We explore the mathematical relationships between generalized functional designs and edge-ray, aplanatic, and
simultaneous multiple surface (SMS) designs. We show that both edge-ray and dual-surface aplanatic designs are special
cases of generalized functional designs. In addition, we show that dual-surface SMS designs are closely related to
generalized functional designs, and that certain computational advantages accrue when the two design methods are
combined. A number of examples are provided.
The evaluation of radiative exchange among quasi-lambertian surfaces has been deemed the domain of raytrace
simulations (quasi-lambertian referring to flux distributions that are uniform spatially but within a numerical aperture
NA less than unity). The familiar view factors for fully-lambertian surfaces are not valid in this domain. Analytic,
physically-transparent solutions are derived for radiation transfer between quasi-lambertian surfaces - solutions that also
obviate the need for case-specific time-intensive simulation methods. A generalized reciprocity relation is shown to
follow in analogy to the reciprocity theorem for fully-lambertian flux exchange. Representative results of flux maps and
flux transfer efficiency for several geometries of practical interest are presented to illustrate the principal features.
It is essential to obtain high values of tolerance for CPV concentrators because manufacturing process always implies
some accuracy errors. This paper presents the Fresnel Köhler concentrator (FK), an advanced optical concentrator
comprising a Fresnel lens as a primary element and a refractive secondary element, both presenting free-form surfaces.
This optic produces both, the desired light concentration and high tolerance (i.e. high acceptance angle), as well as an
excellent light homogenization by Köhler integration simultaneously. A comparison between the FK and other current
conventional Fresnel-based CPV concentrators is also presented, being our concentrator superior to its competitors in
terms of tolerances, irradiance homogeneity and manufacturability.
Optical antennas are critical components in nanophotonics research due to their unparalleled ability to
concentrate electromagnetic energy into nanoscale volumes. Researchers typically construct such antennas
from wavelength-size metallic structures. However, researchers have recently exploited the scattering
resonances of high-permittivity particles to realize all-dielectric optical antennas, emitters, photodetectors,
and metamaterials. Here, we review experimental and theoretical work concerning the resonant modes of
subwavelength rod-shaped dielectric particles and their use as novel light emitters (transmitters) and
photodetectors (receivers). Using a diversity of materials systems, dielectric optical antennas may impact a
variety of photonic technologies throughout the visible and infrared frequency regime.
A nonimaging strategy wherein two mirror contours are tailored for concentration near the étendue limit is explored,
prompted by solar applications where a sizable gap between the optic and absorber is required. Subtle limitations of this
simultaneous multiple surface method approach are derived, rooted in the manner in which phase space boundaries can
be mapped according to the edge-ray principle. The fundamental categories of these optics are identified, only a
minority of which can pragmatically offer maximum concentration at high collection efficiency. Illustrative examples
confirm that acceptance half-angles as large as 30 mrad can be realized at a flux concentration of ~1000.
We have developed a transparent photovoltaic double glazed unit which exhibits three main features - concentrating
direct solar rays on PV cells, allowing a viewer to see through the window a non-distorted image and having good
thermal isolation properties. We describe the structure of the unit, and explain its fundamental optical properties. A
model which simulates seasonal and day/night variations of the optical and thermal behavior of the window as a function
of installation location is presented. The outputs of the model include the PV power generation and the change in the
required power for heating/cooling due to the elimination of direct irradiation into the room. These outputs are used to
optimize the optical design in order to achieve best overall energy saving performance.
At module level (one single solar cell), the Fresnel-Köhler (FK) concentrator comprises a perfect irradiance uniformity
along with quite high concentration-acceptance angle product. At the same time, it maintains the efficiency/simplicity of
other Fresnel-based concentrators. In this work we will show the FK concentrator has loose manufacturing tolerances as
well. All these facts, along with the pill-box shape of its transmission curve, permit an enhanced performance of this
device, compared to its competitors, at array level, because the system is more insensitive to manufacturing errors, and
current mismatch is less likely to occur. Or the same performance can be achieved at a lower cost, exhausting the
tolerance budget by using inexpensive fabrication techniques. Depending on the concentrator, the actual power delivered
by an array might drop significantly with respect to the sum of the power delivered by single modules. Under certain
circumstances, the FK can reach a 1-10% electrical efficiency increase with regards to other concentrators sharing the
Secondary optics are used in concentrating photovoltaic (CPV) systems with Fresnel lens primaries to increase
the optical system efficiency by catching refracted light that otherwise would miss the receiver, better the tracking
tolerance (acceptance half-angle) and enhance the flux uniformity on the cell. Several refractive secondary optics
under the same Fresnel lens primary are designed, analyzed and compared based on their optical performances,
materials, manufacturability, manufacturing tolerancing and cost. The goal of this work is to show the basic two
different design approaches statistical mixing as opposed to deterministic mixing. Caustics are elementary in the
deterministic tailoring approach. We find that statistical mixing offers higher flexibility for the solar application.
It is also shown that there are conventional, i.e. designs based on conic section ("half-egg") that work well as
solar secondaries. It is also made clear that primary and secondary must be designed as optical train.
The XR-Köhler concentrator1 is a design that has the possibility to work under high concentration, maintaining the high
acceptance angle and high irradiance uniformity on the solar cell. It is an on-axis free-form design that consists of a
reflective (X) and refractive (R) surface. For a geometrical concentration of about 800x the simulated results show an
acceptance angle of ±1.79deg with high irradiance uniformity on the solar cell. This article shows the design results of
the XR-Köhler and also a novel passive cooling system (LPI patented) that keeps the solar cell operation temperature
under 100°C at extreme conditions (wind speed = 0 m/s, module tilt angle = 45deg and Ta = 50°C). The results of using
the XR-Köhler device as a collimator when the light source has very high non-uniform luminance distribution, i.e.
multichip LEDs, are also here presented.
We discuss the theoretical limits of concentration for stationary solar concentrators allowed by the law of
thermodynamics. The principles to design systems that approach the theoretical limits are then presented followed by a
few examples, including the first 4x fixed solar concentrator.
This paper presents a novel approach regarding the design of stationary, non imaging, refractive lenses with
high acceptance angles. A lens lies on a stationary aperture and as the sun moves throughout the day, the
concentrated focal spot is tracked by a moving solar cell. The purpose of this work is to replace the 2-axis
tracking of the sun with internal motion of the miniaturized solar cell inside the module. We show families of
linear lenses with wide acceptance angles 60. and 30. achieving moderate concentrations of 10 - 30 suns. The
lens is designed with a variation of the simultaneous multiple surface (SMS) technique which is combined with
a genetic algorithm to optimize the free variables of the problem.
A luminescent solar concentrator (LSC) generally is a sheet of highly transparent materials embedded with luminescent
materials. Incident sunlight is absorbed by the luminescent materials, and then emitted through down conversion process
at longer wavelengths. A large portion of the emitted light is trapped in the sheet and travels to the edges where
photovoltaic solar cells are attached. In this study, we investigate the optical enhancement methods for LSCs with
different sizes mainly by using optical gel and white diffuser. The largest tested LSC is up to 1.2m in length and with
geometrical gain 64. This is, as we know, the largest reported size. It yields electrical gain 3.9 by optical enhancements.
And the optical efficiency is still as large as 10%. The study shows that the enhancement by white diffuser is more
sensitive to the size of the LSCs than that of the optical gel. Such enhancement drops with the increase of the sizes of
LSC, but tends to plateau at certain size.
By adding simple Köhler homogenizers in the form of aspheric lenses generated with an optimization approach, we
solve the problems of non-uniform irradiance distribution and non-square irradiance pattern existing in some image-forming
solar concentrators. The homogenizers do not require optical bonding to the solar cells or total internal
reflection surface. Two examples are shown including a Fresnel lens based concentrator and a two-mirror aplanatic
In our contribution, we discuss an optical system which is able to provide sun-like radiation on a CPV module. This system
is able to realize collimated light with more than 130 klx, with an angle of incidence of less than 0.26°. Special attention
is given to a uniform light distribution on an illuminated area of 8 × 8 inches. The resulting optical efficiency of
the system is 33%, much better than previously achieved with Xe flash lamp designs .
The design is based on a P-VIP 330/1.0 lamp, the latest in a series of OSRAM's P-VIP lamp types for video projectionwhich
is featuring a peak luminance of approximately 9 Gcd/m2. As a result of the enormous operating pressure of
the lamp, its spectrum is similar to the spectrum of the sun and will probably enable at least a class B simulator.
The device based on the described design delivers continuous, sun-like radiation. This way, features of CPV modules as
efficiency, angular sensitivity or tracking behavior can be tested during development or even in production.
A design concept for an extremely compact zoom optics which is suitable for illumination applications is presented.
Such optics is especially useful for camera or flash lights as the illuminated area can be adjusted according to the picture
content of the photo or film camera.
The principle of the design is as follows: Collimated light passes through two lenses, each with a freeform surface. The
freeform surfaces face each other and fit into one another perfectly. When the two lenses are merged together, they
basically represent a coplanar plate: The cone angle entering the merged lenses does not change while passing them.
When the plates are separated, the light is scattered at the freeform surfaces. Due to the smooth characteristics of the
freeform surfaces shape, the cone angle can be adjusted continuously with the distance of the zoom lenses.
The distance of the zoom lenses, which is necessary for maximum angle widening, is dependent on the size of the
structures of the freeform surfaces and can be reduced to the sub-millimeter range. The compactness of the resulting
device is a major advantage of the design concept.
The principle of operation of the design could be shown by the construction of a prototype. It features a LED light source
and a zoom range of 5° to 30° (cone angle). The luminous flux of the device is approx. 650 lm.
High throughput illumination systems are critical component in photolithography, solar simulators, UV
curing, microscopy, and spectral analysis.
A good refractive condenser system has F/# .60, or N.A .80, but it captures only 10 to 15% of energy emitted
by an incandescent or gas-discharge lamp, as these sources emit light in all directions. Systems with
ellipsoidal or parabolic reflectors are much more efficient, they capture up to 80% of total energy emitted by
lamps. However, these reflectors have large aberrations when working with real sources of finite dimensions,
resulting in poor light concentrating capability. These aberrations also increase beam divergence, collimation,
and affect edge definition in flood exposure systems.
The problem is aggravated by the geometry of high power Arc lamps where, for thermal considerations, the
anode has a larger diameter than the cathode and absorbs and obscures part of the energy. This results in an
asymmetrical energy distribution emitted by the lamp and makes efficiency of Lamp - reflector configuration
dependent on orientation of lamp in the reflector.
This paper presents the analysis of different configurations of Lamp - Reflector systems of different
power levels and their energy distribution in the image plane. Configuration, which results in significant
improvement of brightness, is derived.
General lighting applications often require a light patch with a specific shape and distribution. This work presents
examples and details of a practical implementation of Oliker's ellipsoidal faceted reflector algorithm. We present
example designs for various shapes of light patches. Uniformity and limitations of this technique are discussed.
Analytical solution can be used to obtain a starting point for optimization. A technique to generate a smooth best fitting
surface to meet manufacturing requirements is also presented.
A new design of compound Fresnel-R concentrator is presented which is composed of two lenses:
a primary lens (Fresnel lens) that works by total internal reflection at outer facets but refraction
at inner facets, and a secondary lens that works by refraction. In contrast to previous Fresnel lens
concentrator, this design increases the acceptance angle, improves the irradiance uniformity on
the solar cell, and reduces the aspect ratio significantly. Another outstanding advantage of this
concentrator is the fact that it mainly works by performing total internal reflection, reducing
chromatic dependence as well as Fresnel losses. An optical efficiency more than 80% can be
achieved. Moreover, in order to reduce the influence of manufacture accuracy and to increase the
optical efficiency further, the central part of the bottom of the secondary lens which directly
adhered to the solar cell is designed as a cone-shaped prism to collect the sunlight that doesn't
reach the solar cell.