Folded Stacked Lightguides for Thin Transmissive Display Backlights
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional light emitting devices, such as displays and backlights, face challenges in achieving a thin form factor with specific angular light output profiles due to the use of rigid lightguides, which limit design flexibility and illumination modes, and struggle to couple sufficient light flux into thinner lightguides.
Innovation Solution
A display comprising a reflective spatial light modulator with stacked lightguides and cladding or adhesive layers, where a light source emits light that totally internally reflects within the lightguides, extracted from each lightguide to illuminate an active area, with the lightguides folded to form a light mixing region for efficient light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If rigid lightguides are used to reduce thickness, then the form factor is reduced, but design flexibility and illumination modes are limited
Solution Approach 1:
The lightguide is divided into multiple segments or layers that can be independently configured. Each segment can have different optical properties, allowing for customized illumination modes while maintaining overall thinness. The segmented structure enables flexible arrangement to achieve desired design configurations.
Solution Approach 2:
The patent transitions from conventional planar lightguide structures to three-dimensional stacked configurations. By stacking multiple thin lightguide layers vertically, the system achieves thin overall thickness while creating multiple illumination zones and modes within the stacked architecture, thereby gaining design flexibility without increasing footprint.
2Stability of the object's composition
If rigid lightguides are used, then structural stability is maintained, but device flexibility and bending capability are reduced
Solution Approach 1:
The patent employs thin film-based lightguide structures that inherently possess flexibility. These thin films can be bent, folded, or conformally shaped while maintaining optical functionality. The flexible nature allows the lightguide to adapt to various device form factors and mounting configurations without compromising structural integrity.
Solution Approach 2:
By segmenting the lightguide into multiple thin layers connected by flexible interfaces or adhesives, the structure gains bendability while each individual layer maintains its optical stability. The segmented architecture allows the lightguide to flex as a unified structure rather than as rigid monolithic pieces.
3Length of moving object
If thinner lightguides are used to reduce thickness, then the form factor is reduced, but light flux coupling efficiency deteriorates
Solution Approach 1:
The light flux coupling problem is addressed by segmenting the light input across multiple stacked lightguide layers. Each layer has its own light input region, allowing the total light flux to be distributed across multiple coupling surfaces. This segmentation increases the effective coupling area while maintaining thin individual layer thickness, thereby improving overall light flux coupling efficiency.
Solution Approach 2:
The patent moves from single-plane light coupling to multi-plane coupling by stacking lightguide layers vertically. Light can be coupled into each layer from different positions along the stack, effectively utilizing the vertical dimension to increase total coupling area. This three-dimensional coupling approach compensates for the reduced thickness of individual layers.
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 enables a thinner form factor with improved light distribution and flexibility in design, allowing for more efficient illumination and enhanced angular light output profiles.
Implementation Method 1
a light source positioned behind the reflective spatial light modulator to emit light that propagates into the plurality of lightguides such that it totally internally reflects within each lightguide of the plurality of lightguides
Data Source
AI summary
A display includes a transmissive spatial light modulator with an active area; a plurality of lightguides stacked above the active area; and a light source positioned to emit light that propagates into the plurality of lightguides such that the light is totally internally reflected within each lightguide then extracted from each lightguide to illuminate the active area, wherein each lightguide is folded at a first fold. In a first embodiment, each of the plurality of lightguides include a core layer and an emitting region with a plurality of light extraction features arranged in a spatially varying pattern. In a second embodiment, each lightguide is a film-based light guide with a thickness between 0.005 millimeter and 0.175 millimeter. In a third embodiment, the light source is positioned behind the spatial light modulator.