An optical element is provided with one or more sets of diffractive elements. Individual diffractive element transfer functions collectively yield corresponding overall transfer functions between corresponding entrance and exit ports. Diffractive elements are defined by contours that include diffracting...http://www.google.es/patents/US6678429?utm_source=gb-gplus-sharePatente US6678429 - Amplitude and phase control in distributed optical structures
Amplitude and phase control in distributed optical structures
