A diffractive grating element is divided into at least two different grating regions each having different diffractive properties and arranged on opposite sides with respect to a transition point to form a splitted grating structure. The diffractions generated by the at least two different grating regions...http://www.google.es/patents/US7483604?utm_source=gb-gplus-sharePatente US7483604 - Diffractive grating element for balancing diffraction efficiency
Diffractive grating element for balancing diffraction efficiency
