Stacked Film Lightguide for Reflective Display Illumination

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Solution Overview

Problem

Conventional edge-lit light emitting devices with rigid lightguides are thick and inflexible, limiting design configurations and production methods, and struggle to efficiently couple light into thinner lightguides, which restricts the size and illumination modes of displays, especially for larger systems.

Innovation Solution

A reflective display with a frontlight using a film-based lightguide with opposing faces less than 0.5 millimeters thick, featuring an array of coupling lightguides folded to form a stacked light input surface, where light from a source propagates through the lightguides and combines for total internal reflection, with light extraction features to direct light towards a reflective spatial light modulator.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If rigid lightguides with thickness of 2mm or larger are used, then sufficient light flux can be coupled into the lightguide, but the device thickness and overall volume increase

Engineering Contradiction:

Improvelight coupling efficiencyVSAvoiddevice volume

Core Design Contradiction:

Use of energy by moving objectVSVolume of moving object

Solution Approach 1:

The lightguide is divided into multiple thin lightguide layers (each less than 0.5mm thick) stacked together. This segmentation allows sufficient light coupling area to be achieved through the stack while maintaining thin individual layers, thus reducing overall device volume while preserving light coupling efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from a single thick lightguide to multiple thin stacked lightguide layers. By adding the stacking dimension, the system achieves the equivalent light coupling area of a thick lightguide while maintaining thin individual layers, effectively moving the solution from a single-dimension (thickness) problem to a multi-dimensional (stacked layers) solution.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Volume of moving object

If thin lightguides with thickness less than 0.5mm are used, then device thickness and volume are reduced, but difficulty coupling sufficient light flux into the lightguide increases

Engineering Contradiction:

Improvedevice volumeVSAvoidlight coupling difficulty

Core Design Contradiction:

Volume of moving objectVSEase of manufacture

Solution Approach 1:

Multiple thin lightguide layers are optically coupled together in a stack to form a composite lightguide system. The light coupling interfaces of all layers are merged to collectively receive light from LED sources, achieving sufficient total light flux coupling while maintaining thin individual layers and reduced overall device volume.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The stacked lightguide structure serves multiple functions simultaneously: each thin layer provides light guidance while the collective stack provides sufficient light coupling area. The system achieves both thin profile and adequate light flux coupling capability through the multi-functional stacked architecture.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Use of energy by moving object

If large light sources and large input coupling optics are used, then sufficient light flux is provided, but system size increases

Engineering Contradiction:

Improvelight flux outputVSAvoidsystem area

Core Design Contradiction:

Use of energy by moving objectVSArea of stationary object

Solution Approach 1:

The light coupling function is segmented across multiple thin lightguide layers instead of requiring a single large light source or large coupling optics. Each layer provides a light coupling interface, and the collective stack achieves sufficient total light flux coupling with compact LED sources and minimal optics.

Inventive Principle:

Principle #1Segmentation

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 enables thinner, more flexible light emitting devices with improved light coupling efficiency, allowing for larger display sizes and varied illumination modes without the volume constraints of traditional rigid lightguide systems.

Implementation Method 1

light from each coupling lightguide combining and totally internally reflecting within the lightguide region

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

A plurality of light extraction features frustrate totally internally reflected light within the lightguide region such that the light exits the lightguide toward the reflective spatial light modulator

Methodology Applied

Scientific EffectTotal internal reflection frustration: Total Internal Reflection

Data Source

PatentUS9557473B2Reflective spatial light modulator display with stacked light guides and method

Publication Date: 2017.01.31 AZUMO INC

AI summary

A reflective display includes a reflective spatial light modulator and a front light having a lightguide formed by an array of film-based lightguides coupled into a lightguide region of the lightguide. One or more light sources emit light into the array of lightguides, with light extraction features frustrating totally internally reflect light within the lightguide region such that the light exits the lightguide through a cladding region toward a light redirecting optical element that redirects the light toward a reflective spatial light modulator.