Head-Up Display Waveguide Optical Correction for Curved Windshield Distortion
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Solution Overview
Problem
Existing head-up displays (HUDs) face challenges in achieving a large field-of-view (FOV) without bulky projectors and suffer from image distortion due to curved windshields, particularly in the third type of HUDs that use a horizontally arranged waveguide hidden from the user's sight.
Innovation Solution
A head-up display device featuring a waveguide and an optical correction element that corrects image distortions caused by a curved image surface, utilizing a quarter-wave plate to alter polarization and prevent direct out-coupling of uncorrected light, allowing for increased FOV and eyebox without additional visible equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a direct image projector is arranged below the windshield to project images to the windshield, then the image can be displayed on the windshield, but achieving a large field-of-view requires relatively large projectors which are difficult to fit in the instrument board
Solution Approach 1:
The patent replaces the traditional direct image projector with a waveguide-based optical system. The waveguide uses total internal reflection and diffraction gratings to guide and project images, eliminating the need for bulky mechanical projector components while achieving a large field-of-view through optical path manipulation within the windshield structure.
Solution Approach 2:
The patent employs a thin waveguide structure that can be integrated into the windshield. The waveguide uses layered optical elements including diffraction gratings and total internal reflection surfaces to project images, replacing thick projector assemblies with a thin, flexible optical film structure that maintains large field-of-view capability.
2Object-generated harmful factors
If a horizontally arranged waveguide is used to couple images to the user's eye via the windshield, then the image element is hidden from the user's sight, but the curved windshield produces remarkable optical aberration that distorts the image
Solution Approach 1:
The patent introduces an optical correction element as an intermediary component between the waveguide and the windshield. This correction element compensates for the optical aberrations caused by the curved windshield surface, correcting image distortion while allowing the waveguide to remain hidden from direct user view.
Solution Approach 2:
The patent modifies the optical parameters of the light path by using an optical correction element that adjusts the wavefront curvature and direction of light rays. This changes the optical parameters to compensate for the windshield-induced aberrations, restoring image quality without exposing the image element.
3Device complexity
If light is coupled directly from the waveguide to the user's eye without polarization control, then the system is simpler, but uncorrected light can directly couple out towards the image surface causing ghost images
Solution Approach 1:
The patent applies polarization-sensitive optical elements at specific locations within the waveguide system. These elements selectively control light polarization states at critical interfaces, preventing direct out-coupling of uncorrected light towards the image surface while maintaining overall system functionality with minimal added 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 effectively corrects optical distortions on curved windshields, increases the field-of-view and eyebox, and prevents ghost images by using polarization-sensitive elements, enabling a thin, efficient image projection system without visible equipment.
Implementation Method 1
light incident on the light guide prism 40 is completely internally reflected several times
Implementation Method 2
a quarter-wave plate capable of altering the polarization of light and being arranged between the waveguide and the optical correction element so that said light passes twice through the quarter-wave plate
Implementation Method 3
the optical correction element is further configured to perform an optical function for said light that corrects image distortions caused by the curved image surface
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a head-up display device(11), a vehicle comprising such device and a method of forming an image in a head-up display device. The head-up display device is adapted to project an image on an image surface(10), such as a windshield. The device comprises a waveguide (12) capable of guiding light carrying the image to be displayed, and an optical correction element. According to the invention, the waveguide (12)is configured to couple light propagating therein towards the optical correction element(14), and the optical correction element is further configured to perform an optical function for said light and to direct the light towards the image surface (10) through the waveguide(12).