Backlight Device Optical Path Difference Generator Speckle Reduction
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Solution Overview
Problem
Holographic 3D image display devices face issues with speckle formation due to the interference of coherent light with random phase patterns in diffusion plates, leading to unwanted patterns in 3D images.
Innovation Solution
A backlight device with an optical path difference generator that includes multiple layers with varying thicknesses and overlapping patterns, reducing spatial coherence and generating coherent light with different phase distributions, which is then diffused and collimated to minimize speckle brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a diffusion plate is used to uniformly provide coherent light to the spatial light modulator, then uniform illumination is achieved, but speckle patterns are generated due to random phase interference
Solution Approach 1:
The diffusion plate is divided into multiple regions with different optical path lengths (first region with thickness t1, second region with thickness t2 where t1 ≠ t2). This segmentation creates different phase delays for coherent light passing through different regions, causing speckle patterns to shift and overlap in a way that reduces overall speckle brightness while maintaining uniform illumination distribution.
2Measurement precision
If coherent light is used for holographic display, then high image quality and 3D effect are achieved, but speckle formation occurs due to interference with random phase patterns
Solution Approach 1:
Different regions of the diffusion plate are assigned different local optical properties (different thicknesses creating different phase delays). The first region provides coherent light with one phase characteristic while the second region provides coherent light with a different phase characteristic. This local quality variation ensures that speckle patterns generated in different regions have different spatial distributions, and their overlap reduces the visibility of speckle in the final 3D image while preserving the necessary coherence for holographic display.
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 speckle brightness by ensuring different speckle patterns overlap, making them less noticeable in the 3D image, thereby enhancing image clarity.
Implementation Method 1
an optical path difference generator on the light source, the optical path difference generator including an incident surface and a plurality of light emitting surfaces, the light emitting surfaces being parallel to the incident surface and having different separation distances from the incident surface
Implementation Method 2
a diffuser on the light condenser
Implementation Method 3
a collimator on the diffuser
Implementation Method 4
when coherent light is irradiated onto the diffusion plate, a speckle (or speckle pattern) may be generated in a 3D image while the coherent light is being partially mutually interfered by a random phase pattern of the diffusion plate
Data Source
AI summary
A backlight device includes: a light source to emit coherent light; an optical path difference generator on the light source, the optical path difference generator including an incident surface and a plurality of light emitting surfaces, the light emitting surfaces being parallel to the incident surface and having different separation distances from the incident surface; a light condenser on the optical path difference generator; a diffuser on the light condenser; and a collimator on the diffuser.