Anisotropic Diffusion Sheet for Laser Illumination Uniformity
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Solution Overview
Problem
Conventional laser projectors experience uneven illumination due to elliptic-shaped light spots and Gaussian light intensity distribution, leading to non-uniform color images and potential phosphor burn or reduced lifespan.
Innovation Solution
Incorporating a two-dimensional anisotropic diffusion sheet in the illumination system, which adjusts the divergent angle of the laser beam to achieve a circular-shaped light spot with Lambertian distribution, thereby ensuring uniform illumination and preventing phosphor saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If laser beams are used to excite phosphor in a conventional laser projector, then light-emitting efficiency is improved, but uneven illumination and non-uniform color images occur due to elliptic-shaped light spots and Gaussian light intensity distribution
Solution Approach 1:
The patent changes the optical parameters of the laser beam by introducing a diffusion sheet that transforms the Gaussian light intensity distribution into a uniform distribution, and converts the elliptic light spot shape into a circular shape. This parameter transformation resolves the contradiction by maintaining the high light-emitting efficiency of laser while achieving uniform illumination.
Solution Approach 2:
The patent introduces a diffusion sheet as an intermediary component between the laser light source and the phosphor wheel. This diffusion sheet acts as a mediator that modifies the laser beam's intensity distribution and shape, enabling uniform illumination without sacrificing the efficiency benefits of laser excitation.
2Illumination intensity
If high light intensity is concentrated at the central unit area of the light spot, then brightness is enhanced, but phosphor burn occurs or service life is reduced
Solution Approach 1:
The diffusion sheet transforms the Gaussian intensity distribution (with high central concentration) into a uniform intensity distribution across the light spot. This parameter change distributes the brightness uniformly, preventing localized phosphor burn while maintaining overall brightness, thus extending phosphor service life.
Solution Approach 2:
The patent converts the potentially harmful concentrated Gaussian intensity distribution into a beneficial uniform distribution. By using the diffusion sheet to scatter and redistribute the laser energy, the harmful concentration effect is transformed into a beneficial uniform illumination that protects phosphor while maintaining brightness.
3Area of stationary object
If laser beam divergent angle is increased to improve illumination coverage, then area coverage is improved, but light intensity distribution becomes uneven
Solution Approach 1:
The diffusion sheet modifies the divergent angle parameters of the laser beam in a controlled manner, transforming the original asymmetric divergence into a symmetric pattern that provides both adequate coverage area and uniform intensity distribution across the illuminated region.
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 provides uniform illumination, enhances light-emitting efficiency, and extends the lifespan of the phosphor, resulting in improved image quality and brightness.
Implementation Method 1
the two-dimensional anisotropic diffusion sheet allows the laser beam to have an increasing degree of a divergent angle in a first direction greater than an increasing degree of a divergent angle in a second direction
Implementation Method 2
the wavelength conversion device is located on a transmission path of the laser beam... When the wavelength conversion region moves onto the transmission path of the laser beam, the laser beam is converted into at least one converted beam by the wavelength conversion region
Data Source
AI summary
An illumination system including at least one laser light source, a wavelength conversion device, and a two-dimensional (2D) anisotropic diffusion sheet is provided. The laser light source emits a laser beam, and the wavelength conversion device is located on a transmission path of the laser beam. The 2D anisotropic diffusion sheet is located on the transmission path of the laser beam and between the laser light source and the wavelength conversion device. Besides, the 2D anisotropic diffusion sheet allows the laser beam to have an increasing degree of a divergent angle in a first direction greater than an increasing degree of a divergent angle in a second direction. The first direction is substantially parallel to a slow axis of the laser beam. A projection apparatus is also provided.