New Scientist The three-centimetre disc will be the same thickness as a DVD, but the phase-change material that records the data will be a mere 0.1 millimetres thick, compared to 0.6 millimetres for DVDs. Philips says this should mean there is less risk of beam distortion if the disc tilts when the portable device gets jogged. Portable DVD players will not play smoothly if jogged.
This jog-resistance is helped by making the glass and polymer lens that focuses the laser only 1.3 millimetres wide, just one-third the size of the lens in a DVD recorder. This means the optics need be only one-tenth the mass of their counterpart in a DVD, light enough for an electromagnet to keep them steady.
The drive is currently 0.5 centimetres thick, 5.6 centimetres long and 3.4 centimetres wide. The first versions of the disc will store one gigabyte on each side, but the dual-layer coating already used for DVDs will double the capacity to four gigabytes in total.