DIFFRACTIVE OPTICS: Harmonic optical element simplifies Blu-ray optics

摘要

A harmonic optical element added behind the objective lens of a Blu-ray pickup allows it to handle Blu-ray, DVD, and CD wavelengths with a single optical system. Blu-ray is a relatively new format for optical storage that provides higher capacity than DVD. The standards for 12 cm Blu-ray rewritable discs were established in 2002--the discs provide up to two hours of high-definition content with a single-layer recording capacity of 25 GByte. Because this device was intended for the highly competitive consumer market, it needed to be backward compatible with standard DVD and CD media.