Optical Coupler Speckle Reduction in Laser Displays
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Solution Overview
Problem
Laser display devices using coherent laser beams suffer from speckle noise due to the coherence of laser beams, which affects image quality and color reproduction, making it challenging to achieve high-definition displays with natural color representation.
Innovation Solution
An optical coupler with a first coupling unit and a second coupling unit filled with an optical transmission medium, such as thermally twisted optical fibers, is used to reduce coherence, combined with a diffuser to eliminate speckle noise, allowing for uniform mixing of laser beams without the need for complex components like rod lenses and beam combiners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If laser light sources are used in display devices, then color reproduction and color purity are improved, but speckle noise is generated due to beam coherence
Solution Approach 1:
The patent introduces an optical coupler as an intermediary component between the laser light source and the display element. This optical coupler includes a first coupling unit with a guide hole and a second coupling unit, which together form an optical path that mixes multiple laser beams of different colors. The optical coupler acts as a mediator to reduce coherence and eliminate speckle noise while maintaining color purity and reproduction quality.
2Manufacturing precision
If multiple laser beams of different colors are combined, then image quality is improved, but speckle noise and interference fringes are generated
Solution Approach 1:
The patent merges multiple laser beams of different colors (red, green, and blue) into a single optical path using the optical coupler. The first coupling unit receives multiple external beams through guide holes, and the second coupling unit combines them into a unified beam path. This merging process uniformly mixes the laser beams while reducing coherence, thereby eliminating interference fringes and speckle noise that would otherwise degrade image quality.
3Ease of operation
If conventional optical components like rod lenses and beam combiners are used, then laser beams are mixed, but device complexity increases
Solution Approach 1:
The optical coupler is designed as a multi-functional component that performs several functions simultaneously: it acts as a beam combiner, a diffuser, and a coherence reducer all in one structure. The first coupling unit with guide holes and the second coupling unit work together to uniformly mix multiple laser beams while reducing coherence, eliminating the need for separate rod lenses and beam combiners, thus simplifying the overall device structure.
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 noise, enhancing image clarity and color purity in laser display devices by lowering the coherence of laser beams and eliminating interference fringes, thus improving the overall image quality without altering the device's construction or light transmittance.
Implementation Method 1
filled with an optical transmission medium, such as thermally twisted optical fibers
Implementation Method 2
combined with a diffuser to eliminate speckle noise, allowing for uniform mixing of laser beams
Data Source
AI summary
A laser display device, which eliminates speckles generated in the transmission of laser beams and uniformly mixes laser beams of various colors, and an optical coupler therefor. The laser display device includes light sources emitting laser beams; an image display unit displaying an image by the laser beams; and a speckle elimination unit located on a path of the laser beams, and including at least one panel having an uneven part and disposed on an optical axis of the light sources.