disk 4 (AOD) make use of GaN lasers with wavelength ϭ 0.405 m, with BD using a numerical aperture NA ϭ 0.85, AOD a numerical aperture NA ϭ 0.65.…”

“…In order to maintain sufficient tolerance for coma from disk tilt, the increase in NA is accompanied by a decrease in substrate thickness. It is known that coma and spherical aberration scale as NA 3 and NA 4 , respectively, in the limit of small NA. 5,6 The current practice of optical disk readout is increasingly further away from this limit, making the accuracy of these scaling laws questionable.…”