Typical LED array microscopes require multiple image acquisitions for phase retrieval. Here, we propose a polarized LED array microscope for single-shot quantitative phase imaging with aberration correction. We implemented polarization-encoded illumination multiplexing by placing a custom-made polarization filter on top of the LED array. A single image was captured using a polarized sensor under polarized LED illumination. We reconstructed the quantitative phase by incorporating the polarization multiplexing model with a phase retrieval algorithm. We showed that the proposed technique can reconstruct aberration-corrected phase images with a single-shot intensity image.
We propose a high-throughput phase-guided digital histological staining based on Fourier ptychographic microscopy using a generalizable deep neural network. Since the phase information includes the refractive index distribution of the specimen, we can digitally stain the unstained tissue slides from the quantitative phase images, which present the same color features that can be observed under a conventional microscope with the staining process. Here, we utilize Fourier Ptychographic Microscope that enables wide field and high-resolution quantitative phase imaging using multiple measurements by varying illumination angle. Additionally, we design a neural network that has remarkable generalization regarding sample dependence with the learned forward model. Along with this network architecture, we realize the efficient and effective digital staining process that does not require the labeled dataset from unstained tissue slides. We will report on the digital stained result from raw FPM images, the performance comparison, and discuss the future direction of our approach.
We present a novel polarization-sensitive Fourier Ptychographic Microscopy (FPM) method that leverages multiplexing techniques in the Fourier plane, eliminating the need for costly polarization cameras or mechanical polarizer rotations. By simply introducing semicircular 0° and 90° linear polarizers in the Fourier plane of a conventional FPM setup, we can effectively split a single pupil into two half-circle pupils, enabling the simultaneous multiplexing of two channels' signals within a single measurement. By imposing two pupil functions on FP phase retrieval, we reconstructed the amplitude and phase information of the two orthogonal polarization channels, ultimately obtaining the Jones matrix of the anisotropic specimen. To validate our proposed method, we demonstrate its application by accurately reconstructing the orientation of the slow axis and phase retardation of MSU crystals known as the birefringence object.
We present rolling shutter speckle imaging (RSSI), a single-shot temporal speckle imaging technique that can quantitatively measure the fast dynamics of scattering media without high speed cameras. Utilizing a rolling shutter image sensor and vertically elongated speckles, RSSI can quantitatively map the speckle dynamics from a single image capture. We discuss the speckle spatiotemporal intensity correlation model for RSSI, which is validated through simulations and phantom experiments. We show in vivo quantitative blood flow imaging of the mouse brain from a snapshot measurement. In addition to imaging, we also present rolling shutter speckle plethysmography for cardiovascular monitoring.
We report tensorial tomographic Fourier ptychography (T2oFu), a nonscanning label-free tomographic microscopy method for simultaneous imaging of quantitative phase and anisotropic specimen information in 3D. Built upon Fourier ptychography, a quantitative phase imaging technique, T2oFu additionally highlights the vectorial nature of light. The imaging setup consists of a standard microscope equipped with an LED matrix, a polarization generator, and a polarization-sensitive camera. Permittivity tensors of anisotropic samples are computationally recovered from polarized intensity measurements across three dimensions. We demonstrate T2oFu’s efficiency through volumetric reconstructions of refractive index, birefringence, and orientation for various validation samples, as well as tissue samples from muscle fibers and diseased heart tissue. Our reconstructions of healthy muscle fibers reveal their 3D fine-filament structures with consistent orientations. Additionally, we demonstrate reconstructions of a heart tissue sample that carries important polarization information for detecting cardiac amyloidosis.
We report on the design and construction of a goggle-type eye tracker using a low-cost and high-speed lensless camera for monitoring eye movements in neurodegenerative diseases. A Rolling Shutter image sensor combined with lensless computational imaging allows for the reconstruction of a time sequence of images from a single snapshot, effectively improving the framerate of the camera. We constructed and demonstrated the prototype device using a commercial-grade CMOS image sensor and achieved the improvement of framerate from 15 to 480Hz, with the tracking results for 28 clinical measured data. Our device can potentially measure microsaccadic eye movements in a wearable camera format, allowing routine monitoring of abnormal eye movements for the early diagnosis and tracking of Alzheimer’s and Parkinson’s disease.
Fourier ptychography (FP) utilizes angle-varied illumination to achieve resolution improvement and quantitative phase imaging. In this talk, we present a compact microscope using an OLED screen as a programmable illumination for FP reconstruction. We discuss multiplexed reconstruction strategy using multi-pixel illuminations, and a stand-alone smartphone implementation of portable FPM.
We propose a compact and low-cost lensless camera that enables snapshot full-Stokes polarization imaging. Using a polarization-encoded aperture composed of three linear polarizers and a quarter wave plate on a lensless camera, our device can capture 4 images of different linear and circular polarization intensities in a single shot, which can be used to compute full-Stokes images. We can construct an ultra-thin polarization-sensitive lensless camera using a regular image sensor and perform video-rate polarimetry for various applications. We report on the design, construction and imaging performance of our prototype device.
Hyperspectral imaging collects spatio-spectral information of objects useful in a wide range of applications including biomedical imaging. We propose a compact lensless snapshot HSI system, composed only of a monochromatic CMOS image sensor, a transparent phase-mask and a linear variable filter (LVF). The combination of a phase mask and an LVF generates wavelength-dependent transfer functions, and we can computationally recover the hyperspectral image stack from a single measurement. We report on the construction of the device, image reconstruction algorithm and spectral calibration methods and show the hyperspectral imaging performance of our prototype device the entire visible wavelengths.
Lensless photography is a recently-developed computational imaging technique that uses light-modulating phase masks instead of lenses to build ultra-compact and low-cost cameras. Here, we propose a method to design and fabricate custom phase-masks to create deterministic point spread functions for lensless imaging. Phase-masks are designed using our wave-optics-based algorithm and are fabricated in single-shot via grayscale maskless lithography technique. Using this method, we can design and fabricate phase-masks with various surface profiles and have validated that the fabricated masks match the designed profiles. Our technique allows for a fast and efficient process that can be applied to the fab-level fabrication of lensless cameras for commercialization. We also show that lensless cameras using our custom phase-masks can effectively obtain images in a compact form factor.
Fourier Ptychographic Microscopy (FPM) is a computational imaging technique which reconstructs super-resolved amplitude and phase images by combining variably illuminated low-resolution images through an iterative phase retrieval algorithm. However, the phase-retrieval-based reconstruction requires sufficient overlap between spatial frequency bands of the measurements, which creates a trade-off between the number of measurements and the reconstruction quality. We propose a deep-learning-based FPM reconstruction that recovers both amplitude and phase images in high resolution with far fewer measurements than conventional FPM, with model-based constraint. Our model works with almost no overlap between low-resolution measurements in the Fourier domain, only taking into account the total Fourier extent of the measurements.
We propose a simple smartphone attachment module to realize a portable wide-field high-resolution microscope based on Fourier Ptychographic Microscopy (FPM). Using the smartphone's screen as the illumination and the front camera module for image acquisition, we can construct a stand-alone portable FPM, a microscopy technique that can achieve high resolution by computationally combining a number of variably illuminated low-resolution bright-field and dark-field images through an iterative phase retrieval algorithm. With the custom-built android application that performs in situ calculation for acquisition, reconstruction, and display of the images, we can achieve a true stand-alone portable imaging device for field applications.
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