Moving Phosphor Plate for Constant Broad Band Light
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Solution Overview
Problem
Conventional light sources for projection systems, such as those using multiple phosphor wheels, suffer from low efficiency due to wide spectral bandwidths that exceed the accepted spectral bandwidth of color combiners, leading to light rejection and waste, especially in multiple spatial light modulator (SLM) systems like three DLP projectors.
Innovation Solution
A moving phosphor device, such as a rotating phosphor disk or linearly moving phosphor plate, coated with a mixture of phosphors, generates multiple colors simultaneously, allowing for efficient splitting by current color separation devices, and a secondary light source can be added to supplement missing colors, ensuring a broad spectrum output with constant intensity and spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple individual single color phosphor wheels are used to generate red, green and blue lights, then the light source can cover the required wavelength regions for multiple SLM systems, but the spectral bandwidth of each phosphor emission is wider than the accepted bandwidth of color combiners, causing light rejection and energy waste
Solution Approach 1:
The patent combines multiple phosphor materials (yellow phosphor and red phosphor) into a single phosphor wheel that is excited by one excitation source. This merged configuration generates both yellow and red emissions simultaneously, which are then separated by dichroic mirrors in the color separation system. This approach eliminates the need for separate phosphor wheels for each color, reduces the number of excitation sources required, and minimizes energy loss by avoiding the bandwidth mismatch problem of individual single-color phosphors.
2Loss of energy
If a single phosphor wheel with wide spectrum emission is used, then energy efficiency is improved, but the emission spectrum may not sufficiently cover all required wavelength regions for red, green and blue channels
Solution Approach 1:
The patent employs a composite phosphor wheel containing multiple phosphor materials (yellow phosphor and red phosphor) with different emission characteristics. The yellow phosphor provides emission in the yellow region while the red phosphor provides emission in the red region. This composite structure ensures broad spectral coverage across the visible range, enabling sufficient illumination for red, green and blue channels when combined with the excitation source emission, while maintaining high energy efficiency through a single excitation source.
3Ease of operation
If multiple colored lights are generated sequentially by a rotating phosphor wheel, then the system can work with single SLM channel displays, but it cannot support multiple SLM channels that require simultaneous spatial modulation of multiple colored lights
Solution Approach 1:
The patent segments the phosphor wheel into different regions, each coated with different phosphor materials (yellow phosphor region and red phosphor region). As the phosphor wheel rotates, different segments pass through the excitation light path and are excited simultaneously, generating their respective emissions at the same time. This segmented configuration enables the system to produce multiple colors concurrently, supporting simultaneous spatial modulation in multiple SLM channels, while maintaining compatibility with single SLM channel displays.
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 increases energy efficiency and reduces light waste by generating a broad band light with constant spectrum and intensity, optimizing the light output for multiple SLM systems and maintaining compatibility with existing projectors.
Implementation Method 1
a wavelength conversion device having one or more wavelength conversion materials for converting at least some of the excitation light into a converted light
Data Source
AI summary
A solid state light source device for generating a constant broad band light useful in multiple SLM projectors. The light source device includes a blue or UV/near UV excitation light and a moving plate carrying wavelength conversion materials to convert the excitation light into a broad band light. The wavelength conversion materials include red, green, yellow and/or blue phosphors, and may pass some of the blue excitation light. The broad band light outputted by the phosphor plate includes at least two primary color components and has a constant intensity and spectrum as a function of time. The solid state light source device further includes a second light source such as a blue light source, and a light combination device which combines the output light of the moving phosphor plate and the light from the second light source into one beam of constant, broad band light.