Structured Illumination Microscopy Pulse Optimization
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Solution Overview
Problem
Current high-resolution imaging techniques like SIM and SPEM are limited by signal-to-noise ratio, sample bleaching, and environmental conditions, which restrict the achievable resolution and stability of reconstructed images.
Innovation Solution
Optimization of the pulse sequence of illumination using feedback from intermediate images to improve the signal-to-noise ratio and reduce bleaching, allowing for higher resolution imaging by varying parameters such as pulse duration and repetition frequency, and using spatial light modulators for local adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple exposures with different phase positions are used to improve resolution, then the resolution is improved, but the effective refresh rate is reduced
Solution Approach 1:
The patent uses periodic pulsed illumination with structured light patterns at different phase positions to achieve super-resolution imaging. By illuminating the sample with pulsed structured light in multiple phases and reconstructing the image from these periodic measurements, the system achieves resolution beyond the diffraction limit while maintaining a manageable acquisition speed through the periodic nature of the illumination sequence.
2Measurement precision
If high illumination intensity is used to create non-linear excitation for improved resolution, then the resolution is improved, but sample bleaching increases
Solution Approach 1:
The patent employs periodic pulsed illumination instead of continuous high-intensity illumination. By delivering excitation energy in periodic pulses rather than continuously, the system achieves the necessary non-linear excitation for super-resolution while allowing intervals between pulses that reduce cumulative photodamage and sample bleaching.
Solution Approach 2:
The patent maintains continuous imaging capability through rapid sequential acquisition of multiple phase images. By continuously cycling through the phase sequence and accumulating data, the system achieves both high resolution and reduced bleaching per frame, as the total exposure is distributed across many rapid measurements rather than concentrated in a single long exposure.
3Productivity
If the pulse repetition frequency is increased to improve imaging speed, then the imaging speed is improved, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The patent uses periodic pulsed illumination where each pulse is optimized for signal strength, and the repetition frequency is chosen to balance imaging speed with signal accumulation. The periodic structure allows the system to acquire multiple phase images in rapid succession while maintaining sufficient signal-to-noise ratio through the cumulative effect of multiple pulses per phase.
Solution Approach 2:
The patent performs preliminary optimization of the pulse sequence parameters before actual imaging. By pre-determining the optimal pulse repetition frequency and duration based on the specific sample and detection system, the system achieves the best possible balance between imaging speed and signal-to-noise ratio for each imaging condition.
4Measurement precision
If the pulse duration is extended to improve signal-to-noise ratio, then the signal-to-noise ratio is improved, but sample bleaching increases
Solution Approach 1:
The patent uses periodic pulsed illumination where the pulse duration is optimized to deliver sufficient excitation energy for high signal-to-noise ratio within each pulse, while the periodic repetition provides intervals that allow sample recovery and reduce cumulative bleaching. The key is that the useful signal accumulates during each pulse while the harmful bleaching effect has time to diminish between pulses.
Solution Approach 2:
The patent optimizes the pulse duration parameter specifically for each imaging condition and sample type. By adjusting the pulse width, repetition frequency, and total number of pulses as a coordinated set of parameters, the system achieves the optimal balance between signal-to-noise ratio and photodamage, rather than treating pulse duration as an isolated parameter.
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
Enhances the resolution of reconstructed images by improving the signal-to-noise ratio and minimizing sample bleaching, while ensuring system safety and optimal imaging conditions.
Implementation Method 1
generation of a spatial light structure on the sample to be examined, for example by means of sinusoidal interference of the illumination light behind an optical grating
Implementation Method 2
fluorescent light emitted by the sample per phase being recorded in a respective structured individual image
Implementation Method 3
modulating the illumination light incident on the sample in a pupil plane of the microscope objective with a spatial light modulator
Implementation Method 4
Due to the diffraction of the light recorded by the sample in the microscope objective, the resolving power of microscopes depends on its aperture and the wavelength of the light
Implementation Method 5
the support of the optical transfer function (OTF) of the microscope is limited to a finite range around the coordinate origin in the frequency domain
Implementation Method 6
excitation of the sample (by means of illumination or in some other way) in such a way that a non-linear relationship between the excitation intensity and the light intensity emitted by the sample is created (saturated pattern excitation microscopy; SEM)
Implementation Method 7
which leads to partial saturation of the excitation of the fluorescent dye in the area of the illumination structure
Data Source
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AI summary
In structured illumination microscopy, repeatedly capturing individual images at different phase angles of the structuring requires great stability of the optical array and of the sample during the entire measurement. Furthermore, the structuring has to be imaged onto the sample with great homogeneity. During nonlinear fluorescence excitation, the sample and the dyes thereof are subject to bleaching. Also, the nonlinearity depends on the local conditions in the surroundings of the sample in addition to the lighting conditions, potentially resulting in locally different nonlinearities. Said effects negatively affect resolution. The aim of the invention is to make it possible to use the highest possible resolutions. Said aim is achieved by optimizing the process for capturing individual images in order to obtain the best possible resolution in the resulting image also when the samples are problematic. Such an optimization process can be performed in different ways, e.g. by determining an optimal setting for at least one illumination or image-capturing parameter or by means of pulsed illumination such that there is less excitation from one triplet state of the fluorescent dye into a higher triplet state, or by illuminating the sample with absorptive light in order to deplete a triplet state of the fluorescent dye, thus preventing bleaching. The invention can be used in high-resolution fluorescence microscopy.