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.
Nodal Aberration Theory (NAT) was discovered in 1977 and was last presented at this conference 25 years ago. This
paper presents recent discoveries and why this theory is gaining in relevance for the future.
We simulate the predicted Gouy phase anomaly near astigmatic foci of Gaussian beams using a beam
propagation algorithm integrated with lens design software and compare computational results with experimental
Airy beams are a new class of nondiffracting beams predicted in 1979 and observed in 2007. In this paper, we show that
beam propagation methods are an effective way to study the behavior of those beams in propagation and to design such
beams. A lens design software integrated beam propagation feature is implemented to design an Airy beam generation
setup based on Fourier transform in a coherent optical system. The setup was reproduced in the lab for experimental
validation using a "cubic-shaped" mirror. The resulting monochromatic Airy beam presents a main lobe FWHM of
approximately 30 μm over a diffraction-free distance of 15 mm. Computational results show excellent agreement with
experimental data as well as with analytical predictions expressed in terms of the optical setup geometrical parameters.
The alignment of three mirror anastigmatic (TMA) telescopes has been studied since their invention in the 60s.
Recently, Thompson et al.<sup>1</sup> reported that other than the conventional uniform coma over the field caused by
misalignment, TMA telescopes display only one other misalignment induced aberration, field-asymmetric, field-linear
astigmatism. Currently, an instrument with three TMAs is under development as the primary spectrometer on the James
Webb Space Telescope. This paper will report on the application of Nodal Aberration Theory (NAT) to understanding
the optical design of an optical system with multiple TMAs as a first step towards investigating and potentially
independently analyzing the sensitivities to alignment of this key instrument.
There is a long list of new ground-based optical telescopes being considered around the world. While many
are conventional Cassegrain and Ritchey-Chretien designs, some are from a family of three mirror
anastigmatic (TMA) telescopes that are configured with an offset field (but still obscured) that trace back to
designs developed in the 1970s for military applications. The nodal theory of aberrations, developed in the
late 1970s, provides valuable insights into the response of TMA telescopes to alignment errors. Here it is
shown for the first time that the alignment limiting aberration in any TMA telescope is a 3rd order astigmatism
term with a new field dependence, termed field-asymmetric, field-linear 3rd order astigmatism. It is also
shown that a TMA telescope under assembly that is only measured to have excellent/perfect performance onaxis
is not aligned in any significant way. This is because the new astigmatic term is always zero on-axis,
even though it is large over the field of view. Knowledge of this intrinsic misalignment aberration field for
any TMA telescope aids greatly in ensuring it can be aligned successfully. The James Webb Space Telescope
(JWST), is used an example of a relevant TMA system.
The effects of alignment perturbations on the aberration fields of two mirror astronomical telescopes are discussed. It is
demonstrated that expressions describing alignment induced field-linear astigmatism, published by McLeod based on the
work of Schroeder, can be obtained using nodal aberration theory. Rather than merely providing a different derivation
for alignment induced astigmatism, it is shown that nodal theory can provide several insights that are significant for the
development of effective alignment techniques. In the example of a specific telescope sited on Mt. Hopkins (Ritchey-
Chretien), two approaches to identify misalignments of the secondary mirror are demonstrated. One approach utilizes the
eccentricity of defocused star images and their orientation angles to calculate the misalignment of the secondary mirror
after axial coma is removed. A second approach based on the location of the two zeros of the astigmatic aberration field
is then shown to give equivalent results, but at the same time ensuring a complete model of all possible effects of
misalignment on the performance of the telescope.
In this work we present the status of our high repetition-rate/high power EUV source facility. The masslimited
target concept has demonstrated high conversion efficiencies (CE) previously, with precision solid
state lasers. Currently, experiments are in progress with high power high repetition-rate (3-4 kHz) Qswitched
laser modules. We present a new dedicated facility for the high power EUV source. Also, we
present a precision EUV energy-meter, which is developed for absolute EUV energy measurements.
Spectral measurements of the tin-doped droplet laser plasma are performed with a flat-field spectrometer
(FFS) with a back-illuminated CCD camera. We address the issue of maintaining the calibration of the
EUV optics during source operation at non-optimum intensity at high repetition-rate, which is required for
CE improvement studies. Here we present the unique metrology for measuring EUV energies under a
variety of irradiation conditions without degrading EUV optics, even at high repetition rates (multi-kHz).
Tin-doped droplet target has been integrated with several lasers including high power high repetition rate lasers
and demonstrated high conversion efficiencies for all the lasers. This implies the EUV source power is linearly
increasing as the laser frequency goes higher. The target exhibit very low out-of-band radiation and debris emission.
The drawback of increasing the repetition rate of the target and the laser will be limited. The total amount
of tin consumed for a EUVL source system is also small enough to be operated for a long term without large effort
for recycling of the target materials. We address and demonstrate in this paper the primary issues associated
with long-term high power EUV sources for high volume manufacturing (HVM) using tin-doped droplet target.
Tin is one of the most efficient source materials for both gas discharge plasma sources and laser produced plasma
sources for EUV lithography. Unlike Xenon which was the material commonly investigated for the EUVL source
application, recycling of the target materials is not necessary for tin targets because of its low relative cost.
However, in assessing the benefits of different source architectures, there are large differences in the size of the
tin inventory used, and consequences that ensue. In this paper we make a first attempt to compare these differences,
and assess their impact. Utilizing tin as the radiator at 13.5 nm reduces the total cost of the source system significantly.