Multi-Layer Mirror Plate for Spatial Light Modulator

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Solution Overview

Problem

Conventional spatial light modulators (SLMs) suffer from low brightness and contrast ratio due to low active reflection area fill-ratio and optical efficiency, primarily caused by scattered light from inactive areas and the double plate structure, which reduces optical coupling and increases diffraction patterns.

Innovation Solution

A high contrast SLM device is designed with a three-layer mirror structure and embedded torsion hinges, featuring a reflective top layer, a silicon-based spacer layer, and a conductive bottom layer, along with vertical landing tips and step electrodes to enhance electrostatic efficiency and reduce surface adhesion, resulting in a high active reflection area fill-ratio and non-diffractive micro-mirror array.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a conventional single-layer mirror structure is used, then the device structure is simple, but the contrast ratio is low due to scattering and diffraction

Engineering Contradiction:

Improvemirror structureVSAvoidscattered light and diffraction patterns

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The patent employs a multi-layer composite mirror structure consisting of a first reflective layer, a spacer layer, and a second reflective layer. This composite structure is designed to reduce scattered light and diffraction patterns while maintaining high reflectivity. The spacer layer specifically serves to minimize optical interference and scattering effects, thereby improving the contrast ratio of projected images without significantly increasing device complexity.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If a double plate structure is used to achieve acceptable contrast ratio, then the contrast ratio improves, but the active reflection area fill-ratio decreases due to horizontal displacement and vibration

Engineering Contradiction:

Improvecontrast ratioVSAvoidactive reflection area

Core Design Contradiction:

Object-affected harmful factorsVSArea of moving object

Solution Approach 1:

The patent extracts and eliminates the problematic double plate structure that causes horizontal displacement and vibration. Instead, it uses a single mirror plate with a multi-layer composite structure that achieves high contrast ratio without the detrimental side effects of the double plate design, thereby preserving the active reflection area fill-ratio.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the structural parameters of the mirror by introducing a multi-layer composite design with specific layer thicknesses and material properties. This parameter optimization allows the mirror to achieve high contrast ratio performance while maintaining mechanical stability and high active reflection area fill-ratio, avoiding the horizontal displacement issues of conventional designs.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If a vertical mirror support post is used to elevate the mirror plate, then the mirror plate can be positioned above the hinge yoke plate, but the contrast ratio deteriorates due to light scattering from the dimple at the center of the mirror

Engineering Contradiction:

Improvemirror plate positioningVSAvoidlight scattering from dimple

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent removes the vertical mirror support post that creates the problematic dimple structure. By eliminating this support element, the design avoids the light scattering and contrast ratio deterioration while still achieving proper mirror plate positioning through alternative support mechanisms that do not interfere with the optical path.

Inventive Principle:

Principle #2Taking out (Extraction)

4Reliability

If larger gaps are designed between mirrors to accommodate horizontal displacement, then the mechanical operation is reliable, but the active reflection area fill-ratio decreases

Engineering Contradiction:

Improvemechanical operationVSAvoidactive reflection area

Core Design Contradiction:

ReliabilityVSArea of moving object

Solution Approach 1:

The patent optimizes the gap parameters between adjacent mirrors by changing the mechanical design to eliminate horizontal displacement. The multi-layer composite structure and improved support mechanism allow mirrors to rotate without significant horizontal movement, enabling smaller gap spacing that maintains both mechanical reliability and high active reflection area fill-ratio.

Inventive Principle:

Principle #35Parameter changes

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 achieves a high contrast ratio and improved electrostatic efficiency, reducing scattered light and diffraction patterns, thereby enhancing the brightness and contrast of projected images.

Implementation Method 1

The SLM devices operate by tilting individual micro-mirror plates around a torsion hinge with an electrostatic torque

Methodology Applied

Scientific EffectElectrostatic torque: Electrostatics

Implementation Method 2

deflect incident light in a direction that depends on the orientation of the micro-mirror plates

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 3

micro-mirror plates around a torsion hinge

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS7388708B2Spatial light modulator multi-layer mirror plate

Publication Date: 2008.06.17 SPATIAL PHOTONICS INC

AI summary

A spatial light modulator having a multi-layer mirror is described.