Narrow Piezoelectric Sensor for Optical Deflector Resonance Control

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Solution Overview

Problem

Existing one-dimensional optical deflectors face issues with resonant frequency reduction due to rocking semi-ring-shaped piezoelectric actuators, conductive layer weight affecting the circular mirror's resonant frequency, and insufficient accuracy in sense voltage detection, leading to suboptimal deflection angles.

Innovation Solution

A design featuring linear piezoelectric actuators and a narrow piezoelectric sensor element, where the sensor is positioned within two-fifths of the actuator's width from the inner end, allowing for feedback control of sense voltage to drive voltages, thereby achieving a resonant state and improving deflection accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If semi-ring-shaped piezoelectric actuators are used for vibrating the circular mirror, then the deflection function is achieved, but the resonant frequency of the actuators decreases due to rocking motion

Engineering Contradiction:

Improveresonant frequencyVSAvoidrocking motion

Core Design Contradiction:

SpeedVSEase of operation

Solution Approach 1:

The piezoelectric actuator is divided into two independent parts: a linear piezoelectric actuator for driving the mirror and a narrow piezoelectric sensor element for detection. This segmentation allows the actuator to maintain linear motion without rocking, preserving resonant frequency while enabling precise control.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using semi-ring-shaped actuators that rock during operation, the patent inverts the approach by using linear actuators with a separate narrow sensor element positioned within two-fifths of the actuator's width from the inner end. This inversion eliminates the rocking motion problem while maintaining the vibration function.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If conductive layers are extended from piezoelectric sensors through torsion bars to pads on support frame, then electrical connection is achieved, but the weight of conductive layers affects the resonant frequency of the circular mirror

Engineering Contradiction:

Improveelectrical connectionVSAvoidresonant frequency

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent extracts the sensing function from the conductive layers by using a narrow piezoelectric sensor element that generates sense voltage through piezoelectricity during vibration. This eliminates the need for long conductive layers, removing their weight from the system and preserving the resonant frequency.

Inventive Principle:

Principle #2Taking out (Extraction)

3Area of stationary object

If piezoelectric sensor width is the same as piezoelectric actuators, then coverage is achieved, but the accuracy of sense voltage detection is insufficient

Engineering Contradiction:

Improvesensor coverageVSAvoidsense voltage accuracy

Core Design Contradiction:

Area of stationary objectVSMeasurement precision

Solution Approach 1:

The patent applies local quality by making the piezoelectric sensor element narrow (width less than one-fifth of the actuator width) and positioning it specifically within two-fifths of the actuator's width from the inner end. This localized placement at the high-stress region near the torsion bar enhances detection accuracy while maintaining sufficient coverage for resonant state feedback control.

Inventive Principle:

Principle #3Local quality

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 precise control of sinusoidal-wave drive voltages, maximizing deflection angles and achieving a high signal-to-noise ratio, thus enhancing the optical deflector's performance by stabilizing the resonant frequency and improving detection accuracy.

Implementation Method 1

piezoelectric actuators provided between the support frame and the torsion bars for vibrating (rocking) the circular mirror through the torsion bars

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a piezoelectric sensor element between the torsion bar and the piezoelectric actuator... allowing for feedback control of sense voltage to drive voltages

Methodology Applied

Scientific EffectPiezoelectric effect: Converse Piezoelectric Effect

Data Source

PatentEP2706393B1Optical deflector including narrow piezoelectric sensor element between torsion bar and piezoelectric actuator

Publication Date: 2021.01.27 STANLEY ELECTRIC CO LTD

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AI summary

In an optical deflector including a mirror (1), a support frame (2) surrounding the mirror (1), at least one torsion bar (3-2, 3'-2) arranged along an axis (X) of the mirror (1) having an end coupled to an outer circumference of the mirror (1), a pair of piezoelectric actuators (4-2a, 4-2b; 4-a, 4-b) arranged between the support frame (2) and the torsion bar (3-2, 3'-2), and a piezoelectric sensor (5, 5') inserted between the torsion bar (3-2, 3'-2) and one of the piezoelectric actuators (4-2a, 4-a), the piezoelectric sensor (5, 5') includes at least one piezoelectric sensor element (5-1, 5-2; 5'-1, 5'-2) having a width being smaller than two-fifths of a width (W) of the one of the piezoelectric actuators (4-2a, 4-a) and being arranged at a wide portion within two-fifths of the width (W) from an inner end of the one of the piezoelectric actuators (4-2a, 4-a).