Polarized Optical Path Folding for Compact AR-HUD Projection
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Solution Overview
Problem
The increasing requirements for field of view (FOV) and virtual image distance (VID) in augmented reality head-up displays (AR-HUD) lead to a volume increase, which is not compatible with the limited internal space in vehicles, affecting the on-board use of these devices.
Innovation Solution
A projection apparatus utilizing a reflective polarizer and polarization converters to selectively transmit and reflect polarized light beams, reducing the overall volume while increasing FOV and VID.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the field of view (FOV) and virtual image distance (VID) are increased to improve imaging effect and driver experience, then the volume of the AR-HUD device increases, but the limited internal accommodating space in vehicles is exceeded
Solution Approach 1:
The patent employs free-form surfaces with complex three-dimensional geometries to achieve high magnification ratios (100x or more) within a compact volume. The free-form surfaces utilize non-spherical, non-cylindrical curvature variations in multiple dimensions to fold and expand the optical path, enabling large FOV and VID parameters without proportionally increasing device volume. This dimensional complexity allows the optical system to achieve imaging effects comparable to much larger traditional systems while maintaining a compact form factor suitable for vehicle integration.
2Manufacturing precision
If free-form surfaces are used to achieve high magnification and large FOV, then the imaging effect is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent integrates multiple optical functions into the free-form surfaces themselves, combining magnification, field expansion, and optical path folding into single optical elements. By merging these functions that would traditionally require separate components into unified free-form surfaces, the system achieves high imaging performance while reducing the total number of discrete elements and overall system complexity.
Solution Approach 2:
The patent utilizes variable curvature parameters across the free-form surface areas, where the surface geometry changes continuously in multiple directions rather than maintaining fixed curvature radii. This parameter variation allows a single surface to perform multiple optical functions simultaneously, achieving high magnification and large FOV without requiring cascaded optical elements, thereby simplifying the overall system architecture.
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 effectively controls the volume increase, allowing for larger FOV and VID without significantly increasing the projection apparatus' size, optimizing optical design and reducing manufacturing complexity.
Implementation Method 1
a polarization component for changing a polarization state of a light beam
Implementation Method 2
the first polarization converter...is configured to: transmit the polarized light beam and change a polarization state of the polarized light beam
Implementation Method 3
the first curved mirror is configured to reflect the polarized light beam
Data Source
AI summary
A projection apparatus, a display device, a transportation means, and a projection method are provided. A picture generation unit in the projection apparatus emits a polarized light beam to a reflective polarizer, and the polarized light beam passes through the reflective polarizer, which selectively transmits light in different polarization states. The polarized light beam via the reflective polarizer is transmitted through a first polarization converter to change a polarization state, is transmitted through the first polarization converter again after being reflected by a curved mirror to change the polarization state, and passes through the reflective polarizer. The polarized light beam via the reflective polarizer twice has different polarization states. The projection apparatus may selectively process the polarized light beam. Space may be reused by an optical path, so that an inner structure of the projection apparatus is compact.