Head-Up Display Projection Unit Sunlight Secondary Image Suppression
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Solution Overview
Problem
Head-up displays experience luminance inhomogeneity and secondary image issues due to sunlight interaction with the TFT display, leading to unwanted phantom images that are not effectively suppressed by existing technologies.
Innovation Solution
Incorporating a circular polarization filter and a linear polarization filter in the beam path between the optical element and the light exit area of the projection unit, where sunlight is first linearly polarized, then circularly polarized, and finally absorbed by the linear polarization filter due to reversed polarization direction, preventing secondary images from forming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a TFT display is used as an imaging unit in a head-up display, then the display can show information with good clarity, but sunlight passing through the display is reflected by the lens back towards the display, creating unwanted secondary images
Solution Approach 1:
The patent applies polarization filters to change the optical parameter of light passing through the system. A first polarization filter is placed in the beam path to polarize light before it reaches the TFT display, and a second polarization filter is positioned to block the reflected light from the lens. This parameter change in light orientation prevents the secondary image formation while maintaining display functionality.
Solution Approach 2:
The polarization filters act as intermediary elements between the sunlight source and the TFT display-lens system. These filters mediate the interaction by selectively transmitting and blocking light based on polarization orientation, thereby preventing the harmful reflection cycle without interfering with the normal display operation.
2Object-generated harmful factors
If polarization filters are added to suppress secondary images, then secondary image suppression is improved, but the device complexity increases
Solution Approach 1:
The patent employs relatively simple and inexpensive polarization filter elements that can be integrated into the existing head-up display structure. These filters are straightforward optical components that do not require complex mechanisms or expensive materials, allowing for cost-effective implementation 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
This configuration effectively suppresses secondary images with minimal effort and in a compact manner, ensuring improved image quality by preventing sunlight from exiting the projection unit and reducing phantom images.
Implementation Method 1
a circular polarization filter and a linear polarization filter downstream of the circular polarization filter are provided in the beam path between the at least one optical element and a light exit area
Implementation Method 2
the reflected light linearly polarized in the second polarization direction is absorbed by the first, linear polarization filter
Data Source
AI summary
The projection unit comprises a lighting unit, an optical element arranged downstream of the lighting unit, and an imaging unit arranged downstream of the optical element, wherein a circular polarization filter and a linear polarization filter arranged downstream of the circular polarization filter are arranged in the beam path between the optical element and a light emitting area. The method is used to operate a project unit for a head-up display, wherein the head-up display comprises a lighting unit, an optical element arranged downstream of the lighting unit, and an imaging unit arranged downstream of the optical element, wherein sunlight entering the project unit is first linearly polarized in a first polarization direction by means of a first polarization means, the sunlight is then circularly polarized by means of a second polarization means, then partially reflected by the optical element, then linearly polarized in a second polarization direction by means of the second polarization means, wherein the first polarization direction and the second polarization direction are substantially perpendicular to each other and the reflected light linearly polarized in the second polarization direction is absorbed by means of the first polarization means.