MEMS Charge Transfer Circuitry for Longer Mirror Stroke Control
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Solution Overview
Problem
Existing MEMS deformable mirrors require high voltages for actuation, complex drive electronics, short stroke ranges, and can exhibit unwanted topography and light scattering, which affect the performance of optical systems.
Innovation Solution
A MEMS device with a glass substrate, electrodes, hinges, membrane mirrors, and TFTs, utilizing charge-based electrostatic actuation controlled by a multiplexer and drive source, allowing for lower voltage actuation and reduced light scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If high voltage is used to actuate the mirror, then the stroke range is limited, but the actuation force is sufficient
Solution Approach 1:
The patent changes the actuation parameter from voltage to charge. By controlling the charge on the electrode rather than the voltage, the system achieves longer stroke ranges without requiring proportionally higher voltages. The charge-controlled electrostatic actuation allows the mirror to be actuated over an extended range while maintaining stable control, resolving the contradiction between stroke range and voltage requirement.
2Measurement precision
If each array element is addressed with its own control voltage, then the actuation precision is high, but the drive electronics become complex and expensive
Solution Approach 1:
The patent implements a universal charge transfer circuit that can serve multiple array elements through time-multiplexed addressing. Instead of requiring separate control voltages for each element, a single charge transfer circuit can sequentially address multiple electrodes, reducing the overall complexity of the drive electronics while maintaining actuation precision through controlled charge transfer timing.
Solution Approach 2:
The patent employs periodic scanning of rows and columns to address array elements sequentially. By using periodic action to cycle through different electrode combinations, the system achieves precise actuation control without requiring simultaneous independent control voltages for all elements, thereby reducing drive electronics complexity.
3Length of moving object
If voltage mode driving is used for each actuator, then the control is simple, but the stroke range is short and stable control is limited
Solution Approach 1:
The patent changes the control parameter from voltage to charge. Charge-controlled electrostatic actuation provides a more linear and extended stroke range compared to voltage-mode driving. By controlling the charge quantity rather than voltage, the system achieves longer stable control ranges while the added complexity of the charge transfer circuit is offset by the performance gains in stroke range and control stability.
4Object-affected harmful factors
If traditional electrostatic actuators are used, then the actuation is straightforward, but unwanted topography and light scattering occur
Solution Approach 1:
The patent changes from voltage-controlled to charge-controlled electrostatic actuation. This parameter change results in more uniform charge distribution across the electrode surface, which produces more uniform actuation forces and reduces unwanted topography variations. The improved uniformity minimizes light scattering while the charge transfer circuitry provides the necessary control capability.
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
Achieves stable control over a longer stroke range with reduced complexity and cost, while minimizing light scattering, suitable for applications like space-based telescopes and industrial lasers.
Implementation Method 1
the amount of charge generates an electrostatic force for actuating the hinge and a portion of the membrane mirror mechanically coupled to the hinge
Data Source
AI summary
Microelectromechanical system (MEMS) devices, methods of operating the MEMS device, and methods of manufacturing the MEMS device are disclosed. In some embodiments, the MEMS device includes a glass substrate; an electrode on the glass substrate; a hinge mechanically coupled to the electrode; a membrane mirror mechanically coupled to the hinge; a TFT on the glass substrate and electrically coupled to the electrode; and a control circuit comprising: a multiplexer configured to turn on or turn off the TFT; and a drive source configured to provide a drive signal for charging the electrode through the TFT. An amplitude of the drive signal corresponds to an amount of charge, and the amount of charge generates an electrostatic force for actuating the hinge and a portion of the membrane mirror mechanically coupled to the hinge. In some embodiments, the MEMS devices comprise a charge transfer circuit for providing the amount of charge.