Tilted Grating Input Coupler for Holographic Display Stripe Suppression
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Solution Overview
Problem
Holographic display methods face challenges in reducing stripe patterns in illumination light, which affect the quality of the displayed images and viewer comfort due to non-uniform brightness and the formation of bright/dark stripe patterns.
Innovation Solution
A backlight unit incorporating an input coupler with a tilted grating structure is used to suppress the stripe pattern of illumination light, where the grating barriers are tilted at a predetermined angle to prevent overlapping light beams and reduce bright stripes, and a reflective layer is applied to enhance light use efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional input coupler with perpendicular grating structure is used, then the device complexity is low, but stripe patterns appear in the illumination light
Solution Approach 1:
The patent applies asymmetry by tilting the grating structure at a predetermined angle (e.g., 45 degrees) relative to the normal direction of the light guide plate. This asymmetric configuration changes the diffraction angle of light beams, preventing them from overlapping and thereby eliminating the stripe pattern while maintaining manufacturing feasibility.
Solution Approach 2:
The patent changes the geometric parameters of the grating structure, specifically the tilt angle of the gratings, to alter the light diffraction characteristics. By adjusting this parameter, the light beams are diffracted at angles that prevent overlapping, thus suppressing stripe patterns without requiring complex additional components.
2Illumination intensity
If light beams are allowed to overlap in the light guide plate, then the device complexity is low, but non-uniform brightness and stripe patterns occur
Solution Approach 1:
The asymmetric tilt of the grating structure directs light beams at specific angles that prevent overlapping within the light guide plate. This ensures uniform brightness distribution across the illumination area without requiring additional complex light control mechanisms.
Solution Approach 2:
The patent introduces angular distribution (another dimension) by tilting the gratings, which spreads light beams in different directions. This dimensional change in light propagation prevents overlapping and achieves uniform brightness without adding complex spatial control structures.
3Object-affected harmful factors
If a tilted grating structure is used to suppress stripe patterns, then brightness uniformity is improved, but the manufacturing precision requirement increases
Solution Approach 1:
The patent specifies a predetermined tilt angle (e.g., 45 degrees) for the grating structure, which can be precisely controlled during manufacturing processes such as photolithography. This parameter change achieves stripe pattern suppression while maintaining compatibility with standard manufacturing precision capabilities.
4Loss of energy
If a reflective layer is added to enhance light use efficiency, then energy utilization is improved, but device complexity increases
Solution Approach 1:
The patent merges the reflective layer with the existing input coupler structure, forming an integrated component. This combination enhances light use efficiency by reflecting otherwise lost light back into the light guide plate while avoiding the complexity of separate additional layers or components.
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 tilted grating structure in the input coupler effectively minimizes the formation of bright and dark stripe patterns, ensuring more uniform illumination and improved image quality by reducing light loss and enhancing the coherence of the illumination light.
Implementation Method 1
an input coupler configured to cause the illumination light incident on the light incident surface of the light guide plate to travel into the light guide plate... an input coupler having a tilted grating structure... diffracting the reference light
Implementation Method 2
a light guide plate... that comprises an in-coupling diffraction grating for diffracting an external light beam incident on said in-coupling diffraction grating into the light guide in a direction enabling the in-coupled light beam to propagate within the light guide via total internal reflections at the light guide surfaces
Data Source
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AI summary
A backlight unit including an input coupler, a holographic display apparatus including the backlight unit, and a method of manufacturing the input coupler are provided. The backlight unit includes the input coupler configured to cause light incident on a light incident surface of a light guide plate to travel into the light guide plate, the input coupler has a binary grating structure in which a plurality of barriers are arranged parallel to one another at a constant grating period, and the plurality of barriers are tilted from the light incident on the light incident surface.