Fourier Ptychographic Tomography for Thick Sample Imaging
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Solution Overview
Problem
Conventional Fourier ptychography techniques are limited to imaging thin samples up to 25 μm in thickness, as they rely on the thin sample approximation, which fails for thicker samples, leading to a need for methods that can handle thicker samples and provide both high-resolution imaging and depth information.
Innovation Solution
The development of Fourier ptychographic tomography systems and methods that use a denser array of illumination sources and finer step sizes for illumination angles, allowing for the reconstruction of three-dimensional data by updating voxels in overlapping spherical cap regions in the Fourier domain, enabling imaging of thick samples with improved lateral and depth resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Fourier ptychography techniques are used, then high-resolution imaging is achieved for thin samples, but the method fails for thicker samples exceeding 25 μm
Solution Approach 1:
The patent extends conventional two-dimensional Fourier ptychography to three-dimensional tomographic reconstruction by adding the axial dimension (kz) to the Fourier domain analysis. This dimensional extension enables the system to handle thick samples while maintaining high resolution through volumetric data reconstruction rather than planar projection
Solution Approach 2:
The patent segments the thick sample into multiple thin slices along the axial dimension, reconstructing each slice independently through tomographic algorithms. This segmentation approach allows the system to process thick samples by treating them as stacks of manageable thin sections, each reconstructed with high precision
2Loss of information
If a denser array of illumination sources is used, then three-dimensional data reconstruction is enabled, but device complexity increases
Solution Approach 1:
The patent employs a two-dimensional array of illumination sources that serves multiple functions: it provides variable angle illumination for Fourier ptychography, enables three-dimensional tomographic reconstruction, and maintains compatibility with standard microscope optics. This multi-functional illumination system achieves volumetric data collection without requiring complex specialized hardware
3Measurement precision
If finer step sizes for illumination angles are used, then lateral and depth resolution are improved, but the number of measurements increases
Solution Approach 1:
The patent performs preliminary computational preparation by pre-calculating the expected Fourier domain patterns for different illumination angles and sample structures. This preliminary action enables more efficient iterative reconstruction algorithms that converge faster, reducing the total number of measurements needed while maintaining high resolution
Solution Approach 2:
The patent implements feedback mechanisms in the iterative tomographic reconstruction algorithm, where each measurement is evaluated and used to adjust subsequent reconstruction steps. This feedback approach optimizes the measurement sequence, allowing the system to achieve high resolution with fewer total measurements by intelligently selecting which measurements provide the most information gain
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
This approach enables high-resolution, three-dimensional imaging of thick samples by reconstructing a three-dimensional sample spectrum, providing improved lateral resolution and depth information, overcoming the limitations of conventional methods by handling samples thicker than 25 μm and offering enhanced spatial resolution along the axial dimension.
Implementation Method 1
a variable illumination source (e.g. LED matrix) configured to provide plane wave illumination sequentially at different illumination angles to a thick sample being imaged
Implementation Method 2
an optical system (e.g. objective lens) configured to collect light passing through the thick sample from the variable illumination source and focus the collected light
Implementation Method 3
an image sensor configured to receive the focused light from the optical system and acquire a sequence of uniquely illuminated intensity measurements
Implementation Method 4
a processor for constructing three-dimensional tomographic data of the thick sample by iteratively determining three-dimensional tomographic data in the Fourier domain that is self-consistent with the uniquely illuminated intensity measurements
Data Source
AI summary
Certain aspects pertain to Fourier ptychographic tomographic systems and methods for acquiring a plurality of uniquely illuminated intensity measurements based on light passing through a thick sample from plane wave illumination at different angles and for constructing three-dimensional tomographic data of the thick sample by iteratively determining three-dimensional tomographic data in the Fourier domain that is self-consistent with the uniquely illuminated intensity measurements.