Micro-LED Directional Backlight for Spatial Uniformity Control

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Solution Overview

Problem

Existing displays face challenges in achieving high spatial uniformity and efficiency in directional backlighting for transmissive spatial light modulators, particularly in liquid crystal displays, due to non-uniform spatial distributions and inefficiencies in light output from catadioptric optical elements, leading to issues like Moiré and mura artefacts.

Innovation Solution

A directional backlight system is developed using micro-LEDs aligned with catadioptric optical elements, incorporating light recycle systems and diffuser elements to achieve spatial uniformity and efficiency, with the system comprising a plurality of micro-LEDs and catadioptric optical elements arranged in arrays, along with reflective polarizers for increased efficiency and reduced power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If catadioptric optical elements are used to achieve narrow directional light output distribution, then viewing angle control is improved, but spatial uniformity deteriorates causing Moiré and mura artefacts

Engineering Contradiction:

Improveviewing angle controlVSAvoidspatial uniformity

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent segments the optical system into multiple independent catadioptric optical elements, each corresponding to a specific LED light source. This segmentation allows individual optimization of each optical element to compensate for non-uniform light distribution, thereby improving spatial uniformity while maintaining narrow directional light output control.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies local quality by varying the optical properties of different catadioptric optical elements based on their position in the array. Each element is specifically designed with tailored reflective and refractive characteristics to compensate for local non-uniformities in light distribution, ensuring uniform spatial output across the entire display while maintaining directional control.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If micro louvered film is added to achieve narrow directional light output, then privacy and night time display are improved, but light efficiency deteriorates due to absorption and attenuation

Engineering Contradiction:

Improveprivacy display capabilityVSAvoidlight efficiency

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent replaces the mechanical micro louvered film structure with catadioptric optical elements that use optical principles (reflection and refraction) to achieve directional light control. This substitution eliminates the light absorption and attenuation problems inherent in louvered films, maintaining privacy capability while significantly improving light efficiency.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent converts the naturally omnidirectional light emission from LEDs into a beneficial narrow directional distribution through catadioptric optical elements. Instead of treating the wide light emission as a problem to be blocked (which causes energy loss), the system harnesses this characteristic and redirects it usefully, achieving privacy and directional control without energy waste.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Adaptability or versatility

If fixed layers such as prismatic films and diffusers are added to alter directional light output, then light distribution control is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improvelight distribution controlVSAvoidbacklight assembly structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges the functions of prismatic films and diffusers into integrated catadioptric optical elements. Each element combines reflective and refractive properties in a single component, eliminating the need for separate fixed layers and reducing overall device complexity while maintaining precise light distribution control.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The catadioptric optical elements serve multiple functions simultaneously: they provide directional light control, ensure spatial uniformity, and compensate for non-uniform LED emission patterns. This multi-functionality replaces what would otherwise require multiple separate components, reducing device complexity and manufacturing cost.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Ease of manufacture

If packaged LEDs with conventional assembly techniques are used, then ease of manufacture is improved, but manufacturing precision and display resolution deteriorate due to component size and tolerance limitations

Engineering Contradiction:

Improveassembly process simplicityVSAvoidcomponent placement accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent segments the LED array into individually addressable micro-LED elements with precise spatial positioning. Each micro-LED is paired with a corresponding catadioptric optical element, creating modular units that can be manufactured with high precision using conventional techniques while achieving overall high-resolution display performance.

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

The system provides high spatial uniformity, reduced power consumption, and improved privacy and comfort by directing light only to desired viewing angles, while minimizing stray light and maintaining high luminance without increasing power usage.

Implementation Method 1

catadioptric optical elements which employ both refraction and reflection

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

catadioptric optical elements which employ both refraction and reflection, including total internal reflection or reflection from metallised surfaces

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 3

catadioptric optical elements which employ both refraction and reflection, including total internal reflection

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 4

incorporating light recycle systems and diffuser elements to achieve spatial uniformity

Methodology Applied

Scientific EffectLight scattering: Scattering

Data Source

PatentEP3631553B1Illumination apparatus

Publication Date: 2025.08.27 OPTOVATE

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Figure 1B
Figure 1C~1D

AI summary

An illumination apparatus comprises an array of micro-LEDs (3), an aligned plurality of directional catadioptric optical elements (38), light redirecting micro-optics (200) and a reflective polariser (310). The directional illumination apparatus is arranged to provide a uniform spatial distribution across its output area by recirculating reflected high luminous intensity regions into low luminous intensity regions of the catadioptric optical element. A thin and efficient illumination apparatus with high spatial uniformity may be provided for illumination in environmental lighting, display backlighting or direct display.