Light Guide Panel Anisotropic Layer Polarization Recycling
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Solution Overview
Problem
Conventional light guide panels (LGP) used in back light units for displays, such as LCDs, suffer from reduced luminous efficiency due to the inability to change the polarization direction of incident light, resulting in unpolarized light being emitted, which is not utilized effectively by LCDs that require light polarized in a specific direction.
Innovation Solution
The LGP incorporates an isotropic layer with a polarization recycling unit and an anisotropic layer, where the anisotropic layer has different refractive indices for light polarized in different directions, allowing for the transmission and reflection of light to change its polarization direction, thereby enhancing the luminous efficiency by ensuring only polarized light is emitted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a conventional LGP with a planar reflection surface is used, then the structure is simple and easy to manufacture, but the polarization direction of light is not changed, resulting in unpolarized light being emitted and reducing luminous efficiency
Solution Approach 1:
The patent introduces an anisotropic layer with different refractive indices for different polarization directions. This changes the optical parameter of the LGP from isotropic to anisotropic, enabling selective transmission and reflection of polarized light to improve luminous efficiency
Solution Approach 2:
The patent combines an isotropic layer with an anisotropic layer to form a composite structure. The anisotropic layer is positioned at the emission surface to selectively transmit polarized light, while the isotropic layer maintains the overall structure simplicity
2Use of energy by moving object
If an anisotropic layer is added to change polarization direction, then luminous efficiency is improved, but the device structure becomes more complex
Solution Approach 1:
The anisotropic layer is placed only at the emission surface where polarization control is needed, rather than throughout the entire LGP structure. This localized approach improves luminous efficiency while minimizing the increase in structural complexity
Solution Approach 2:
The patent utilizes the property of anisotropic materials having different refractive indices for different polarization directions. By changing the refractive index parameter at the emission surface, the system achieves selective light transmission without requiring complex multi-layer structures
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
This configuration increases the luminous efficiency of the display by effectively polarizing the emitted light in a predetermined direction, improving the brightness of LCDs by recycling and redirecting light polarization, thus overcoming the limitations of conventional LGPs.
Implementation Method 1
The anisotropic layer has a first refractive index, identical to the first refractive index of the isotropic layer, with respect to light having a first polarization. The anisotropic layer has a second refractive index, different from the first refractive index, with respect to light having a second polarization. Thus, light having the first polarization is transmitted without refraction at a boundary between the anisotropic layer and the transmission surface of the isotropic layer, and light having the second polarization is refracted and transmitted at the boundary between the anisotropic layer and the transmission surface of the isotropic layer.
Implementation Method 2
The polarization recycling unit changes a polarization direction of light
Implementation Method 3
The anisotropic layer comprises a selectively transmitting and reflecting surface, disposed opposite the transmission surface of the isotropic layer, which reflects a first portion of incident light and transmits a second portion of incident light
Data Source
AI summary
A light guide panel and a back light unit having the same are provided. The light guide panel includes an isotropic layer and an anisotropic layer. The isotropic layer includes an incident light surface, a transmission surface, and a polarization recycling unit, disposed opposite the transmission surface, which changes a polarization direction of light. The isotropic layer has a first refractive index. The anisotropic layer is formed on the transmission surface and includes a selectively transmitting and reflecting surface opposite the transmission surface, which reflects a first portion of incident light and transmits a second portion of incident light. The anisotropic layer has a first refractive index, identical to the first refractive index of the isotropic layer, with respect to light having a first polarization and has a second refractive index, different from the first refractive index with respect to light having a second polarization.