High Stiffness Torsion Spring Hinge for Spatial Light Modulators
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Solution Overview
Problem
Spatial light modulators (SLMs) face challenges with stiction forces that can cause micro-mirrors to stick, leading to device failure and affect dynamic performance, particularly when the stiction force exceeds the restoring force of the torsion spring hinge, and increasing the stiffness of the hinge while addressing stiction introduces issues like higher actuation voltage and increased wear.
Innovation Solution
The implementation of a high stiffness torsion spring hinge in spatial light modulators, combined with resonant activation and dynamic switching modes, reduces sagging, minimizes contact impact, and decreases electrode voltage requirements, while maintaining or improving operational speed and manufacturability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the stiffness of the torsion spring hinge is increased to overcome stiction forces, then the reliability of the device is improved, but the actuation voltage required increases
Solution Approach 1:
The patent applies dynamic switching by utilizing the resonant frequency of the micro-mirror-torsion spring system. By driving the system at its resonant frequency, the micro-mirror can be actuated with lower voltages while maintaining reliable operation. The dynamic approach exploits the oscillatory nature of the system to achieve switching without requiring high static actuation voltages that would be needed with a purely stiff hinge design.
Solution Approach 2:
The patent changes the operational parameters by using resonant frequency excitation instead of static actuation. By tuning the drive frequency to match the natural resonant frequency of the micro-mirror-torsion spring system, the system achieves maximum amplitude response with minimal energy input, thereby reducing the required actuation voltage while maintaining the high stiffness needed to overcome stiction.
2Manufacturing precision
If the stiffness of the torsion spring hinge is increased to reduce sagging, then the manufacturing precision is improved, but the device complexity increases
Solution Approach 1:
The patent achieves precise mirror plate positioning by changing the operational parameters - specifically by utilizing resonant frequency excitation. This allows the system to achieve precise control through dynamic operation rather than relying solely on a mechanically complex stiff hinge structure, thereby improving positioning precision without proportionally increasing device complexity.
3Productivity
If the stiffness of the torsion spring hinge is increased to improve switching speed, then the productivity is improved, but the wear and tear on the device increases
Solution Approach 1:
The patent uses dynamic resonant actuation to achieve fast switching speeds. By exciting the micro-mirror at its resonant frequency, the system achieves rapid switching through oscillatory motion rather than through high-force mechanical impacts. This dynamic approach maintains high switching speed while reducing mechanical wear compared to using an extremely stiff hinge that would require high impact forces for switching.
Solution Approach 2:
The patent exploits mechanical vibration at the resonant frequency of the micro-mirror-torsion spring system to achieve fast switching. The vibrational energy efficiently transfers to the system, producing rapid angular displacement without requiring high impact forces that would cause wear. The resonant vibration enables fast switching while the oscillatory nature of the motion reduces cumulative mechanical wear compared to direct impact switching.
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 approach effectively reduces stiction forces, enhances the reliability and longevity of SLMs by allowing faster switching and lower actuation voltages, while maintaining or improving operational speed and manufacturability, and reduces wear and tear on the device.
Implementation Method 1
a flexible member coupled to the support substrate... The flexible member is adapted such that the mirror plate is operative to rotate from the first activated position to a second activated position
Implementation Method 2
The incident light may be modulated in phase, intensity, polarization, or deflection direction... actuated by a bias voltage applied between the mirror and one of two electrodes
Implementation Method 3
Merely by way of example, the invention has been applied to initializing the micro-mirrors of a spatial light modulator using a resonant activation process
Data Source
AI summary
A spatial light modulator for use in display applications. The spatial light modulator includes a support substrate and a flexible member coupled to the support substrate. The spatial light modulator also includes a mirror plate coupled to the flexible member and characterized by an activated position. The mirror plate is adapted to rotate in relation to the flexible member from the activated position to a second activated position in a time less than 6.0 μs.