2,162 research outputs found
Double freeform illumination design for prescribed wavefronts and irradiances
A mathematical model in terms of partial differential equations (PDE) for the
calculation of double freeform surfaces for irradiance and phase control with
predefined input and output wavefronts is presented. It extends the results of
B\"osel and Gross [J. Opt. Soc. Am. A 34, 1490 (2017)] for the illumination
design of single freeform surfaces for zero-\'etendue light sources to double
freeform lenses and mirrors. The PDE model thereby overcomes the restriction to
paraxiality or the requirement of at least one planar wavefront of the current
design models in the literature. In contrast with the single freeform
illumination design, the PDE system does not reduce to a Monge-Amp\`ere type
equation for the unknown freeform surfaces, if nonplanar input and output
wavefronts are assumed. Additionally, a numerical solving strategy for the PDE
model is presented. To show its efficiency, the algorithm is applied to the
design of a double freeform mirror system and double freeform lens system.Comment: Copyright 2018 Optical Society of America. One print or electronic
copy may be made for personal use only. Systematic reproduction and
distribution, duplication of any material in this paper for a fee or for
commercial purposes, or modifications of the content of this paper are
prohibite
Systematic investigation of methods for multiple freeform optimization in multi-lens imaging systems
With the development in freeform technology, it has now become more and more
feasible to use freeform surfaces in real system designs. While the freeform
surfaces helping optical designers achieve more and more challenging system
features, the methods for multiple freeform implementations are still
underdeveloped. We therefore investigate strategies to use freeform surfaces
properly in imaging optical systems with one Scheimpflug system and one
lithographic system. Based on the studies of the influences of the freeform
normalization radius, freeform order and system eccentricity, the methods of
determining the optimal location for implementing one freeform surface are
discussed. Different optimization strategies to optimize two freeform surfaces
are discussed to compare their resulting influences on the system performance.
On top of that, ways to implement more than one freeform surface in the optical
system is also investigated. In the end, a workflow is presented as guidance
for implementing multiple freeform surfaces with respect to system aberration
constitutions
Single freeform surface design for prescribed input wavefront and target irradiance
In beam shaping applications, the minimization of the number of necessary
optical elements for the beam shaping process can benefit the compactness of
the optical system and reduce its cost. The single freeform surface design for
input wavefronts, which are neither planar nor spherical, is therefore of
interest. In this work, the design of single freeform surfaces for a given
zero-\'etendue source and complex target irradiances is investigated. Hence,
not only collimated input beams or point sources are assumed. Instead, a
predefined input ray direction vector field and irradiance distribution on a
source plane, which has to be redistributed by a single freeform surface to
give the predefined target irradiance, is considered. To solve this design
problem, a partial differential equation (PDE) or PDE system, respectively, for
the unknown surface and its corresponding ray mapping is derived from energy
conservation and the ray-tracing equations. In contrast to former PDE
formulations of the single freeform design problem, the derived PDE of
Monge-Amp\`ere type is formulated for general zero-\'etendue sources in
cartesian coordinates. The PDE system is discretized with finite differences
and the resulting nonlinear equation system solved by a root-finding algorithm.
The basis of the efficient solution of the PDE system builds the introduction
of an initial iterate constuction approach for a given input direction vector
field, which uses optimal mass transport with a quadratic cost function. After
a detailed description of the numerical algorithm, the efficiency of the design
method is demonstrated by applying it to several design examples. This includes
the redistribution of a collimated input beam beyond the paraxial
approximation, the shaping of point source radiation and the shaping of an
astigmatic input wavefront into a complex target irradiance distribution.Comment: 11 pages, 10 figures version 2: Equation (7) was corrected;
additional minor changes/improvement
Tolerancing of centering of a reflective dual field-of-view optical system based on Alvarez-Principle
A new dual state reflective optical relay system based on the Alvarez principle is proposed, which can be used for remote sensing applications. Using the solution found, two different object fields can be imaged using the same optical system. A Three-Mirror-Anastigmat telescope (TMA) is proposed with an intermediate image plane that incorporates a double reflective freeform subsystem as a relay system. By mechanically moving two freeform mirror substrates, this subsystem allows for a discrete change in the total focal length. A deep understanding of the effects of geometric deviations on the system is a crucial prerequisite for ensuring mechanical feasibility and stable optical imaging performance. For this reason, this article focuses on the method and results of tolerancing the subsystem
Dynamically Triangulated Ising Spins in Flat Space
A model describing Ising spins with short range interactions moving randomly
in a plane is considered. In the presence of a hard core repulsion, which
prevents the Ising spins from overlapping, the model is analogous to a
dynamically triangulated Ising model with spins constrained to move on a flat
surface. It is found that as a function of coupling strength and hard core
repulsion the model exhibits multicritical behavior, with first and second
order transition lines terminating at a tricritical point. The thermal and
magnetic exponents computed at the tricritical point are consistent with the
exact two-matrix model solution of the random Ising model, introduced
previously to describe the effects of fluctuating geometries.Comment: (10 pages + 4 figures), CERN-Th-7577/9
Kaon and Antikaon Production in Heavy Ion Collisions at 1.5 AGeV
At the Kaon Spectrometer KaoS at SIS, GSI the production of kaons and
antikaons in heavy ion reactions at a beam energy of 1.5 AGeV has been measured
for the collision systems Ni+Ni and Au+Au. The K-/K+ ratio is found to be
constant for both systems and as a function of impact parameter but the slopes
of K+ and K- spectra differ for all impact parameters. Furthermore the
respective polar angle distributions will be presented as a function of
centrality.Comment: 4 pages, 4 figures, SQM2001 in Frankfurt, Sept.2001, submitted to
Journal of Physics
Radiation enhancement and "temperature" in the collapse regime of gravitational scattering
We generalize the semiclassical treatment of graviton radiation to
gravitational scattering at very large energies and finite
scattering angles , so as to approach the collapse regime of impact
parameters . Our basic tool is the
extension of the recently proposed, unified form of radiation to the ACV
reduced-action model and to its resummed-eikonal exchange. By superimposing
that radiation all-over eikonal scattering, we are able to derive the
corresponding (unitary) coherent-state operator. The resulting graviton
spectrum, tuned on the gravitational radius , fully agrees with previous
calculations for small angles but, for sizeable angles
acquires an exponential cutoff of the large
region, due to energy conservation, so as to emit a finite fraction
of the total energy. In the approach-to-collapse regime of we find
a radiation enhancement due to large tidal forces, so that the whole energy is
radiated off, with a large multiplicity and a
well-defined frequency cutoff of order .
The latter corresponds to the Hawking temperature for a black hole of mass
notably smaller than .Comment: 5 pages, 2 figures, talk presented at the European Physical Society
Conference on High Energy Physics, 5-12 July, Venice, Ital
results of a mixed methods pilot study
Background ‘Kneipp Therapy’ (KT) is a form of Complementary and Alternative
Medicine (CAM) that includes a combination of hydrotherapy, herbal medicine,
mind-body medicine, physical activities, and healthy eating. Since 2007, some
nursing homes for older adults in Germany began to integrate CAM in the form
of KT in care. The study investigated how KT is used in daily routine care and
explored the health status of residents and caregivers involved in KT. Methods
We performed a cross-sectional pilot study with a mixed methods approach that
collected both quantitative and qualitative data in four German nursing homes
in 2011. Assessments in the quantitative component included the Quality of
Life in Dementia (QUALIDEM), the Short Form 12 Health Survey (SF-12), the
Barthel-Index for residents and the Work Ability Index (WAI) and SF-12 for
caregivers. The qualitative component addressed the residents’ and caregivers’
subjectively experienced changes after integration of KT. It was
conceptualized as an ethnographic rapid appraisal by conducting participant
observation and semi-structured interviews in two of the four nursing homes.
Results The quantitative component included 64 residents (53 female, 83.2 ±
8.1 years (mean and SD)) and 29 caregivers (all female, 42.0 ± 11.7 years).
Residents were multimorbid (8 ± 3 diagnoses), and activities of daily living
were restricted (Barthel-Index 60.6 ± 24.4). The caregivers’ results indicated
good work ability (WAI 37.4 ± 5.1), health related quality of life was
superior to the German sample (SF-12 physical CSS 49.2 ± 8.0; mental CSS 54.1
± 6.6). Among both caregivers and residents, 89% considered KT to be positive
for well-being. The qualitative analysis showed that caregivers perceived
emotional and functional benefits from more content and calmer residents, a
larger variety in basic care practices, and a more self-determined scope of
action. Residents reported gains in attention and caring, and recognition of
their lay knowledge. Conclusion Residents showed typical characteristics of
nursing home inhabitants. Caregivers demonstrated good work ability. Both
reported to have benefits from KT. The results provide a good basis for future
projects, e.g. controlled studies to evaluate the effects of CAM in nursing
homes
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