Piezoelectric Sensor Stack Structure for Optical Scanning S/N Ratio
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Solution Overview
Problem
The existing optical scanning devices face challenges in improving the signal-to-noise (S/N) ratio due to limited output of piezoelectric sensors, which affects the accuracy and efficiency of light scanning.
Innovation Solution
The optical scanning device incorporates a mirror support unit with a pair of drive beams and a piezoelectric sensor formed on connection beams, where the number of piezoelectric thin films in the sensor is less than in the drive source, utilizing a stack structure to enhance drive efficiency and sensor output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a piezoelectric element having a multilayer structure is used as a drive source with parallel connection of lower and upper layer piezoelectric thin films, then drive efficiency is improved, but wiring is difficult due to narrow surface area
Solution Approach 1:
The patent divides the piezoelectric sensor into separate functional layers: the lower layer piezoelectric thin film serves as the drive source, while the upper layer piezoelectric thin film serves as the sensor. This segmentation allows each layer to be optimized independently - the lower layer can be connected in parallel for high drive efficiency, while the upper layer provides sensing capability without requiring complex wiring connections.
Solution Approach 2:
The piezoelectric element structure is designed to perform multiple functions: the lower layer piezoelectric thin film functions as both a drive source (when voltage is applied) and a sensor (when displacement occurs), while the upper layer piezoelectric thin film primarily functions as a sensor. This multi-functionality reduces the need for separate components and simplifies wiring requirements.
2Device complexity
If lower and upper layer piezoelectric thin films are connected in series for piezoelectric sensor, then wiring is simplified, but sensor output voltage is reduced to 1/2 of parallel connection case
Solution Approach 1:
The patent segments the piezoelectric element into distinct functional zones where the lower layer is optimized for drive function and the upper layer for sensor function. This allows the lower layer to be connected in parallel configuration for high drive efficiency while the upper layer provides sensing output, avoiding the voltage loss associated with series connections.
Solution Approach 2:
Instead of connecting both layers in series or parallel for identical functions, the patent inverts the approach by assigning different functions to different layers. The lower layer is connected in parallel for drive efficiency, while the upper layer provides sensor output, thereby achieving both high drive efficiency and adequate sensor output without the compromises of series or parallel connections for single-function elements.
3Measurement precision
If piezoelectric sensor output is increased to improve S/N ratio, then scanning accuracy is improved, but element breakage risk increases due to higher withstand voltage requirements
Solution Approach 1:
The patent segments the piezoelectric sensor function across two layers: the lower layer piezoelectric thin film and the upper layer piezoelectric thin film. By using the upper layer primarily for sensing with fewer stacked films, the sensor output voltage is sufficient for accurate measurement while the reduced number of films decreases the cumulative stress and breakage risk compared to using a thick multilayer structure for sensing alone.
Solution Approach 2:
The patent applies different quality characteristics to different parts of the piezoelectric element: the lower layer is designed with sufficient thickness and parallel connection for high drive capability, while the upper layer is optimized for sensing with appropriate thickness to provide adequate output voltage without excessive stress accumulation. This local optimization allows the sensor to achieve high S/N ratio while maintaining reliability.
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 improves the S/N ratio by increasing the output of the piezoelectric sensor, leading to enhanced scanning performance and accuracy without increasing production complexity.
Implementation Method 1
A piezoelectric element is used as a drive source utilizing the inverse piezoelectric effect and drives a drive beam
Implementation Method 2
a piezoelectric element is used as a piezoelectric sensor by utilizing the piezoelectric effect, and senses a displacement and a drive state of a drive beam
Data Source
AI summary
An optical scanning device includes: a mirror that has an optical reflection surface; a mirror support unit configured to support the mirror; a pair of drive beams arranged on both sides of the mirror support unit and connected such that the mirror support unit is swingable; a drive source provided on the drive beams and configured to swing the mirror support unit, the drive source including a stack structure of a plurality of piezoelectric thin films; and a piezoelectric sensor formed on a connection beam connected to the drive source or the drive beams, a number of piezoelectric thin films included in the piezoelectric sensor being less than a number of the piezoelectric thin films included in the drive source.