Polymer MEMS Deformable Mirror with Pillar Spacers

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Solution Overview

Problem

Conventional autofocus or zoom systems require large space due to mechanical motors, and existing refractive and reflective optical systems face limitations in packaging thickness and deformation range, especially with traditional inorganic materials used in MEMS deformable mirrors.

Innovation Solution

A polymer MEMS deformable mirror with a reflective design that includes a top membrane and a bottom electrode with pillars to prevent contact when a voltage is applied, allowing for higher deformation and reduced packaging thickness, achieved through a specific manufacturing process involving metal layers and isolating layers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If traditional inorganic materials (silicon or silicon nitride) are used for MEMS deformable mirrors, then mechanical stiffness is high, but deformation range is limited

Engineering Contradiction:

Improvemechanical stiffnessVSAvoiddeformation range

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The patent changes the material parameter from traditional inorganic materials (silicon, silicon nitride) to polymer materials. This material substitution fundamentally alters the mechanical properties, enabling much larger deformation ranges (12-μm displacement) while maintaining sufficient structural integrity for optical applications.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The deformable mirror employs a composite structure combining polymer materials with metal electrodes and isolating layers. This composite design allows the polymer to provide large deformation capability while the metal components provide electrical conductivity and structural support, achieving both flexibility and mechanical strength.

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If refractive design forms (liquid lens, liquid crystal lens) are used, then optical power can be varied, but packaging thickness is increased due to straight optical path requirement

Engineering Contradiction:

Improveoptical power variationVSAvoidpackaging thickness

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

The patent inverts the optical design approach by using a reflective deformable mirror instead of a refractive lens system. The reflective design allows the optical path to be folded back on itself, enabling compact packaging thickness (5.4 mm) while still achieving variable optical power through surface deformation (12-μm displacement corresponding to 20 diopter focusing power).

Inventive Principle:

Principle #13The other way round (Inversion)

3Device complexity

If pillars are not added to prevent contact, then structure is simpler, but top membrane may touch second metal layer causing short circuit when voltage is applied

Engineering Contradiction:

Improvestructural simplicityVSAvoidelectrical insulation

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent introduces pillars as intermediary support structures between the top membrane and the second metal layer. These pillars serve as mechanical spacers that maintain a minimum gap, preventing direct contact and potential short circuits when high voltage is applied, while still allowing the membrane to deform freely within the available space.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The pillars are pre-positioned during manufacturing to establish the minimum gap before operation. This preliminary structural arrangement ensures that even under maximum voltage and deformation conditions, the top membrane cannot contact the second metal layer, preventing short circuits without requiring complex active control mechanisms.

Inventive Principle:

Principle #10Preliminary action

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 polymer MEMS deformable mirror achieves a 12-μm displacement over a 3-mm aperture, corresponding to 20 diopter focusing power, with an optical system design that is 5.4 mm thick and 6.7 mm after packaging, enabling efficient auto-focusing without stepping motors and moving lenses, while maintaining low power consumption.

Implementation Method 1

when a voltage is applied between the first and the second metal layers

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Data Source

PatentUS9140897B2Optical system, optical module and method of manufacture thereof

Publication Date: 2015.09.22 NAT TAIWAN UNIV

AI summary

An optical system, an optical module and a method of manufacture thereof are provided. The optical module includes a top membrane and a bottom electrode. The top membrane includes a supporting layer, a first metal layer and an isolating layer with an opening. The first metal layer is disposed on lower surface of the supporting layer. The isolating layer is disposed on lower surface of the first metal layer. The bottom electrode, disposed below the top membrane, includes a second metal layer and a plurality of pillars. The pillars are disposed on upper surface of the second metal layer and below the isolating layer, wherein some of the pillars support the isolating layer. Wherein the pillars are used for preventing the top membrane from being pulled down to touch the second metal layer through the opening when a voltage is applied between the first and the second metal layers.