Phosphor Wheel Wavelength Conversion Eliminates Laser Speckle
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Solution Overview
Problem
Solid state illuminators, such as LEDs and lasers, face limitations in luminance and flux within the etendue of a spatial light modulator, and high-power LEDs are difficult to cool, while laser sources create image speckle artifacts due to their narrow bandwidth, necessitating a low-cost, efficient method for wavelength conversion that avoids introducing additional artifacts.
Innovation Solution
A method involving a moving surface with annular bands of phosphors that absorbs and reemits radiant energy, allowing for variable duration and intensity of illumination on different phosphor tracks to match image color needs, using a tilting mirror or multiple sources to direct energy onto specific tracks, and an integrator rod to homogenize light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser sources are used to provide high luminance, then luminance is improved, but image speckle artifacts are introduced due to narrow bandwidth
Solution Approach 1:
The color wheel is divided into multiple annular bands, each containing phosphors with different emission characteristics. This segmentation allows the system to select specific wavelength regions to convert laser energy, thereby maintaining high luminance while avoiding the narrow bandwidth issue that causes speckle artifacts.
Solution Approach 2:
The patent changes the wavelength parameter by using phosphors that convert laser energy to different wavelength bands. This wavelength transformation maintains the high luminance of laser sources while broadening the effective bandwidth to eliminate speckle artifacts.
2Illumination intensity
If high-power LEDs are used to provide illumination, then luminance is improved, but cooling difficulty increases in small packages
Solution Approach 1:
The patent introduces phosphors as intermediary materials that convert laser energy to visible light. This intermediary conversion allows the use of lower-power laser sources that generate less heat, thereby reducing cooling requirements while still achieving high luminance output through efficient wavelength conversion.
3Duration of action of stationary object
If solid state illuminators are used to replace arc lamps, then lifetime is improved, but luminance and flux within etendue are limited
Solution Approach 1:
The patent merges the advantages of solid state illuminators (long lifetime) with the high luminance characteristics of laser sources by using phosphor-based wavelength conversion. The system combines the durability of LEDs/lasers with the high flux output needed for projection displays through efficient phosphor conversion.
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 provides a long-life, high-luminance illumination source that eliminates speckle artifacts and allows for dynamic color period durations based on image needs, improving display system efficiency and reducing noise and cooling requirements.
Implementation Method 1
phosphors are deposited on the inside of cathode ray tubes to convert a stream of electrons into visible light
Implementation Method 2
absorbing a portion of the first radiant energy beam
Data Source
AI summary
A wavelength conversion device comprising a plurality of regions. Each region for absorbing radiant energy and emitting light having a characteristic dependent upon which region of the device emits the light.