Phase SLM Focus Array Generation with Phase-Locked Fourier Iteration
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Solution Overview
Problem
Existing algorithms for generating uniform large-scale optical focus arrays, such as the traditional weighted Gerchberg-Saxton algorithm, are inefficient and require a large number of iterations to produce highly uniform patterns, leading to unwanted phase rotations and reduced efficiency in light modulation.
Innovation Solution
A modified weighted Gerchberg-Saxton algorithm that locks the phase after a certain number of iterations, reducing unwanted phase changes and improving light modulation efficiency by iteratively performing Fourier transforms and inverse Fourier transforms to produce focal plane amplitude and phase functions until phase-locking conditions are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional iterative algorithms (e.g., Gerchberg-Saxton) are used to generate optical focus arrays, then the target amplitude pattern can be achieved, but a large number of iterations are required leading to computational inefficiency and unwanted phase rotations
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing a lookup table of phase values corresponding to different amplitude values before the main iterative process. During iteration, instead of calculating phase from scratch, the algorithm directly retrieves pre-computed phase values from the lookup table, significantly reducing computational overhead and number of iterations required to achieve the target amplitude pattern with high intensity uniformity
Solution Approach 2:
The patent changes the parameter representation by transforming the continuous phase calculation problem into a discrete lookup table indexing problem. By pre-computing phase values for a range of amplitude values and storing them in a lookup table, the algorithm transforms complex iterative phase calculations into simple table lookups, thereby reducing the number of iterations needed while maintaining precision in achieving the target amplitude pattern
2Manufacturing precision
If amplitude SLMs are used to control light amplitude, then the target amplitude pattern can be achieved, but optical power efficiency is reduced due to light attenuation
Solution Approach 1:
The patent substitutes amplitude modulation (which physically attenuates light) with phase modulation (which redirects light through interference patterns). By using a phase SLM to modulate the phase of incident light and relying on interference effects to create the desired amplitude pattern, the system avoids direct light attenuation and achieves superior optical power efficiency while maintaining precise amplitude pattern control
Solution Approach 2:
The patent changes the controlled parameter from light amplitude to light phase. Instead of directly controlling amplitude (which causes energy loss through attenuation), the system controls phase and uses optical interference to indirectly achieve the desired amplitude distribution. This parameter transformation eliminates the need for light attenuation while maintaining precise amplitude pattern control
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 modified algorithm significantly reduces the number of iterations required to achieve highly uniform optical focus arrays with >98% intensity uniformity, improving the reliability and efficiency of light modulation and compensating for optical system imperfections.
Implementation Method 1
phase SLMs shift the phase of an incident light beam on a local scale, and these phase shifts result in interference patterns on the image plane
Implementation Method 2
these phase shifts result in interference patterns on the image plane
Implementation Method 3
perform a Fourier transform on the light source amplitude function and the phase function to produce a focal plane amplitude function and a focal plane phase function
Data Source
AI summary
A method of generating uniform large-scale optical focus arrays (LOT As) with a phase spatial light modulator (SLM) includes identifying and removing undesired phase rotation in the iterative Fourier transform algorithm (IFTA), thereby producing computer-generated holograms of highly uniform LOT As using a reduced number of iterations as compared to a weighted Gerchberg-Saxton algorithm. The method also enables a faster compensation of optical system-induced LOT A intensity inhomogeneity than the conventional IFTA.