Patent ID: 9658378
Date: 2017-05-23
CPC Classifications: G02B,G03H

Claim:
1. An illumination unit comprising: a first coherent light source which emits a first white visible light beam; a second coherent light source which emits a second white visible light beam; a projection optical element which focuses the first white visible light beam and the second white visible light beam, respectively emitted from the first coherent light source and the second coherent light source, onto a focal plane; a first holographic optical element disposed on an optical path between the first coherent light source and the projection optical element, such that the first white visible light beam is incident on the first holographic optical element, wherein the first holographic optical element comprises a first fixed interference pattern which diffracts the first white visible light beam incident thereon; and a second holographic optical element disposed on an optical path between the second coherent light source and the projection optical element, such that the second white visible light beam is incident on the second holographic optical element, wherein the second holographic optical element comprises a second fixed interference pattern which diffracts the second white visible light beam incident thereon; wherein the first fixed interference pattern comprises information which diffracts the first white visible light beam incident thereon and thereby cancels an aberration of the projection optical element and the second fixed interference pattern comprise information which diffracts the second white visible light beam incident thereon and thereby cancels an aberration of the projection optical element, and wherein the projection optical element and the first holographic optical element are configured to focus the first white visible light beam onto a first point on the focal plane, and the projection optical element and the second holographic optical element are configured to focus the second white visible light bean onto a second point on the focal plane, the second point being different from the first point.