MEMS Offset Mirror Structure for Lower Off-State Reflectivity
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Solution Overview
Problem
The contrast of displays or projectors using microelectromechanical system (MEMS) devices is negatively affected by the off-state reflectivity of the MEMS devices, which reduces the clarity and quality of the projected image.
Innovation Solution
The MEMS devices incorporate offset mirrors that are laterally offset relative to the mechanical layer, reducing the exposure of reflective components to the projection aperture in the off-state, thereby minimizing stray light reflections and enhancing the contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the mirror is laterally offset from the mechanical layer, then the contrast ratio is improved by reducing off-state reflectivity, but the device complexity increases due to additional alignment requirements
Solution Approach 1:
The mirror is intentionally positioned asymmetrically relative to the mechanical layer, creating a deliberate offset that prevents the mirror from directly reflecting light back through the projection aperture in the off state. This asymmetric positioning is the core mechanism for improving contrast ratio while maintaining device functionality
Solution Approach 2:
The offset is specifically applied to the mirror position rather than the entire device structure, allowing contrast improvement in the optical path while keeping other device components relatively simple and maintaining overall manufacturing feasibility
2Object-affected harmful factors
If the mirror is laterally offset from the mechanical layer, then the off-state reflectivity is reduced improving image quality, but the manufacturing precision requirements increase
Solution Approach 1:
The design accepts and utilizes the asymmetric offset position as a feature rather than treating it as a deviation from symmetry. By designing the offset position into the device architecture from the beginning, the manufacturing process can target this specific offset position, converting a potential precision challenge into a controlled design parameter
Solution Approach 2:
The mirror position parameter is deliberately changed from the conventional centered position to an offset position. This parameter change is optimized to provide sufficient contrast improvement while remaining within achievable manufacturing tolerances, balancing performance gains with fabrication capabilities
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 use of offset mirrors improves the contrast between on and off states by up to 20% without significant redesign of the MEMS device layout, resulting in a darker off-state and better image quality.
Implementation Method 1
The mirror is laterally offset relative to the mechanical layer in a direction... reducing the exposure of reflective components to the projection aperture in the off-state, thereby minimizing stray light reflections
Data Source
AI summary
A microelectromechanical system (MEMS) device includes: a mechanical layer; a mirror; and a mirror via coupling the mechanical layer and the mirror. The mirror is laterally offset from the mechanical layer in a direction.