Backlight Assembly Slanted Grating Stray Light Control
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Solution Overview
Problem
Transparent display devices face issues with stray light generation when using light-extracting gratings, leading to reduced contrast and brightness due to the inability to accurately achieve L0 gray scale, as the light-shielding layer fails to shield non-perpendicular light rays.
Innovation Solution
A backlight assembly with a light guide, a first grating having a diffraction direction slanted relative to the thickness direction, and a light direction adjuster that changes diffractive light to a target direction, typically parallel to the thickness direction, along with a filling layer and planarizing layer, to minimize stray light and enhance beam collimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light-extracting grating is used to extract light perpendicularly from the light guide, then light extraction efficiency is improved, but stray light rays are generated that cannot be shielded by the light-shielding layer, resulting in reduced contrast
Solution Approach 1:
A liquid crystal layer is introduced as an intermediary between the light-extracting grating and the light-shielding layer. This liquid crystal layer acts as a controllable mediator that can dynamically adjust light transmission based on applied voltage, allowing perpendicular light to pass through while blocking stray light rays that would otherwise reach the display surface.
Solution Approach 2:
The optical properties of the liquid crystal layer are dynamically changed by adjusting the voltage parameter. By varying the voltage applied to the liquid crystal layer, the transmission characteristics are modified to achieve different gray scales, with the ability to completely block stray light at certain voltage levels while maintaining perpendicular light transmission at other levels.
2Object-affected harmful factors
If a light-shielding layer is arranged to block stray light, then contrast is improved, but the light-shielding layer cannot shield non-perpendicular light rays, resulting in inaccurate L0 gray scale representation
Solution Approach 1:
The liquid crystal layer serves as a precise intermediary control element positioned between the light-extracting grating and the light-shielding layer. It provides fine-grained control over light transmission, enabling accurate achievement of the L0 gray scale by completely blocking light paths that would otherwise leak through the light-shielding layer's inability to shield non-perpendicular rays.
Solution Approach 2:
The system transitions from a static light-shielding layer to a dynamic liquid crystal-based control mechanism. The liquid crystal layer can dynamically adjust its transmission state in response to voltage changes, providing active control over light blocking to achieve precise gray scale representation, particularly for the L0 state where complete light blocking is required.
3Adaptability or versatility
If voltage is applied to the liquid crystal layer to form a liquid crystal light grating, then light direction is changed to emit through intervals between light-shielding layers, but the complexity of the system increases
Solution Approach 1:
The liquid crystal layer performs multiple functions within a single component: it acts as a light-shielding element, a light-direction controller, and a gray scale modulator. By applying different voltages, the same liquid crystal layer can achieve L0 gray scale by blocking light, intermediate gray scales by partial transmission, and L255 gray scale by forming a liquid crystal light grating to redirect light through intervals between light-shielding 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
The solution effectively reduces stray light, improves contrast, and increases brightness by ensuring accurate L0 gray scale representation and enhancing liquid crystal light efficiency without the need for a light-shielding layer, thereby improving the overall display performance.
Implementation Method 1
a first grating on a first surface of the light guide, the first grating having a diffraction direction slanted relative to a thickness direction of the light guide
Implementation Method 2
the light direction adjuster has a first refractive index and the first filling layer has a second refractive index smaller than the first refractive index
Implementation Method 3
The light reflector is configured to reflect light emitted by the light emitter into the light guide for propagation inside the light guide with total reflection
Data Source
AI summary
Disclosed includes a backlight assembly, a display device including such a backlight assembly and a method of obtaining backlight. The backlight assembly may comprise a light guide, a first grating on a first surface of the light guide and a light direction adjuster on a side of the first grating away from the light guide. The first grating may have a diffraction direction slanted relative to a thickness direction of the light guide and the light direction adjuster may be configured to change diffractive light coming from the first grating to a target direction.