Dr. João Mendes-Lopes Profile

Dr. João Mendes-Lopes

Lead R&D Engineer

SPIE Involvement:

Conference Program Committee | Author

Publications (16)

Proceedings Article | 18 June 2024 Presentation

Stress birefringence in optical systems: simulation and analysis

João Mendes-Lopes, Stefano Guazzotti, Michael Cheng, Matthias Schlich, Chris Normanshire, Esteban Carbajal

Proceedings Volume 13019, 130191L (2024) https://doi.org/10.1117/12.3022953

KEYWORDS: Birefringence, Polarization, Optical simulations, Finite element methods, Wavefronts, Systems modeling, Optical design, Image quality, GRIN lenses, Equipment

Read Abstract +

Proceedings Article | 17 June 2024 Presentation + Paper

Simulation of the impact of propagation through optical fluids and turbulent flow on optical system performance

Chris Normanshire, Steven La Cava, Craig Miller, Walter Schwarz, Felipe Mercado, Esteban Carbajal, David Vega, João Mendes-Lopes, Mohammed Kamel, Valerio Viti, Nick Herringer, Erin Elliott

Proceedings Volume 13019, 130190P (2024) https://doi.org/10.1117/12.3021890

KEYWORDS: Computational fluid dynamics, Geometrical optics, Near field optics, Refractive index, Wavefronts, Optical components, Design, Sensors, Finite element methods, Wavefront errors

Read Abstract +

Proceedings Article | 15 May 2024 Paper

System NA Vs. beam NA. How we should change the ray tracing analysis paradigm to enable realistic non-sequential optical system analysis

David Vega, Erin Elliott, João Mendes-Lopes, Han-Hsiang Cheng, Xu Chen, Alessandra Croce

Proceedings Volume 12798, 127981K (2024) https://doi.org/10.1117/12.2692125

Read Abstract +

Proceedings Article | 12 March 2024 Poster + Paper

Optical fluids: modeling the near field and far field optical effects of atmosphere and turbulent flow of an airborne laser communication system

Steven LaCava, Felipe Mercado, David Vega, Joao Mendes Lopez, Esteban Carbajal, Mohammed Kamel, Valerio Viti, Craig Miller, Walter Schwarz, Nick Herringer, Erin Elliott

Proceedings Volume 12877, 128771W (2024) https://doi.org/10.1117/12.3003225

KEYWORDS: Atmospheric optics, Design, Refraction, Near field optics, Finite element methods, Thermography, Imaging systems, Fluid dynamics, Computational fluid dynamics, Atmospheric modeling

Read Abstract +

Proceedings Article | 28 September 2023 Presentation

Optical effects of fluids: simulation and analysis

David Vega, Steven La Cava, Felipe Mercado, Joao Mendez Lopes

Proceedings Volume PC12664, PC1266407 (2023) https://doi.org/10.1117/12.2691481

KEYWORDS: Computer simulations, Refractive index, Optical simulations, Finite element methods, Failure analysis, Design and modelling, Wavefronts, Turbulence, Systems modeling, Optical design

Read Abstract +

Proceedings Article | 11 June 2021 Open Access

Optical alignment, characterization, and testing through image-based output beam analysis: application to Sentinel 5 OGSE

R. Henriques, J. K. Abrantes, J. Mendes-Lopes

Proceedings Volume 11852, 118524D (2021) https://doi.org/10.1117/12.2599652

Read Abstract +

An image-based method used for optical alignment, characterization and testing of the Sentinel 5 AIT OGSE output beams is described here. The OGSEs will be used in the AIT campaign of the Sentinel 5 spectrograph instruments, and each of them comprises two modules assembled in a common mechanical base, one generating point sources and the other an astigmatic optical beam. The methods described in the present work evaluate optical beam parameters such as the spatial and spectral F-numbers, relative beam pointing (rotations about X and Y, Z being the optical axis) and astigmatic beam parameters, among others. Such evaluation is made possible through the acquisition and processing of series of images along the optical axis, by scanning a CCD module with controlled small displacements /1Z imposed by a precision motorized linear stage. Special attention is given in this paper to the alignment of the optical components of the astigmatic module of the OGSEs, performed with the aid of described method. To this end, the astigmatic beam parameters to be optimized – spatial and spectral F-numbers, relative pointing, and astigmatism – are described as a function with linear dependence on each of the system opto-mechanical degrees of freedom, considering small variations around their nominal values. These dependencies can be described by a set of equations arranged in matrix form. Solution of the linear system then provides a direct indication of the dimensional adjustments that must be imposed to each degree of freedom in order to align the optical system from a set of initial values. To calculate each coefficient of the matrix M, the sensitivity of the dependent variables with each of the actuators was previously simulated in raytracing software Zemax OpticStudio. The overall methodology was successfully applied to the alignment phase of the set of OGSEs, with accuracies – based – of ±0.02 for spatial and spectral F-numbers, ±10μm for the distance between foci of the astigmatic beam, and ±0.2arcmin for relative beam pointing.

DOWNLOAD PAPER

Proceedings Article | 11 June 2021 Open Access

Sentinel-5 OGSE: large aperture sun simulator

J. Mendes-Lopes, J. Meyer, P. Borges, J. Pereira, R. Henriques, J. Pimentao, D. Mesquita

Proceedings Volume 11852, 118524E (2021) https://doi.org/10.1117/12.2599653

Read Abstract +

This paper reports on the development of a sun simulator (SUSI) as an optical ground support equipment (OGSE) for the calibration and characterization (CC) of the Sentinel-5 spectrometers. The illumination system is based on a Xenon continuous light source, a homogenizer and a telescope. A Xenon plasma source is significantly non-uniform, both spectrally and spatially. To meet the stringent spatial homogeneity requirements, a large homogenizer based on a kaleidoscope configuration was designed and manufactured. The proper collimation and large exit pupil are achieved through a mirror-based Offner telescope, avoiding large incidence angles, which would affect spatial uniformity and polarization. SUSI covers a very wide spectral range, from 270 to 2300nm, with an irradiance of 80 mW/cm2. SUSI provides an illuminated exit pupil with a very high spatial uniformity. The collimated beam of 0.27º divergence illuminates an exit pupil 160mm diameter with continuous light, reaching a non-uniformity of irradiance better than 1% for most spectrum (according to IEC 60904-9 definition) which is, to the best of the authors’ knowledge, the highest level of spatial uniformity for large aperture sun simulators. A breadboard was manufactured to test and validate the performance of the homogenizer coupled with the Xenon light. Due to the large diameter of the exit pupil, a set of tests were specifically developed to evaluate the performance across the entire aperture and spectral range. Using a fiber-tip based spectrometer, the exit pupil was scanned to measure the irradiance profile. Results from the breadboard showed a performance better than 1% spatial uniformity at 0.27º divergent beam, for the spectral range 270nm to 800nm. The ray tracing model was compared and validated with the experimental data. Simulation results showed an equivalent performance for SWIR1 and SWIR3 spectral bands. The Critical Design Review (CDR) was successfully achieved, and SUSI is currently being assembled. This work will present the development of the instrument, details on the tests developed to evaluate its performance, and the experimental results of the upcoming test campaign.

DOWNLOAD PAPER

Proceedings Article | 29 September 2016 Paper

Design of compact optical systems using multichannel configurations

Milena Nikolic, Juan Miñano, P. Benítez, B. Narasimhan, J. Mendes-Lopes, P. Zamora, M. Buljan, D. Grabovickic

Proceedings Volume 9948, 99480M (2016) https://doi.org/10.1117/12.2237641

KEYWORDS: Nonimaging optics, Optical design, Head-mounted displays, Imaging systems, Head, Optics manufacturing, Solar concentrators, Eye, Prototyping, Multichannel imaging systems

Read Abstract +

Proceedings Article | 7 September 2016 Paper

Recent advances in the SMS design method: 3D aplanatism and diffraction

Juan Miñano, P. Benitez, B. Narasimhan, M. Nikolic, J. Mendes-Lopes, D. Grabovickic

Proceedings Volume 9955, 99550D (2016) https://doi.org/10.1117/12.2237402

KEYWORDS: Optical design, Freeform optics, Diffraction, Wavefronts, Imaging systems, Optical components, Monochromatic aberrations, Mirrors, Nonimaging optics, Imaging spectroscopy

Read Abstract +

Proceedings Article | 23 September 2015 Paper

Design of diffractive optical surfaces within the nonimaging SMS design method

João Mendes-Lopes, Pablo Benítez, Juan Miñano

Proceedings Volume 9629, 96290O (2015) https://doi.org/10.1117/12.2191976

KEYWORDS: Wavefronts, Nonimaging optics, Electroluminescent displays, Optical design, Computer generated holography, Spherical lenses, Colorimetry, Chromatic aberrations, Refractive index, Direct methods

Read Abstract +

Proceedings Article | 25 August 2015 Paper

Design of diffractive optical surfaces within the SMS design method

João Mendes-Lopes, Pablo Benítez, Juan Miñano

Proceedings Volume 9572, 95720K (2015) https://doi.org/10.1117/12.2189102

KEYWORDS: Wavefronts, Optical design, Nonimaging optics, Electroluminescent displays, Spherical lenses, Colorimetry, Computer generated holography, Refractive index, Direct methods, Control systems

Read Abstract +

SPIE Journal Paper | 10 July 2014 Open Access

Recent trends in concentrated photovoltaics concentrators’ architecture

Marina Buljan, João Mendes-Lopes, Pablo Benítez, Juan Carlos Miñano

JPE, Vol. 4, Issue 01, 040995, (July 2014) https://doi.org/10.1117/12.10.1117/1.JPE.4.040995

KEYWORDS: Solar concentrators, Fresnel lenses, Photovoltaics, Solar cells, Optical design, Mirrors, Sun, Solar energy, Glasses, Reflectivity

Read Abstract +

DOWNLOAD PAPER

Proceedings Article | 18 September 2013 Paper

New Fresnel Köhler optical design: 9-fold photovoltaic concentrator

João Mendes-Lopes, Pablo Benítez, Pablo Zamora, Juan Carlos Miñano

Proceedings Volume 8834, 88340A (2013) https://doi.org/10.1117/12.2024050

KEYWORDS: Solar concentrators, Optical design, Solar cells, Photovoltaics, Fresnel lenses, Sun, Optics manufacturing, Tolerancing, Ray tracing, Coating

Read Abstract +

Proceedings Article | 9 September 2013 Paper

9-fold Fresnel-Köhler concentrator for increased uniform irradiance on high concentrations

João Mendes-Lopes, Pablo Benítez, Pablo Zamora, Juan Carlos Miñano

Proceedings Volume 8821, 88210F (2013) https://doi.org/10.1117/12.2024156

KEYWORDS: Solar concentrators, Fresnel lenses, Sun, Photovoltaics, Silicon, Optical design, Ions, Neodymium, Thermal effects, Optics manufacturing

Read Abstract +

Proceedings Article | 10 October 2012 Paper

1000x shadow-free mirror-based Köhler concentrator

Maikel Hernandez, Pablo Benítez, João Mendes-Lopes, Aleksandra Cvetkovic, Yupin Sun, Juan Carlos Miñano, Julio Chaves, Rubén Mohedano

Proceedings Volume 8468, 84680C (2012) https://doi.org/10.1117/12.931657

KEYWORDS: Solar concentrators, Solar cells, Glasses, Optics manufacturing, Mirrors, Sun, Optical components, Coating, Prisms, Antireflective coatings

Read Abstract +

Proceedings Article | 10 October 2012 Paper

Photovoltaic performance of the dome-shaped Fresnel-Köhler concentrator

Pablo Zamora, Pablo Benítez, Li Yang, Juan Carlos Miñano, Joao Mendes-Lopes, Kenji Araki

Proceedings Volume 8468, 84680D (2012) https://doi.org/10.1117/12.929698

KEYWORDS: Solar concentrators, Fresnel lenses, Tolerancing, Optical design, Photovoltaics, Antireflective coatings, Manufacturing, Optics manufacturing, Solar cells, Optical components

Read Abstract +

Showing 5 of 16 publications

Conference Committee Involvement (1)

Optical Design and Engineering IX

8 April 2024 | Strasbourg, France

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years