Vehicle HUD Optical Path Layout for 3D Image Contrast
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Solution Overview
Problem
Conventional display devices for vehicles struggle to maintain contrast while displaying three-dimensional virtual images, which are essential for effective route guidance and attention alerts.
Innovation Solution
A display device incorporating a liquid crystal display with an optical system that includes a first reflecting surface and a magnifying reflecting surface, where the display surface is inclined towards the optical axis of the display light, and the optical path width is reduced in the vertical direction from the display surface to the first reflecting surface, ensuring that the upper part of the virtual image is formed in front of the lower part in the vehicle longitudinal direction, and the backlight unit collects illumination light in the vertical direction to enhance contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the display surface is inclined toward the optical axis to form a three-dimensional virtual image, then the virtual image visibility is improved, but the contrast of the virtual image is lowered
Solution Approach 1:
The patent applies local quality by making the display surface inclined at a specific angle (α) toward the optical axis, rather than being perfectly perpendicular. This localized angular adjustment creates a three-dimensional virtual image effect while the optical system compensates for contrast loss through precise optical path design, including the use of a half-mirror and specific reflection angles.
Solution Approach 2:
The patent changes the parameter of the display surface inclination angle (α) to optimize the balance between three-dimensional virtual image formation and contrast maintenance. By adjusting this angle parameter, the system achieves improved virtual image visibility while the optical path width reduction in the vertical direction compensates for contrast degradation.
2Reliability
If the optical path width in the vertical direction is reduced from the display surface toward the first reflecting surface, then the contrast is maintained, but the device complexity increases
Solution Approach 1:
The patent addresses contrast maintenance by reducing the optical path width in the vertical direction (image vertical direction) from the display surface toward the first reflecting surface. This dimensional adjustment in the vertical axis allows the system to maintain contrast while the inclined display surface provides three-dimensional virtual image formation, effectively using dimensional trade-offs to resolve the contradiction.
Solution Approach 2:
The patent introduces a half-mirror (first reflecting surface) as an intermediary element in the optical path. This half-mirror serves as a mediator that reflects display light while allowing precise control of the optical path width in the vertical direction, enabling contrast maintenance without requiring direct modification of the display surface itself.
3Shape
If the display surface is inclined toward the optical axis, then the upper part of the virtual image is formed in front of the lower part, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-setting the display surface inclination angle (α) during the design and manufacturing phase. This predetermined angular configuration ensures that the upper part of the virtual image is formed in front of the lower part, creating the desired three-dimensional shape. The angle is carefully predetermined to balance visual effectiveness with manufacturing feasibility.
Solution Approach 2:
The patent optimizes the display surface inclination angle parameter (α) to achieve an acceptable balance between three-dimensional virtual image formation and manufacturing precision requirements. By carefully selecting and standardizing this angular parameter, the system makes the inclined configuration practically manufacturable while still achieving the desired spatial arrangement of the virtual image.
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 prevents contrast reduction, improving the visibility and clarity of the virtual image by maintaining the necessary contrast and ensuring that the virtual image is displayed with enhanced visibility on the foreground.
Implementation Method 1
a liquid crystal panel that transmits or blocks backlight on a pixel basis in accordance with image signals
Implementation Method 2
an optical system that includes a first reflecting surface and that forms an optical path of display light from the display surface toward a windshield of the vehicle
Implementation Method 3
a magnifying reflecting surface that magnifies and reflects the display light
Implementation Method 4
a virtual image of the display light is formed by reflecting the display light by a windshield of the vehicle toward the eye point
Data Source
AI summary
A display device for a vehicle includes a liquid crystal display device including a display surface for displaying an image; and an optical system including a reflecting surface, and forming an optical path of display light from the display surface toward an eye point of a vehicle. The optical system includes a first reflecting surface placed closest to the display surface in the optical path of the display light, and a magnifying reflecting surface that magnifies and reflects the display light. When viewed from an image horizontal direction, the display surface is inclined toward an optical axis of the display light extending from the display surface toward the first reflecting surface. The optical system is configured so that a width of the optical path of the display light in an image vertical direction is reduced, gradually from the display surface toward the first reflecting surface.