This paper reports on advances in optical coherence tomography (OCT) for application in dermatology. Full-field OCT is a particular approach of OCT based on white-light interference microscopy. FF-OCT produces en face tomographic images by arithmetic combination of interferometric images acquired with an area camera and by illuminating the whole field of view with low-coherence light. The major interest of FF-OCT lies in its high imaging spatial resolution (∼ 1.0 μm) in both lateral and axial directions, using a simple and robust experimental arrangement. Line-field OCT (LFOCT) is a recent evolution of FF-OCT with line illumination and line detection using a broadband spatially coherent light source and a line-scan camera in an interference microscope. LF-OCT and FF-OCT are similar in terms of spatial resolution. LF-OCT has a significant advantage over FF-OCT in terms of imaging penetration depth due to the confocal gate achieved by line illumination and detection. B-scan imaging using FF-OCT requires the acquisition of a stack of en face images, which usually prevents in vivo applications. B-scan imaging using LF-OCT can be considerably faster due to the possibility of using a spatially coherent light source with much higher brightness along with a high-speed line camera. Applied in the field of dermatology, the LF-OCT images reveal a comprehensive morphological mapping of skin tissues in vivo at a cellular level similar to histological images.
Fresnel lens solar concentrators continue to fulfill a market requirement as a system component in high volume cost
effective Concentrating Photovoltaic (CPV) electricity generation. Design and optimization may be performed
using comprehensive system simulation tools, but before investing in the effort to build a complete virtual
model framework, much insight can be gathered beforehand by generating a parameterized simulation cache and
referencing those results.
To investigate the performance space of the Fresnel lens, a fast simulation method which is a hybrid between
raytracing and analytical computation is employed to generate a cache of simulation data. This data is postprocessed
to yield results that are not readily achieved via derivation. Example plots that can be used for look-up
purposes will be included.
Lens parameters that will be interrogated include focal length, index of refraction, prism fidelity, aperture,
transmission and concentration ratio. In order to compactly represent a large variety of lens configurations, some
variables that define the Fresnel lens will be parameterized.
Analysis will be limited to Fresnel lens prisms oriented toward the photovoltaic (PV) cell and the plano
surface directed toward the sun. The reverse of this configuration is rarely encountered in solar concentration
applications and is omitted.
In consideration of the broad range of possible Fresnel lens applications, it is desirable to find a fast way of
approximating optical performance that is not specific to a particular lens geometry. This is potentially useful
for gaining deeper insight into a lens system and affording accelerated development times.
Additionally, a Fresnel lens manufactured using a molded polymer process has limitations on how accurately
it can replicate a microstructured prismatic pattern. This is especially true at the prismatic peaks of the part
where it is more difficult to completely "fill-out" the moldbase. Inclusion of this effect in performance evaluation
is important.
Using transmission efficiency (or transmittance) as the metric, a Fresnel lens model which includes imperfect
peak replication is sought. The system description will be parameterized so that the formulations are not specific
to a particular geometry and can be generally applied. The parameter space will be explored with raytracing
and the results compiled for convenient reference.
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