34 research outputs found
Soft thresholding schemes for multiple signal classification algorithm
Multiple signal classification algorithm (MUSICAL) exploits temporal
fluctuations in fluorescence intensity to perform super-resolution microscopy
by computing the value of a super-resolving indicator function across a fine
sample grid. A key step in the algorithm is the separation of the measurements
into signal and noise subspaces, based on a single user-specified parameter
called the threshold. The resulting image is strongly sensitive to this
parameter and the subjectivity arising from multiple practical factors makes it
difficult to determine the right rule of selection. We address this issue by
proposing soft thresholding schemes derived from a new generalized framework
for indicator function design. We show that the new schemes significantly
alleviate the subjectivity and sensitivity of hard thresholding while retaining
the super-resolution ability. We also evaluate the trade-off between resolution
and contrast and the out-of-focus light rejection using the various indicator
functions. Through this, we create significant new insights into the use and
further optimization of MUSICAL for a wide range of practical scenarios.Comment: 15 pages, 5 figure
Fabrication of submicrometer high refractive index tantalum pentoxide waveguides for optical propulsion of microparticles
Design, fabrication, and optimization of tantalum pentoxide (Ta2O5) waveguides to obtain low-loss guidance at a wavelength of 1070 nm are reported. The high-refractive index contrast (Δn ~ 0.65, compared to silicon oxide) of Ta2O5 allows strong confinement of light in waveguides of submicrometer thickness (200 nm), with enhanced intensity in the evanescent field. We have employed the strong evanescent field from the waveguide to propel micro-particles with higher velocity than previously reported. An optical propelling velocity of 50 µm/s was obtained for 8 µm polystyrene particles with guided power of only 20 mW
Hilbert phase microscopy based on pseudo thermal illumination in Linnik configuration
Quantitative phase microscopy (QPM) is often based on recording an
object-reference interference pattern and its further phase demodulation. We
propose Pseudo Hilbert Phase Microscopy (PHPM) where we combine pseudo thermal
light source illumination and Hilbert spiral transform phase demodulation to
achieve hybrid hardware-software-driven noise robustness and increase in
resolution of single-shot coherent QPM. Those advantageous features stem from
physically altering the laser spatial coherence and numerically restoring
spectrally overlapped object spatial frequencies. Capabilities of the PHPM are
demonstrated analyzing calibrated phase targets and live HeLa cells in
comparison with laser illumination and phase demodulation via temporal phase
shifting and Fourier transform techniques. Performed studies verified unique
ability of the PHPM to couple single-shot imaging, noise minimization, and
preservation of phase details
Mitochondrial dynamics and quantification of mitochondria-derived vesicles in cardiomyoblasts using structured illumination microscopy
Mitochondria are essential energy-providing organelles of particular importance in energy-demanding tissue such as the heart. The production of mitochondria-derived vesicles (MDVs) is a cellular mechanism by which cells ensure a healthy pool of mitochondria. These vesicles are small and fast-moving objects not easily captured by imaging. In this work, we have tested the ability of the optical super-resolution technique 3DSIM to capture high-resolution images of MDVs. We optimized the imaging conditions both for high-speed video microscopy and fixed-cell imaging and analysis. From the 3DSIM videos, we observed an abundance of MDVs and many dynamic mitochondrial tubules. The density of MDVs in cells was compared for cells under normal growth conditions and cells during metabolic perturbation. Our results indicate a higher abundance of MDVs in H9c2 cells during glucose deprivation compared with cells under normal growth conditions. Furthermore, the results reveal a large untapped potential of 3DSIM in MDV research
From Hours to Seconds: Towards 100x Faster Quantitative Phase Imaging via Differentiable Microscopy
With applications ranging from metabolomics to histopathology, quantitative
phase microscopy (QPM) is a powerful label-free imaging modality. Despite
significant advances in fast multiplexed imaging sensors and
deep-learning-based inverse solvers, the throughput of QPM is currently limited
by the speed of electronic hardware. Complementarily, to improve throughput
further, here we propose to acquire images in a compressed form such that more
information can be transferred beyond the existing electronic hardware
bottleneck. To this end, we present a learnable optical
compression-decompression framework that learns content-specific features. The
proposed differentiable quantitative phase microscopy () first
uses learnable optical feature extractors as image compressors. The intensity
representation produced by these networks is then captured by the imaging
sensor. Finally, a reconstruction network running on electronic hardware
decompresses the QPM images. In numerical experiments, the proposed system
achieves compression of 64 while maintaining the SSIM of
and PSNR of dB on cells. The results demonstrated by our experiments
open up a new pathway for achieving end-to-end optimized (i.e., optics and
electronic) compact QPM systems that may provide unprecedented throughput
improvements
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Super-condenser enables labelfree nanoscopy.
Labelfree nanoscopy encompasses optical imaging with resolution in the 100 nm range using visible wavelengths. Here, we present a labelfree nanoscopy method that combines Fourier ptychography with waveguide microscopy to realize a 'super-condenser' featuring maximally inclined coherent darkfield illumination with artificially stretched wave vectors due to large refractive indices of the employed SiN waveguide material. We produce the required coherent plane wave illumination for Fourier ptychography over imaging areas 400 m in size via adiabatically tapered single-mode waveguides and tackle the overlap constraints of the Fourier ptychography phase retrieval
algorithm two-fold: firstly, the directionality of the illumination wave vector
is changed sequentially via a multiplexed input structure of the waveguide chip layout and secondly, the wave vector modulus is shortend via step-wise increases of the illumination light wavelength over the visible spectrum. We validate the method via in silico and in vitro experiments and provide details on the underlying image formation theory as well as the reconstruction algorithm
Super-condenser enables labelfree nanoscopy.
Labelfree nanoscopy encompasses optical imaging with resolution in the 100 nm range using visible wavelengths. Here, we present a labelfree nanoscopy method that combines coherent imaging techniques with waveguide microscopy to realize a super-condenser featuring maximally inclined coherent darkfield illumination with artificially stretched wave vectors due to large refractive indices of the employed Si3N4 waveguide material. We produce the required coherent plane wave illumination for Fourier ptychography over imaging areas 400 μm2 in size via adiabatically tapered single-mode waveguides and tackle the overlap constraints of the Fourier ptychography phase retrieval algorithm two-fold: firstly, the directionality of the illumination wave vector is changed sequentially via a multiplexed input structure of the waveguide chip layout and secondly, the wave vector modulus is shortend via step-wise increases of the illumination light wavelength over the visible spectrum. We test the method in simulations and in experiments and provide details on the underlying image formation theory as well as the reconstruction algorithm. While the generated Fourier ptychography reconstructions are found to be prone to image artefacts, an alternative coherent imaging method, rotating coherent scattering microscopy (ROCS), is found to be more robust against artefacts but with less achievable resolution
Squeezing red blood cells on an optical waveguide to monitor cell deformability during blood storage
Red blood cells squeeze through micro-capillaries as part of blood circulation in the body. The deformability of red blood cells is thus critical for blood circulation. In this work, we report a method to optically squeeze red blood cells using the evanescent field present on top of a planar waveguide chip. The optical forces from a narrow waveguide are used to squeeze red blood cells to a size comparable to the waveguide width. Optical forces and pressure distributions on the cells are numerically computed to explain the squeezing process. The proposed technique is used to quantify the loss of blood deformability that occurs during blood storage lesion. Squeezing red blood cells using waveguides is a sensitive technique and works simultaneously on several cells, making the method suitable for monitoring stored blood