Structured Illumination Microscopy Artifact Suppression via Birefringent Offset
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Solution Overview
Problem
Structured illumination microscopy systems using digital spatial light modulators face limitations in economy, versatility, and accuracy due to the production of higher harmonic artifacts, such as 'ripples,' which interfere with Z-height measurements, reducing the precision of micron and submicron level measurements.
Innovation Solution
Incorporating a projector artifact suppression element with birefringent materials in the projection path to split light rays and replicate structured illumination patterns with an offset, reducing intensity variations and spatial harmonic content, thereby minimizing 'ripple' errors and enhancing measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a digital spatial light modulator is used to generate structured illumination patterns, then the system achieves improved measurement resolution and accuracy, but higher harmonic artifacts are produced that interfere with Z-height measurements
Solution Approach 1:
The patent applies the principle of converting harm into benefit by using the higher harmonic artifacts generated by the DMD SLM in a constructive manner. Instead of simply filtering out these artifacts, the system uses them to create additional structured illumination patterns that help cancel out the harmful ripple effects in the final measurement images, thereby converting the harmful harmonics into useful measurement correction signals
Solution Approach 2:
The patent introduces an intermediary component - a second DMD SLM positioned in the imaging path - that acts as a mediator between the projection path SLM and the detector. This intermediary SLM receives the structured illumination patterns containing higher harmonics and transforms them into corrected patterns that eliminate the harmful artifacts while preserving the useful measurement information
2Measurement precision
If a projector artifact suppression element is added to reduce harmonic artifacts, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the second DMD SLM to serve multiple functions simultaneously: it acts as both an artifact suppression element for reducing higher harmonics and as a structured illumination pattern generator for maintaining measurement resolution. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity
3Ease of manufacture
If conventional imaging methods are used, then the system is simpler and more economical, but measurement resolution is limited by optical diffraction limits
Solution Approach 1:
The patent applies segmentation by dividing the illumination function into multiple independent DMD SLM units - one in the projection path for generating structured patterns and another in the imaging path for artifact suppression. Each SLM operates independently to handle specific aspects of the illumination and detection process, enabling the system to overcome diffraction limits while maintaining economic feasibility through the use of standard SLM technology
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 solution effectively reduces Z-height errors and improves measurement accuracy by distributing gap image artifacts uniformly across the imaging pixel array, resulting in higher resolution and more precise SIM measurements without altering the numerical aperture of the projection optical elements.
Implementation Method 1
Incorporating a projector artifact suppression element with birefringent materials in the projection path to split light rays and replicate structured illumination patterns with an offset
Data Source
AI summary
A structured illumination microscopy optical arrangement includes a projection path and an imaging path. The imaging path includes an imaging sensor and imaging optical elements. The projection path includes a light generator, a pattern generating element such as a spatial light modulator (SLM), and projection optical elements including an output lens and a projector artifact suppression element (PASE) located in the projection path between the SLM and the output lens. The PASE may include birefringent material which splits respective light rays of the structured illumination pattern source light to provide at least one replication of the structured illumination pattern with an offset transverse to the projection path. The offset replication of the structured illumination pattern increases the accuracy of the system by reducing spatial harmonic errors and spurious intensity variations due to projector pixel gap artifacts which may otherwise produce errors in resulting Z-height measurements.