Partially Coherent Illumination for Inverse Scattering Microscopy
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Solution Overview
Problem
Conventional interferometric synthetic aperture microscopy (ISAM) methods are inadequate for handling partially coherent illumination sources, as they were derived assuming fully coherent sources, leading to inapplicable solutions for imaging with partially coherent light.
Innovation Solution
A synthetic aperture microscope utilizing partially coherent illumination sources, with a variable aperture and a processor for deconvolving scattered light to reconstruct a three-dimensional image of the sample, and a method involving steps like illuminating with partially coherent light, superposing scattered radiation, and solving an inverse scattering problem to determine the sample's susceptibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fully coherent illumination source is used, then spatial resolution is improved, but interference noise and multiple scattering artifacts increase
Solution Approach 1:
The patent changes the coherence parameter of the illumination source from fully coherent to partially coherent. By adjusting the spatial coherence of the light source, the system achieves a balance between maintaining spatial resolution and reducing interference noise and multiple scattering artifacts that plague fully coherent systems.
Solution Approach 2:
The patent converts the harmful effect of coherence (which causes interference noise and artifacts) into a benefit by deliberately using partial coherence. The partial coherence reduces the harmful interference effects while the computational imaging algorithms recover the lost spatial frequency information, effectively turning the coherence problem into an advantage for artifact reduction.
2Object-generated harmful factors
If partially coherent illumination source is used, then interference noise is reduced, but conventional ISAM solutions become inapplicable
Solution Approach 1:
The patent introduces computational imaging algorithms as an intermediary between the partially coherent illumination and the final image reconstruction. These algorithms act as a mediator that can process the data acquired under partial coherence conditions and reconstruct images that would otherwise be inaccessible using conventional ISAM methods.
Solution Approach 2:
The patent replaces the conventional optical processing approach with computational processing. Instead of relying on optical components and conventional ISAM algorithms to handle the illumination, the system uses computer-based reconstruction algorithms to process the scattered field data and generate the final susceptibility distribution images.
3Object-generated harmful factors
If spatially incoherent illumination is used, then multiple scattering artifacts are reduced, but image resolution deteriorates
Solution Approach 1:
The patent applies partial coherence rather than fully incoherent illumination. This partial action provides enough coherence to maintain image resolution while being insufficient to cause severe multiple scattering artifacts. The degree of partial coherence is optimized to achieve the right balance between these two competing requirements.
Solution Approach 2:
The patent optimizes the spatial coherence parameter to a specific intermediate value that balances resolution and artifact reduction. By carefully controlling the degree of partial coherence, the system achieves better overall image quality than either fully coherent or fully incoherent illumination would provide alone.
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
Enables accurate three-dimensional susceptibility imaging of samples using partially coherent light, reducing interference noise and improving image quality by mitigating multiple scattering artifacts, and allowing operation in various coherence regimes.
Implementation Method 1
a source of illumination characterized by a degree of partial spatial coherence for illuminating a sample... detecting a field of light scattered by the sample
Implementation Method 2
a sensor for detecting a field of light scattered by the sample
Implementation Method 3
a processor for deconvolving the field at the sensor to recover a three-dimensional image of the sample
Implementation Method 4
the synthetic aperture microscope may also have a reference arm for relaying a portion of the illumination onto the sensor
Data Source
AI summary
Methods and apparatus for three-dimensional imaging of a sample. A source is provided of a beam of light characterized by partial spatial coherence. The beam is focused onto a sample and scattered light from the sample is superposed with a reference beam derived from the source onto a focal plane detector array to provide an interference signal. A forward scattering model is derived relating measurement data to structure of an object to allow solutions of an inverse scattering problem, based upon the interference signal so that a three-dimensional structure of the same may be inferred. The partial spatial coherence of the source, which may be fixed or variable, may advantageously provide for rejection of multiple scattering artifacts and thus improve image quality.