Tailoring allows designing a freeform optical surface which precisely produces a desired irradiance distribution on a
desired target from a known small source by solving a partial differential equation. Existence and uniqueness of the
solution depends on the boundary conditions. We present two alternative types of boundary conditions which ensure a
unique exact solution. We have implemented and tested these boundary conditions in our freeform tailored optics
Field method, also called geometrical vector flux field method, is a well established technique to design concentrators
and in general nonimaging optical systems. The method is based on building reflective concentrators with the geometry
of field lines, these concentrators do not disturb the flux field and become ideal. In this paper we study the properties of
surfaces orthogonal to the field vector J. For rotational symmetric systems J is orthogonal to its curl, then exist a family
of surfaces orthogonal to the lines of J, surfaces of constant pseudopotential. From the definition of J, pseudopotential
surfaces can be interpreted as surfaces of maximum flux density and can play an important role in the design of
nonimaging systems. We study refractive concentrators with the geometry of pseudopotential surfaces. Dielectric
material modifies the field lines and then the geometry of the system, including compactness and reflective parts, it also
introduce total internal reflection which must be considered in the design. We apply this concept to study hyperbolic
concentrator modified with pseudopotential refractive optics and we shown that it achieves the theoretical limit of concentration.
We present a new strategy to calculate an optimized refractive freeform surface for illumination purposes with a LED source. The goal of this paper is to present a new iterative flux based strategy to design plastic lens for LED lighting solutions. The new strategy considers the energy emission pattern of the LED and adjusts a plastic refractive surface to accomplish the target intensity distribution. This paper is divided in four parts, a brief introduction to LED systems and reviewing optical design strategies, the method of calculus is exposed in the second part, third part presents the results for a particular refractive optical design developed by new presented algorithm and finally, a set of conclusions about strategy is showed in fourth part.
Manufacturing technologies as injection molding or embossing specify their production limits for minimum radii of the
vertices or draft angle for demolding, for instance. In some demanding nonimaging applications, these restrictions may
limit the system optical efficiency or affect the generation of undesired artifacts on the illumination pattern. A novel
manufacturing concept is presented here, in which the optical surfaces are not obtained from the usual revolution
symmetry with respect to a central axis (z axis), but they are calculated as free-form surfaces describing a spiral
trajectory around z axis. The main advantage of this new concept lies in the manufacturing process: a molded piece can
be easily separated from its mold just by applying a combination of rotational movement around axis z and linear movement along axis z, even for negative draft angles. Some of these spiral symmetry examples will be shown here, as well as their simulated results.
Free form surfaces allow elegant solutions in illumination optics. A complex function of the system can be achieved by a single optical element. Free form elements are usually manufactured by reproduction techniques, such as injection moulding of plastic. Manufacturing tolerances are crucial to maintain the required function while at the same time yielding the lowest possible price. We implemented a Monte Carlo tolerancing method for illumination systems. Tolerances include shape deviations of optical elements and assembly tolerances. In the absence of standards for free form tolerances and illumination optics tolerancing, communication between optics design, manufacturing and testing is often inefficient. In order to enable a highly automated evaluation of part measurement data to assess compliance with tolerances, we developed an approach to combine information from optics design, mechanical construction, manufacturing and testing into one continuous data chain. The research project is granted by the German Ministry of Education and Research.
Light emitting diodes are routinely used for general and specialized lighting tasks such as automotive headlights,
streetlights, luminaires, and medical illuminators. Because of their small size and directionality, LEDs enable unique
light collection and shaping techniques. This paper reviews strategies that can be used to shape light according to a
desired target distribution given target uniformity and system compactness constraints imposed by each application. We
address design techniques for LED secondary optics, including TIR lenses, freeform reflectors, and lens and mirror
Recent years have seen a surge in LED-based automotive headlamps including a variety of lighting functions like lowbeam,
high-beam, day-time running light as well as fog-light. Many of those lighting functions have been realized by
designs that statically provide specific illumination patterns. In contrast, existing adaptive designs rely on either moving
shutters or electronically-complex matrix sources.
In this paper, alternative options will be explored for an automotive headlamp that combines low-beam and high-beam
out of a single LED.
The light source comprises two rows of chips arranged on a common carrier resulting in a compact LED. At the same
time, electronic complexity is reduced by driving just the two rows independently.
Primary optics collects the emission of the two closely-spaced chip rows and simultaneously provides a way to separate
respective contributions. The subsequent secondary optics is based on facetted reflector shapes to realize low-beam and
Efficiency, tolerances, system size, and cross talk will be evaluated for different primary optics based on refraction,
reflection as well as TIR.
The evolution of lighting devices based on light-emitting diodes (LEDs) leads to increase of energy efficiency of such
devices and, as a partial case, increase of light efficiency of LED optics. The conventional LED optics with the only freeform
refractive surface cannot provide high light efficiency for street- and road-illumination applications. The reason is
the performance limitations of the refractive surface in terms of ray rotation. Exploiting the total internal reflection
effect, we devised a novel design of LED optics allowing to reach the value of light efficiency up to 80%-90%. This
paper details the work principle of our LED optics design and the methods of its surfaces computation. The simulation
results show that the proposed LED secondary optics design provides light efficiency by 15.5% more than the
conventional LED optics in the case of uniformly illuminated region with size of 40 meters by 8 meters. The usage of the
proposed novel LED optics design makes possible to reduce the number of LED chips that are used in modern road
lamps and, as a consequence, to reduce the power consumption of road lamps. Still, such optical elements have to be
made and tested with real LED sources.
This paper propose an optical design of adaptive automotive headlight system with advanced light-emitting diodes
(LEDs) and digital micro-mirror device (DMD). In recent days, safety of on-road drive plays the role at automotive
industries so that fast response of adaptive automotive headlight system becomes a critical issue especially in mountain
road drive. In order to integrate the function of low and high beam into a single headlight without sacrifice of volumetric
size of whole system, a DMD is employed in this optical design. Simulation shows that new optical design not only
promotes light efficiency but also reduce volumetric size. Besides, light from adaptive automotive headlight system
could make the projected light much suitable for drivers according to individual driver's vision experience. Results show
that volumetric size of all system might be reduced up to 30 percent but light efficiency could be promoted up to 20 percent.
Many laser applications, for example material processing or fluorescence imaging, require intense and uniform
illumination over a rectangular, slit shaped area with extreme aspect ratio: The short dimension of the illumination field
typically requires diffraction limited imaging, respectively focusing, on a micrometer scale. In contrast the extension in
the long dimension can be hundreds of millimeters. This class of systems requires a highly anamorphic system design for
the homogenization as well as for the projection of the illumination pattern. Aberrations within the projection optical
system, as for example induced by cylindrical optical components, need to be analyzed and controlled. In some cases the
application additionally requires the substrate to be illuminated under some tilted angle, which requires specific solutions
within the optical design. We will illustrate corresponding design examples and solutions for this class of illumination systems.
For very long-range flash active imaging applications, a powerful and narrow beam divergence pulsed laser illuminator is
needed. Conventional high fill factor 1-centimeter diode bars are not well suited to produce a homogeneous and narrow
beam divergence in an easy way. In the present paper, a concept based on a QCW mini-bars laser diode stack, focusing
lenses and beam homogenisation is presented. With fifteen 1.5 mm conductively cooled fast axis collimated mini-bars, a
peak power of 803 Watt at a wavelength of 810 nm is achieved with a maximum duty cycle of 2 percent. After
collimation, the laser beam on the scene shows very homogeneous rectangular illumination geometry with a ratio of 4:3
well adapted for active imaging purposes. The beam divergence is reduced to 3.35 × 2.53 mrd with a two lenses objective
of focal length f = 573 mm and f-number f# = 4.8.
Speckle degrades the contrast of the fringe patterns in laser interferometers that measure rough objects. In this paper, we
describe a speckle reduction system that can be used with high speed cameras to increase the frame rates of the interferometer and creates less vibration in the system.
Mask Aligners are used in the Semiconductor Industry to transfer structures with moderate resolution requirements onto
substrates. With the casting of the shadow a photochemical reactive resist is exposed. As diffraction appears at the mask
structures the exposure wavelength and the proximity gap between mask and wafer influence the quality of the image in
the resist. As both parameters are very often not changeable for processes there is a big need to find another way to
improve the resist image. In this paper a new approach to enhance the exposure result will be presented. MO Exposure
Optics, a novel illumination system for Mask Aligners, uses a combination of two microlens Köhler Integrators. MO
Exposure Optics decouples the illumination system in a Mask Aligner from the lamp and ensures a uniform angular
spectrum over the whole mask plane. Spatial filtering of the illumination light allows to reduce the diffraction effects at
the mask structures and to improve the lithographic process in a Mask Aligner.
Throughout present study will be discusses the influence of the manufacturing margins, adjustment precision and ray model accuracy of a collimating LED unit in the overall system performance. It will be also analyzed the angular performance and the collimated in relation to the relative position of the LED and the collimator's dimensions. Finally the results will be compared with existing publications in this field.
A metal-less RXI collimator has been designed using the Simultaneous multiple surface method (SMS). The collimator
is completely made of plastic (PMMA) and does not include any mirrored surface, unlike to the convectional RXI
collimators, whose back surface is metalized to provide a specular reflection. The back surface of the V-groove RXI is
designed as a grooved surface providing two TIR reflections for all rays impinging on it. The main advantage of the
presented design is lower manufacturing cost since there is no need for the expensive process of metalization. Also,
unlike to the conventional RXI collimators this design performs good colour mixing. The experimental measurements of
the first prototype are presented.
LEDs emit light over a broad range of angles. Additionally, a narrow collimation of LED light is difficult because of the
broad emission area of the LED. In order to implement an efficient beam shaping with small optics we propose to use a
glass lens design with a refractive index (nd) greater than 1.7. Our design is characterized by a very small size and a high
efficiency. This enables us to design optical arrays with an extremely high packing density of LEDs. Additional
advantages are the high temperature resistance, the climate resistance and the stability against solarization.
For many applications the footprint of the light beam should not only be collimated but also formed into a specific shape.
Design results for a rectangular or oval beam shaping using high refractive index glass are presented. The designs
collimate the broad emitted LED light and are optimized to incorporate also the manufacturability of the lens. Our
proposed lens designs can easily be manufactured by modern pressing techniques, thus, these solutions are suitable for
A new approach is described to couple light from high-power blue LEDs (1x1mm2) into a thin large area light guide
using a dielectric interference multilayer as an angular filter. The goal is to achieve large area luminaires such as
backlight systems. The method overcomes the drawback of structuring holes or recessions in light guides when using a
system with side-emitting LEDs. Several new LED-masking filters have been designed to improve the polarization
dependency and coupling efficiency from a previous design that used a stack of inorganic bi-layers. Firstly, a polymeric
multilayer manages to increase the coupling efficiency from 52% to 69%. Secondly, a birefringent multilayer filter
enables to fully suppress the Brewster's angle effect and to realize identical behaviour for both s- and p- polarized light
at large angles. Thirdly, by adding layers of a third inorganic material to the original bi-layer stack with refractive index
in between the other two, the transmittance equality is improved and the coupling efficiency can reach up to 63%.
A novel angular filter is proposed for a large area planar collimating luminaire. A planar collimator of 2x18o cone angle
with scalable and simplified structure is demonstrated. It has a thickness of only 5mm. Compact collimators and planar
collimators have been analyzed with the ray tracing software LightTools. Measurements on this collimator filter and
optical designs match well with the predicted performance.
A new approach to thin film filter design, the so called saddle-point method of global optimization was explored and
showed promising initial results. A 40-layer collimator filter with a 30% lower merit function was obtained and is
Within the framework of a project conducted together with an industrial partner, a self-disinfecting operation interface
with a glass panel is being developed. The concept of self-disinfection is based on the exploitation of the photocatalytical
effect induced by a TiO2-coating on the glass surface under UV(A) light, which would make the touch screen
antimicrobial. High-power UV-LEDs instead of conventional UV-lamps have been employed as light source.
The main goal and challenge of the optical design is to generate an efficient and preferably homogeneous UV field on
the TiO2-coated side while keeping the UV-LEDs concealed, i.e. invisible to the user. Therefore common backlighting
systems have been used as reference and modified to meet the concrete requirements. Primary analysis and optical
simulations have been performed with the software LightTools®. Several patterns for light redirection (i.e. 3D-spherical
texture, 3D-rectangular texture and 2D-circular serigraph) have been investigated, compared and evaluated. Finally the
pattern design which both fulfills all the predefined boundary conditions and simultaneously reduces the costs has been
This research proposes the concept of Light Guide Film (LGF) at the back side of Back Light Unit (BLU). This new design may induce the exterior light, and then improve the power-saving of existent BLU. Two design models are reseated: One is design for 14 inch LCD monitor of notebook computer, which might improve 21% compared to traditional one. Another is designed for 3.5 inch LCD for mobile phone display, which might improve 15% compared to traditional one.
The Bidirectional scattering distribution function (BSDF) is used to describe the multidimensional aspect of light
scattering properties of a surface. Often, the BSDF is broken into the two parts: the bidirectional reflectance distribution
function (BRDF), and the bidirectional transmittance distribution function (BTDF). In this paper, we investigate the onaxis
BTDF at a dielectric surface (i.e., a surface where the index of refraction is different on the two sides of the surface)
and show how it relates to the off-axis BRDF and BTDF of textured surfaces that are commonly used in illumination modeling and design. Numerous interesting Monte Carlo simulation results are provided.
On the general lighting market of LED lamps for professional applications there are still mainly products for single
purpose solutions existing. There is a lack of standardised lamp systems like they are common for conventional lighting
Therefore, an LED lamp family system was studied using high power LED with the objective to entirely substitute
standard conventional lamp families in general lighting applications in the professional market segment. This comprises
the realization of sets of lamp types with compact and linear shapes as well as with light distribution characteristics
ranging from diffuse to extreme collimation and exceptionally high candle power.
Innovative secondary optics concepts are discussed which allow both, the design of lamps with non-bulky shape and to
obtain sufficient colour mixing when using multicolour LED combinations in order to achieve a very high colour
For the purpose of optical simulation, a plethora of formats exist to describe the properties of a light source.
Except for the EULUMDAT and IES formats which describe sources in terms of aperture area and far field
intensity, all these formats are vendor specific, and no generally accepted standard exists. Most illumination
simulation software vendors use their own format for ray sets, which describe sources in terms of many rays.
Some of them keep their format definition proprietary. Thus, software packages typically can read or write only
their own specific format, although the actual data content is not so different. Typically, they describe origin
and direction of each ray in 3D vectors, and use one more single number for magnitude, where magnitude may
denote radiant flux, luminous flux (equivalently tristimulus Y), or tristimulus X and Z. Sometimes each ray also
carries its wavelength, while other formats allow to specify an overall spectrum for the whole source. In addition,
in at least one format, polarization properties are also included for each ray. This situation makes it inefficient
and potentially error prone for light source manufacturers to provide ray data sets for their sources in many
different formats. Furthermore, near field goniometer vendors again use their proprietary formats to store the
source description in terms of luminance data, and offer their proprietary software to generate ray sets from this
data base. Again, the plethora of ray sets make the ray set production inefficient and potentially error prone. In
this paper, we propose to describe ray data sets in terms of phase space, as a step towards a standardized ray set
format. It is well known that luminance and radiance can be defined as flux density in phase space: luminance
is flux divided by etendue. Therefore, single rays can be thought of as center points of phase space cells, where each cell possesses its volume (i.e. etendue), its flux, and therefore its luminance. In addition, each phase space cell possesses its spectrum, and its polarization properties. We show how this approach leads to a unification of the EULUMDAT/IES, ray set and near field goniometer formats, making possible the generation of arbitrarily many additional rays by luminance interpolation. We also show how the EULUMDAT/IES and individual ray set formats can be derived from the proposed general format, making software using a possible standard format downward compatible.
Dark-field defect inspection is an essential quality control method for the semiconductor fabrication industry, and it is broadly applied for micro particles detection in almost every fabrication process. Diode laser based dark-field illumination systems (LDFs) play a critical role in such illumination schemes due to its unique optical/mechanical properties. This paper discusses a complete LDF system model, includes the mathematical and optical descriptions of LDF system fundamentals. A series of trade-off curves are developed in this model, which describe system performance under different constraints. This model can either efficiently facilitate system design work for generic/unique applications, or can be used to evaluate existing LDF system performance.
In addition to the design of an optical system with high efficiency, one goal may be to reach homogeneity in illuminance
and color distribution. There is a strong need of optical systems for color mixing due to the increasing use of sources of
different color to reach good color rendering.
The use and functionality of micro lens arrays (also known as fly's eye condensers), diffuser materials and setups based
on multiple reflections are presented.
In this article, we introduce the quasi-Monte Carlo (QMC) method that applies a low-discrepancy sequence (LDS) for
the evaluation of illumination optical systems. LDS is used in sequence-generation methods for numerical calculation,
with high-order integration, and a characteristic of the QMC method that adopts a LDS is that it can deliver faster
convergence than the Monte Carlo (MC) method, which uses random numbers. In this study, we have applied a LDS to
the evaluation of illumination optical systems, which are conventionally evaluated by using the MC method, and verified
its effectiveness. By assuming the evaluated system to have a gradient-index (GRIN) lens and comparing its illuminance
distribution with the theoretical illuminance distribution, we confirmed that by using the QMC method, the evaluation
process could be sped up by approximately five times compared to the MC method at the equivalent precision level.
Furthermore, we established a method to reconstruct the image by using the QMC method that applies a LDS to evaluate
the image-forming characteristics of the lens system and compared its results with those of the conventional MC method.
It was found that the QMC method that applies a LDS was superior to the MC method even in this case, in both precision
and conversion speed. On the basis of these results, it is evident that the QMC method that applies a LDS is extremely
useful in the evaluation of illumination optical systems.
Recent advances in LED technology have relegated the use of optical fibre for general lighting, but there are
several applications where it can be used as scanners lighting systems, daylight, cultural heritage lighting,
sensors, explosion risky spaces, etc. Nowadays the use of high intensity LED to inject light in optical fibre
increases the possibility of conjugate fibre + LED for lighting applications. New optical fibres of plastic
materials, high core diameter up to 12.6 mm transmit light with little attenuation in the visible spectrum but there
is no an efficient and controlled way to extract the light during the fibre path. Side extracting fibres extracts all
the light on 2π angle so is not well suited for controlled lighting. In this paper we present an extraction system for
mono-filament optical fibre which provides efficient and controlled light distribution. These lighting parameters
can be controlled with an algorithm that set the position, depth and shape of the optical extraction system. The extraction system works by total internal reflection in the core of the fibre with high efficiency and low cost. A 10 m length prototype is made with 45° sectional cuts in the fibre core as extraction system. The system is tested with a 1W white LED illuminator in one side.
The use of high reflectance aluminum lighting guides is most frequently used material for actual natural lighting systems.
Spectral Reflectance over the entire length of a light guide changes the color of the output light at the end of the guide.
When light guides are made of a prismatic film, the influence of the reflectance is minimizing and absortance is not
important when the sheets are thin. Color Rendering index and color temperature will be important parameters in order to
evaluate Lighting quality and therefore in Museums, office buildings and production centers to get the normative
approval. In this paper a theoretical simulation and 3D ray tracing for aluminum and prismatic light guides of different
shapes (rectangular and cylindrical) and lengths over the entire visible spectrum are studied. Output light color
temperature related to several illuminants and CRI are evaluated for the simulated aluminum and prismatic light guides.
Thus, prismatic light guides seem more robust in lighting quality maintenance regardless of conditionals like angle
acceptance for TIR guiding, aluminum guides are efficient and maintain light quality only for short distances.
Original construction is proposed to collimate light into a narrow beam. The solution is very compact and provides high efficiency. Two elements are used. Freeform reflector and a plate of PMMA with a special pyramid structure on the first surface. LED source is mounted in a plastic plate and emits light into opposite direction. After reflection from freeform reflector light beam suffers TIR in plastic plate and is collimated with a very high efficiency into desired direction. Thickness of proposed design is about 5 mm. Efficiency and divergence depends on the size of emitting area and diode's package size. For diode with a size of emitting area of 2 mm and a package size of 6 mm last ones were 88% and 7 degree.