Wavelength Selective Reflection Display Backing Member
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Solution Overview
Problem
Current wavelength selective reflection (WSR) displays cannot produce a true white state, with the closest approximation being a 'process white' that only reflects one third of incident light, which is not sufficient for effective color representation.
Innovation Solution
A WSR display is enhanced with a backing member that has a first non-reflective optical state and a second reflective optical state, switchable on a pixel-by-pixel basis, allowing for the generation of intermediate gray levels and a true white state by aligning its pixels with the WSR medium, and optionally using a dual-mode variable medium to switch between reflective and transmissive states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a dark surface is provided on the opposed side of the WSR medium to absorb transmitted light, then the dark state is improved, but the white state cannot be achieved since light passing through the WSR medium is reflected back through the medium which muddies the colors
Solution Approach 1:
The display is divided into two independently controllable layers: the WSR medium layer for wavelength-selective reflection and the backing member layer for reflective/non-reflective switching. This segmentation allows each layer to perform its specific function without interfering with the other, solving the color mudding problem while maintaining effective light absorption in the dark state.
Solution Approach 2:
The backing member acts as an intermediary element between the WSR medium and the viewer. It can be switched between reflective and non-reflective states to control the light path: in reflective state, it enhances the white appearance by reflecting light back through the WSR medium without muddying colors; in non-reflective state, it allows light absorption for the dark state.
2Object-affected harmful factors
If the wavelength of maximum reflection is moved into the near-ultra-violet or near-infra red range to achieve a good dark state, then the dark state is improved, but the ability to reflect white light is lost
Solution Approach 1:
The backing member is made dynamically switchable between reflective and non-reflective states on a pixel-by-pixel basis. This dynamic capability allows the display to adapt its optical properties: when the WSR medium is in its dark state with maximum reflection in the UV/IR range, the backing member can be switched to reflective state to still allow white light reflection, providing versatility in display modes.
Solution Approach 2:
The optical parameters of the backing member are changed by applying electric fields to switch between reflective and non-reflective states. This parameter change enables the system to transition between different display modes: reflective mode for white light reflection and non-reflective mode for dark state optimization, allowing both capabilities to coexist.
3Manufacturing precision
If multiple pixels of the backing member are aligned with each pixel of the WSR medium to enable intermediate gray levels, then the gray level representation is improved, but the device complexity increases
Solution Approach 1:
Instead of requiring a one-to-one pixel alignment, the invention uses partial alignment where multiple backing member pixels can be associated with a single WSR medium pixel. This partial action approach enables intermediate gray levels by controlling the reflectivity of multiple backing pixels, achieving the desired gray level precision without the full complexity of perfect one-to-one alignment.
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 enables the WSR display to achieve a true white state by ensuring that all incident light is reflected, improving color representation and allowing the display to function in both reflective and backlit modes, with the ability to produce fully saturated colors in reflection and unsaturated colors in transmission.
Implementation Method 1
IMOD (interferometric modulator display) devices in which the spacing between a mirror and a partial reflector is controlled in response to an applied field may be constructed such that only certain wavelengths are strongly reflected, depending upon the relationship between the spacing and the wavelength of the light, as described for example in U.S. Pat. No. 5,835,255.
Implementation Method 2
synthetic photonic crystals have been developed whose refractive index varies periodically on a length scale comparable to the wavelength of visible light. Such materials behave similarly to minerals such as opals, in which Bragg diffraction causes certain wavelengths of light to be strongly reflected from the surface of the material while other wavelengths are transmitted through the structure.
Implementation Method 3
If this binder material undergoes a dimensional change in response to, for example, an electrochemical reaction or other electro-activated process, the spacing between the silica particles is changed and the wavelength of light that is reflected is changed also.
Data Source
AI summary
A wavelength selective reflection display (10) comprises a wavelength selective reflection medium (20) and a backing member (30) having a first, non-reflective optical state, and a second, reflective optical state. Both the wavelength selective reflection medium (20) and the backing member (30) are divided into pixels (40, 50, 60), and the backing member (30) is switchable between its first and second optical states on a pixel-by-pixel basis. The pixels of the backing member (30) are substantially aligned with those of the wavelength selective reflection medium (20).