Moire interference resistant diffuser for heads up displays
An apparatus, system, and method is described for partially or completely eliminating Moiré interference artifacts generated in a heads up display having a diffuser with a micro lens array. Each lenslet of the micro lens array is faceted with micro facets positioned at least partially randomized. Aspects of the faceting may be selected to prevent Moiré interference artifacts but permit the diffuser to be used in a heads up display.
1 . An optical diffuser for a Heads Up Display (HUD), comprising:
a micro lens array having an array of lenslets shaped to implement an optical diffuser function;
each individual lenslet having micro facets following a topological contour of a curved base lenslet shape for the individual lenslet with a placement of the micro facets selected to prevent Moiré interference artifacts in response to the micro lens array being illuminated by a digital light projector.
2 . The optical diffuser of claim 1 , wherein the placement of the micro facets is at least partially randomized.
3 . The optical diffuser of claim 2 , wherein each micro facet is selected to have a random position on a base lenslet.
4 . The optical diffuser of claim 2 , wherein the micro facets further have a random spatial position within an overall pattern.
5 . The optical diffuser of claim 1 , wherein the array of lenslets is shaped to implement one of: a flat top diffuser function, an asymmetric flat top diffuser function, and a gaussian diffuser function.
6 . The optical diffuser of claim 1 , wherein the micro facets are randomly placed on the surface of the lenslet.
7 . The optical diffuser of claim 1 , wherein a lenslet size is less than a size of one projected pixel.
8 . The optical diffuser of claim 1 , wherein a micro facet size is selected such that its diffraction limit angle is smaller than a diffuser angle.
9 . The optical diffuser of claim 1 , wherein each micro facet has a size less than 1% of a projected pixel size.
10 . A Heads Up Display (HUD), comprising:
a micro lens array having an array of mirrored lenslets to implement an optical diffuser, with each individual lenslet having micro facets following a topological contour of a curved base lenslet shape where the micro facets are placed in randomized positions on the curved base lenslet shape to prevent Moiré interference artifacts in response to the micro lens array being illuminated by a digital light projector.
11 . The HUD of claim 10 , wherein each micro facet is selected to have a random position on the curved base lenslet.
12 . The HUD of claim 11 , wherein the micro facets further have a random spatial position within an overall pattern.
13 . The HUD of claim 10 , wherein the micro facets are curved, with the curvature of the micro facets with a curvature derived from optical function lenslet.
14 . The HUD of claim 10 , wherein a lenslet size is less than a size of one projected pixel.
15 . The HUD of claim 10 , wherein a micro facet size is selected such that its diffraction limit angle is smaller than a diffuser angle.
16 . The HUD of claim 10 , wherein a micro facet size is less than 1% of a projected pixel size.
17 . The HUD of claim 10 , wherein the array of lenslets is shaped to implement one of: a flat top diffuser function, an asymmetric flat top diffuser function, and a gaussian diffuser function.
18 . An optical diffuser for a Heads Up Display (HUD), comprising:
a micro lens array having an array of lenslets to implement a flat top diffuser, with each individual lenslet having micro facets following a topological contour of a curved base lenslet shape with the micro facets placed in randomized positions on the curved base lenslet shape to prevent Moiré interference artifacts in response to the micro lens array being illuminated by a digital light projector, wherein the micro facets are curved, with the curvature of the micro facets being derived from an optical function of the lenslet, a micro facet size is below a diffraction limit size, and a micro facet size is less than 1% of a projected pixel size.
19 . A method of operating a heads up display, comprising:
providing a digital light projector;
providing a micro lens array having an array of lenslets to implement an optical diffuser, with each individual lenslet having micro facets following a topological contour of a curved base lenslet shape with the micro facets placed in randomized positions on the base lenslet shape to prevent Moiré interference artifacts in response to the micro lens array being illuminated by a digital light projector, wherein the micro facets are curved, with the curvature of the micro facets being derived from an optical function of the lenslet, a micro facet size is below a diffraction limit size, and a micro facet size is less than 1% of a projected pixel size; and
operating the digital light projector to generate a heads up display without Moiré interference artifacts.
20 . The HUD of claim 19 , wherein the array of lenslets is shaped to implement one of: a flat top diffuser function, an asymmetric flat top diffuser function, and a gaussian diffuser function.