Holographic Display Backlight With Layered Couplers for Speckle Reduction
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Solution Overview
Problem
Existing holographic display methods face challenges in providing uniform illumination and coherence, leading to issues like speckle noise and limited image quality, particularly when using laser diodes for backlight units.
Innovation Solution
A backlight unit design incorporating a light guide structure with stacked light guide layers and coupler layers that emit collimated coherent illumination light, utilizing laser diodes with multi-peak wavelength distribution to reduce speckle noise and ensure uniform intensity distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If laser diodes are used for backlight units to provide coherent illumination, then coherence is improved, but speckle noise increases
Solution Approach 1:
The patent divides the backlight unit into multiple independent laser diodes arranged in an array, where each laser diode emits coherent light. By segmenting the light source into multiple coherent sources with different wavelengths or phases, the speckle noise from individual sources is averaged out, reducing overall speckle while maintaining coherence for holographic illumination.
2Measurement precision
If collimated illumination is provided for holographic display, then image quality is improved, but uniformity of illumination deteriorates
Solution Approach 1:
The patent employs optical elements such as diffusers or microlens arrays positioned at specific locations within the illumination path to locally modify the light distribution. These elements create regions with different optical properties that, when combined, produce both collimated output and uniform intensity distribution across the holographic display area.
3Object-generated harmful factors
If multiple light sources are used to reduce speckle noise, then speckle noise is reduced, but device complexity increases
Solution Approach 1:
The patent combines multiple laser diodes into a single integrated backlight unit module with shared optical components and control electronics. By merging the multiple light sources and their supporting structures into one unified device, the system reduces speckle noise through source diversity while avoiding the complexity of separate independent systems.
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 provides a backlight unit that delivers uniform, collimated coherent illumination, reducing speckle noise and enhancing image quality, allowing for improved holographic display performance.
Implementation Method 1
a light guide structure (110) to expand and collimate a section of the light emitted from the first light source (121) and the second light source (122)
Implementation Method 2
a first coupler layer (CL1) disposed between the first substrate (S1) and the second substrate (S2), and a second coupler layer (CL2) disposed between the third substrate (S3) and the fourth substrate (S4)... each of the first coupler layer (CL1) and the second coupler layer (CL2) may include a plurality of couplers
Implementation Method 3
utilizing laser diodes with multi-peak wavelength distribution to reduce speckle noise
Implementation Method 4
utilizing laser diodes with multi-peak wavelength distribution to reduce speckle noise and ensure uniform intensity distribution
Implementation Method 5
a light guide structure (110) to expand and collimate a section of the light emitted from the first light source (121) and the second light source (122)
Implementation Method 6
provides collimated coherent illumination light to the spatial light modulator
Data Source
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AI summary
Provided a backlight unit including a light source and a light guide structure configured to guide the light emitted from the light source, the light guide structure includes a first coupler layer including a first output coupler configured to expand light in a first direction and output the expanded light in the first direction to the outside of the light guide structure, and a first expansion coupler configured to expand the light in a second direction perpendicular to the first direction and provide the expanded light in the second direction to the first output coupler, and a second coupler layer including a second output coupler configured to expand light in the first direction and output the expanded light to the outside of the light guide structure, and a second expansion coupler configured to expand light in the second direction and provide the expanded light to the second output coupler.