Head-Up Display Cover Geometry to Suppress Double Images
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Solution Overview
Problem
Conventional head-up display devices suffer from the issue of light propagating through the lens being recognized as a double image due to guidance to the occupant's eye point.
Innovation Solution
A head-up display device is designed with a display unit that includes a display instrument, a reflection mirror, and a transparent cover. The transparent cover has specific surface portions that control the incidence angle of irregular light, ensuring it is 65° or less, thereby reducing its luminance to 2% or less compared to regular light, preventing the double image effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent cover is used to block the housing opening and transmit enlarged display light, then the display light can reach the front windshield, but irregular light reflected by the first and second surface portions is visually recognized as a double image
Solution Approach 1:
The patent applies local quality by differentiating the functions of different surface portions of the transparent cover. The first surface portion (incidence surface) is designed with a specific incidence angle of 65° or less to control irregular light, while the second surface portion allows regular light to pass through. This local differentiation enables the cover to simultaneously transmit display light while suppressing double image formation by controlling how different types of light interact with different surfaces.
Solution Approach 2:
The patent employs parameter changes by specifying a critical incidence angle parameter (65° or less) for the first surface portion. By controlling this angular parameter, the optical path of irregular light is modified to prevent it from reaching the eye point as a visible double image. This parameter adjustment transforms the transparent cover from a simple light transmitter into an active optical element that selectively manages different light paths.
2Object-affected harmful factors
If the incidence angle of irregular light is reduced to 65° or less, then the luminance of irregular light is reduced to 2% or less of regular light, but the structural complexity of the transparent cover increases
Solution Approach 1:
The patent resolves the complexity issue by applying local quality - only the first surface portion (incidence surface) requires the specific 65° incidence angle design, while the second surface portion maintains a simpler configuration. This localized complexity approach minimizes the overall structural complexity increase while achieving the desired suppression of irregular light luminance to 2% or less of regular light.
3Object-affected harmful factors
If the first surface portion is designed with an incidence angle of 65° or less, then irregular light is effectively controlled, but the manufacturing precision requirements increase
Solution Approach 1:
The patent addresses manufacturing precision challenges by establishing a clear parameter threshold (65° incidence angle) that provides a measurable target for manufacturing. This specific angular parameter serves as a controllable variable that can be monitored and adjusted during the molding or fabrication process, transforming an abstract optical requirement into a concrete manufacturing specification that can be quality-controlled.
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 effectively prevents the virtual image made by irregular light from being visually recognized as a double image, allowing for appropriate display of the virtual image by regular light, enhancing the clarity and accuracy of the displayed information.
Implementation Method 1
a reflection mirror that is accommodated inside the housing, and reflects enlarged display light obtained by enlarging the display light emitted from the display instrument
Implementation Method 2
the display light guided to the eye point includes regular light transmitted through the transparent cover without being reflected by the first surface portion and the second surface portion of the transparent cover
Implementation Method 3
the first surface portion of the transparent cover has an incidence surface with an incidence angle of 65° or less, the incidence angle being an angle at which the irregular light enters the first surface portion
Data Source
AI summary
In a head-up display device, a transparent cover includes an inner surface portion positioned on a reflection mirror side, and an external side surface portion positioned on an opposite side of the reflection mirror side. Here, display light guided to an eye point includes a regular light transmitted through the transparent cover without being reflected by the inner surface portion and the outer surface portion of the transparent cover, and guided to the eye point, and irregular light transmitted through the transparent cover after being reflected by the inner surface portion and the outer surface portion of the transparent cover, and guided to the eye point. The inner surface portion of the transparent cover has an incidence surface with an incidence angle of 65° or less. The incidence angle is an angle at which the irregular light enters the incidence surface.