MEMS Optical Deflector Recessed Side Surface Inertia Reduction
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Solution Overview
Problem
Optical deflectors using MEMS techniques face challenges in reducing the moment of inertia of mirrors while maintaining an effective reflecting surface area and accommodating additional elements like magnets and sensors, as the increased moment of inertia due to larger mirror areas complicates driving torque and limits surface usage.
Innovation Solution
The optical deflector design features a movable plate with a recessed side surface that reduces its moment of inertia by positioning the mass further from the rotational axis, allowing the front and back surfaces to be used for reflecting and mounting other elements, while maintaining a high precision in shape control through crystallographic planes and precise etching techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the mirror area is increased, then the reflecting surface area is improved, but the moment of inertia increases resulting in higher driving torque requirements
Solution Approach 1:
The patent applies dimensionality change by recessing the side surface of the movable plate toward the rotation axis, creating a stepped or tapered structure. This modifies the mass distribution in the radial dimension, moving mass closer to the rotation axis without reducing the front surface reflecting area, thereby reducing the moment of inertia while maintaining the required reflecting surface area.
Solution Approach 2:
The patent applies local quality by creating a non-uniform mass distribution within the movable plate. The side surface is selectively recessed in specific regions to reduce moment of inertia, while the front surface maintains its full area for reflection. This localized modification allows different parts of the plate to serve different functions: the front surface for reflection and the recessed side surfaces for moment of inertia reduction.
2Weight of moving object
If lightening portions are provided on the back surface of the mirror, then the moment of inertia is reduced, but the back surface cannot be used for arranging elements such as magnets, coils and sensors
Solution Approach 1:
Instead of modifying the back surface in the vertical dimension, the patent recesses the side surfaces of the movable plate. This lateral modification reduces the moment of inertia by moving mass closer to the rotation axis while leaving the back surface completely intact and available for mounting elements such as magnets, coils, and sensors.
Solution Approach 2:
The patent applies local quality by selectively recessing only the side surfaces of the movable plate while maintaining the back surface in its original flat state. This localized modification allows the side surfaces to serve the function of moment of inertia reduction, while the back surface retains its full functionality for element arrangement and mounting.
3Weight of moving object
If recesses are provided in the front or back surface of the movable plate, then the moment of inertia is reduced, but the reflecting surface area or mounting surface area is compromised
Solution Approach 1:
The patent avoids modifying the front or back surfaces and instead recesses the side surfaces of the movable plate. This dimensional shift allows moment of inertia reduction without compromising the front surface reflecting area or the back surface mounting area, as the recesses are located on the lateral surfaces that do not serve primary functional purposes.
Solution Approach 2:
The patent applies local quality by selectively recessing only the side surfaces of the movable plate, which are not critical for reflection or element mounting. This localized modification allows the side surfaces to serve the function of moment of inertia reduction, while the front and back surfaces retain their full functionality for reflection and element arrangement respectively.
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 effectively reduces the moment of inertia by up to 20% without compromising the mirror's effective area, allowing for precise rotational control and preventing stress concentration damage to support structures, enabling miniaturization and increased deflection angles.
Implementation Method 1
a movable plate having a reflecting surface and a side surface; and a support portion that supports the movable plate in such a manner that the movable plate is able to rotate around a predetermined axis
Data Source
AI summary
An optical deflector has: a movable plate having a reflecting surface and a side surface; and a support portion that supports the movable plate in such a manner that the movable plate is able to rotate around a predetermined axis, in which the side surface of the movable plate is recessed toward the axis.