Curved Spring Suspension for Micromirror Stress Distribution

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Solution Overview

Problem

Existing micromirror technologies face challenges in achieving high resonant frequencies and large deflections simultaneously while avoiding material stress and maintaining energy efficiency, with previous solutions either compromising mechanical stability, experiencing material failure, or requiring increased space and energy inefficiency.

Innovation Solution

The use of curved spring elements to suspend a micromirror, allowing for the absorption of forces and distribution of stress, thereby preventing material failure and enabling high operating frequencies and deflections, with the spring elements designed to have a specific histogram of local orientations to optimize force transfer and reduce mechanical stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If conventional spring elements are used to connect micromirror to actuators, then large deflections can be achieved, but high material stress causes spring failure at moderate mirror deflections

Engineering Contradiction:

Improvemirror deflectionVSAvoidspring material stress

Core Design Contradiction:

Length of moving objectVSStrength

Solution Approach 1:

The patent employs curved spring elements with specific geometric curvature to distribute mechanical stress more evenly throughout the spring structure. The curved geometry allows the spring to absorb and dissipate forces more effectively, preventing stress concentration at specific points and enabling large mirror deflections without spring failure.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Speed

If high resonant frequency is achieved, then operating speed increases, but large deflection becomes difficult to achieve simultaneously

Engineering Contradiction:

Improveresonant frequencyVSAvoidmirror deflection

Core Design Contradiction:

SpeedVSLength of moving object

Solution Approach 1:

The patent optimizes multiple parameters including spring element curvature radius, spring thickness, spring length, and actuator positioning to achieve a balance between resonant frequency and deflection amplitude. By carefully adjusting these geometric and dimensional parameters, the system achieves both high resonant frequency (e.g., 304 Hz or higher) and large mirror deflection (e.g., 9 mm or more).

Inventive Principle:

Principle #35Parameter changes

3Length of moving object

If actuators are mounted movably on both ends to allow large scanning angles, then space requirements increase and energy efficiency decreases

Engineering Contradiction:

Improvescanning angleVSAvoidenergy efficiency

Core Design Contradiction:

Length of moving objectVSUse of energy by moving object

Solution Approach 1:

The patent segments the mechanical system into fixed actuator mounts and movable mirror suspension, rather than allowing movement at both ends. The actuators are fixedly mounted to provide stable force application, while the curved spring elements provide the necessary compliance and movement range for large scanning angles. This segmentation improves energy efficiency by ensuring complete force transfer from actuators to the mirror.

Inventive Principle:

Principle #1Segmentation

4Speed

If small layer thickness of actuators is used to achieve high operating frequency, then mechanical stability becomes sensitive to damage and constant load

Engineering Contradiction:

Improveoperating frequencyVSAvoidmechanical stability

Core Design Contradiction:

SpeedVSStability of the object's composition

Solution Approach 1:

The patent employs composite construction for the actuator assembly, combining piezoelectric layers with supporting structural layers. This composite approach allows the actuator to maintain high resonant frequency while achieving sufficient mechanical stability and damage resistance, overcoming the limitations of thin-layer single-material construction.

Inventive Principle:

Principle #40Composite materials

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 allows for robust operation with high resonant frequencies and large deflections, reducing material fatigue and increasing the device's operating time while maintaining energy efficiency by effectively transferring forces through the use of curved spring elements.

Implementation Method 1

an optical element suspended to be vibratable via curved spring elements; and at least two actuators, each mounted fixedly on one side, which are connected to the vibratably suspended optical element via the curved spring elements

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

a vibratable, oscillating system comprises laterally arranged actuators and a micromirror arranged in the center which, connected to one another via a torsion spring, form a vibratable overall system and exhibit a common resonant frequency

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS9733470B2Device comprising a vibratably suspended optical element

Publication Date: 2017.08.15 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

The underlying invention presents a device which connects a vibratably suspended optical element to at least two actuators mounted fixedly on one side via curved spring elements, wherein the actuators are implemented to cause the vibratably suspended optical element to vibrate via the curved spring elements. Both the actuators and the entire system may be implemented to be more robust and be operated more reliably due to the curved shaping of the spring elements.