Plenary Event
Tuesday Plenary Session
14 April 2026 • 09:00 - 10:35 CEST | Auditorium Erasme (Niveau/Level 0)
9:00 – 9:05 hrs CEST
Welcome and Opening Remarks
Speaker Introduction
9:05 - 9:50 hrs
Multi-LED illumination: from freeform optics design to spectroscopic sensing
LED-based illumination has become increasingly attractive for spectroscopy, imaging, and sensing applications thanks to their spectral diversity and compactness. However, efficiently combining the emission from multiple LEDs into a single, well-defined output remains a major optical design challenge. The overlap of multiple LED sources often leads to significant étendue mismatch, non-uniform illumination, and reduced optical efficiency.
We present an overview of recent advances in the optical design of multi-LED systems, from state-of-the-art methodologies to a novel compact illumination architecture employing a single freeform mirror to collect and combine the LED emission beams. Particular attention is given to the role of the freeform mirror to spatially and angularly merge different LED channels, alongside an evaluation of the system’s optical efficiency, compactness, spectral homogeneity, and robustness. This design performance is supported by experimental validation within a proof-of-concept demonstration, paving the way towards its implementation in spectroscopic sensing applications.
Lien Smeesters is a professor at B-PHOT Brussels Photonics, at the Faculty of Engineering of the Vrije Universiteit Brussel (VUB). Lien focuses on multidisciplinary research in the field of optical design and optical spectroscopy, pursuing the development of novel spectroscopic detection systems. She investigates the full supply chain, starting from the optimization of the spectroscopic sensing technology, and the advanced optical design of the illumination and detection system, benefitting from freeform optics, to a proof-of-concept demonstrator. Lien is coordinating and working on applied-oriented research projects in collaboration with industry, via bilateral collaborations, and within the European Commission funded PhotonHub programme.
9:50 - 10:35 hrs CEST:
An optical design journey through the computer age
The design of optics has seen very significant advances over the last seven decades or so, a lot of which has been due to the tremendous increase in the power of computing & software.
In 1675, Isaac Newton said that “If I have seen further, it is by standing on the shoulders of giants”. The same is true of the optical designers of my generation in that we have benefitted so much from the work of the “giants” of previous generations. The presentation will therefore include brief synopses of the contributions of a few of these giants.
Some selected examples will be given of the advances over the computer age in the means of designing optics and also the developments in specific optical devices. The presentation will be dedicated to the memory of John Greivenkamp, a great educator in optics, who was to have been its joint author.
Phil Rogers has been a professional optical designer for 65 years, originally at Hilger & Watts in London and then at Pilkington PE (now Qioptic Teledyne) in St Asaph UK where he was chief optical designer for 36 years. Currently he owns the optical design consulting company VNF Ltd, and is visiting professor of optical design at the OpTIC Centre of Wrexham University, having previously been a visiting professor at Cranfield University.
Rogers is a Fellow of SPIE, past board member & recipient of the 2018 A E Conrady Award; a Fellow of the UK Institute of Physics; and an Emeritus Fellow of both Optica and the Royal Academy of Engineering. He was awarded an MBE (British national honour) in 1990 for contributions to optical design.
Welcome and Opening Remarks
 |
Thierry Lépine
Institut d’Optique & Hubert Curien Lab (France) 2026 Symposium Chair |
Speaker Introduction
 |
Marta C. de la Fuente
ASE Optics Europe (Spain) 2026 Symposium Chair |
9:05 - 9:50 hrs
Multi-LED illumination: from freeform optics design to spectroscopic sensing
 |
Lien Smeesters
Vrije Univ. Brussel (Belgium) |
LED-based illumination has become increasingly attractive for spectroscopy, imaging, and sensing applications thanks to their spectral diversity and compactness. However, efficiently combining the emission from multiple LEDs into a single, well-defined output remains a major optical design challenge. The overlap of multiple LED sources often leads to significant étendue mismatch, non-uniform illumination, and reduced optical efficiency.
We present an overview of recent advances in the optical design of multi-LED systems, from state-of-the-art methodologies to a novel compact illumination architecture employing a single freeform mirror to collect and combine the LED emission beams. Particular attention is given to the role of the freeform mirror to spatially and angularly merge different LED channels, alongside an evaluation of the system’s optical efficiency, compactness, spectral homogeneity, and robustness. This design performance is supported by experimental validation within a proof-of-concept demonstration, paving the way towards its implementation in spectroscopic sensing applications.
Lien Smeesters is a professor at B-PHOT Brussels Photonics, at the Faculty of Engineering of the Vrije Universiteit Brussel (VUB). Lien focuses on multidisciplinary research in the field of optical design and optical spectroscopy, pursuing the development of novel spectroscopic detection systems. She investigates the full supply chain, starting from the optimization of the spectroscopic sensing technology, and the advanced optical design of the illumination and detection system, benefitting from freeform optics, to a proof-of-concept demonstrator. Lien is coordinating and working on applied-oriented research projects in collaboration with industry, via bilateral collaborations, and within the European Commission funded PhotonHub programme.
9:50 - 10:35 hrs CEST:
An optical design journey through the computer age
 |
Philip J. Rogers
VNF Ltd. (United Kingdom) Wrexham Univ. (United Kingdom) |
The design of optics has seen very significant advances over the last seven decades or so, a lot of which has been due to the tremendous increase in the power of computing & software.
In 1675, Isaac Newton said that “If I have seen further, it is by standing on the shoulders of giants”. The same is true of the optical designers of my generation in that we have benefitted so much from the work of the “giants” of previous generations. The presentation will therefore include brief synopses of the contributions of a few of these giants.
Some selected examples will be given of the advances over the computer age in the means of designing optics and also the developments in specific optical devices. The presentation will be dedicated to the memory of John Greivenkamp, a great educator in optics, who was to have been its joint author.
Phil Rogers has been a professional optical designer for 65 years, originally at Hilger & Watts in London and then at Pilkington PE (now Qioptic Teledyne) in St Asaph UK where he was chief optical designer for 36 years. Currently he owns the optical design consulting company VNF Ltd, and is visiting professor of optical design at the OpTIC Centre of Wrexham University, having previously been a visiting professor at Cranfield University.
Rogers is a Fellow of SPIE, past board member & recipient of the 2018 A E Conrady Award; a Fellow of the UK Institute of Physics; and an Emeritus Fellow of both Optica and the Royal Academy of Engineering. He was awarded an MBE (British national honour) in 1990 for contributions to optical design.