Diffractive Optical Element for Laser Speckle Elimination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Laser speckle noise degrades image definition and resolution due to coherent interference, posing discomfort and limiting visibility in laser illumination systems, especially when used in projection applications, and existing solutions complicate the system with increased cost and volume.
Innovation Solution
A laser illumination system incorporating a diffractive optical element that redistributes spatial phase and energy of scanning laser beams, forming illuminating beams which superpose their energy at a point to eliminate speckle noise within the reaction time of the image detecting unit, thereby reducing interference and enhancing image clarity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a projection screen is added with an actuator to move or rotate the screen, then laser speckle is reduced by destroying coherence, but device complexity and production cost increase
Solution Approach 1:
The patent replaces the mechanical actuator system with an optical diffuser placed at the laser source. The diffuser creates multiple scattering paths that destroy coherence optically rather than mechanically moving the screen, thereby eliminating speckle without adding mechanical complexity.
Solution Approach 2:
The patent introduces a diffuser as an intermediary element between the laser source and the projection path. This diffuser mediates the coherent laser light by scattering it into multiple paths, destroying coherence and reducing speckle without requiring mechanical movement of the screen.
2Object-affected harmful factors
If a time-varying diffuser is used to vibrate at high frequency, then laser speckle is reduced by disordering phase difference, but device complexity and volume increase
Solution Approach 1:
The patent extracts the coherence-destroying function from the complex time-varying diffuser system and implements it through a simple static diffuser placed at the laser source. The static diffuser inherently creates multiple scattering paths that destroy coherence without requiring vibration or time-variation, thereby eliminating speckle reduction while simplifying the device.
3Adaptability or versatility
If laser light is passed through phosphor coating for wavelength conversion, then white light is generated with low directionality, but quantum efficiency decreases
Solution Approach 1:
The patent uses a dynamic scattering approach with a static diffuser that creates time-varying scattering patterns as the laser beam propagates. This dynamic scattering effect allows the system to generate diffuse white light appearance without phosphor conversion, maintaining high quantum efficiency while achieving adaptability for various illumination applications.
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 eliminates laser speckle noise, improving image resolution and comfort by using a diffractive optical element to redistribute and superpose the energy of scanning beams, thus enhancing the visibility and efficiency of laser illumination without the need for additional moving parts or energy conversion.
Implementation Method 1
at least one diffractive optical element which the scanning beams are passed through to form illuminating beams... causes changes in spatial phase redistribution or light energy distribution of the scanning beams while being passed through the diffractive optical element
Implementation Method 2
A coherent light source is emitted to a rough surface such as a projection screen or a translucent diffuser plate. The light intensity distribution of the projected image is irregular due to constructive or destructive interference of scattered light at different points of the rough surface.
Data Source
AI summary
A laser illumination system and a method for eliminating laser speckles thereof are revealed. The laser illumination system includes laser module emitting a laser beam, a scanning unit for scanning the laser beam to form scanning beams, and a diffractive optical element which the scanning beams are passed through to form illuminating beams that are projected to an area to be illuminated or an object. Thus an image detecting unit can capture an image of the area or the object. The scanning beams are converted into the illuminating beams by the diffractive optical element that causes changes in spatial phase redistribution or light energy distribution thereof. One point in the area or on the object shows energy of partial light of at least two of the laser beams. Thus a laser speckle of the image can be eliminated by the superposition of the energy of the partial light.