Car Windshield HUD Screen with Position-Dependent Microlenses
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Solution Overview
Problem
In head-up displays, the brightness of images is uneven due to varying scanning speeds of laser light across the screen, leading to discomfort for observers and difficulties in maintaining image visibility due to interference fringes caused by precise alignment requirements and temperature-induced deformations.
Innovation Solution
The screen is configured with a constant divergence angle in the center and increasing divergence angles towards the edges in the scanning direction, and the pitch of scan lines is set smaller than the pitch of lens regions to average out interference fringes, allowing for easier construction and maintaining image brightness and visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the laser light scans the screen at constant speed, then the scanning is simple, but the brightness becomes uneven with edges brighter than center
Solution Approach 1:
The patent applies local quality by varying the divergence angle of microlenses based on their position on the screen. Central microlenses have a first divergence angle while edge microlenses have a second, larger divergence angle. This local differentiation compensates for the scanning speed variation, ensuring uniform brightness across the entire screen while maintaining simple constant-speed scanning.
2Reliability
If the beam spot is aligned with the center of lens groups, then interference fringes are suppressed, but complex adjustment work is required and visibility degrades with temperature changes
Solution Approach 1:
The patent changes the divergence angle parameter of microlenses according to their position on the screen. By making the divergence angle position-dependent (smaller for central lenses, larger for edge lenses), the system achieves uniform brightness distribution without requiring complex alignment adjustments. This parameter variation simplifies the device setup while maintaining stable image visibility under temperature 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
This configuration ensures nearly even image brightness and suppresses interference fringes, making the image display more comfortable and stable, even with temperature-induced deformations.
Implementation Method 1
a plurality of first lens portions 108a which are formed on an incident surface of the laser light and diverge the laser light in the scanning direction (X-axis direction)
Implementation Method 2
a plurality of second lens portions 108b which are formed on an emission surface of the laser light and diverge the laser light in a direction perpendicular to the Y-axis direction
Data Source
AI summary
Image display device includes; light source; screen on which an image is drawn by being scanned two-dimensionally by laser light; scanner that causes the laser light to scan the screen; mirror drive circuit that chives scanner; and an optical system that generates a virtual image of the image drawn on screen. On screen, there are arranged a plurality of lens regions so as to be arranged individually in a first direction and a second direction perpendicular to the first direction, and mirror drive circuit sets a plurality of scan lines such that a pitch of the scan lines can become smaller than a pitch of lens regions in the second direction.