Head-Up Display Optics for Compact Size and Inclined Image Quality
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Solution Overview
Problem
Existing head-up displays face challenges in downsizing while maintaining excellent image quality, as inclining virtual images leads to increased vertical display size due to optical aberration limitations.
Innovation Solution
A head-up display design featuring a projection optical system with a free-form surface lens and mirror, where the free-form surface lens has a stronger diverging action in the horizontal direction and the free-form surface mirror has a stronger converging action in the horizontal direction, allowing for a shorter focal length in the vertical direction and a longer focal length in the horizontal direction, thus reducing the vertical size and increasing the horizontal size of the display device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a virtual image is significantly inclined to allow correct perception of independent virtual images, then the driver can correctly perceive independent virtual images, but the use region in the vertical direction of the display device is widened and the size of the display device is increased
Solution Approach 1:
The patent changes the optical parameters by introducing a telephoto optical system with specific focal length relationships (focal length in vertical direction is shorter than in horizontal direction). This parameter change allows the virtual image to be inclined for correct perception while controlling the vertical size of the display device through optimized optical path length and focal length ratios.
Solution Approach 2:
The patent employs an asymmetric optical system where the focal lengths differ between vertical and horizontal directions. This dimensional differentiation allows independent control of image inclination and display device size, resolving the contradiction by operating in different dimensional parameters for different functions.
2Length of stationary object
If the size of the display device is reduced in the vertical direction, then the display device can be downsized, but a virtual image with excellent image quality cannot be presented due to optical aberration limitations
Solution Approach 1:
The patent optimizes optical parameters including focal length ratios, optical path lengths, and telephoto ratio (0.3 < telephoto ratio < 0.8) to achieve both compact vertical size and excellent image quality. By carefully controlling these parameters, the system reduces optical aberrations while maintaining small display device dimensions.
Solution Approach 2:
The patent replaces conventional optical configurations with a telephoto optical system that uses free-form surfaces and asymmetric lens designs. This substitution enables better aberration control in a compact form factor by utilizing advanced optical designs rather than traditional mechanical arrangements.
3Length of stationary object
If the focal length in the vertical direction is made short to downsize the display device, then the vertical size is reduced, but the focal length in the horizontal direction must be long to maintain image quality
Solution Approach 1:
The patent deliberately introduces asymmetry in the optical system by designing different focal lengths for vertical and horizontal directions. The telephoto optical system has a shorter focal length in the vertical direction and a longer focal length in the horizontal direction, creating an asymmetric configuration that simultaneously achieves compact size and high image quality through optimized focal length ratios.
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 head-up display to be downsized without compromising image quality, even when the virtual image is inclined, by optimizing the focal lengths and reducing the vertical size while maintaining a larger horizontal size, thereby preventing an increase in the display device's vertical size.
Implementation Method 1
the free-form surface lens has a stronger diverging action in the horizontal direction than in the vertical direction
Implementation Method 2
the free-form surface mirror has a stronger converging action in the horizontal direction than in the vertical direction
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The present disclosure provides a head-up display capable of being downsized yet presenting a virtual image with excellent image quality. The head-up display 100 displays an image as a virtual image I and includes a display device 110 to display the image, and a projection optical system 140 to enlarge and project the image. The projection optical system 140 includes a first optical element 123 and a second optical element 125 arranged in this order in an optical path from the image. The first optical element 123 has a diverging action that is stronger in a horizontal direction than in a vertical direction. The second optical element 125 has a converging action that is stronger in the horizontal direction than in the vertical direction.