Virtual Image Generation Element with Relay Lens for HUD
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Solution Overview
Problem
Conventional head-up displays (HUDs) face challenges in providing a large viewing angle for virtual images while minimizing the attenuation of luminance, particularly when the combiner is mounted near the ceiling, which can lead to an oppressive feel and complex installation due to the need for power lines, and existing configurations often result in reduced visibility of virtual images.
Innovation Solution
A virtual image generation device using a transmission-type combiner with a dielectric multilayer and cholesteric liquid crystal layer, which selectively reflects and transmits light to maintain a wide field of view and reduce optical effects on background light, allowing for a combiner placement around the ceiling without the need for ceiling-mounted power sources, thereby enhancing user experience and installation ease.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the combiner is positioned close to the driver, then the viewing angle of the virtual image becomes large, but the luminance of the virtual image is heavily attenuated
Solution Approach 1:
The patent introduces a relay lens as an intermediary optical element between the combiner and the driver's eyes. This relay lens collects and redirects light rays that would otherwise be lost, effectively coupling the combiner to the eye through an extended optical path. The intermediary lens system maintains luminance while enabling a larger viewing angle by redirecting light from the combiner to cover a wider angular range at the eye position.
Solution Approach 2:
The patent extends the optical path by introducing a relay lens system that creates a virtual image of the combiner at a different spatial location. This dimensional transformation allows the combiner to be positioned close to the driver while the relay lens projects the image to an effective viewing distance, simultaneously achieving large viewing angle and adequate luminance through spatial rearrangement of the optical elements.
2Area of moving object
If the combiner is mounted near the ceiling to enlarge the viewing angle, then the viewing angle becomes large, but the driver feels a sense of oppression and power lines must be drawn to the ceiling making mounting troublesome
Solution Approach 1:
Instead of mounting the combiner near the ceiling to achieve large viewing angle, the patent inverts the approach by positioning the combiner close to the driver and using a relay lens to achieve the large viewing angle effect. This inversion eliminates the need for ceiling mounting and associated power line routing, making installation straightforward while maintaining the desired viewing angle.
Solution Approach 2:
The relay lens acts as an intermediary that decouples the combiner position from the effective viewing geometry. By introducing this intermediate optical element, the system achieves ceiling-mounted viewing angles without physically mounting the combiner on the ceiling, thereby avoiding the installation complexity of routing power lines to the ceiling while maintaining ease of operation.
3Area of moving object
If the combiner is mounted near the ceiling, then the viewing angle becomes large, but the real image display device must be arranged on the driver side with respect to the combiner requiring ceiling-mounted power sources
Solution Approach 1:
The patent inverts the conventional ceiling-mounted combiner configuration by placing the combiner near the driver and using a relay lens to achieve the desired viewing angle. This inversion eliminates the need for complex ceiling-mounted power source arrangements, reducing installation complexity while maintaining large viewing angle through the relay lens optical path extension.
Solution Approach 2:
The relay lens serves as an intermediary that separates the combiner position from the effective image projection location. This allows the real image display device to remain in a convenient position near the driver while the relay lens creates the optical effect of a ceiling-mounted system, thereby reducing device complexity and installation requirements without sacrificing viewing angle.
4Illumination intensity
If a transmission-type combiner with dielectric multilayer and cholesteric liquid crystal layer is used, then the field of view is wide and luminance attenuation is reduced, but the structure becomes more complex
Solution Approach 1:
The patent employs a composite structure combining dielectric multilayer and cholesteric liquid crystal layer in the combiner. The dielectric multilayer provides wavelength-selective reflection with high efficiency, while the cholesteric liquid crystal layer provides circular polarization-selective reflection. This composite material approach achieves superior luminance transmission and wide field of view by selectively reflecting only the specific wavelengths and polarizations of the display light, while the relay lens compensates for the increased structural complexity by simplifying the overall optical path management.
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 provides a wide field of view for virtual images with reduced luminance attenuation, minimizing the oppressive feel and installation complexity by using a combiner that refracts real image display light and transmits background light, ensuring proper visibility and ease of installation.
Implementation Method 1
a dielectric multilayer having wavelength selectivity and incident angle dependency
Implementation Method 2
refracts real image display light
Implementation Method 3
a cholesteric liquid crystal layer having a helical structure
Implementation Method 4
selectively reflects and transmits light
Implementation Method 5
refracts real image display light and transmits background light
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A virtual image generation element, which constitutes, for example, a combiner, includes a first optical element and a second optical element. Circularly polarized image light is incident on the first optical element. On the second optical element which has a circular dichroism, the image light having passed through the first optical element is incident. The surface of the first optical element is angled with respect to the surface of the second optical element. The second optical element reflects the image light having passed through the first optical element and thereafter transmits the image light reflected by the first optical element.