Reflective Display Color Saturation via Retro-Reflection
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Solution Overview
Problem
Existing reflective displays using hemi-spherical protrusions for total internal reflection fail to achieve a white appearance due to a significant portion of incident light rays passing through the dark pupil region, leading to low reflectivity and color saturation, especially when incident light deviates from a perpendicular direction.
Innovation Solution
Incorporating a reflective element with spherical indentations beneath the hemi-spherical array, where the radius of curvature of the indentations coincides with the center of curvature of the hemi-spheres, to retro-reflect light rays that pass through the dark pupil regions, enhancing semi-retro-reflection and improving brightness and color saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If hemi-spherical protrusions are used for total internal reflection, then reflectivity is improved, but a significant portion of light rays pass through the dark pupil region leading to reduced color saturation and white appearance
Solution Approach 1:
A planar reflective element is introduced as an intermediary component beneath the hemi-spherical array to intercept and redirect light rays that would otherwise be lost through the dark pupil regions. This mediator captures approximately 50% of incident light rays and redirects them to achieve semi-retro-reflection, thereby improving both reflectivity and color saturation without disrupting the original TIR mechanism.
Solution Approach 2:
The invention recovers light rays that were previously discarded or lost through the dark pupil regions of the hemi-spherical protrusions. By positioning a planar reflective element to intercept these lost rays and redirect them back through the hemi-spheres, the system recovers approximately 50% of the incident light that would otherwise be wasted, significantly improving overall reflectivity and color appearance.
2Illumination intensity
If a planar reflective element is placed beneath the hemi-spherical array, then reflectivity is improved, but the reflected light does not achieve desired semi-retro-reflection characteristic
Solution Approach 1:
The invention merges two reflective mechanisms into a unified system: the total internal reflection from the hemi-spherical protrusions and the specular reflection from the planar reflective element. By combining these two reflection types, the system achieves both high reflectivity (from the planar element recovering lost light) and semi-retro-reflection characteristics (from the hemi-spheres redirecting the recovered light back toward the viewer).
Solution Approach 2:
The dual-reflection system ensures continuous useful action across different viewing angles. The planar reflective element continuously recovers light rays that pass through the dark pupil regions, and the hemi-spherical protrusions continuously redirect these recovered rays back toward the viewer. This continuous operation maintains high reflectivity and color saturation across a range of incident angles, not just at perpendicular incidence.
3Adaptability or versatility
If incident light deviates from perpendicular direction, then viewing flexibility is improved, but color saturation and reflectivity deteriorate due to increased light loss through dark pupil region
Solution Approach 1:
The planar reflective element acts as an intermediary that compensates for angular deviations in incident light. When light rays strike the hemi-spherical array at oblique angles, more rays pass through the dark pupil regions. The planar reflective element intercepts these angularly-deviated rays and redirects them back through the hemi-spheres, maintaining semi-retro-reflection characteristics and color saturation even when incident light deviates from the perpendicular direction.
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 increases reflectivity and color saturation by directing unreflected light rays back towards the viewer, achieving a bright, paper-like white appearance with high efficiency across a range of viewing angles, suitable for reflective color displays.
Implementation Method 1
an array of convex or hemi-spherical protrusions or hemi-spheres (it should be noted that the terms 'convex protrusions' and 'hemi-spherical protrusions' and 'hemi-spheres' will henceforth be used interchangeably). Depicted in FIG. 1 is a front sheet 100 of a reflective display with an outward front surface 102 facing the viewer and an inward surface 104 comprising of a plurality of hemi-spherical protrusions 106 which reflects light by means of total internal reflection (TIR) within the individual hemi-spheres 108
Implementation Method 2
Another approach to reflecting light rays that pass through the dark pupil regions of the individual convex or hemi-spherical protrusions as shown in FIG. 2 but in a semi-retro-reflective manner is to place a reflective element beneath the hemi-spherical array such that it reflects the light substantially back towards the direction of origin of the light rays.
Data Source
AI summary
A reflective image display comprising of a reflection enhancing layer comprising of a plurality of approximately spherical indentations is placed adjacent a sheet comprising of a plurality of hemispherical protrusions. The radii of curvature of the spherical indentations substantially coincides with the center of curvature of the adjacently located hemispheres to enhance the white paper-like appearance of the display while efficiently enabling optional color filters to yield saturated color.