Head mounted display device with fresnel lens with varying facet angles and method thereof

Abstract

A head mounted display device includes a display panel and a lens assembly mounted so that an optical axis of the lens assembly intersects the display panel. The lens assembly includes a lens body having a surface facing the display panel and defining Fresnel prisms. A Fresnel prism of the Fresnel prisms has a first facet angle when viewed in a first cross-section and has a second facet angle when viewed in a second cross-section parallel to the first cross-section. The first facet angle is different than the second facet angle.

What is claimed is: 
     
         1 . A head mounted display (HMD) device comprising:
 a housing;   a first display panel disposed in the housing; and   a first lens assembly disposed adjacent to the first display panel, the first lens assembly having a first lens body with a first surface defining a first set of Fresnel prisms, wherein each Fresnel prism of the first set has a varying facet angle.   
     
     
         2 . The HMD device of  claim 1 , further comprising:
 a second display panel disposed in the housing; and   a second lens assembly disposed adjacent to the second display panel, the second lens assembly having a second lens body with a second surface defining a second set of Fresnel prisms, wherein each Fresnel prism of the second set has a varying facet angle.   
     
     
         3 . The HMD device of  claim 2 , wherein the second set of Fresnel prisms is a reflection of the first set of Fresnel prisms. 
     
     
         4 . The HMD device of  claim 1 , wherein the first surface of the lens body faces the first display panel. 
     
     
         5 . The HMD device of  claim 1 , wherein the facet angle of each Fresnel prism of the first set varies linearly. 
     
     
         6 . The HMD device of  claim 1 , wherein the facet angle of each Fresnel prism of the first set varies non-linearly. 
     
     
         7 . The HMD device of  claim 1 , wherein the lens body has a second surface opposite the first surface, the second surface defining a second set of Fresnel prisms, wherein each Fresnel prism of the second set has a varying facet angle. 
     
     
         8 . The HMD device of  claim 1 , wherein a Fresnel prism of the first set has a first facet angle when viewed in a first cross-section and has a second facet angle when viewed in a second cross-section parallel to the first cross-section, the first facet angle different than the second facet angle. 
     
     
         9 . The HMD device of  claim 8 , wherein the first lens body has a first fitted radius of curvature in the first cross-section and a second fitted radius of curvature in the second cross-section, the first fitted radius smaller than the second fitted radius. 
     
     
         10 . The HMD device of  claim 8 , wherein the Fresnel prism has equal facet heights in the first and second cross-sections. 
     
     
         11 . The HMD device of  claim 8 , wherein Fresnel prisms adjacent the Fresnel prism have approximately equal facet heights as the Fresnel prism. 
     
     
         12 . The HMD device of  claim 8 , wherein pitches between adjacent pairs of Fresnel prisms including the Fresnel prism are approximately equal. 
     
     
         13 . The HMD device of  claim 1 , wherein the first lens body is curved in each orthogonal pair of cross-sections intersecting at a location within the first lens body. 
     
     
         14 . The HMD device of  claim 1 , wherein the first lens body is anamorphic. 
     
     
         15 . In a head mounted display (HMD) device, a method comprising:
 displaying imagery via a display panel of the HMD device; and   directing the displayed imagery to a user's eye via a lens assembly adjacent to the display panel, the lens assembly comprising a lens body having a first surface that defines a first set of Fresnel prisms, wherein each Fresnel prism of the first set has a varying facet angle.   
     
     
         16 . The method of  claim 15 , wherein the first surface of the lens body faces the display panel. 
     
     
         17 . The method of  claim 15 , wherein the facet angle of each Fresnel prism of the first set varies linearly. 
     
     
         18 . The method of  claim 15 , wherein the facet angle of each Fresnel prism of the first set varies non-linearly. 
     
     
         19 . The method of  claim 15 , wherein the lens body has a second surface opposite the first surface, the second surface defining a second set of Fresnel prisms, wherein each Fresnel prism of the second set has a varying facet angle. 
     
     
         20 . The method of  claim 15 , wherein a Fresnel prism of the first set has a first facet angle when viewed in a first cross-section and has a second facet angle when viewed in a second cross-section parallel to the first cross-section, the first facet angle different than the second facet angle.