MEMS Electrostatic Actuator for Super Resolution and Autofocus
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Solution Overview
Problem
Existing MEMS electrostatic actuators face challenges in achieving high accuracy and speed for super resolution imaging due to compromised rotor stiffness, coupling across axes, and size limitations, which affect their performance in both autofocus and super resolution functionalities.
Innovation Solution
A novel MEMS electrostatic actuator design featuring parallel-plate electrodes and mechanical springs for decoupled translations along the x, y, and z axes, allowing for precise sub-micron to micron-level motion while maintaining large translation strokes, utilizing a separate piston-tube configuration for z-axis motion and mechanical trenches for bi-axial tilt decoupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the same electrostatic electrodes are used for both large translation stroke (handshake compensation) and sub-micron motion (super resolution), then the actuator can perform multiple functions, but the rotor stiffness must be made relatively low which compromises the accuracy and speed for super resolution imaging
Solution Approach 1:
The actuator is divided into two independent parts: a first electrostatic actuator for large translation stroke (handshake compensation) and a second electrostatic actuator for sub-micron motion (super resolution imaging). This segmentation allows each part to be optimized for its specific function without compromising the other, resolving the contradiction between multi-functionality and precision.
Solution Approach 2:
A decoupling mechanism is introduced as an intermediary between the first and second electrostatic actuators. This mechanism mechanically isolates the two actuators, allowing the first actuator to provide large translations while the second actuator provides precise sub-micron motion, thereby enabling both handshake compensation and super resolution imaging with high accuracy.
2Speed
If the translation stroke is limited to few microns for super resolution, then the rotor stiffness can be made large which increases natural frequency, but the same electrodes cannot provide large translation stroke for handshake compensation
Solution Approach 1:
The translation function is segmented between two actuators: the first electrostatic actuator handles large translation stroke (70-100 microns) for handshake compensation, while the second electrostatic actuator handles small precision motion (sub-micron to few microns) for super resolution imaging. This allows the second actuator to have high rotor stiffness and fast response without compromising the overall translation capability.
3Ease of operation
If comb-drive electrode configuration is used to generate motion, then the actuator can provide translation, but the damping is significantly less compared to parallel plate configuration which has large thin film damping
Solution Approach 1:
The electrode configuration parameter is changed from comb-drive to parallel plate configuration for the second electrostatic actuator. This parameter change increases the damping through large thin film damping due to air trapped between the plates, which reduces overshoot and enables faster settling for super resolution imaging while maintaining translation capability.
4Device complexity
If flexure mechanisms are used to reduce coupling effects across different axes, then some coupling is reduced, but the flexures do not completely eliminate couplings as they transmit part of the motion across moving parts
Solution Approach 1:
The actuator is segmented into two independent electrostatic actuators with a decoupling mechanism between them. This segmentation completely eliminates coupling effects across different axes, as each actuator operates independently without motion transmission through flexures, thereby achieving micron level motion accuracy required for super resolution imaging.
5Device complexity
If the middle rotor holds the entire inner rotor and inner stator to provide y-axis motion, then the motion is decoupled, but a significant load is added to the middle rotor which results in slower response along the y-axis
Solution Approach 1:
The actuator is segmented into two independent electrostatic actuators, eliminating the need for the middle rotor to hold the entire inner rotor and inner stator. This segmentation distributes the load appropriately and maintains fast response along the y-axis while achieving complete motion decoupling across all axes.
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 actuator achieves total decoupling between axes, enabling high accuracy and fast translations for super resolution imaging while maintaining autofocus functionality, with improved stiffness and reduced overshoot, effectively mitigating handshake effects and size constraints.
Implementation Method 1
A novel MEMS electrostatic actuator design featuring parallel-plate electrodes and mechanical springs for decoupled translations along the x, y, and z axes
Implementation Method 2
A novel MEMS electrostatic actuator design featuring parallel-plate electrodes and mechanical springs for decoupled translations along the x, y, and z axes
Implementation Method 3
utilizing a separate piston-tube configuration for z-axis motion
Implementation Method 4
mechanical trenches for bi-axial tilt decoupling
Implementation Method 5
the parallel plate electrode configuration which is known to have large thin film damping due to the air trapped between the large areas between the plates. This large air-damping is very important to have less overshoot in the response of the actuator and thus enables the actuator to settle fast.
Data Source
AI summary
A MEMS electrostatic actuator that achieves autofocus and super resolution imaging in cameras is disclosed. The actuator is able to provide multi-degrees of freedom motion (of up to 5-degrees-of-freedom). It consists of a moving and fixed parts. The moving part comprises an inner and outer rotor. The inner rotor contains a load stage and the moving plates of the parallel-plate electrodes and is attached to the outer rotor via a plurality of mechanical springs. The outer rotor holds the inner rotor and contains a plurality of openings or tubes surrounded by walls and are attached to the outer periphery of the actuator via multiple mechanical springs. The present device can be used to achieve super resolution functionality in compact cameras.