Optical Element Using Shape Memory Alloy Actuator

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Solution Overview

Problem

Conventional optical elements using VCM actuators with heavy magnets are prone to compression, deformation, or breakage during drop tests due to increased pressure in sealed volumes, which can lead to damage of the windows or membrane.

Innovation Solution

The optical element employs Shape Memory Alloy actuators, which are lightweight and provide pulling forces, reducing the risk of damage by contracting when heated and expanding when cooled, thus reducing the moving mass and stress on the prism during drop tests.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If a VCM actuator with a heavy magnet is used to tilt the window, then the actuator can provide sufficient force, but the heavy mass causes severe compression, deformation, or breakage of the prism during drop tests

Engineering Contradiction:

Improveactuator forceVSAvoidshock resistance

Core Design Contradiction:

ForceVSReliability

Solution Approach 1:

The patent replaces the conventional VCM (Voice Coil Motor) actuator with a Shape Memory Alloy (SMA) actuator. The SMA actuator uses thermal-mechanical coupling instead of electromagnetic fields, eliminating the heavy permanent magnet while providing sufficient tilting force through phase transformation of the alloy material.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the actuation mechanism from electromagnetic (VCM) to thermomechanical (SMA). The SMA actuator utilizes temperature-induced phase transformation parameters to generate force, replacing the magnet-based electromagnetic force generation, thereby reducing mass while maintaining functionality.

Inventive Principle:

Principle #35Parameter changes

2Force

If a VCM actuator with a heavy magnet is used, then the actuator can tilt the window effectively, but the heavy mass increases stress on the prism and membrane during acceleration

Engineering Contradiction:

Improveactuator forceVSAvoidstress on prism

Core Design Contradiction:

ForceVSStress or pressure

Solution Approach 1:

The patent substitutes the heavy electromagnetic VCM actuator with a lightweight Shape Memory Alloy actuator. This replacement eliminates the permanent magnet mass that generates inertial forces during acceleration, thereby reducing stress on the prism and membrane while maintaining the necessary tilting force through thermal actuation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If a lightweight actuator is used to reduce mass, then shock resistance improves, but the actuator must still provide sufficient force to tilt the window

Engineering Contradiction:

Improveshock resistanceVSAvoidactuator force

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The patent utilizes the phase transformation properties of Shape Memory Alloy to generate high force from a lightweight structure. The SMA material undergoes martensitic phase transformation when heated, producing substantial mechanical force despite the low mass of the alloy wire, thus achieving both lightweight design and sufficient actuation force.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent exploits the phase transition of Shape Memory Alloy between austenite and martensite phases. When heated above the transformation temperature, the SMA wire contracts and generates force; when cooled, it expands and returns to its original state. This phase transition mechanism enables the lightweight actuator to deliver the necessary tilting force.

Inventive Principle:

Principle #36Phase transitions

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 use of Shape Memory Alloy actuators in the optical element enhances shock resistance and reliability, reducing the risk of damage from acceleration forces and allowing for a leaner design that is more resistant to shock and compression.

Implementation Method 1

The first actuator comprises a Shape Memory Alloy and is formed in the shape of a wire

Methodology Applied

Scientific EffectShape Memory Alloy: Shape Memory Alloy

Implementation Method 2

which are lightweight and provide pulling forces, reducing the risk of damage by contracting when heated and expanding when cooled

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS20230185077A1Optical element and method for operating an optical element

Publication Date: 2023.06.15 OPTOTUNE SWITZERLAND AG

AI summary

Optical element (1) comprising a first window (21) and a second window (22), wherein the first window (21) is connected to the second window (22) by an elastic membrane (41) such that the first window (21), the second window (22) and the membrane (41) enclose a deformable, sealed volume (42), which is filled with a fluid, wherein at least one first actuator (51) is arranged to tilt the first window (21) with respect to the second window (22) around a first tilting axis (81) in a first direction, wherein the first actuator (51) comprises a Shape Memory Alloy and has the shape of a wire.