Laser-Phosphor Projector White Point Control With Green Phosphor
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Solution Overview
Problem
Current laser-phosphor projectors face significant light losses and non-compliance with DCI standards due to the use of yellow phosphors, which lack sufficient red content and result in excessive green light, necessitating additional red lasers and electronic corrections, leading to brightness reduction and color gamut issues.
Innovation Solution
Employ a laser phosphor light source utilizing a green phosphor excited by blue lasers, combined with direct red lasers, to minimize light losses by optimizing spectral distribution, reducing the green-red transition zone content, and eliminating the need for notch filters, thereby achieving a balanced white point and color gamut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If yellow phosphor is used in laser-phosphor projectors, then the system achieves simplicity and lower cost, but significant light losses occur and DCI compliance is not achieved
Solution Approach 1:
The patent changes the fundamental parameter of phosphor emission wavelength from yellow (560-580nm) to green (520-540nm). This parameter change fundamentally alters the spectral distribution to reduce losses in the green-red transition zone while maintaining simplicity of the single-phosphor architecture.
Solution Approach 2:
The patent creates a composite light source by combining blue laser light (440-470nm) with green phosphor emission (520-540nm) and adds red laser (620-650nm) to achieve DCI compliance. This composite approach maintains the simplicity of the laser-phosphor architecture while optimizing spectral output.
2Device complexity
If yellow phosphor is used, then the system structure remains simple, but the red content is insufficient and green light is excessive
Solution Approach 1:
Changing the phosphor emission from yellow to green shifts the spectral power distribution, naturally increasing red content relative to green. This parameter change eliminates the need for complex additional phosphors or filters while achieving proper color balance.
3Manufacturing precision
If electronic corrections are applied to compensate for color imbalances, then color accuracy improves, but brightness is reduced
Solution Approach 1:
The patent performs preliminary spectral optimization by selecting green phosphor that inherently produces the correct color ratios. This preliminary action eliminates the need for subsequent electronic corrections, preserving brightness while achieving color accuracy.
4Loss of energy
If the green-red transition zone content is reduced, then light losses in the Philips prism are minimized, but the spectral distribution must be precisely controlled
Solution Approach 1:
The patent changes the phosphor peak emission wavelength parameter to 520-540nm (green), which inherently minimizes the green-red transition zone content. This parameter change simultaneously achieves energy loss reduction and provides a well-defined spectral distribution that is easier to control.
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 enhances projector efficiency by up to 32% compared to yellow phosphor systems, achieving DCI compliance with reduced brightness loss and improved color performance through optimized spectral distribution and beam combination.
Implementation Method 1
blue lasers to excite a green wavelength conversion element such as a green phosphor
Implementation Method 2
beam combiners to combine the different color contributions to a white light beam
Data Source
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Figure 5~6
AI summary
The invention relates to a light projection system for generating an image with three primary colors, each primary color being respectively defined by a first, second and third wavebands. The system comprises a first blue laser source (5) emitting a first beam (5') in a fourth waveband, said first blue laser source (5) having a first laser driver (4), a second blue laser source (3) emitting a second beam (2') having a central wavelength and a fifth waveband, said second blue laser source (3) having a second laser driver (2), a substrate having a wavelength conversion element (8) for emitting light (2'') at a plurality of wavelengths after absorption of a light beam at an excitation wavelength within a fifth waveband of the second blue laser source (3) and a beam combiner (11) for combining the combined first beam and the converted beam (2''), which combination results in a white beam (14). Dichroic losses can be reduced by using a green phosphor together with red laser assistance. White point and color primaries can be controlled by using a variable green waveband reduction filter and/or by using a multi-band color sensor (22) and a controller (24) for deriving driving levels for the drivers of the laser sources.