MEMS Interferometric Modulator with Etalon for Uniform Dark State
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Solution Overview
Problem
Interferometric modulators in displays often fail to present a uniformly dark or black appearance in the dark state, leading to reduced contrast and washed-out colors in the bright state due to bright regions.
Innovation Solution
Incorporating a light-absorbing optical element, such as an etalon, over a substrate with a buffer layer and a support structure aligned with the etalon, which absorbs visible light to create a dark appearance and enhances contrast by using principles of optical interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a conventional interferometric modulator structure is used, then the device can modulate light, but the dark state appearance is not uniformly dark leading to reduced contrast
Solution Approach 1:
The patent introduces an optical element with spatially varying optical properties - specifically, an etalon structure that absorbs visible light at different locations to create a uniformly dark appearance. The etalon is positioned over selected regions (such as support structures) to locally modify light absorption characteristics, achieving uniform dark state across the entire display area.
Solution Approach 2:
The patent introduces an intermediary optical element (etalon) between the support structures and the viewer. This etalon acts as a mediator that absorbs stray light and prevents it from reaching the viewer, thereby improving the uniformity of the dark state without interfering with the light modulation function of the interferometric modulator.
2Ease of manufacture
If the interferometric modulator uses reflective layers and air gaps, then light modulation is achieved, but bright regions appear causing washed-out colors
Solution Approach 1:
The patent converts the harmful effect of stray light reflections into a beneficial effect by using the etalon structure to absorb these reflections. The etalon transforms the problematic bright regions caused by reflective layers into uniformly dark areas, thereby improving color saturation while maintaining the light modulation capability of the original structure.
3Strength
If support structures are added to hold the light modulating element, then structural stability is improved, but the support structures create bright regions that reduce contrast
Solution Approach 1:
The patent applies the etalon optical element specifically over the support structures, creating a local solution to the problem. The etalon is positioned only where needed - over the support structures that cause bright regions - while leaving the light modulating areas unaffected, thus maintaining structural stability while improving contrast ratio.
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 achieves a more uniformly dark or black appearance in the dark state and vibrant colors in the bright state, improving contrast and visual performance of interferometric modulator displays.
Implementation Method 1
an interferometric modulator or interferometric light modulator refers to a device that selectively absorbs and/or reflects light using the principles of optical interference
Data Source
AI summary
MEMS devices are fabricated by a method that involves forming an optical element (e.g., etalon) over a substrate and then forming a light modulating element (e.g., interferometric modulator) over the optical element. In an embodiment, a support structure for the light modulating element is aligned with the underlying optical element to thereby alter the appearance of the support structure to a viewer. Such an optical element is separated from the support structure by one or more buffer layers.