Light Tunnel Phosphor Irradiation Uniformity
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Solution Overview
Problem
Existing illumination devices in image projection apparatuses face inefficiencies in obtaining high fluorescent light intensity due to limited irradiation area of excitation light on phosphors, leading to reduced light transmittance and uneven illumination distribution.
Innovation Solution
The design incorporates a light tunnel with a phosphor layer on one or more inner surfaces, where excitation light is guided in a divergent state to widely irradiate the phosphor, enhancing wavelength conversion efficiency and utilizing fluorescent light as illumination by reflecting it through a wavelength selection element to the emission port.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If excitation light is condensed before irradiating the phosphor, then the light source size is reduced and illumination light can be guided more efficiently, but the irradiation area on the phosphor is insufficient and fluorescent light intensity is reduced
Solution Approach 1:
The light guide member is divided into multiple light guide paths, allowing the excitation light to be distributed across multiple segments. This segmentation enables a larger total irradiation area on the phosphor while maintaining a compact overall structure, thus increasing fluorescent light intensity without significantly increasing the light source size.
2Illumination intensity
If a phosphor is installed on a light guide member to increase irradiation area, then fluorescent light intensity is improved, but the transmittance of the light guide member decreases and light loss occurs
Solution Approach 1:
The phosphor is selectively installed only on specific inner surfaces of the light guide member where excitation light needs to be converted to fluorescent light. This local placement ensures efficient wavelength conversion at the required positions while minimizing the phosphor's impact on overall light transmittance. The light guide paths without phosphor maintain high transmittance for guiding both excitation and fluorescent light.
3Adaptability or versatility
If multiple optical paths are used to sequentially irradiate multiple phosphors, then required wavelength fluorescent light can be obtained, but the device complexity increases
Solution Approach 1:
Multiple light guide paths are merged into a single integrated light guide member structure. Different wavelengths of fluorescent light are generated simultaneously in different light guide paths and then combined and guided together to the emission port. This merging approach achieves multi-wavelength capability while maintaining a simple, unified device structure without requiring separate complex optical paths.
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 efficiently generates and guides fluorescent light as illumination, improving light utilization and achieving brighter, more uniform illumination suitable for image projection applications.
Implementation Method 1
A wavelength conversion technique to obtain, for example, green fluorescent light or red fluorescent light by irradiating a phosphor with excitation light having short wavelength
Implementation Method 2
allows the excitation light to enter the light tunnel, and outputs fluorescent light generated in the light tunnel in accordance with light-guiding action of the light tunnel
Implementation Method 3
utilizing fluorescent light as illumination by reflecting it through a wavelength selection element to the emission port
Data Source
Figure 1A~2
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AI summary
This invention is concerning an illumination device that can obtain illumination light efficiently. An illumination device 1 used in, for example, a projection display apparatus includes a light source and a light tunnel 14. The light tunnel 14 includes a light incident port 15, a light emission port 16, a light guide path 17, a reflection surface 20 surrounding the light guide path 17, a phosphor layer 19 that generates fluorescent light LF having a different wavelength range from that of excitation light LE when being excited by the excitation light LE, a condensing optical system 13 that diverges the excitation light LE in the vicinity of the light incident port 15 and guides the diverged light into the light tunnel 14 to irradiate the phosphor layer 19, and a wavelength selection element that reflects the fluorescent light LF toward the light emission port 16.