Freeform Penta Prism Collimator for Wide-FOV Thin Waveguides
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Solution Overview
Problem
The development and adoption of wearable electronic display devices have been limited by constraints imposed by the optics, aesthetics, manufacturing process, thickness, and field of view (FOV) of existing optical systems, resulting in displays with small FOVs and thick optical combiners.
Innovation Solution
The use of a penta prism collimator with freeform surfaces, which folds the optical path and is formed from a single injection-molded element, combined with a field flattener to increase FOV and mitigate artifacts, allowing for a compact design and improved optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional optical systems are used, then the optical combiner can be manufactured, but the field of view remains small and the combiner thickness is large
Solution Approach 1:
The optical system is divided into distinct functional elements: the freeform penta prism collimator handles collimation and path folding, while the waveguide handles light transmission. This segmentation allows each component to be optimized independently, enabling a compact overall design that increases FOV without requiring increased combiner thickness
Solution Approach 2:
The freeform penta prism collimator folds the optical path into a compact three-dimensional configuration. By using multiple reflective surfaces at different angles and positions, the optical path is folded back on itself, achieving a wide field of view within a thin profile by utilizing the third dimension (depth) rather than expanding in the lateral plane
2Device complexity
If conventional collimating lenses are used, then light can be collimated, but the optical path becomes unfolded and the design becomes less compact with more complex manufacturing
Solution Approach 1:
The collimating function and the optical path folding function are merged into a single freeform penta prism collimator component. This integration eliminates the need for separate collimating lenses and folding mirrors, reducing the number of manufacturing steps and alignments required while achieving both collimation and compact path folding
Solution Approach 2:
The freeform surfaces of the penta prism collimator utilize complex curved geometries that are optimized for both collimation and path folding. These freeform surfaces, while complex in design, can be manufactured as single molded elements, simplifying the overall manufacturing process compared to assembling multiple conventional optical components
3Length of stationary object
If the optical combiner is made thinner, then wearability is improved, but the field of view and optical performance are reduced
Solution Approach 1:
The freeform penta prism collimator changes the angular parameters of the light rays through its multiple reflective surfaces. By carefully designing the surface angles and positions, the system achieves wide field of view coverage and proper collimation within a thin profile, maintaining optical performance without increasing combiner thickness
Solution Approach 2:
The patent replaces conventional mechanical optical systems (multiple lenses and mirrors) with an integrated freeform optical element that achieves the same functions through geometric design. This substitution enables thin combiner design while maintaining or improving optical performance through optimized light path control
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 solution achieves a wider field of view and reduces the thickness of the optical combiners, enhancing the user experience by minimizing artifacts and improving optical performance.
Implementation Method 1
A first freeform surface refracts the light toward a second freeform surface
Implementation Method 2
The second freeform surface reflects light received from the first freeform surface toward a third freeform surface
Implementation Method 3
propagates along the waveguide via total internal reflection (TIR)
Implementation Method 4
A fourth freeform surface refracts the light received from the third freeform surface in substantially parallel rays toward an input pupil of a waveguide
Data Source
AI summary
A penta prism collimator having four freeform surfaces that fold the optical path of light received from a microdisplay collimates light for coupling to a waveguide. In some embodiments, the freeform surfaces are toroidal surfaces made from a single injection-molded element, such as a single piece of plastic. The freeform surfaces collimate the light at a variety of distances from an input pupil of a waveguide, allowing for more freedom of placement within a frame of a WHUD.