Light Diffuser for Uniform LED Backlight Illumination
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Solution Overview
Problem
Existing display technologies using LED backlights face challenges in achieving uniform planar illumination and minimizing parallax effects, leading to undesirable image blurring and light loss due to the point source nature of LEDs, which affects luminance and efficiency.
Innovation Solution
An optical structure comprising a rear reflector with transparent regions, a light-diffusing volume, an optional reflective polarizer, and an angularly selective light transmitter is used to distribute light from point sources like LEDs, ensuring uniform illumination and minimizing parallax by diffusing and polarizing light effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If point type light sources (LEDs) are used in the backlight array, then energy efficiency and robustness are improved, but uniform planar illumination deteriorates due to the point source nature of LEDs
Solution Approach 1:
A light-diffusing volume is introduced as an intermediary between the LED array and the display layer. This diffuser medium scatters the point source light from LEDs to create uniform planar illumination across the display area, resolving the contradiction between energy efficiency of point sources and uniformity of illumination.
Solution Approach 2:
The optical properties of the space between LEDs and display are changed by introducing a light-diffusing volume with specific scattering characteristics. This transforms the illumination pattern from point-source directional light to uniform diffuse light, maintaining LED energy efficiency while achieving uniform illumination.
2Length of stationary object
If point type light sources are positioned close to the display layer, then device thickness is reduced, but parallax effects worsen causing image blurring artifacts
Solution Approach 1:
The light-diffusing volume acts as an intermediary that decouples the positioning relationship between LEDs and display layer. By introducing this scattering medium, the system can maintain small physical separation (reducing thickness) while the diffuser ensures each LED illuminates only its corresponding display area, eliminating parallax-induced blurring.
3Area of stationary object
If light is allowed to spread in all directions from LEDs, then illumination coverage is improved, but luminance in normal viewing direction deteriorates due to light loss
Solution Approach 1:
The optical structure implements local quality control by using the light-diffusing volume to scatter light uniformly across the display area while the display layer's light modulator selectively directs light in the normal viewing direction. This ensures broad illumination coverage while maintaining high luminance where needed.
4Adaptability or versatility
If reflective polarizers are used in the display layer, then viewing angle performance is improved, but light loss worsens due to polarization effects
Solution Approach 1:
The light-diffusing volume changes the polarization state of light through multiple scattering events before it reaches the reflective polarizers in the display layer. This randomization of polarization reduces the effectiveness of polarization-based light loss, allowing reflective polarizers to maintain their viewing angle performance while minimizing energy loss.
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 achieves uniform planar illumination, reduces image artifacts, and maximizes luminance by ensuring that light is efficiently distributed and polarized, maintaining high brightness across various viewing angles with minimal light loss.
Implementation Method 1
a light-diffusing volume, an optional reflective polarizer, and an angularly selective light transmitter is used to distribute light from point sources like LEDs, ensuring uniform illumination and minimizing parallax by diffusing and polarizing light effectively
Implementation Method 2
an optional reflective polarizer, and an angularly selective light transmitter is used to distribute light from point sources like LEDs, ensuring uniform illumination and minimizing parallax by diffusing and polarizing light effectively
Data Source
AI summary
An optical structure placeable between a backlight array of point light sources and a planar display. The structure distributes light emitted by the point light sources to uniformly illuminate the plane of the display, without introducing significant viewing parallax. The emitted light is partially collimated within a preferred angular viewing range, maximizing the display's luminance when viewed from the normal direction. The structure is highly reflective, such that a substantial portion of any non-emitted light rays are internally reflected by the structure, increasing the likelihood that those rays will be subsequently emitted by the structure.