We have developed a multimode dermoscope (SkinSpect™) capable of illuminating human skin samples in-vivo with spectrally-programmable linearly-polarized light at 33 wavelengths between 468nm and 857 nm. Diffusely reflected photons are separated into collinear and cross-polarized image paths and images captured for each illumination wavelength. In vivo human skin nevi (N = 20) were evaluated with the multimode dermoscope and melanin and hemoglobin concentrations were compared with Spatially Modulated Quantitative Spectroscopy (SMoQS) measurements. Both systems show low correlation between their melanin and hemoglobin concentrations, demonstrating the ability of the SkinSpect™ to separate these molecular signatures and thus act as a biologically plausible device capable of early onset melanoma detection.
A polarization-sensitive hyperspectral imaging system (SkinSpect) has been built and evaluated using two-layer tissue phantoms, fabricated to mimic the optical properties of melanin in different epidermal thickness and hemoglobin in dermal layers. Multiple tissue-mimicking phantoms with varying top layer thicknesses were measured for optical system calibration and performance testing. Phantom properties were characterized and validated using SkinSpect. The resulting analysis shows that the proposed system is capable of distinguishing and differentiating the layer-dependent absorption spectra and the depths at which this absorption occurs.
We present a polarization-sensitive hyperspectral imaging system (SkinSpect) that employs a spectrally-programmable
light source in the visible and NIR domains. Multiple tissue-mimicking phantoms were fabricated to mimic the optical
properties of normal skin as well as pigmented light and dark moles. The phantoms consist of titanium dioxide and a
mixture of coffee, red food dye, and naphthol green as the scattering and the three absorptive agents in a
polydimethylsiloxane (PDMS) base. Phantoms were produced with both smooth and rough textured surfaces and tested
using Spatial Frequency Domain Imaging (SFDI) and Spatially Modulated Quantitative Spectroscopy (SMoQS) for
homogeneity as well as determining absorption and scattering variance, respectively. The reflectance spectral images
were also recorded using the SkinSpect research prototype; the spectral signatures of the phantoms were calculated using
a two-flux single-layer Kubelka-Munk model and non-negative least square fitting routine was applied to extract the
relative concentrations of the individual phantom components.
We introduce a multimode dermoscope (SkinSpectTM) we developed for early detection of
melanoma by combining fluorescence, polarization and hyperspectral imaging. Acquired reflection
image datacubes were input to a wavelength-dependent linear model to extract the relative
contributions of skin chromophores at every pixel. The oxy-hemoglobin, deoxy hemoglobin,
melanin concentrations, and hemoglobin oxygen saturation by the single step linear least square
fitting and Kubelka-Munk tissue model using cross polarization data cubes were presented. The
comprehensive data obtained by SkinSpect can be utilized to improve the accuracy of skin
chromophore decomposition algorithm with less computation cost. As an example in this work, the
deoxy-hemoglobin over-estimation error in highly pigmented lesion due to melanin and deoxy
hemoglobin spectral cross talk were analyzed and corrected using two-step linear least square fitting
procedure at different wavelength ranges. The proposed method also tested in skin with underlying
vein area for validating the proof of concept.
The Faint Intergalactic Redshifted Emission Balloon (FIREBALL) had its first scientific flight in June 2009.
The instrument is a 1 meter class balloon-borne telescope equipped with a vacuum-ultraviolet integral field
spectrograph intended to detect emission from the inter-galactic medium at redshifts 0.3 < z < 1.0. The
scientific goals and the challenging environment place strict constraints on the pointing and tracking systems of
the gondola. In this manuscript we briefly review our pointing requirements, discuss the methods and solutions
used to meet those requirements, and present the aspect reconstruction results from the first successful scientific
flight.
FIREBALL (the Faint Intergalactic Redshifted Emission Balloon) is a balloon-borne 1m telescope coupled to an
ultraviolet fiber-fed spectrograph. FIREBALL is designed to study the faint and diffuse emission of the intergalactic
medium, until now detected primarily in absorption. FIREBALL is a path finding mission to test new technology
and make new constraints on the temperature and density of this gas. We report on the first successful science flight
of FIREBALL, in June 2009, which proved every aspect of the complex instrument performance, and provided the
strongest measurements and constraints on IGM emission available from any instrument.
The unique attributes of magnetostrictive materials have been used to develop a wide variety of electromechanical transducers and devices. Most of these applications have been at or above room temperature. However, many applications at cryogenic temperatures also require high authority, high precision, efficient actuation. Other technologies, including all piezoelectric systems, tend to be inoperable or impractical and unreliable at cryogenic temperatures. Magnetostrictive materials have already demonstrated improved performance at low temperature down to near absolute zero with strains as high as 1% possible. These unique material attributes combine with novel magnetic field generation, transducer and mechanism concepts to meet the challenges of resolution, size, weight, power, thermal and reliability requirements of actuators for many cryogenic applications. Positioning and shaping optics in space, cryogen valving and pumping, heat switches, industrial processing, and active vibration control are just some examples of the many commercial, military and space applications where cryogenic magnetostrictive technologies are overcoming barriers to provide solutions.
Recent advances in material science have lead to the development of new, very low temperature actuators of Terbium and Dysoprosium with hitherto unavailable stroke, energy efficiency and force. The test instrument described here was developed to investigate the performance characteristics of these new materials and the devices based upon them. The instrument, referred to as a cryogenic dilatometer, is designed for measuring linear displacements, at accuracies of 0.1 micron, in a material, actuator or sensor operating at low temperatures including that of liquid helium. The instrument, just completed, maintains the sample at a known temperature between 4.2 and 77 K, subjects the actuator material to a known and variable magnetic field of up to 1,500 gauss, places a specific and variable preload of 750 N maximum against the actuator or sample, and measures the resulting actuator displacement. A secondary capability is to provide a reference measurement for calibrating commercial capacitance, eddy current, linear variable differential transformers and other displacement gages at low temperatures. The primary linear displacement measurement tool is a fringe counting interferometer. A liquid helium cooled probe provides the sample test environment.
An optical test Dewar has been constructed with the unique capability to test mirrors of diameter <EQ 1 m, f <EQ 6, at temperatures from 300 to 5 K with a ZYGO Mark IV interferometer. The facility possesses extensive thermometry throughout for characterization of the test chamber thermal environment and Dewar performance. Optical accesss is controlled with cryogenically cooled shutters. The entire Dewar is vibration isolated by 40 dB where the fundamental resonances of the Dewar structure are highest. The facility has been brought on line for its first user, the Infrared Telescope Technology Testbed for the Space Infrared Telescope Facility at JPL. The design requirements for this facility and the resultant design and implementation experiences and challenges will be presented.
A two axis optical gimbal mechanism for aligning 1 meter diameter telescope primaries and test flat mirrors at temperatures from 300 to 4.2 K was constructed for use in the SIRTF Telescope Test Facility (STTF). This mechanism consists of an aluminum frame, pivoting on a monoball bearing, and driven in tip and tilt by tungsten di-sulfide lubricated lead screws with external drive motors. Flexures decouple the optical support frame from stresses generated by differential rates of cooling. A second set of flexures decouples the mirror mechanically and thermally from distortion in the gimbal mechanism. The mechanism provides sub arc-second resolution in either axis, while limiting the heat leak to less than 100 mW at 4.2 K. Linear variable differential tranformers are used at temperatures from 300 to 4.2 K to measure a home position. The STTF and gimbal are presently operational, and have been used in two separate interferometric measurements of a 0.5 meter, f 4.0 beryllium spherical mirror at 6 K. The gimbal will be used in the interferometric testing of a beryllium telescope primary mirror from the Infrared Technology Testbed, for the Space Infrared Telescope Facility at JPL.
End-to-end tests of the second generation Wide Field and Planetary Camera for the Hubble Space Telescope were performed with an optical stimulus that accurately simulates the optical configuration of the aberrated Hubble Space Telescope. This paper describes the optical design of the stimulus and the tooling used to control its alignment and validate is performance.
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