The Blu-ray disc system not only employs a short wavelength blue-violet laser (405nm), but also uses an objective lens with a numerical aperture (NA) of 0.85. It’s small spot size can allows 5 times higher recording capacity than a standard DVD. The Blu-ray discs are designed with a 0.1 mm optically transparent protection layer, which diminishes aberration caused by disc tilt, yet is durable enough to protect the disc’s recording layer. The track pitch on the discs is a mere 0.32 μm, nearly half that of the DVD.