Off-Axis Pancake Lens HUD Layout for Clear Driver Sightlines
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Solution Overview
Problem
Existing head-up display devices obstruct the user's line of sight due to the positioning of the imaging unit between the display screen and the user, limiting display flexibility and causing visual inconvenience during vehicle operation.
Innovation Solution
A head-up display device utilizing a pancake lens with a half transmittive concave mirror and reflective polarizer, where the picture generation unit is positioned opposite to the user, allowing off-axis image formation to avoid overlap and enhance display flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the picture generation unit is arranged between the display screen and the user, then the imaging function is achieved, but the line of sight is obstructed and installation area is limited
Solution Approach 1:
The patent introduces an off-axis angle between the optical path of the virtual image and the image light, transitioning from a coaxial arrangement to a separated spatial configuration. This dimensional change allows the picture generation unit to be positioned without blocking the user's line of sight while maintaining imaging functionality.
Solution Approach 2:
The patent employs asymmetric optical path design where the virtual image optical path and the image light optical path are deliberately separated by an off-axis angle. This asymmetric arrangement resolves the contradiction by allowing the picture generation unit to function without creating symmetry-based obstruction to the user's view.
2Ease of operation
If the picture generation unit is positioned to avoid blocking line of sight, then line of sight is clear, but display quality and image formation may be compromised
Solution Approach 1:
By introducing the off-axis angle as a new spatial dimension, the system achieves both clear line of sight and high display quality. The separated optical paths allow independent optimization of each function without compromising the other.
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 off-axis design improves display quality by preventing overlap between the image generation unit and the user's view, increasing spatial flexibility and aesthetic appeal while ensuring a good visual experience for various users.
Implementation Method 1
the half transmittive concave mirror includes a light incident surface and a reflective surface
Implementation Method 2
the reflective polarizer reflects the s-polarized light to the half transmittive concave mirror, after reflection, the image light passes through the quarter wave plate again to be converted to p-polarized light which penetrates the reflective polarizer
Implementation Method 3
the image light generated by the picture generation unit may be a p-polarized light, which enters the reflective space, then being converted to a s-polarized light by the quarter wave plate
Data Source
AI summary
A head up display device includes a pancake lens and a picture generation unit. The pancake lens includes a half transmittive concave mirror and a reflective polarizer. The half transmittive concave mirror has a light incident surface and a reflective surface. The reflective polarizer is disposed next to the half transmittive concave mirror at the side of the reflective surface for forming a reflective space therebetween. The picture generation unit is disposed in the direction of the pancake lens opposite to the user's eyes. The picture generation unit generates image light and the image light enters the reflective space from the light incident surface. After the reflection, the image light is directed towards the user's eyes to form a virtual image. The optical path of the virtual image and the image light has an off-axis angle.