Aspheric Mirror Reverse Curvature HUD Optical Quality
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Solution Overview
Problem
Head-Up Display (HUD) systems suffer from poor optical quality due to imperfections in mirrors, such as inaccuracies in curvature and surface defects, which can decrease safety by making it harder for users to read projected information, and there is a demand for larger AR HUD images that are difficult to produce with current optical components.
Innovation Solution
The use of glass or glass-ceramic materials for 3D mirrors with aspheric surfaces and reverse curvature, formed using a ditch-type vacuum hole mold to prevent surface damage and achieve high shape accuracy and low surface roughness, allowing for larger, high-quality AR HUD images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional mirrors are used in HUD systems, then the system can be manufactured with standard components, but the optical quality of the projected image deteriorates due to surface imperfections and curvature inaccuracies
Solution Approach 1:
The patent applies parameter changes by transitioning from conventional spherical mirrors to aspheric mirrors with specifically optimized curvature parameters. The aspheric surface profile is defined by mathematical equations that control the radius of curvature at different zones, enabling precise control of light reflection paths to eliminate spherical aberration and improve optical quality while maintaining manufacturability through controlled parameter specifications.
Solution Approach 2:
The patent implements spheroidality by designing an aspheric mirror surface that deviates from a simple spherical shape. The mirror surface is defined by an aspheric equation that incorporates higher-order curvature terms, allowing the surface to be more accurately shaped to focus reflected light and correct optical aberrations, thereby improving image quality without requiring complex multi-element optical systems.
2Area of stationary object
If the mirror size is increased to produce larger AR HUD images, then the field of view and image size improve, but manufacturing precision deteriorates due to difficulties in producing large mirrors with suitable quality
Solution Approach 1:
The patent applies segmentation by dividing the large mirror into smaller sub-apertures or zones during the manufacturing process. This allows each zone to be formed and polished independently with higher precision, then combined or used together as a large effective aperture. The aspheric design also segments the optical function across different radial zones of the mirror, with each zone contributing to the overall image formation with controlled curvature.
Solution Approach 2:
The patent employs dimensionality change by transitioning from two-dimensional flat mirrors to three-dimensional aspheric surfaces. This adds a curvature dimension that enables large mirrors to maintain optical precision by controlling the third dimension (surface height profile) to compensate for aberrations that would otherwise require smaller apertures. The aspheric profile in the third dimension allows large aperture mirrors to achieve the optical quality previously only attainable with smaller mirrors.
3Manufacturing precision
If the mirror surface is highly polished to improve optical quality, then surface roughness decreases, but edge imperfections from cutting and shaping increase
Solution Approach 1:
The patent applies preliminary action by performing edge finishing operations (cutting, shaping, polishing) before the final high-precision surface polishing and coating processes. This sequence allows edge imperfections to be addressed and minimized before the mirror undergoes the costly and time-consuming high-precision surface preparation, preventing the propagation of edge defects through subsequent manufacturing steps and reducing the need for extensive rework.
Solution Approach 2:
The patent implements local quality by applying different surface treatments and polishing procedures to different regions of the mirror. The center optical zone receives the most intensive polishing to achieve the highest surface smoothness for optimal light reflection, while the edge zones receive targeted treatment to minimize imperfections without requiring the same level of polish as the central optical path. This localized approach optimizes overall optical quality while managing manufacturing complexity.
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 results in HUD systems with improved optical quality and larger AR HUD images, enhancing user safety and convenience by providing clear, readable information without edge distortion, while maintaining superior surface and edge quality.
Implementation Method 1
conforming the mirror preform to the curved support surface of the molding apparatus
Data Source
AI summary
A three-dimensional (3D) mirror is provided that includes a glass substrate with a first major surface, a second major surface opposite to the first major surface, and a minor surface connecting the first and second major surfaces. The 3D mirror also includes a reflective layer on the first major surface of the glass substrate. The first major surface comprises an aspheric curvature and a reverse curvature that is disposed in a reverse curve region of the glass substrate. The first major surface has a surface roughness Ra in the reverse curve region of about 3 nm or less, and a peak to valley (PV) surface roughness in the reverse curve region of about 30 nm or less.