Segmented Backlight Structure for Thin Display Contrast

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Solution Overview

Problem

Conventional full array local dimming techniques for LCD displays are not feasible in smaller devices like laptops and tablets due to the thinness of the backlight, which prevents effective reduction of black values and contrast enhancement.

Innovation Solution

An LED backlight system with sidelight emitting LEDs and a light waveguide structure that includes a reflective layer and out-coupling structures to achieve near uniform light output and modular layouts, allowing for precise control of light levels and contrast.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If top-lighting LEDs are used in thin backlights, then light output is achieved, but the LED is clearly visible through the light guide layer creating non-uniform illuminance

Engineering Contradiction:

Improvelight outputVSAvoiduniformity of illuminance

Core Design Contradiction:

Illumination intensityVSStability of the object's composition

Solution Approach 1:

The patent inverts the conventional top-lighting LED approach by using sidelight-emitting LEDs that emit light from the sides rather than the top. This inversion places the light source orientation perpendicular to the traditional direction, allowing the LED to be positioned in a cavity within the light guide where it emits light laterally into the waveguide structure, achieving uniform illuminance without visible LED spots.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent introduces a light guide waveguide as an intermediary structure between the sidelight-emitting LED and the display panel. The waveguide with its specific refractive index and optical properties mediates the light transmission, converting the lateral LED emission into uniform forward light output through total internal reflection and controlled outcoupling, thereby hiding the LED while maintaining illumination.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If conventional FALD techniques are used, then local dimming is achieved, but the technique is not feasible in smaller displays with thin backlights

Engineering Contradiction:

Improvelocal dimming capabilityVSAvoidapplicability to thin backlights

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by implementing segmented backlight regions where each segment has its own sidelight-emitting LED and can be independently controlled. The optical barrier structures create distinct local zones with different light transmission properties, enabling local dimming functionality tailored to each region while adapting to the thin backlight form factor of portable devices.

Inventive Principle:

Principle #3Local quality

3Length of moving object

If the backlight thickness is reduced for portable devices, then device thinness is achieved, but contrast resolution and black value reduction capability are lost

Engineering Contradiction:

Improvebacklight thicknessVSAvoidcontrast resolution

Core Design Contradiction:

Length of moving objectVSMeasurement precision

Solution Approach 1:

The patent transitions from the conventional vertical (top-down) light emission dimension to a lateral (side) emission dimension. By positioning LEDs in cavities within the light guide and emitting light from the sides rather than the top, the system achieves local dimming and contrast control in a thin profile without requiring the traditional thick backlight structure with top-mounted LEDs.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

Enables high contrast and dynamic range in smaller displays by reducing top emission and improving light homogeneity, supporting full array local dimming even in thin backlight configurations.

Implementation Method 1

At least one of a reflective layer and a top out-coupling structure can be positioned between the top of the cavity and the sidelight emitting LED

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

An integral light waveguide... defines a cavity having a top and sidewalls, with the sidelight emitting LED positioned in the cavity

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 3

A sidewall out-coupling structure can be positioned between the sidewalls of the cavity and the sidelight emitting LED

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS11181682B2Segmented backlight structure

Publication Date: 2021.11.23 LUMILEDS SINGAPORE PTE LTD

AI summary

An LED backlight system having a plurality of backlight segments including an integral light waveguide, each backlight segment supporting a sidelight emitting LED. A light guide having a rectangular shape, a flat top surface, and a curved lower surface defines a cavity having a top and sidewalls, with the sidelight emitting LED positioned in the cavity. At least one of a reflective layer and a top out-coupling structure can be positioned between the top of the cavity and the sidelight emitting LED.