SPANISH OPTICAL DESIGN MEETING
Thursday, 23rd March 2017
CeDInt - Universidad Politécnica de Madrid (UPM)
Campus Montegancedo
28223 Pozuelo de Alarcón, Madrid
Abstracts
Design of compact optical systems using multichannel configurations
Pablo Benítez 1, Juan C. Miñano 1, Dejan Grabovickic 2, Pablo Zamora 2
Marina Buljan 2, Milena Nikolic 1, Bharathwaj Narasimhan 2
1 - Universidad Politécnica de Madrid, Cedint
2 - Limbak, Madrid
Compacting devices is an increasingly demanding requirement for many applications in both nonimaging and imaging optics. “Compacting” means here decreasing the volume of the space between the entry and the exit aperture without decreasing the optical performance. After reviewing the different techniques to design compact systems, we analyze here the multichannel strategies. These type of designs split the incoming bundle of rays in different sub-bundles that are optically processed (independently) and then recombined in a single outgoing bundle. The optics volume decreases rapidly with the number of sub-bundles. These designs usually need to be combined with freeform optics in order to get optimum performance.
High-precision surface reconstruction from ray mapping with Cn continuity control
Co-authors Fabian Duerr and Hugo Thienpont
Brussels Photonics (B-PHOT), Vrije Universiteit Brussel (VUB)
Pleinlaan 2 B-1050 Brussels
Many illumination design problems can be solved using a ray mapping formalism that describes the ray paths from source to target. Once a ray mapping is found, the surface(s) are typically reconstructed numerically from the normal vector field(s). In previous work, we have presented a new solution approach that allows direct calculation of two (or more) surfaces for laser beam shaping applications. This design approach can be modified to not only achieve a high-precision surface reconstruction but also to ensure a simultaneous control of surface continuity. The shown example of C2 surface continuity control can enable better and faster manufacturing.
The Raman Laser spectrometer (RLS) for Mars exploration
Tomas Belenguer Dávila
INTA, Instituto Nacional de Técnica Aerospacial
Carretera de Ajalvir Km4.5
28850 Torrejon de Ardoz, Madrid
INTA carried out over the last decade an intense activity of scientific research and development related to Mars surface instrumentation. The main optical aspects of this R&D are summarized in the presented paper.
Principal optical features related to the RLS (Raman Laser Spectrometer), the principal design drivers, the most critical Assembly features, aspects of the integration and validation phase (AIV) and actual program status are reported and discussed.
The RLS instrument is one of the most complex payloads for Mars exploration in which INTA has been involved. The requirement for specialized facilities like the Protection Planetary Facility (PPF) for handling planetary instrumentation, or the qualification campaign performed for validating optical components such as holographic gratings, glasses substrates or micro laser components are additional challenges included in the development of this complex payload. INTA is also part of other small missions for scientific knowledge on weather, solar irradiance or magnetic characteristics of Mars.
Modelling the optical properties of the accommodating, ageing human lens
Conor Sheil 1,2 and Alexander V Goncharov 2
1 - FotoNation
2 - National University of Ireland, (NUI Galway)
A new age-dependent model of the human crystalline lens is proposed, with two separate gradient index (GRIN) power profiles (axial and radial). Together with a logarithmic model of the lens core, these allow decoupling of three fundamental optical features of the lens, namely optical power, third-order spherical aberration and axial optical path length, without changing the lens external shape. Exact raytracing is used to calculate spherical aberration, which is in line with experimental data. The structure of the GRIN medium near the lens surface has the same shape as the lens external surface, which is necessary for modelling accommodation. The current model is compared to previous GRIN models in the literature, and it can be concluded that the new model will be useful for reconstructing the GRIN medium of the lens in future experimental studies; in particular, studies of the accommodative properties of the ageing human lens. The additional flexibility of this model allows us to examine the so-called lens paradox and perhaps suggest the origin of age-related defects in human vision.
Characterization of diffraction gratings scattering in UV and IR
for space applications
Quentin Kuperman-Le Bihan 1, Sakina Achour (speaker) 1, Pierre Etcheto 2
1 - Light Tec, France
2 - CNES, France
The use of Bidirectional Scatter Distribution Function (BSDF) in space industry and especially when designing telescopes is a key feature. Indeed when speaking about space industry, one can immediately think about stray light issues. Those important phenomena are directly linked to light scattering. Standard BSDF measurement goniophotometers often have a resolution of about 0.1° and are mainly working in or close to the visible spectrum. This resolution is far too loose to characterize ultra-polished surfaces. Besides, wavelength range of BSDF measurements for space projects needs to be done far from visible range.
How can we measure BSDF of ultra-polished surfaces and diffraction gratings in the UV and IR range with high resolution? We worked on developing a new goniophometer bench in order to be able to characterize scattering of ultra-polished surfaces and diffraction gratings used in everyday space applications. This ten meters long bench was developed using a collimated beam approach as opposed to goniophotometer using focused beam. Sources used for IR characterization were CO2 (10.6µm) and Helium Neon (3.39µm) lasers. Regarding UV sources, a collimated and spatially filtered UV LED was used. The detection was ensured by a photomultiplier coupled with synchronous detection as well as a MCT InSb detector.
The so-built BSDF measurement instrument allowed us to measure BSDF of ultra-polished surfaces as well as diffraction gratings with an angular resolution of 0.02° and a dynamic of 1013 in the visible range. In IR, as well as in UV, we managed to achieve 109 with the same angular resolution of 0.02°. The 1m arm and translation stages allowed us to measure samples up to 200mm. Thanks to such a device allowing scattering characterization of ultra-polished materials as well as diffraction gratings, it is possible to implement the BSDF measurements into simulation software and predict stray light issues. This is a big help for space industry engineers to apprehend stray light due to surface finishes and to delete those effects before the whole project is done.
We are now contemplating possible improvements to our optical bench in order to achieve dynamic in IR and UV similar to what we have in visible range (e.g. 1013).
Optical design of a high speed in-line inspection system based on low coherence interferometry
A. Cifuentes, T. Siegel, P. Symeonidou, A. Sansà
ASE Optics Europe
ASE Optics Europe has developed an high speed low coherence interferometry based inspection system that allows measuring depth of micro features within transparent materials. The optical design included the design of the interferometer arm, the light source coupling, as well as the design of a custom spectrometer. We report on some of the design challenges during the development of the instrument.
Analysis of Stray Light in an Imaging Lens Using Multiple, Integrated Simulation Techniques
Jake Jacobsen, Chenglin Xu, Dan Herrmann
Optical Solutions Group, Synopsys IncAnalysis of stray light in an imaging system is an important, but complex task. In addition to ghost imaging from pairs of optical surfaces, there is also the potential for stray light arising from the reflection of light off of the detector as well as other, non-imaging surfaces. The periodic structure of the detector gives rise to diffraction effects that may alter the stray light performance of the lens. Because of the small structure size, the effect of the detector is best simulated using FDTD techniques rather than through traditional ray tracing. In this paper we will report on a stray light analysis integrating traditional lens design and ghost analysis, rigorous modelling of the reflected light off of a CMOS detector structure using FDTD calculation techniques, and non-sequential modelling of stray light reflected off of non-lens surfaces such as mounts and element edges.
Applications of Advanced Optical Technologies in Automotive Lighting
Rubén Mohedano Arroyo
Light Prescriptions Innovators Europe
LED technology has greatly changed the way cars handle illumination and signaling functions. Apart from enhanced performance features (advanced beam patterns, accurate color control, low consumption, instant switch on and off), LEDs offer important aesthetical advantages which are radically changing the way cars look these days. How every brand handles exterior and interior lighting has a direct impact on their signature look. In this work, we will show how advanced optical technologies (such as free-form optics or thin multi-lens approaches) can address the new performance and design challenges.
New TPI Wavefront Sensor
S. Bonaque-González 1, J.J. Fernández-Valdivia 1, J.M. Trujillo-Sevilla 1,
O. Gómez-Cárdenes 1, L.F. Rodríguez-Ramos 2, J.G. Marichal-Hernández 1,
D. Carmona-Ballester 1, J.M. Rodríguez-Ramos 1,2
1 - Affiliation: Wooptix S.L.
2 - Affiliation: Universidad de La Laguna
Tenerife, Canary Islands
In this work we propose the use of a new full definition wave front sensing technique for aberration measurement in optical elements. The technique apparatus doesn't need additional optics elements and wave front map resolution is only limited by the resolution of the imaging sensor being used. We outline some of the analitical details and the advantages of this method compared with classic wave front sensors.
Poster Abstracts
Freeform aplanatic systems
Bharathwaj Narasimhan, Juan Carlos Miñano, Pablo Benítez
CeDInt-UPM, Madrid
We formulate freeform aplanatic systems as a limiting case of a 3D SMS design. We establish how two optical surfaces when considered for achieving freeform aplanatism leads to no solution and thus, prove that freeform aplanatic systems need three optical surfaces with the exception of afocal aplanatic systems. We also present basic formulations governing a three surface freeform aplanat along with few examples.
An analytic solution of an afocal two freeform mirror design problem
Milena Nikolic, Pablo Benítez, Juan Carlos Miñano
CeDInt-UPM, Madrid
We investigate a new afocal two freeform mirror design problem in first order optics. The resulting first-order partial differential equations for the freeform two mirror system have an analytic solution with the only condition that the x-y and x’-y’ axes are parallel. Two selected solutions are presented. One of them is semi-aplanatic (fulfilling the aplanatic condition only for the x-coordinates), while the other is a full aplanat. The latter is, to our knowledge, the first example of an aplanatic two-mirror system without rotational symmetry.
Irradiance Tailoring for Extended Sources in 3D by
Implicit Integral Equation Solution
Adam Hirst
OSRAM, Munchen & CeDInt-UPM, Madrid
A new method for solving the problem of irradiance tailoring in 3D for extended sources is introduced, in which the integral expression for the flux at each of a set of target points for a given Lambertian source is approximated and expressed in terms of parameters defining a freeform surface, and the resulting set of equations solved through said parameters using standard numerical methods to yield the freeform surface satisfying a desired irradiance prescription. The method has previously been shown to work at least in principle for extremely restricted cases, but current work extends the work to apply to more general and more useful set of cases, namely by utilising a B-Spline surface along with the means to counter the virtual edge(s) of a projected source, and some solutions are presented.