Induced Resonance Comb Drive Scanner for MEMS
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Solution Overview
Problem
Existing comb drive biaxial scanners face challenges in reducing the slow scan resonant frequency to accommodate fast scan lines within a single frame, leading to motion artifacts and susceptibility to environmental accelerations, while high scan angles result in high energy losses due to aerodynamic damping, requiring high drive voltages.
Innovation Solution
The solution involves a three-body scanning platform with a slow scan drive frame, where the slow scan comb fingers are eliminated from the scanning body and placed on an outer frame, allowing torsional deformation to resist external vibrations and reducing damping by relocating comb fingers to a fast scan frame, increasing capacitance and drive torque efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the slow scan resonant frequency is reduced to permit all fast scan lines within one slow scan frame, then the scanning pattern completeness is improved, but the scanner becomes susceptible to environmental accelerations causing comb crashes
Solution Approach 1:
The scanner is divided into two independent resonant systems: a fast scan resonant system operating at high frequency and a slow scan resonant system operating at low frequency. This segmentation allows each system to operate optimally without compromising the other, enabling complete frame scanning while maintaining comb finger clearance through the fast scan resonance
Solution Approach 2:
The system changes the operating parameters by utilizing resonance at two different frequency levels. The fast scan operates at its resonant frequency to provide sufficient torque and maintain clearance, while the slow scan operates at a lower resonant frequency to accommodate all scan lines within one frame cycle
2Speed
If the flexures are lengthened or made thinner to reduce slow scan resonance frequency, then the resonant frequency is reduced, but the scanner becomes softer and more susceptible to lateral motions causing comb crashes
Solution Approach 1:
The support structure is segmented into fast scan flexures and slow scan flexures with different design priorities. The slow scan flexures can be optimized for low frequency without compromising lateral stiffness, as the fast scan resonance provides the necessary torque to maintain comb finger clearance
Solution Approach 2:
The system utilizes mechanical vibration at resonant frequency to maintain comb finger clearance. The fast scan resonant vibration provides sufficient torque to keep the comb fingers from crashing, allowing the slow scan flexures to be designed for low frequency operation
3Productivity
If high scan angles are used to achieve required scanning coverage, then the scanning range is improved, but aerodynamic damping increases leading to high energy losses and high drive voltage requirements
Solution Approach 1:
The system exploits mechanical resonance to amplify the scanning motion. By driving the fast scan comb at its resonant frequency, the scanner achieves large scan angles with minimal drive voltage, as the resonant vibration naturally amplifies the motion and overcomes aerodynamic damping
Solution Approach 2:
The system changes the operating parameter by utilizing resonance to achieve the required scanning range. Instead of using high drive voltages to overcome damping, the system operates at resonant frequency where the system's natural response provides the necessary motion amplification
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 configuration reduces the risk of comb crashes, lowers damping energy losses, and decreases the required drive voltage, enabling stable scanning with reduced motion artifacts and energy efficiency.
Implementation Method 1
The drive torques are generated by electrostatic comb drive actuators
Implementation Method 2
The scanning mirror is supported by first and second torsional flexures
Implementation Method 3
Existing comb drive biaxial scanners typically operate very close to resonance
Implementation Method 4
the high horizontal axis scan angle and scanning frequency may lead to high energy losses through aerodynamic damping. The damping forces and torques may be generated by airflow around the comb fingers and by air drag on the mirror itself
Data Source
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AI summary
Briefly, in accordance with one or more embodiments, a MEMS based scanning platform (114) is arranged to have increased efficiency by driving a first frame (116) of the scanning platform directly by applying a drive voltage to a set of comb fingers (214, 216) disposed on the first frame to cause the first frame to oscillate via torsional rotation of a first flexure (210) and by driving a second frame (212) of the scanning platform indirectly via mechanical coupling of the second frame with the first frame via a second flexure, wherein damping losses and work capacity are such that the operation of the scanning mirror is more efficient than if the set of comb fingers were disposed on the second frame and directly driven by the drive voltage. The scanning platform may comprise a 1D scanner, a 2D scanner, or a multiple-dimensional scanner.