Flat-top beam generation via incoherent spot interlacing
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Solution Overview
Problem
Generating a flat-top illumination profile with coherent laser light is challenging due to its intolerance to beam quality variations and the occurrence of speckle patterns caused by interference, which results in non-uniform distributions.
Innovation Solution
A system that splits a coherent input beam into multiple sub-beams with different optical path lengths, which are then diffracted by a diffractive optical element to create a flat-top beam with a uniform intensity profile, mitigating speckle by ensuring the sub-beams are incoherent and partially overlapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If beam shaping techniques are used to generate a flat-top profile, then a uniform spatial profile can be achieved, but the system becomes intolerant to variations in beam quality and shape parameters
Solution Approach 1:
The input laser beam is divided into multiple separate beams using a beamsplitting apparatus. Each beam is then independently diffracted by the DOE to create multiple spot patterns. By segmenting the original beam and processing each segment separately, the system reduces sensitivity to variations in the original beam's quality parameters while achieving uniform illumination through the superposition of multiple independent patterns.
2Illumination intensity
If coherent light is used to generate a flat-top profile, then a laser source can be utilized, but interference between different portions of the beam produces speckle patterns that create non-uniform distributions
Solution Approach 1:
The system introduces different optical path lengths for different segments of the beam, creating periodic variations in the phase relationships between beams. This causes the coherent interference patterns to vary over time, and when averaged, the speckle patterns are reduced. The temporal averaging of periodic phase changes converts the harmful static speckle into a more uniform time-averaged intensity distribution.
Solution Approach 2:
The invention transitions from spatial coherence to temporal incoherence by introducing optical path length differences. This adds a temporal dimension to the problem, where the relative phases of different beam segments change over time. The speckle patterns become time-varying rather than static, and their time average produces a uniform intensity distribution, effectively moving the solution from a purely spatial domain to a space-time domain.
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 produces a flat-top beam with a uniform intensity distribution, reducing speckle and ensuring stability across the illumination profile, suitable for applications requiring uniform illumination.
Implementation Method 1
a beamsplitting apparatus including one or more beamsplitters to split an input beam into three or more sub-beams that propagate along optical paths with different optical path lengths
Implementation Method 2
a diffractive optical element (DOE) configured to diffract the three or more sub-beams into diffracted sub-beams
Data Source
AI summary
A flat-top beam generating system may include a beamsplitting apparatus including one or more beamsplitters to split an input beam into three or more sub-beams that propagate along optical paths with different optical path lengths. The system may further include a diffractive optical element (DOE) to diffract the three or more sub-beams into a plurality of diffracted sub-beams. The system may further include one or more optical elements configured to collect the plurality of diffracted sub-beams to provide a flat-top beam.