Silicon Mirror on Metal Substrate for Optical Scanning
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Solution Overview
Problem
Existing optical scanners face challenges with complex structures, increased manufacturing time and costs, limited ability to reduce device thickness, and difficulties in achieving large torsion angles and accurate laser beam scanning due to inefficient vibration transmission and unnecessary vibration modes.
Innovation Solution
An optical scanning device with a simple structure using a piezoelectric actuator on a substrate with torsion bars, where the piezoelectric film is formed on the substrate rather than the cantilever beams, allowing for efficient torsional vibration generation and reducing unnecessary vibration modes, and a Si mirror is attached to an unpolished metal sheet to minimize warpage and dynamic deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a silicon micromirror is used with torsion bars for oscillation, then the device achieves compact size and integrated structure, but the mirror surface undergoes dynamic deformation during high-speed oscillation, reducing scanning accuracy
Solution Approach 1:
The patent combines a metal substrate (providing mechanical strength and rigidity) with a silicon mirror layer (providing optical quality surface) to create a composite mirror structure. This composite design allows the mirror to maintain structural integrity and resist dynamic deformation during high-speed oscillation while preserving the compact size benefits of silicon micromachining.
Solution Approach 2:
The patent increases the mirror thickness parameter by combining the metal substrate with the silicon mirror layer. This thickness increase directly reduces dynamic deformation during oscillation, as a thicker mirror has greater rigidity and resists bending and warpage better than a thin silicon mirror alone.
2Length of stationary object
If the mirror is made thinner to reduce device thickness, then the device becomes more compact, but the mirror becomes more susceptible to dynamic deformation during oscillation
Solution Approach 1:
The metal substrate provides mechanical support and rigidity, allowing the overall device to be compact while the combined thickness of the composite mirror (metal substrate + silicon mirror layer) maintains sufficient stiffness to prevent deformation during oscillation.
3Speed
If piezoelectric actuators are placed on cantilever beams to drive the mirror, then the device achieves torsional vibration, but unnecessary vibration modes are generated and transmission efficiency is reduced
Solution Approach 1:
The patent extracts the piezoelectric actuators from the cantilever beam location and relocates them to the substrate. This repositioning eliminates the generation of unnecessary vibration modes that occur when actuators are mounted on the flexible cantilever beams, while maintaining efficient torsional vibration transmission to the mirror.
4Stability of the object's composition
If a metal sheet is used for the mirror to increase thickness and reduce deformation, then dynamic deformation is suppressed, but warpage occurs due to polishing processes
Solution Approach 1:
The silicon mirror layer is deposited on the metal substrate to provide a precision optical surface without requiring extensive polishing of the metal sheet itself. The silicon layer can be formed with atomic-level flatness through vapor deposition processes, eliminating warpage issues associated with metal polishing while maintaining the rigidity benefits of the metal substrate.
Solution Approach 2:
The patent applies different material properties to different parts of the mirror structure: the metal substrate provides bulk rigidity and structural support, while the thin silicon mirror layer provides the optically precise surface. This local differentiation of material functions allows each layer to optimize its specific role without compromising the other.
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 solution enables efficient torsional vibration, suppresses dynamic deformation, and achieves high accuracy in optical beam scanning with reduced size and cost, while maintaining the structural integrity and flatness of the scanning device.
Implementation Method 1
an optical scanning device with a simple structure using a piezoelectric actuator on a substrate with torsion bars
Implementation Method 2
a Si mirror is attached to an unpolished metal sheet to minimize warpage and dynamic deformation
Data Source
AI summary
An optical scanning device, having: a substrate main body; two cantilever beams protruded from the respective side portion of one side of the substrate main body; a mirror supported by torsion bars from the respective side, between the cantilever beams; a drive source to causes the substrate main body to vibrate; and a light source to project light onto the mirror, wherein a fixed end of the substrate main body is fixed to a supporting member, on the opposite side from the mirror side, and wherein the mirror resonantly vibrates according to vibration applied to the substrate by the drive source, thereby to change a direction of reflection light of the light projected onto the mirror from the light source according to the vibration of the mirror, characterized in that a Si mirror is attached to and fixed on the mirror.