Holographic Back Light Unit With Dual Diffraction Gratings
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Solution Overview
Problem
Conventional back light units for holographic displays are complex and require multiple parts, limiting the viewing zone to a narrow region, making them inefficient in terms of light utilization and requiring multiple viewing zones for proper viewing.
Innovation Solution
A back light unit design featuring a waveguide with a first and second diffraction grating, a light reflection element that redirects light, and a single light source, which increases light utilization efficiency and simplifies the structure by eliminating the need for multiple light sources, allowing for a wider viewing zone through controlled light reflection and diffraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional back light unit structure is used, then the hologram image can be displayed, but the structure is complicated and requires a relatively large number of parts
Solution Approach 1:
The patent combines multiple light sources and optical components into a single integrated back light unit structure. The first and second light sources are positioned at different locations but both illuminate through the same waveguide, merging their functions into one unified system that reduces overall structural complexity while maintaining reliable hologram display capability
Solution Approach 2:
The waveguide serves multiple functions: it guides light from both the first and second light sources, supports the diffraction grating, and directs light to form the hologram image. This multi-functional design reduces the number of separate components needed, simplifying the overall structure while ensuring reliable operation
2Area of stationary object
If a conventional back light unit is used, then the hologram image can be displayed, but the viewing zone is limited to a narrow region
Solution Approach 1:
The patent divides the light source function into two separate light sources (first and second light sources) positioned at different locations. This segmentation allows each light source to illuminate different angular ranges, collectively expanding the viewing zone while maintaining a manageable structural complexity through their coordinated arrangement
Solution Approach 2:
The patent expands the viewing zone by utilizing angular distribution in addition to spatial positioning. By arranging light sources at different locations and angles, the system creates multiple viewing zones that accommodate different viewing angles, effectively expanding the viewing area without proportionally increasing structural complexity
3Adaptability or versatility
If multiple viewing zones are formed at fixed locations, then the hologram can be viewed from different angles, but the viewer must fix the locations where the viewing zones are formed
Solution Approach 1:
The patent creates multiple viewing zones that are distributed across different angular ranges and locations. This dynamic arrangement allows the viewing zones to cover a broader spatial area, enabling viewers to move more freely while still accessing hologram viewing capability, thus improving ease of operation while maintaining viewing angle flexibility
4Use of energy by moving object
If a conventional back light unit is used, then the hologram image can be displayed, but light utilization efficiency is low
Solution Approach 1:
The patent positions the first and second light sources and their corresponding diffraction gratings to create overlapping or adjacent viewing zones. This continuous arrangement ensures that light from both sources is effectively utilized to illuminate different portions of the hologram, improving overall light utilization efficiency while maintaining a cohesive structural design
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 design enhances light utilization efficiency and simplifies the structure by creating two viewing zones with a single light source, enabling a wider viewing area without the need for multiple light sources, thus improving the hologram display experience.
Implementation Method 1
A diffraction grating is used to maintain coherency of light emitted from the waveguide
Implementation Method 2
a second diffraction grating that redirects light toward the first diffraction grating
Implementation Method 3
a light reflection element that reflects light that is emitted from a rear side of the waveguide toward the first diffraction grating
Data Source
AI summary
Provided is a back light unit (BLU) for holographic display. The BLU includes a first diffraction grating attached to a waveguide, a second diffraction grating that supplies light to the first diffraction grating, a light source that supplies light to the second diffraction grating, and a light reflection element that reflects light towards the first diffraction grating. The back light unit may further include a lens that is disposed in front of the waveguide. The light reflection element may be disposed parallel to a rear surface of the waveguide. The light reflection element may be inclined with respect to the rear surface of the waveguide. The light reflection element may be a mirror or a prism array.