Laser Scanning Display Speckle Reduction via Beam Segmentation
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Solution Overview
Problem
Phase-coherent light sources, such as solid-state illuminators, produce unwanted speckle effects in display systems due to scattering from rough surfaces, significantly degrading image quality by creating quantized areas with randomly varying intensities.
Innovation Solution
The method involves splitting an input laser beam into two output beams with different polarization directions using an optical element like a birefringent crystal wedge, which are then scanned onto a display surface to generate illumination spots that are integrated by the eye, reducing the perceived speckle effect by creating decorrelated speckle patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If phase-coherent light is used in display systems, then efficiency and compact size are improved, but speckle effect degrades image quality
Solution Approach 1:
The invention segments the single coherent light beam into multiple independent coherent beams by passing through different regions of the spatial light modulator. Each beam generates independent speckle patterns that are uncorrelated, and when integrated by the human eye, these patterns average out to reduce the overall speckle effect while maintaining the efficiency benefits of coherent light sources.
2Device complexity
If single coherent beam is used, then system complexity is reduced, but speckle pattern visibility increases
Solution Approach 1:
The spatial light modulator divides the optical beam into multiple spatial regions, each generating a separate coherent beam. This segmentation creates multiple uncorrelated speckle patterns without requiring complex additional optical components, thus reducing speckle visibility while adding minimal system complexity.
Solution Approach 2:
The invention introduces spatial diversity by utilizing different spatial regions of the spatial light modulator to generate multiple beams. This dimensional approach creates uncorrelated speckle patterns through spatial separation rather than requiring temporal or polarization diversity, simplifying the overall system architecture.
3Object-affected harmful factors
If multiple uncorrelated coherent beams are used, then speckle effect is reduced, but device complexity increases
Solution Approach 1:
The spatial light modulator serves multiple functions simultaneously: it modulates the intensity of the coherent beam to create the image, divides the beam into multiple spatial regions to generate uncorrelated speckle patterns, and controls the timing of beam generation. This multi-functionality reduces device complexity by eliminating the need for separate components for each function.
Solution Approach 2:
The spatial light modulator inherently provides the beam segmentation function as part of its normal operation. By utilizing different spatial regions of the same device, the system generates multiple uncorrelated beams without requiring additional external components, allowing the existing device to serve multiple purposes.
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 approach reduces the speckle effect by averaging out the different speckle patterns perceived by the viewer, resulting in a 3 dB or 1/â2 reduction in contrast ratio, making the speckle patterns less noticeable, thereby improving image quality.
Implementation Method 1
splitting an input laser beam into two output beams with different polarization directions using an optical element like a birefringent crystal wedge
Implementation Method 2
Speckle effect arises when phase-coherent light, such as light from solid-state illuminators is scattered from a rough surface
Implementation Method 3
The illumination spots are scanned at a speed so that the eye integrates the speckle effect produced by each of the different polarizations
Data Source
AI summary
Speckle effect in scanning display systems that employs polarized phase-coherent light is reduced by depolarizing the phase-coherent light using a depolarizer and scanning the depolarized light for producing desired images.