MEMS Mirror Piezoelectric Actuation for Planarity Error Compensation

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Solution Overview

Problem

MEMS mirror devices suffer from deformations due to residual stresses and environmental factors, leading to direction errors of reflected light beams and distortions in projected images, which existing reinforcement ribs fail to fully mitigate.

Innovation Solution

A microelectromechanical mirror device is designed with a piezoelectric actuation structure that includes a piezoelectric compensation actuator extending around the reflective layer, allowing for controlled modification of the plate's curvature to counteract deformations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If reinforcement ribs are added to stiffen the plate structure, then overall deformation is reduced, but local strain concentrations and artifacts are caused

Engineering Contradiction:

Improveoverall plate stabilityVSAvoidlocal planarity precision

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent replaces the mechanical reinforcement rib structure with a piezoelectric actuation system that uses electrical fields to generate mechanical compensation forces. The piezoelectric actuators convert electrical signals into precise mechanical displacements to counteract plate deformations without introducing physical strain concentrations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state and properties of the plate by using piezoelectric materials that convert electrical parameters into mechanical deformation. By controlling the electrical voltage applied to the piezoelectric actuators, the plate's curvature and shape can be dynamically adjusted to compensate for deformations caused by residual stresses and environmental factors.

Inventive Principle:

Principle #35Parameter changes

2Area of moving object

If the plate size is increased to accommodate the mirror, then the mirror area is improved, but deformations due to residual stresses are amplified

Engineering Contradiction:

Improvemirror areaVSAvoidplate planarity

Core Design Contradiction:

Area of moving objectVSStability of the object's composition

Solution Approach 1:

The patent replaces passive mechanical reinforcement with an active piezoelectric compensation system that can dynamically counteract deformations. The piezoelectric actuators generate forces that oppose the deformation tendencies of the large plate, maintaining planarity despite the increased size and associated residual stress effects.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a dynamic compensation mechanism using piezoelectric actuators that can actively adjust the plate's shape in real-time. This allows the system to adapt to and compensate for deformations that occur with larger plate sizes, transforming a static structural problem into a dynamically controllable one.

Inventive Principle:

Principle #15Dynamics

3Manufacturing precision

If reinforcement ribs are used to counteract residual stresses, then image quality is improved, but device complexity increases

Engineering Contradiction:

Improveprojected image qualityVSAvoidstructural complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical reinforcement ribs with a more compact piezoelectric actuation system. The piezoelectric actuators can be integrated directly onto the plate surface or attached to strategic locations, eliminating the need for protruding mechanical ribs and reducing overall structural complexity while maintaining image quality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The piezoelectric actuators serve multiple functions: they compensate for residual stress deformations, counteract environmental factor effects (temperature changes), and can potentially provide additional functions such as fine positioning or focus adjustment. This multi-functionality reduces the need for separate compensation mechanisms.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The solution effectively reduces overall deformation and planarity errors, improving the quality of projected images by minimizing distortions and artifacts, while maintaining modularity and adaptability in compensation actions.

Implementation Method 1

a piezoelectric actuation structure extending on a second region of the plate adjacent to the reflective layer and configured to apply forces that modify a curvature of the plate

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS12292567B2Microelectromechanical mirror device with compensation of planarity errors

Publication Date: 2025.05.06 STMICROELECTRONICS SRL

AI summary

A microelectromechanical mirror device includes a supporting frame of semiconductor material and a plate of semiconductor material. The plate is connected to the supporting frame so as to be orientable around at least one rotation axis. A reflective layer is arranged on a first region of the plate. A piezoelectric actuation structure extends on a second region of the plate adjacent to the reflective layer. The piezoelectric actuation structure is configured to apply forces such as to modify a curvature of the plate.