Projector Color Wheel Phosphor Segmentation for Luminance and Purity
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Solution Overview
Problem
Projection-type video image display apparatuses face a trade-off between achieving high luminance and maintaining color purity, as using a yellow light component instead of a green component reduces color reproduction range and purity.
Innovation Solution
A projection-type video image display apparatus that includes an excitation light source and phosphors emitting light of multiple colors, with a drive mechanism to adjust the intensity of excitation light for each phosphor based on video signal analysis, allowing for the use of yellow light as a fourth color component in addition to red, green, and blue, optimizing luminance and color reproduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light of a yellow component is used instead of light of a green component to improve luminance, then luminance is improved, but color purity is lowered and color reproduction range is restricted
Solution Approach 1:
The patent divides the green light generation into two separate phosphor components: a first phosphor that emits green light with high color purity and a second phosphor that emits yellow light with high luminance. By segmenting the green light source into these two distinct components, the system can simultaneously achieve high color purity from the first phosphor and high luminance from the second phosphor, resolving the contradiction between luminance improvement and color purity maintenance.
Solution Approach 2:
The patent uses a composite phosphor system combining multiple phosphor materials with different emission characteristics. The first phosphor (e.g., beta-SiAlON:Eu2+) provides green light with narrow bandwidth and high color purity, while the second phosphor (e.g., YAG:Ce3+) provides yellow light with broader spectrum and higher luminance. This composite approach allows the system to leverage the complementary strengths of different phosphor materials to achieve both high luminance and acceptable color purity.
2Illumination intensity
If light of a yellow component is used instead of light of a green component to improve luminance, then luminance is improved, but color reproduction range is restricted
Solution Approach 1:
The patent segments the green illumination into two distinct phosphor-based light sources with different spectral characteristics. The first phosphor maintains color purity for accurate color reproduction, while the second phosphor boosts luminance. This segmentation allows the system to preserve color reproduction range while achieving higher luminance output.
Solution Approach 2:
The patent applies different phosphor materials with optimized local characteristics to different portions of the green light spectrum. The first phosphor is optimized for color purity in the green region, while the second phosphor is optimized for luminance enhancement in the yellow-green region. This local quality differentiation allows simultaneous achievement of color reproduction fidelity and high luminance.
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
Enhances image luminance by utilizing yellow light while maintaining color reproducibility by dynamically controlling the intensity of excitation light to balance luminance and color purity within the projector.
Implementation Method 1
a phosphor including a plurality of fluorescent portions which emit light of a plurality of colors as they are excited by excitation light from the excitation light source
Data Source
AI summary
A projector includes an excitation light source and a color wheel which is rotatable, with an axis in parallel to an optical axis of the excitation light source serving as a rotation axis. The color wheel includes two phosphors arranged adjacent to each other in a direction of rotation and emitting G light and Ye light respectively as they are excited by excitation light from the excitation light source. The projector further includes a phosphor drive portion which drives the color wheel to rotate such that the two phosphors emit light in a time-division manner within 1 frame period, a video signal analysis portion which analyzes a video signal for each piece of image data in each frame, and an excitation light source drive portion which sets an intensity of excitation light emitted to each phosphor in accordance with a result of analysis by the video signal analysis portion.