Rotating Phosphor Illumination Device Thermal Management
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Solution Overview
Problem
Existing illumination devices face issues with increased thermal load on the phosphor layer due to excessive excitation light, leading to reduced conversion efficiency and axial chromatic aberration causing a shift in focal positions between excitation light and fluorescence, resulting in decreased condensing efficiency.
Innovation Solution
The illumination device incorporates a phosphor layer and a scattering layer positioned at different distances from the axis of rotation, with independent pickup optical systems optimized for each wavelength band, utilizing a dichroic mirror and retardation films to manage light polarization and separation, and an achromatic lens to minimize chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a large amount of excitation light is used to obtain a predetermined amount of white light, then the white light output is improved, but the thermal load on the phosphor layer increases causing temperature rise and reduction in conversion efficiency
Solution Approach 1:
The patent segments the illumination device into multiple independent light sources (first light-emitting element emitting blue light and second light-emitting element emitting green light) that illuminate different regions of the phosphor layer. This segmentation allows the excitation light to be distributed across multiple wavelengths and regions, reducing the thermal concentration on any single area of the phosphor layer while maintaining overall white light output.
2Device complexity
If both excitation light and fluorescence are extracted through a common condensing optical system, then the device structure is simplified, but axial chromatic aberration causes focal position shift between different wavelengths reducing condensing efficiency
Solution Approach 1:
The patent divides the optical extraction system into separate optical paths: a first optical system extracts blue light (excitation light) from the first light-emitting element, while a second optical system extracts green light (fluorescence) from the phosphor layer. This segmentation eliminates axial chromatic aberration by providing dedicated optical paths for each wavelength, ensuring accurate focal positions for both blue and green light without requiring a complex chromatic correction system.
Solution Approach 2:
The patent introduces a beam combining element that merges the blue light from the first optical system with the green light from the second optical system to form combined white light. This intermediary component allows the two wavelength-specific optical paths to be integrated into a single output beam, achieving both wavelength-specific optimization and system integration.
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 configuration reduces thermal load on the phosphor layer, enhances light use efficiency, and improves extraction efficiency by optimizing focal positions for both excitation and fluorescence wavelengths, thereby maintaining high display quality in projectors.
Implementation Method 1
a phosphor layer that is provided on the substrate at a first distance from the axis of rotation and excited by the light in the first wavelength band to emit light in a second wavelength band different from the first wavelength band
Implementation Method 2
a scattering layer that is provided on the substrate at a second distance, different from the first distance, from the axis of rotation and on which the light in the first wavelength band emitted from the light-emitting element is incident
Data Source
AI summary
An illumination device includes: a light-emitting element that emits light in a first wavelength band; a substrate rotatable about a predetermined axis of rotation; a phosphor layer that is provided on the substrate at a first distance from the axis of rotation and excited by the light in the first wavelength band to emit light in a second wavelength band different from the first wavelength band; a scattering layer that is provided on the substrate at a second distance, different from the first distance, from the axis of rotation and on which the light in the first wavelength band emitted from the light-emitting element is incident; a first pickup optical system that is provided on the side of the phosphor layer opposite to the substrate; and a second pickup optical system that is provided on the side of the scattering layer opposite to the substrate.