Super-Lambertian Lens for Uniform Large-Area Illumination

Solution Overview

Problem

Existing LED-based backlights for large-screen liquid crystal displays face challenges in achieving uniform illuminance over a larger area due to the Lambertian light distribution characteristic, which results in increased heat generation density and difficulty in dissipating heat, making it hard to position and maintain light sources effectively.

Innovation Solution

A lighting device with a rotationally symmetric lens design that includes a first and second light exit surface, where the rate of inclination decreases discontinuously at a change point, allowing for increased light intensity with increasing emission angles, thereby enhancing illuminance uniformity across a larger area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a Lambertian light source is used, then the light distribution follows a predictable pattern, but the illuminance decreases sharply with increasing angle, making it difficult to illuminate a large area uniformly

Engineering Contradiction:

Improveilluminance uniformityVSAvoidilluminated area

Core Design Contradiction:

Illumination intensityVSArea of stationary object

Solution Approach 1:

The patent changes the light distribution parameter from Lambertian (Cosθ) to a super-Lambertian distribution (Cos^nθ where n<1), thereby altering the angular dependence of light intensity to achieve more uniform illuminance across a wider area. This is accomplished by designing the lens with a specific refractive index and curvature radius that satisfy the mathematical relationship n×sin(α) = sin(β) to produce the desired light distribution pattern.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a lens with a spheroidal surface geometry to control light refraction. The curved surface of the lens, characterized by its curvature radius, is specifically designed to transform the point source light into a super-Lambertian distribution, enabling uniform illumination over a larger area by controlling the angular distribution of emitted light.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Area of stationary object

If the screen size increases, then the display area increases quadratically, but the light source length increases only linearly, causing heat generation density to increase

Engineering Contradiction:

Improvedisplay areaVSAvoidheat generation density

Core Design Contradiction:

Area of stationary objectVSTemperature

Solution Approach 1:

The patent changes the light distribution parameter from Lambertian (Cosθ) to a super-Lambertian distribution (Cos^nθ where n<1), thereby altering the angular dependence of light intensity to achieve more uniform illuminance across a wider area. This is accomplished by designing the lens with a specific refractive index and curvature radius that satisfy the mathematical relationship n×sin(α) = sin(β) to produce the desired light distribution pattern.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a lens with a spheroidal surface geometry to control light refraction. The curved surface of the lens, characterized by its curvature radius, is specifically designed to transform the point source light into a super-Lambertian distribution, enabling uniform illumination over a larger area by controlling the angular distribution of emitted light.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Area of stationary object

If the screen size increases, then the display area increases quadratically, but the light source length increases only linearly, making it difficult to position the light source

Engineering Contradiction:

Improvedisplay areaVSAvoidlight source positioning

Core Design Contradiction:

Area of stationary objectVSEase of operation

Solution Approach 1:

The patent creates a universal lighting solution where a single point light source with a super-Lambertian distribution lens can illuminate large areas uniformly, replacing the need for multiple light sources or complex positioning systems. This multi-functional approach allows the same lens design to serve various display sizes while maintaining uniform illuminance distribution.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 solution enables the lighting device to illuminate a larger area with nearly uniform illuminance, reducing the thickness of the display and improving heat dissipation, making it suitable for large-screen liquid crystal displays.

Implementation Method 1

a lens disposed on the substrate so as to cover the LED element. The lens has a light exit surface that is rotationally symmetric with respect to an optical axis

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS8147100B2Lighting device

Publication Date: 2012.04.03 SHENZHEN JUFEI OPTOELECTRONICS CO LTD

AI summary

A lighting device includes a substrate, a LED element, and a lens. A light exit surface of the lens includes a first light exit surface and a second light exit surface. A curve obtained by cutting the light exit surface by a plane including the optical axis has, on a boundary between the first light exit surface and the second light exit surface, a change point at which a rate of inclination decreases discontinuously. An angle between the optical axis and a line segment connecting the change point and a light emission center of the LED element is approximately equal to an emission angle with the highest light intensity, among emission angles, when light rays emitted from the light exit surface are sorted by respective emission angles.