Piezoelectric Optical Deflector with Feedback Control
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Solution Overview
Problem
Existing optical deflectors using piezoelectric actuators face challenges in precise control of deflection angle and velocity due to complex structures, signal crosstalk, and limitations in torque generation, leading to increased size and power consumption, as well as mechanical stress on moving parts.
Innovation Solution
The optical deflector incorporates a mirror, torsion bars, and piezoelectric cantilevers with a second piezoelectric element installed between the mirror and torsion bar to generate piezoelectric electromotive force for precise status detection and control, allowing for high-precision feedback control and increased deflection angles without increasing device size or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a piezoresistive element or strain gauge is installed at the anchor end part of the torsion bar to detect the twist angle, then the rotation angle of the mirror can be detected, but the structure becomes complex
Solution Approach 1:
The patent extracts the detection function from the anchor end part of the torsion bar and relocates it to the free end part. By installing the piezoresistive element or strain gauge at the free end where the mirror is attached, the detection is performed at a location with larger displacement, avoiding the need for complex structures at the anchor end while maintaining measurement precision.
Solution Approach 2:
The patent introduces the free end part of the torsion bar as an intermediary element between the mirror and the detection mechanism. The piezoresistive element or strain gauge is installed at this intermediary location to detect the twist angle, which is then used to determine the rotation angle of the mirror, simplifying the overall structure.
2Ease of manufacture
If a separate piezoelectric sensor is installed to detect angle displacement by piezoelectric electromotive force, then the detection mechanism can be formed using the manufacturing process of the piezoelectric actuator, but signal crosstalk occurs due to close position of the sensor to the actuator
Solution Approach 1:
The patent separates the detection function from the actuation function by using different piezoelectric elements. The first piezoelectric element is dedicated to actuation, while the second piezoelectric element is dedicated to detection. This extraction of functions allows the sensor to be positioned close to the actuator for compact manufacturing while minimizing signal crosstalk through functional separation.
Solution Approach 2:
The patent segments the piezoelectric components into distinct first and second piezoelectric elements with different functions. The first element generates torque for actuation, while the second element detects angle displacement through piezoelectric electromotive force. This segmentation allows independent optimization of each element's position and design, reducing interference between them.
3Measurement precision
If the twist displacement of the torsion bar is measured directly, then the rotation angle can be detected, but the measurement has poor S/N ratio due to minute displacement
Solution Approach 1:
The patent changes the measurement dimension from direct twist displacement at the anchor end to angular displacement at the free end where the mirror is attached. By measuring the rotation angle of the mirror through the piezoelectric element at the free end, the system converts a difficult-to-measure minute linear displacement into a more easily detectable angular displacement with larger magnitude, improving the signal-to-noise ratio.
4Force
If piezoelectric actuators are used to drive the mirror, then the device is small in size and provides large driving force, but the torque generation is limited and mechanical stress is applied to moving parts
Solution Approach 1:
The patent changes the operational parameters of the piezoelectric actuators by using two elements that can be driven in complementary phases. This allows the system to achieve larger deflection angles and more efficient torque generation by coordinating the deformation of both piezoelectric elements, thereby reducing the mechanical stress on individual components while maintaining the compact size and large driving force advantages.
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 enables fast and precise deflection and sweeping operations with improved mechanical strength and reduced stress on components, allowing for larger deflection angles and efficient light scanning while maintaining a compact design.
Implementation Method 1
the piezoelectric cantilever including a piezoelectric material formed on a supporting body to exhibit bending deformation due to piezoelectricity when a driving voltage is applied thereto
Implementation Method 2
a second piezoelectric element having one or more piezoelectric cantilevers, one end of the piezoelectric cantilever being connected to the torsion bar, the other end being connected to and supported by the mirror, the piezoelectric cantilever including a piezoelectric material formed on a supporting body to exhibit bending deformation due to piezoelectricity
Data Source
AI summary
An optical deflector includes a mirror having a reflective plane; a torsion bar extending outwardly from an end of said mirror; a support surrounding said mirror; a first piezoelectric element, one end of said first piezoelectric element being connected to said torsion bar, the other end of the first piezoelectric element being connected to and supported by said support, said first piezoelectric element having at least one piezoelectric cantilever, the cantilever including a supporting body and a piezoelectric body formed on the supporting body to exhibit bending deformation due to piezoelectricity when a driving voltage is applied to the piezoelectric body, said piezoelectric element rotarily driving said mirror through said torsion bar when said driving voltage is applied; and a second piezoelectric element, one end of said second piezoelectric element being connected to said torsion bar, the other end of the second piezoelectric element being connected to and supported by said mirror.