Head-Up Display Virtual Image Tilt to Avoid Road Overlap
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Solution Overview
Problem
Conventional head-up displays can cause discomfort due to overlap of virtual images at a far focus position with the road surface, depending on the observer's viewpoint position, depression angle, and field of view in the vertical direction.
Innovation Solution
A head-up display system with a movable second lens or display device that adjusts the position of virtual images between near and far focus positions, inclining them to prevent overlap with the road surface, using a projection optical system with free-form surface lenses and mirrors to project images onto the windshield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If virtual images are displayed at a far focus position, then the display distance is increased, but the virtual images may overlap with the road surface causing observer discomfort
Solution Approach 1:
The patent applies dimensional change by tilting the virtual image display surface relative to the horizontal plane. Instead of displaying virtual images on a purely horizontal plane at far focus position, the system introduces a vertical tilt angle, transforming the display geometry from 2D horizontal to 3D inclined space. This dimensional adjustment allows the virtual images to be positioned at far focus distances while preventing overlap with the road surface by elevating the lower portion of the image plane.
Solution Approach 2:
The patent implements dynamics by making the virtual image display surface tiltable or adjustable. The system can dynamically change the tilt angle of the virtual image plane according to different display conditions, observer positions, and focus distances. This dynamic adjustment capability allows the display system to adaptively prevent road surface overlap while maintaining far focus positioning when needed.
2Adaptability or versatility
If the viewpoint position changes, then the observer's line of sight varies, but the visibility of virtual images may be compromised
Solution Approach 1:
The patent applies local quality by creating an inclined virtual image display surface where different portions of the image plane have different spatial orientations relative to the observer. The tilt is applied locally to the display surface geometry, allowing the upper and lower portions of virtual images to be positioned at different effective distances and angles, thereby maintaining visibility across varying viewpoint positions while preserving the far focus effect for the overall image.
3Length of stationary object
If the virtual image is positioned farther from the observer, then the far focus effect is enhanced, but the image may extend below the road surface level
Solution Approach 1:
The patent applies asymmetry by tilting the virtual image display surface at an angle rather than keeping it horizontal or perpendicular to the observer's line of sight. This asymmetric orientation causes the virtual image to be displayed with its lower portion elevated relative to what would be expected on a horizontal plane, preventing the image from extending below road surface level even when positioned at far focus distances.
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
Prevents virtual image overlap with the road surface, reducing observer discomfort and improving visibility by adjusting the virtual image position and inclination relative to the line of sight, enhancing cognitive ability and safety during driving.
Implementation Method 1
a projection optical system configured to project light from the display device to the windshield
Implementation Method 2
free-form surface lenses and mirrors to project images onto the windshield
Implementation Method 3
free-form surface lenses and mirrors to project images onto the windshield
Data Source
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AI summary
An object is to provide a head-up display capable of preventing an overlap of a virtual image at a far focus position with a road surface. The head-up display includes an imaging position changer (150) that includes a display device (110) to display an image and a projection optical system (140) for enlarging and projecting the image and is configured to change a position of a virtual image (I2) between a far visual position (P2) far from an observer (d) and a near visual position (PI) close to the observer (d). The imaging position changer (150) is configured to incline the virtual image (I2) at the far visual position (P2) by a second inclination angle with respect to a perpendicular plane to a reference light beam (Lc) reaching a center of a viewpoint region (300) in which a viewpoint of the observer (D) is located, to move an upper end (I2-u) thereof in a forward direction of the moving object (200), and incline the virtual image (I1) at the near visual position (PI) by a first inclination angle smaller than the second inclination angle with respect to the perpendicular plane to the reference light beam (Lc), to move the upper end (I1-u) in the forward direction of the moving object (200).