Phase Modulator Compensation for Angle-Dependent Amplitude

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Solution Overview

Problem

Phase-modulating light modulators experience angle-dependent amplitude modulation issues, leading to reduced reconstruction quality in holographic display devices, especially at large viewing angles, due to insufficient compensation of transmittance and reflectance variations.

Innovation Solution

A phase-modulating light modulator with an optically active layer and a transparent compensation bulk region using birefringent materials with fixed refractive index ellipsoids, oriented to minimize averaged amplitude modulation across various viewing angles, combined with a polariser on the exit side, and optionally using compensation films on the boundary surfaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If phase modulation is implemented in light modulators, then holographic reconstruction capability is improved, but angle-dependent amplitude modulation occurs leading to reduced reconstruction quality at large viewing angles

Engineering Contradiction:

Improveholographic reconstruction qualityVSAvoidangle-dependent amplitude modulation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A compensation bulk region with birefringent material is introduced as an intermediary element between the optically active layer and the observer. This compensation layer mediates the optical interaction by providing counteracting phase modulation that compensates for the angle-dependent amplitude modulation effects, thereby maintaining reconstruction quality across large viewing angles

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The refractive index ellipsoids of the birefringent material in the compensation bulk region are specifically oriented to change the optical parameters in a way that compensates for viewing angle variations. By adjusting the orientation and optical properties of the compensation layer, the system maintains consistent amplitude modulation characteristics across different viewing angles

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the viewing angle range is increased, then observer flexibility is improved, but amplitude modulation variations increase leading to polarisation state changes

Engineering Contradiction:

Improveviewing angle rangeVSAvoidpolarisation state stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The compensation bulk region acts as an intermediary optical element that stabilizes the polarisation state across different viewing angles. By introducing this additional layer with specific birefringent properties, the system maintains polarisation stability even when the viewing angle range is expanded

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The light modulator employs a composite structure combining the optically active layer with the compensation bulk region containing birefringent material. This composite design allows the system to achieve both wide viewing angle range and stable polarisation state by leveraging the complementary optical properties of the different layers

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 configuration significantly reduces angle-dependent amplitude modulation, enhancing the reconstruction quality of color scenes at large viewing angles by compensating for the polarisation state changes, thereby improving the holographic display performance.

Implementation Method 1

at least one transparent compensation bulk region which comprises at least one birefringent material with fixed refractive index ellipsoids

Methodology Applied

Scientific EffectBirefringence: Birefringence

Implementation Method 2

phase-modulating light modulator comprises an optically active layer with at least one optically active bulk region... whose orientation can be controlled discretely for each pixel

Methodology Applied

Scientific EffectPhase modulation: Phase Modulation

Data Source

PatentUS8928825B2Method for ensuring a minimal amplitude modulation in phase-modulating light modulators

Publication Date: 2015.01.06 SEEREAL TECHNOLOGIES SA

AI summary

The invention relates to a phase-modulating light modulator and to a method for ensuring a minimal amplitude modulation in phase-modulating light modulators, wherein the phase-modulating light modulator comprises an optically active layer with at least one optically active volume region and with boundary surfaces, wherein the optically active layer is assigned at least one transparent compensation volume region which comprises at least one birefringent material with fixed refractive index ellipsoids, and has a polarizer arranged on the output side. An object is to achieve a reduced angle-dependence of the averaged amplitude modulation in the observation angle region. The object is achieved by optimizing the orientation with respect to one another of the refractive index ellipsoids of the optically active layer and of the compensation layers in a simulative manner.