Optical Design & Image Reconstruction:Activities in Optical design
In the field of optical systems design, the team is developing a strong collaborative activity, focusing mainly on 3 fields of applications: astronomy, space and ophthalmology. Its high level of expertise is recognized both nationally and internationally (e.g., one of us was Symposium Chair of the leading international conference “SPIE Optical Systems Design” in April 2024).
Our work focuses on off-axis, high apertures and wide fields of view imaging systems, requiring the use of so-called "freeform" optical surfaces ([Houllier & Lépine 2019], [Duveau et al 2023a], [Duveau et al 2023b], [Freslier et al. 2024]) for which new optical design (cf. Thomas Houiller's thesis) and metrology methodologies are required. The team is at the origin of the creation in 2019 of the French Center on freeform optics (FO-RS) bringing together 4 academics and 12 companies (such as Safran and Essilor) to advance innovation based on freeform surfaces.
Since April 2022, we are also part of the international consortium Theia, which is an ESA project led by the Grenoble Observatory (Dr. Fabien Malbet). We are working on the design of a space telescope for astrometry, with the aim of detecting Earth-like extrasolar planets [Malbet et al, 2024].
At the end of 2024, we also joined the international WST (Wide field Spectroscopic Telescope) consortium, led by the Lyon Observatory (Dr. Roland Bacon) and ESO. We are designing a giant telescope (12 m) dedicated to spectroscopy, with two simultaneous modes: MOS (Multi Object Spectroscope) for the wide field (between 2 and 5 square degrees) and IFS (Integral Field Spectroscope) for the small field (10’ x 10’). This project should become ESO’s flagship, after the ELT is commissioned in 2027 [Dierickx et al, 2024].
In the field of ophthalmology (collaboration with CHU de Saint-Etienne, BiiO laboratory/Pr Gain and Pr Thuret, [Garcin et al. 2022], [Ain et al. 2025]), a highlight is the development of a high-resolution anterior segment (cornea, lens) imager for the early detection of Fuchs endothelial corneal dystrophy (FECD) and cataract. This device, which achieves unrivalled image quality by eliminating the reflection of the illumination source on the cornea, has been patented. It is now in industrial development at Lumibird Quantel Medical. A bio-spectral microscope designed to detect dry eye syndrome (ANR FLUOSSICA) is also under development.
High-resolution image of a cornea in vivo (ie. on a patient in consultation) affected by Fuchs' dystrophy or droplet disease. The size of the drops is around 10 µm. Note the absence of glare in the images (Anthony Ain's Ph.D. thesis).
Publications illustrative of our scientific activity :
[Houllier & Lépine 2019] Thomas Houllier, Thierry Lépine. Comparing optimization algorithms for conventional and freeform optical design. Optics Express, 2019, 27 (13), pp.18940. DOI Preprint
[Duveau et al 2023a] Louis Duveau, Clement Freslier, Guillaume Druart, Thierry Lepine. Freeform TMA without planar symmetry for compact catoptric imaging system. Results in Optics, 2023, 12, pp.100434. DOI Preprint
[Duveau et al 2023b] Louis Duveau, Guillaume Druart, Thierry Lepine. Design and manufacture of a large field of view thermal infrared catoptric imaging system in an αZ configuration. Optics Express, 2023, 31 (16), pp.26659-26672. DOI Preprint
[Freslier et al. 2024] Clément Freslier, Guillaume Druart, Alice Fontbonne, Thierry Lépine, Christophe Buisset, et al.. Comparative Study on the Interest in Non-Uniform Rational B-Splines Representation versus Polynomial Surface Description in a Freeform Three-Mirror Anastigmat. Photonics, 2024, 11 (9), pp.875. DOI Preprint
[Garcin et al. 2022] Thibaud Garcin, Emmanuel Crouzet, Chantal Perrache, Thierry Lepine, Philippe Gain, et al.. Specular Microscopy of Human Corneas Stored in an Active Storage Machine. Journal of Clinical Medicine, 2022, 11 (11), pp.3000. DOI Preprint
[Ain et al. 2025] Anthony Ain, Sylvain Poinard, Thierry Lepine, Oliver Dorado-Cortez, Sébastien Urbaniak, Jean-Marie Papillon, Philippe Gain, Gilles Thuret. Far-Red, High-Resolution, Reflection-Free Images of the Anterior Segment in Retro-Illumination. Translational Vision Science & Technology June 2025, Vol.14, 11. DOI Preprint
[Malbet et al, 2024] Fabien Malbet, Manon Lizzana, Fabrice Pancher, Sébastien Soler, Alain Léger, Thierry Lépine, Gary A. Mamon, Alessandro Sozzetti, Alberto Riva, Deborah Busonero, Lucas Labadie, Pierre-Olivier Lagage, and Renaud Goullioud. Challenges in focal plane and telescope calibration for high-precision space astrometry. Proc. SPIE 13092, Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave, 130920B (23 August 2024). DOI Preprint
[Dierickx et al, 2024] P. Dierickx, T. Travouillon, G. Gausachs, R. Bacon, C. Cudennec, I. Bryson, D. Lee, J. Kragt, E. Muslimov, K. Dohlen, J. Kosmalski, J. Vernet, T. Lépine, P. Doel, and D. Brooks. WST - Widefield Spectroscopic Telescope: design of a new 12m class telescope dedicated to widefield multi-object and integral field spectroscopy. Proc. SPIE 13094, Ground-based and Airborne Telescopes X, 1309431 (28 August 2024). DOI Preprint