Head-Up Display Diffuser Tilting for Parasitic Reflection Control
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Solution Overview
Problem
Existing head-up display systems for motor vehicles face challenges in achieving uniform illumination and avoiding parasitic reflections from external light sources, particularly the sun, which interfere with the driver's ability to read projected information.
Innovation Solution
A projection device comprising a light beam generator, a diffuser that scatters light into a diffused beam, and a flat imaging screen, where the diffuser is parallel and inclined relative to the imaging screen, optimizing optical efficiency and minimizing parasitic reflections by aligning the diffuser's optical diffusion indicator with the main light beam direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a folding mirror and partially reflecting plate are used to project information to the driver, then the driver can see projected information without looking away from the road, but parasitic reflections from external light sources interfere with the driver's ability to read the projected information
Solution Approach 1:
The patent applies asymmetry by tilting the diffuser and imaging screen at specific non-perpendicular angles (5°-30°) relative to the light beam direction. This asymmetric configuration breaks the symmetry of parasitic reflection paths, directing reflected light away from the driver's field of view while maintaining proper light transmission for image projection
Solution Approach 2:
The patent converts the harmful effect of external light reflections into a beneficial configuration by strategically positioning and tilting optical elements. The same optical elements that transmit projected light are configured to redirect parasitic reflections away from the driver, transforming potential interference into a means of eliminating ghost images
2Object-affected harmful factors
If the diffuser and imaging screen are tilted to avoid parasitic reflections, then ghost images are eliminated, but the optical path length and system complexity increase
Solution Approach 1:
The patent merges the diffuser and imaging screen into a closely integrated assembly where the diffuser is positioned immediately adjacent to the imaging screen. This combination allows both elements to be tilted together as a unit, achieving parasitic reflection elimination while minimizing the increase in optical path length that would result from separating the elements
Solution Approach 2:
The patent addresses the reflection problem by introducing a angular dimension (tilt angle) to the optical element arrangement. Rather than increasing path length in the longitudinal dimension, the solution rotates the optical elements in the angular dimension, eliminating ghost images through spatial reorientation rather than extended optical paths
3Illumination intensity
If the diffuser is positioned to optimize light diffusion, then illumination uniformity improves, but the alignment precision required increases
Solution Approach 1:
The patent optimizes illumination uniformity by carefully controlling the angular parameter (tilt angle) of the diffuser and imaging screen. By establishing specific angle ranges (5°-30°), the patent achieves optimal diffusion characteristics while providing sufficient tolerance for manufacturing and assembly variations
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 ensures uniform illumination and reduces parasitic reflections, enhancing the driver's ability to read projected information by optimizing the optical efficiency of the system and tilting the diffuser and imaging screen relative to the light beam, thereby preventing ghost images and external light interference.
Implementation Method 1
a means for diffusing the light from the illuminating light beam generated by the generating device into a diffused light beam, the light scattering means consisting of a flat diffuser
Implementation Method 2
a flat imaging screen comprising two faces opposite, an input face receiving the diffused light beam and an opposite output face producing a display light beam of determined main direction
Implementation Method 3
the device for generating an illuminating light beam comprises a reflector consisting of a hollow conduit and internally reflecting
Data Source
Figure 1~2
AI summary
The invention relates to a projecting apparatus (1) comprising: at least one device (2) for generating an illuminating light beam of set main direction (15); a means for scattering the light of the illuminating light beam generated by the generating device (2) into a scattered light beam, and a planar imaging screen (4) having two opposite faces, an entrance face that receives the scattered light beam and an opposite exit face that produces a display light beam of set main direction (16), the means for scattering the light consisting of a planar diffuser (3) placed between the exit of the generating device (2) and the imaging screen (4). According to the invention, the diffuser (3) is parallel to the imaging screen (4) and is applied against the entrance face of the imaging screen (4), the diffuser (3) and the imaging screen (4) are inclined with respect to the main direction (15) of the illuminating light beam generated by the generating device (2), and the diffuser (3) has an optical scattering indicatrix having a maximum for a direction aligned with the main direction (15) of the illuminating light beam generated by the generating device (2). A head-up display system comprising the apparatus is also presented.