Folded Optics Virtual Image Assembly for Vignetting and Ghost Reduction
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Solution Overview
Problem
Commercially available display devices are not designed for folded optics lens modules, leading to issues such as high contrast at the center, lower light intensity at the far field, vignetting, and ghost images due to non-optimal angular output profiles, which adversely impact the viewing experience in virtual and augmented reality applications.
Innovation Solution
An optical system centered on an optical axis, incorporating a display panel, illumination source, light redirecting film, and lens assembly, including a reflective polarizer, to redirect and focus cones of light uniformly across the display panel, reducing vignetting and improving luminance uniformity and contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional display device is used with folded optics lens module, then the device can be implemented, but light intensity decreases at far field due to vignetting
Solution Approach 1:
The patent applies local quality by varying the emission surface characteristics across different regions of the display device. The emission surface is designed with position-dependent properties to compensate for vignetting effects, ensuring uniform light intensity distribution across the entire field of view including far field regions.
Solution Approach 2:
The patent employs parameter changes by adjusting the emission surface parameters (such as size, shape, or intensity distribution) based on the viewing angle and position. This dynamic parameter adjustment compensates for the vignetting effect that normally causes light intensity to decrease at far field angles.
2Reliability
If conventional display devices are used with folded optics lens module, then the system can operate, but ghost images are generated
Solution Approach 1:
The patent extracts and eliminates the harmful ghost image artifacts by carefully designing the emission surface to prevent stray light paths that cause ghost images. The emission surface configuration ensures that only the desired direct light paths reach the viewer's eye, while unwanted reflected or scattered light paths are blocked or redirected.
3Area of stationary object
If the emission surface is made smaller than the display panel, then the optical system becomes more compact, but light coverage must be optimized
Solution Approach 1:
The patent uses parameter changes by optimizing the emission surface dimensions and intensity distribution to achieve uniform light coverage across the entire display panel despite the smaller emission surface area. The emission surface parameters are carefully tuned to compensate for the reduced size through enhanced intensity concentration and strategic positioning.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The optical system enhances luminance uniformity, brightness, and reduces optical artifacts like ghost images, providing a compact and high-resolution display with improved viewing experience.
Implementation Method 1
a light redirecting film disposed between the display panel and the emission surface of the illumination source, and including a regular array of light redirecting elements configured to receive, transmit, and redirect at least some of, the cones of light emitted from the emission surface
Implementation Method 2
a lens assembly disposed between the display panel and the eye location, and including at least one of a lens, a partial reflector, and a reflective polarizer, such that the cones of image light pass to the eye location in the eye box after being focused by the lens assembly
Implementation Method 3
including at least one of a lens, a partial reflector, and a reflective polarizer
Implementation Method 4
including at least one of a lens, a partial reflector, and a reflective polarizer
Data Source
AI summary
An optical system includes a display, at least one lens, and at least one of a partial reflector and a reflective polarizer. The optical system forms a virtual image of an image emitted by the display for viewing by an eye. The emitted image includes a plurality of cones of image light. Each cone of image light propagates from a different corresponding location on the emitted image and includes a central light ray propagating along a central axis, such that in each of orthogonal first and second planes that include the central axis, an intensity distribution of the cone of image light as a function of angle relative to the central axis includes a substantially flat peak having a full width of at least 15 degrees across which the peak changes by less than about 20%, and a corresponding fullwidth at half maximum that is less than about 60 degrees.