Head-Up Display Lens Array Curvature for Windshield Luminance
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Solution Overview
Problem
Existing head-up display devices in vehicles experience luminance variations when the occupant's viewpoint position changes vertically due to differences in windshield light reflectivity, affecting image brightness.
Innovation Solution
A head-up display device with a lens array that diffuses light from a condensing lens, where the curvature radius of lens surfaces varies continuously from smaller to larger, ensuring consistent luminance across the windshield, minimizing luminance differences when the viewpoint position changes vertically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional head-up display device projects an image on the windshield, then the image can be displayed in front of the windshield, but the luminance of the image varies when the viewpoint position of the occupant changes in the vertical direction due to differences in light reflectivity of the windshield
Solution Approach 1:
The lens array is designed with non-uniform lens surface curvature where the curvature radius varies in the vertical direction. Specifically, the curvature radius at the upper side of each lens surface is smaller than that at the lower side, creating local optical property variations that compensate for the vertical reflectivity gradient of the windshield. This local quality adjustment ensures uniform luminance perception across different viewpoint positions.
Solution Approach 2:
The patent changes the optical parameter (curvature radius) of the lens surfaces in the vertical direction to compensate for windshield reflectivity variations. By making the curvature radius smaller at the upper side and larger at the lower side, the light distribution is adjusted to maintain consistent image luminance regardless of the occupant's vertical viewpoint position.
2Ease of manufacture
If the curvature radius of lens surfaces is made uniform, then the lens array is easier to manufacture, but the luminance varies when viewpoint position changes
Solution Approach 1:
Rather than using uniform curvature for ease of manufacture, the patent implements local quality variation by making the curvature radius differ between upper and lower sides of lens surfaces. This design choice prioritizes optical performance (luminance consistency) over manufacturing simplicity, accepting the added complexity of creating non-uniform lens surfaces.
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 maintains consistent image brightness across different viewpoint positions, reducing luminance variations and enhancing display quality by adjusting the curvature radius of lens surfaces to match varying windshield reflectivity.
Implementation Method 1
a lens array 24 having an incident surface 24a opposed to the condensing lens 23 and an emitting surface 24b that is an opposite surface to the incident surface 24a and diffusing the light from the condensing lens 23; in the lens array 24, in the emitting surface 24b, a plurality of lens surfaces 24s projecting toward the liquid-crystal display unit 10 and having an aspherical sectional shape are provided, and, in the lens surfaces 24s, the curvature radius of a part 24t emitting the display light to be projected on the upper part 103t of the windshield 103 is smaller than the curvature radius of a part 24u emitting the display light to be projected on the lower part 103u of the windshield 103
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The head-up display device (1) includes a light source (22); a condensing lens (23); a lens array (24) diffusing light from the condensing lens (23); a liquid-crystal display unit (10) emitting light from the lens array (24) as display light; and a reflecting member (30) reflecting the display light emitted from the liquid-crystal display unit (10) and projecting the display light on a windshield (103). The lens array (24) has, in an emitting surface (24b), a plurality of lens surfaces (24s) projecting toward the liquid-crystal display unit (10) and having an aspherical sectional shape, and, in the lens surface (24s), the curvature radius of a part (24t) emitting display light to be projected on an upper part (103t) of the windshield (103) is smaller than the curvature radius of a part (24u) emitting display light to be projected on a lower part (103u) of the windshield (103).