Variable Focus Lens Illumination System for Laser Speckle Reduction
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Solution Overview
Problem
Conventional projection devices using laser diodes suffer from high coherence leading to laser speckles, which result in non-uniform light distribution and poor imaging quality, as existing methods to mitigate speckles either compromise light concentration or imaging quality.
Innovation Solution
An illumination system comprising a first and second variable focus lens, synchronized by a control unit to adjust focal lengths, ensuring the excitation light beam remains parallel and continuously changes the light spot size, reducing speckles and enhancing uniformity, while maintaining imaging quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a diffusion plate is used to reduce laser speckles, then light uniformity is improved, but light concentration capability deteriorates
Solution Approach 1:
The patent employs a variable focus lens that dynamically adjusts its focal length to change the position of the light spot continuously. This dynamic adjustment reduces laser speckles by preventing them from remaining at fixed positions, while the lens maintains the ability to concentrate light when needed, thus resolving the contradiction between light uniformity and light concentration capability.
Solution Approach 2:
The patent changes the focal length parameter of the lens dynamically to achieve different light spot positions and sizes. By adjusting this parameter, the system can reduce laser speckles through continuous position changes while maintaining light concentration capability when the focal length is set to appropriate values, thereby solving the technical contradiction.
2Illumination intensity
If a variable focus lens is used to reduce laser speckles, then light uniformity is improved, but imaging quality deteriorates when parallel light is required
Solution Approach 1:
The patent uses a variable focus lens that can dynamically adjust its focal length. When reducing laser speckles, the lens changes the light spot position continuously. When parallel light is required for imaging, the lens can be adjusted to maintain the appropriate wave front shape, thus achieving both light uniformity and imaging quality through dynamic adaptation.
Solution Approach 2:
The system can periodically adjust the focal length of the variable focus lens to cycle through different light spot positions and sizes. This periodic action helps reduce laser speckles over time while maintaining the capability to produce parallel light for imaging when needed, resolving the contradiction between light uniformity and imaging quality.
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 laser speckles and increases light uniformity, thereby improving the imaging quality of projection devices by dynamically adjusting the focal lengths of the lenses to maintain a parallel light beam.
Implementation Method 1
a first variable focus lens, a second variable focus lens... The first variable focus lens is disposed on a transmission path of the excitation light beam. The second variable focus lens is disposed on the transmission path of the excitation light beam
Implementation Method 2
the laser diode provides an excitation light beam to excite the phosphor layer on the phosphor wheel to generate a fluorescent light beam
Implementation Method 3
excite the phosphor layer on the phosphor wheel to generate a fluorescent light beam
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~4
AI summary
An illumination system includes an excitation light source, a first variable focus lens, a second variable focus lens, and a control unit. The excitation light source is adapted to provide an excitation light beam. The first variable focus lens is disposed on a transmission path of the excitation light beam. The first variable focus lens is located between the excitation light source and the second variable focus lens. The second variable focus lens is adapted to receive the excitation light beam exited from the first variable focus lens. The control unit is electrically connected to the first variable focus lens and the second variable focus lens, and is adapted to synchronously adjust focal lengths of the first variable focus lens and the second variable focus lens. A projection device including the above-mentioned illumination system of the invention is further provided.