Light is emitted from a light-emitting element toward an irradiated medium, and returning light reflected by the irradiated medium is diffracted by a hologram device. A polarizer polarizes the light diffracted by the hologram device to produce first polarized light that has passed through ...http://www.google.com/patents/US5703861?utm_source=gb-gplus-sharePatent US5703861 - Integrated confocal optical pick-up head with a hologram and a polarizer mounted on each side of a transparent heat sink 
