Lens-free Multi-Laser Spectral Light-Field Fusion Microscopy

We present a device and method for performing lens-free spectrallight-field fusion microscopy at sub-pixel resolutions while takingadvantage of the large field-of-view capability. A collection oflasers at different wavelengths is used in pulsed mode and enablesthe capture of interferometric light-field encodings of a specimenplaced near the detector. Numerically fusing the spectral complexlight-fields obtained from the encodings produces an image of thespecimen at higher resolution and signal-to-noise-ratio while suppressingvarious aberrations and artifacts

Simultaneous Multispectral Imaging: Using Multiview Computational Compressive Sensing

Multispectral imaging is traditionally performed using a combination of an imaging device with a filter bank such as a filter wheel or a form of tunable filter, or a combination of many imaging devices with various spectral beam splitting optics. The complexity and size of these devices seem to be the limiting factor of their adoption and use in various fields that could potentially benefit from this imaging modality. With the advent of nanophotonics, there has been a surge in single camera, snapshot, multispectral imaging exploiting the capabilities of nanotechnology to devise pixel-based spectral filters. This new form of sensing, which can be classified as compressive sensing, has its limitations. One example is the laborious process of fabricating the filter bank and installing it into a detector since the detector fabrication process is completely removed from the filter fabrication process. The work presented here will describe an optical design that would enable a single-camera, simultaneous multispectral imaging via multiview computational compressive sensing. A number of points-of-view (POVs) of the field-of-view (FOV) of the camera are generated and directed through an assortment of spectral pre-filters en route to the camera. The image of each of the POVs is then captured on a different spatial location on the detector. With the spectral response of the detector pixels well characterized, spatial and spectral compressive sensing is performed as the images are recorded. Various computational techniques are used in this work which would: register the images captured from multiple views resulting in even more sparsely sensed images; perform spatial interpolation of the sparsely sampled spectral images; implement hyper-focusing of the images from all POVs captured as some defocusing will happen as the result of the discrepancy in the optical paths in each view; execute numerical dimensionality reduction analysis to extract information from the multispectral images. The spectral imaging capabilities of the device are tested with a collection of fluorescent microspheres. The spectral sensing capability of the device is examined by measuring the fluorescent spectra of adulterated edible oils and demonstrating the ability of the imaging system to differentiate between various types of oil as well as various levels of contamination. Lastly, the system is used to scrutinize samples of black ink from different pen manufacturers, and is able to discriminate between the different inks

Laser Interference Fringe Tomography - A Novel 3D Imaging Microscopy Technique

Laser interference fringe tomography (LIFT) is within the class of optical imaging devices designed for volumetric microscope applications. LIFT is a very simple and cost-effective three-dimensional imaging device which is able to reliably produce low-quality imagery. It measures the reflectivity as a function of depth within a sample and is capable of producing three-dimensional images from optically scattering surfaces. The first generation of this instrument is designed and prototyped for optical microscopy. With an imaging spot size of 42 μm and a 180 μm axial resolution kernel, LIFT is capable of producing one- and two- dimensional images of various samples up to 1.5 mm thickness. The prototype was built using commercial-off-the-shelf components and cost ~ $1,000. It is possible that with effort, this device can become a reliable, stable, low-quality volumetric imaging microscope to be readily available to the consumer market at a very affordable price. This document will present the optical design of LIFT along with the complete mathematical description of the instrument. The design trade-offs and choices of the instrument are discussed in detail and justified. The theoretical imaging capabilities of the instrument are tested and experimentally verified. Finally, some imaging results are presented and discussed

Compact, Field-Portable Lens-free Microscope using Superresolution Spatio-Spectral Light-field Fusion

We present a compact, field-portable lens-free microscope basedon the principle of spatio-spectral light-field fusion. This is the firsttime a device of this kind has been introduced whereby both superresolutionand signal-to-noise ratio are enhanced via the marriageof synthetic aperture imaging and spectral light-field fusionholography, culminating in a system that is self-contained and fieldportablewhile achieving high resolution, contrast, strong signal fidelity,and ultra-wide field-of-view. The active spatio-spectral illuminationis accomplished in the presented microscope by arranginga series of pulsing LEDs emitting at different spectral wavelengthsin a specific spatial formation. To demonstrate the performance ofthe presented microscope, the system was used to observe twohistology samples: a bovine lung, and corn stem. The imaging resultsdemonstrate the ultra-wide field-of-view advantage of the presentedmicroscope over any other system of its kind, thus enablingfor acquisition of the entire sample without the need for scanning,while producing high-resolution, high-contrast microscopy images(168 megapixels in the current system) that makes it well-suited forscientific and clinical examinations

Enhanced Smartphone Spectroscopy via High-throughput Computational Slit

High-performance spectroscopy is often limited by its portability, size, and cost, therefore limiting its reach into various applications that may benefit from it. In this paper, we present a low-cost, low-complexity slitless smartphone-based spectrometer that can be useful for carrying out field studies. Omitting a slit in a spectrometer means loss of spectral resolution in conventional spectrographs; however, we overcome this limitation via the use of a high-throughput computational slit to produce spectra with enhanced spectral resolution and enhanced signal-to-noise characteristics

Compact, Field-Portable Smartphone Chiral Molecule Concentration Estimation System via Multi-sensor Computational Polarimetry

In this paper, we present a compact, field-portable smartphone chiralmolecule concentration estimation system based on the principleof multi-sensor computational polarimetry. The presented systemwas designed as an attachment for a smartphone, thus leveragingthe computational power to achieve full autonomy and smallform factor, while greatly reducing the cost of the system. In addition,by leveraging Maul’s Law, the size and complexity of thepresented system can be greatly reduced, consisting of just fourstatic components: i) a diode laser source, ii) a linear polariser, iii)a cell for chiral solution, and iv) a linear analyser. Finally, the highmegapixel count of the smartphone camera is leveraged via multisensorcomputational polarimetry, where a multitude of measurementsby different sensors are made in a single acquisition to enhancethe estimation of the angle of linear polarisation, and therebyenhance the estimation of the concentration of chiral molecules insolution. Such a system can have potential for enabling low-cost,mobile chiral molecule concentration analysis, which would be wellsuitedfor a wide range of industrial and clinical applications wherefield testing or on-site testing is required

Numerical Spectral Demulitplexing Microscopy of Measurements from an Anatomical Specimen

Multispectral microscopy is a method of capturing spectral bandsusing a microscope, and is used to observe specimens on a micronor nano scale. However, these systems are limited because theycannot capture transient phenomena since they cannot capture simultaneousspectral information. We propose a new method callednumerical spectral demultiplexing microscopy (NSDM) which utilizesa Raspberry Pi camera to capture RGB measurements andthen infer narrow-band multispectral spectra. This is accomplishedby training a non-linear regression random forest model based onthe spectral sensitivity of the camera which allows for a low-cost,portable, and simultaneous capture multispectral microscopy system.We use the NSDM system as a bright-field multispectral microscopeand a dark-field fluorescence multispectral microscopeon an anatomical specimen and show that additional informationcan be gathered by combining a bright-field and dark-field fluorescencemicroscope