Diffractive Display Screen for Daylight Visibility
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Solution Overview
Problem
Existing display systems projecting images onto semi-transparent screens in vehicles face challenges with low transparency and luminosity, especially under daylight conditions, due to isotropic screens that do not account for varying light incidence angles, leading to inefficient diffusion and increased solar scattering.
Innovation Solution
A display system with a screen featuring regularly distributed diffractive patterns on its transparent faces, oriented to match the projector's angles of incidence, minimizing solar scattering and optimizing light diffusion specifically for the observer's location, with patterns of tens of microns to hundreds of microns in size occupying 20% of the screen surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent diffusing film is used to project images onto a semi-transparent screen, then the image can be displayed facing the user, but the transparency and brightness are insufficient under daylight conditions due to isotropic diffusion scattering sunlight in all directions
Solution Approach 1:
The patent applies local quality by making the diffusing properties of the screen anisotropic rather than isotropic. The screen contains elongated diffusing elements (such as cylindrical particles or rod-like structures) oriented in a specific direction, creating different diffusion characteristics for different directions of incident light. This allows the screen to efficiently diffuse projector light toward the observer while minimizing diffusion of sunlight from other directions, thereby improving image brightness without proportionally increasing solar scattering.
Solution Approach 2:
The patent changes the physical parameters of the diffusing medium by using elongated particles or structures with specific aspect ratios (length-to-diameter ratios) and controlling their orientation distribution. By adjusting the orientation parameter (from isotropic to anisotropic distribution) and the aspect ratio of diffusing elements, the screen achieves direction-dependent diffusion properties that improve image visibility while reducing solar glare.
2Illumination intensity
If a diffusing film is used to spread the projected image towards the observer's eye, then the image becomes visible, but the transmission is reduced and the film appears milky, limiting transparency
Solution Approach 1:
The patent uses diffusing elements with specific geometric characteristics (elongated shape, controlled size distribution) and orientation to create direction-selective diffusion. The diffusion is concentrated in the direction toward the observer rather than being uniform in all directions. This localized diffusion approach maintains higher overall transparency compared to conventional isotropic diffusers that scatter light equally in all directions, reducing the milky appearance while preserving image visibility.
3Productivity
If the screen is designed to optimize diffusion for a specific observer position, then diffusion efficiency improves, but the screen becomes anisotropic and cannot account for variations in light incidence angles from different sources
Solution Approach 1:
The patent optimizes diffusion for the primary observer position by using elongated particles with specific orientation, achieving high diffusion efficiency in the forward direction. The anisotropic structure creates a preferred diffusion direction that maximizes image brightness for the intended viewing angle.
Solution Approach 2:
The patent incorporates a reflective coating on the diffusing elements that can redirect light rays. This dynamic element allows the screen to adapt to varying incidence angles by reflecting light at different angles, providing some degree of versatility while maintaining optimized diffusion for the primary viewing direction. The combination of anisotropic diffusion and reflective redirection enables the screen to handle both optimized forward diffusion and varying incident light angles.
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 high transparency and brightness for the projected image while minimizing solar scattering, ensuring efficient light diffusion towards the observer and maintaining low diffraction, resulting in improved visibility and luminosity, even in daylight conditions.
Implementation Method 1
the patterns have a diffractive structure designed to diffract light rays having at least the average incidence in one or more directions corresponding to the observer's specific location
Implementation Method 2
The diffuser spreads the projected image towards the observer's eye Y, while remaining relatively transparent and thus allowing vision from the outside
Data Source
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AI summary
The general field of the invention is that of display systems comprising an image projector (P) and an associated display screen (E), said display system intended for use by an observer located at a predetermined position, said display screen having two transparent and substantially parallel faces, said display screen having on at least one of its transparent faces a plurality of regularly distributed light-diffusing patterns. The image projector according to the invention illuminates the screen from a plurality of angles of incidence determined by the position and size of the display screen, said angles of incidence centered on a mean angle of incidence, the diffusing patterns (10) having a diffractive structure so as to diffract light rays having at least the mean angle of incidence in one or more directions corresponding to said predetermined position of the observer.