Aspherical Combiner for Head-Up Display Aberration Control
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Solution Overview
Problem
Head up displays for vehicles face challenges in minimizing image distortion due to aberration when a small combiner is used, which is necessary for limited space installations, while maintaining clear visibility for the driver.
Innovation Solution
The design incorporates a rotatable optical unit and a combiner with an aspherical reflection surface, allowing for adjustable attachment angles and positions to minimize distortion, using a biconic surface for the combiner to reduce spherical aberration and astigmatism, and employing a transmission-type or reflection-type intermediate image screen with specific diffusion layers for high resolution and wide viewing angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a small combiner is used to reduce device size for limited space installation, then the device can be mounted in compact vehicle spaces, but image distortion due to aberration increases
Solution Approach 1:
The patent applies an aspherical surface design to the combiner instead of a traditional spherical or flat surface. This aspherical curvature is specifically engineered to reduce optical aberrations (spherical aberration and astigmatism) that cause image distortion, while still maintaining the compact size of the combiner. The aspherical shape allows light rays to converge more accurately at the virtual image position, improving image quality without increasing device volume.
Solution Approach 2:
The patent changes the optical parameters of the combiner by introducing a specific aspherical coefficient (k值) in the aspherical surface equation. By adjusting this parameter and other optical parameters (curvature radius, thickness distribution), the system optimizes the balance between combiner size and image quality. This parameter optimization reduces aberration-induced distortion while maintaining compact dimensions suitable for vehicle mounting.
2Volume of moving object
If a small combiner is used to minimize device dimensions, then attachment space requirements are reduced, but the virtual image size and visibility decrease
Solution Approach 1:
The patent employs an intermediate image screen positioned between the projection optical system and the combiner to create a real intermediate image. This intermediate image is then reflected by the combiner to form a virtual image at a desired position. By introducing this intermediate imaging stage, the system can achieve a larger effective virtual image size while using a compact combiner, as the intermediate screen acts as an additional dimensional element in the optical path.
Solution Approach 2:
The intermediate image screen serves as an intermediary element that converts the projected light into a real image first, which is then reflected by the combiner to create the final virtual image. This intermediary approach allows the compact combiner to present a larger virtual image with improved visibility, as the intermediate screen effectively magnifies the image before it reaches the combiner.
3Length of stationary object
If the combiner is positioned closer to the projection optical system to reduce overall device size, then mounting space is minimized, but optical aberration effects are amplified
Solution Approach 1:
The aspherical surface of the combiner is specifically designed to compensate for the shortened optical path. The aspherical curvature parameters are optimized to reduce spherical aberration and astigmatism that are typically amplified when the combiner is positioned close to the projection optical system. This allows the system to maintain compact length while minimizing aberration-induced distortion.
Solution Approach 2:
The patent adjusts the aspherical coefficient and other optical parameters of the combiner to optimize performance at short object distances. By changing these parameters, the system reduces the impact of optical aberrations that are magnified when the combiner is positioned close to the projection system, thereby maintaining image quality in a compact configuration.
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
This configuration enables the presentation of a clear, distortion-free virtual image to the driver with improved visibility and resolution, even in compact vehicle installations, by optimizing the optical path and image screen technology.
Implementation Method 1
a combiner (400) having a reflection surface formed by an aspherical surface
Implementation Method 2
the aspherical surface to reduce spherical aberration and astigmatism
Implementation Method 3
a transmission-type or reflection-type intermediate image screen with specific diffusion layers for high resolution and wide viewing angles
Data Source
AI summary
An image display device (10) includes: a projection port (301) that projects image display light generated based on an image signal; and a combiner (400) that presents a virtual image by reflecting the image display light projected from the projection port (301). With respect to a specific direction along a reflection surface (410) of the combiner (400), the curvature of the combiner (400) in the specific direction becomes smaller as a distance from the projection port (301) becomes larger. The reflection surface (410) of the combiner (400) may be formed by a biconic surface.