Light Source Optical System for Projectors with Phosphor Temperature Management
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Solution Overview
Problem
Projectors using laser or LED light sources face challenges in achieving high light use efficiency and compact size due to the lower luminous efficacy of green and red lasers compared to blue lasers, and the inefficiencies in wavelength conversion using phosphors, which result in increased phosphor temperature and decreased conversion efficiency.
Innovation Solution
A light source device with multiple light source units that convert blue laser light into green and red light using phosphors, optimizing energy density and spot size to increase light use efficiency, and combining conjugate images to form a uniform intensity distribution on the entrance surface of a light uniformizing element, satisfying specific conditional expressions to minimize vignetting and etendue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If blue laser light is converted to green and red light using phosphors, then color light beams for projection are generated, but phosphor temperature increases and conversion efficiency decreases
Solution Approach 1:
The patent divides the single phosphor conversion process into multiple separate conversion stages. Blue laser light is first converted to green light by a green phosphor, then another blue laser light is converted to red light by a red phosphor. This segmentation distributes the energy load across separate conversion paths, preventing excessive temperature accumulation in a single phosphor material and maintaining higher conversion efficiency.
Solution Approach 2:
The patent introduces optical elements (lenses, mirrors, beam combiners) as intermediaries to manage the blue laser light before it reaches the phosphors. By using beam splitting and optical path management, the intensity of blue light incident on each phosphor is controlled, preventing overheating while ensuring sufficient conversion to green and red light for efficient color projection.
2Adaptability or versatility
If multiple light source units are used to generate different color light beams, then color reproduction is improved, but device size increases
Solution Approach 1:
The patent combines multiple light source units (blue laser, green phosphor conversion unit, red phosphor conversion unit) into a single integrated light source device. The optical paths of different color light beams are merged through beam combiners and directed through a common illumination optical system to the spatial light modulator. This merging approach maintains excellent color reproduction by providing all three primary colors while avoiding the size penalty of completely separate projection systems for each color.
Solution Approach 2:
The patent designs the illumination optical system and projection optical system to handle multiple color light beams simultaneously through a single spatial light modulator. The system is made multi-functional by enabling one set of optical components to work with blue, green, and red light beams from different source units, thereby achieving full color projection without requiring separate projection paths for each color, thus minimizing overall device size.
3Illumination intensity
If conjugate images are combined on the entrance surface of the light uniformizing element, then light intensity distribution is uniformized, but vignetting occurs if the combined image area does not match the entrance surface area
Solution Approach 1:
The patent precisely controls the parameters of the optical system to ensure that the combined conjugate image area (SC) matches the entrance surface area (SI) of the light uniformizing element. By satisfying the conditional expression 0.7 < SC/SI < 1.3, the optical design optimizes the size and position of the combined image relative to the entrance surface, achieving uniform light intensity distribution across the entire entrance surface while minimizing vignetting losses through proper parameter matching.
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 light use efficiency and miniaturizes the projector while maintaining high conversion efficiency, reducing phosphor temperature and vignetting, and improving the contrast ratio by optimizing the light source optical system and uniformizing energy density.
Implementation Method 1
convert blue laser light into green and red light using phosphors
Data Source
AI summary
A light source device includes: multiple light source units each including a light source to emit a first color light beam, each of the multiple light source units configured to: convert at least part of the first color light beam into a second color light beam emitted from an emitting region; and emit the second color light beam to form a conjugate image; and a light combiner to combine the conjugate images formed by the multiple light source units to form a combined image, in which the conjugate images partially overlap each other, on a plane of an entrance surface of a light uniformizing element along a central axis of the light uniformizing element. A conditional expression below is satisfied:1.3>SC/SI>0.7where SC is an area of the combined image, and SI is an area of the entrance surface of the light uniformizing element.