Polarized Wavelength Conversion Wheel Using Rotating Segments
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Solution Overview
Problem
Conventional phosphor-based wavelength conversion systems face challenges in reducing etendue, achieving efficient polarization, and maintaining high conversion efficiency, especially at high brightness levels, which limits their application in projectors and requires expensive laser solutions.
Innovation Solution
A light conversion system using a multilayer birefringent interference polarizer (MBIP) with reflective polarizing sheets aligned to optimize polarization and reduce etendue, combined with a rotatable support structure for efficient heat management and polarization switching, allowing for increased light output without increasing etendue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the excitation light source is limited to illuminating a smaller area of the phosphor to reduce etendue, then the etendue of the light source is reduced, but the energy density increases making it more difficult to cool the phosphor and maintain high conversion efficiency
Solution Approach 1:
The phosphor layer is divided into multiple segments arranged in a circular pattern, each segment illuminated by a separate excitation light source. This segmentation allows the total illumination area to be distributed across multiple zones, reducing the etendue of each individual light source while preventing excessive energy concentration in any single phosphor region, thus facilitating heat management.
Solution Approach 2:
The phosphor segments are arranged in a circular configuration around the excitation light sources, transitioning from a linear or planar arrangement to a three-dimensional spatial distribution. This dimensional change allows the system to reduce etendue by distributing light emission in multiple directions and spaces, while the circular geometry provides uniform heat distribution and access for cooling mechanisms.
2Ease of operation
If a wiregrid reflective polarizer is used to polarize the converted light, then the light is polarized, but the power density on the polarizer is high requiring a heat sink, and bonding options are limited
Solution Approach 1:
The support structure serving the phosphor segments is designed to simultaneously function as a heat sink for the polarizer. This multi-functional element provides both mechanical support for the phosphor and thermal management for the polarizer, dissipating the high power density without requiring a separate heat sink component.
Solution Approach 2:
The polarizer is integrated directly with the support structure through optical bonding, merging two previously separate components (polarizer and support/heat sink) into a single unified assembly. This integration eliminates the need for separate heat dissipation mechanisms and simplifies the overall system architecture while maintaining effective polarization.
3Loss of energy
If bonding the wire-grid polarizer at the wire-grid side to the phosphor, then thermal resistance is reduced, but embedding the wire-grid in a medium with different refractive index inhibits proper functioning
Solution Approach 1:
A specialized bonding medium with refractive index matched to the wire-grid polarizer is introduced as an intermediary layer between the polarizer and the support structure. This intermediary layer eliminates refractive index mismatch that would inhibit polarizer functioning, while the bonding process maintains direct thermal contact to minimize thermal resistance.
Solution Approach 2:
The refractive index parameter of the bonding medium is specifically selected and adjusted to match that of the wire-grid polarizer, changing the optical parameters of the interface to enable proper polarizer functioning. This parameter optimization allows the polarizer to operate effectively while maintaining thermal efficiency through direct bonding.
4Reliability
If bonding the wire-grid polarizer at the opposite side of the substrate, then the wire-grid is not embedded in mismatched medium, but thermal resistance increases and spacing widens leading to increased etendue
Solution Approach 1:
The system employs a rotatable support structure that dynamically adjusts the orientation and positioning of the phosphor segments and polarizer assembly. This dynamic capability allows optimization of the spacing between components to minimize etendue while maintaining proper polarizer functioning, adapting the configuration to achieve both thermal and optical performance.
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 system effectively reduces the etendue of the phosphor light source by half, doubling the coupled area, and increases projector light output while maintaining high conversion efficiency, enabling more compact and efficient polarized light generation for applications like 3D projection.
Implementation Method 1
A light conversion system using a multilayer birefringent interference polarizer (MBIP) with reflective polarizing sheets
Implementation Method 2
multilayer birefringent interference polarizer
Implementation Method 3
the short wavelength excitation light, for example blue or near-UV laser light, can be converted into light with longer wavelength, for example green, yellow or red light
Implementation Method 4
A phosphor material can emit a longer wavelength than it is illuminated with
Data Source
Figure 1a~1c
Figure 2~3a
Figure 3b~4a
AI summary
A light conversion system and method is described comprising at least one light source providing at least one beam of polarized light. The system comprises a support structure being rotatable around one of its axes, said support structure having a reflective surface which is fully or partly covered with at least one type of light conversion layer comprising wavelength conversion material, which is in turn covered with at least one segment of a reflective polarizing sheet.