Synthetic Aperture Phase Microscopy for Subwavelength Resolution
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Solution Overview
Problem
Conventional imaging techniques, such as scanning electron microscopy (SEM) and atomic force microscopy (AFM), are impractical for high-speed and high-resolution imaging of large sample areas, especially when structures are encapsulated in dielectric claddings or are thin and transparent, limiting the ability to resolve subwavelength structures and track fast cellular dynamics.
Innovation Solution
The development of high spatial and temporal resolution synthetic aperture phase microscopy (HISTR-SAPM) system using a fiber coupler, digital micromirror devices (DMDs), and a beam splitter to generate multiple illumination angles, allowing for simultaneous capture of off-axis interferograms and synchronization of DMD patterns to enhance imaging speed and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional bright-field microscopy is used to image thin and transparent structures, then the imaging process is simple and label-free, but the structures cannot be well resolved due to weak light absorptions
Solution Approach 1:
The patent transforms the imaging modality from amplitude-based (bright-field) to phase-based detection. By measuring optical pathlength differences caused by refractive index variations in transparent structures, the system converts invisible phase shifts into visible contrast in the reconstructed images, enabling resolution of thin and transparent structures without staining or labeling.
Solution Approach 2:
The patent uses digital holography to capture and reconstruct the complex optical field. Multiple holographic recordings at different illumination angles are synthesized computationally to create a high-resolution phase map, effectively copying the optical information into a usable image format that reveals transparent structures.
2Measurement precision
If scanning electron microscopy (SEM) or atomic force microscopy (AFM) is used to image encapsulated structures, then high resolution can be achieved, but the dielectric claddings obscure the imaging contrast or inhibit probe contact
Solution Approach 1:
The patent replaces physical probing methods (AFM) and electron beam imaging (SEM) with optical phase measurement. By detecting optical pathlength differences through the dielectric claddings, the system achieves high-resolution imaging of encapsulated structures without requiring physical contact or electron beam penetration, thus avoiding the limitations imposed by the claddings.
Solution Approach 2:
The patent uses optical phase information as an intermediary to probe the structures beneath dielectric claddings. The phase shifts caused by the encapsulated structures modulate the transmitted light, allowing indirect detection of the hidden structures through the claddings without direct optical or physical contact.
3Measurement precision
If conventional wide-field coherent imaging is used, then the imaging process is simple, but the lateral resolution is limited to k/NA due to the diffraction limit
Solution Approach 1:
The patent extends the imaging from 2D wide-field coherent imaging to 3D angular space by collecting holographic data at multiple illumination angles. This angular dimension provides additional spatial frequency information that, when synthesized, exceeds the diffraction limit of a single-angle imaging system, achieving super-resolution without complex optical hardware.
Solution Approach 2:
The patent employs dynamic illumination angle scanning combined with digital holography. By rapidly changing the illumination angle and capturing corresponding holographic frames, the system dynamically accumulates spatial frequency information from different directions, enabling super-resolution reconstruction through computational synthesis rather than static optical design.
4Measurement precision
If multiple image recordings are used to improve lateral resolution through computational imaging methods, then resolution can be enhanced, but the imaging speed decreases to less than 20 frames per second
Solution Approach 1:
The patent uses periodic modulation of the illumination angle combined with snapshot digital holography. By systematically varying the illumination angle in periodic steps and capturing holographic frames at each angle, the method efficiently accumulates angular diversity information. The periodic scanning protocol optimizes the balance between data acquisition completeness and imaging speed, achieving super-resolution at higher frame rates than conventional methods.
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
HISTR-SAPM achieves improved lateral resolution of 233 nm, nearly twice the coherent imaging limit, and high-speed imaging capabilities, enabling the visualization of subwavelength structures and fast cellular dynamics with reduced speckle noise and mechanical vibrations.
Implementation Method 1
a fiber coupler receiving an input illumination beam, configured to provide a first illumination beam to propagate along a sample-illumination path and a second illumination beam to propagate along a reference-beam path
Implementation Method 2
a first digital micromirror device (DMD) disposed in the sample-illumination path to receive the first illumination beam from the fiber coupler and configured to actively generate a plurality of sample illumination beams at different angles
Implementation Method 3
a beam splitter (BS) disposed both in the sample-illumination path and in the reference-beam path to combine the sample illumination beam and the second illumination beam from the fiber coupler to form an interferogram at a final image plane
Implementation Method 4
a first scanning objective lens disposed in the sample-illumination path and at a first side adjacent to the sample to receive the sample illumination beams from the third lens and propagate the sample illumination beams through the sample for imaging
Data Source
AI summary
A high spatial and temporal resolution synthetic aperture phase microscopy (HISTR-SAPM) system and methods are provided for sample imaging and metrology. The HISTR-SAPM system includes a sample-illumination path along which a first illumination beam propagates and a reference-beam path along which a second illumination beam propagates. A first digital micromirror device (DMD), a second DMD, and a first scanning objective lens are disposed in the sample-illumination path and at a first side adjacent to the sample. A second scanning objective lens passes the sample information to a beam splitter (BS), where the sample illumination beam and the reference-beam are combined to form an interferogram at a final image plane for imaging the sample. A Fourier spatial spectrum analysis and a synthetic aperture are then used to reconstruct a quantitative phase map of the sample with a high resolution and at a high-speed.