1937: The creation of Reosc

1937: The Reosc company (Recherche et Etudes en Optique et Sciences Connexes) is created on March 1st, 1937. Its 14 share holders and administrators (with underligned names here after) are mostly originating from scientific institution and the defense with: Albert Arnulf, André Bayle, Henri Chrétien, Louis Clerc, Charles Devé, Louis Dunoyer, Charles Fabry, Georges Guadet, Martial Lachenaud, Paul Libessart, Louis Lumière, Georges Penciolelli, Georges Perrier and Lucien Roux.

André Bayle is the first president of Reosc.

The offices are located 163 rue de Sèvres in Paris, just beside the Paris Institute of Optics building. A bridge is even constructed between the two buildings to ease the exchanges and cooperations.

Timeline Reosc 1937_création


1947: Pioneering work in IR

During its first years of activity REOSC worked in the domain of IR for science and defence and pioneered several developments:

          Rapid detectors: thermopiles, gaz thermometer, bolometer
          Electrical circuits for amplification and transformation of the images
          Studies of the IR transparency of fogs
          Cloud temperature measurment
          Patrol detector


1957: Telescopes & Spectrographs

By this second deceny of activity the company evolved to the field of astronomy.

REOSC supplied large astronomy optics as well as turn-key telescopes up to 1.8-m diameter with a smooth friction drive system.

Among them the 2-m optics for the Pic du Midi observatory is one of the most famous. Another one is fitting the Laser-Moon telescope at the CERGA observatory.

Jean ESPIARD, who joined the Company in 1947, developped catadioptric optical designs for spectrograph camera of high NA and over a broad spectral domain. Many spectrograph instruments were then developed and installed in astronomical observatories all through the world.

Timeline Reosc 1957_Telescopes & Spectrographs


1967: The 3.6-m optics for ESO

The recently created European Southern Observatory is ordering from REOSC the optics for the 3.6-m giant telescope of that time.

The company is leaving Paris and move to the village of Ballainvilliers, 20 km south of Paris to set-up its large polishing shop and high test tower.

The large CERVIT blank from Corning which showed a defect on the optical surface is 'saved' thanks to a 15-cm plug accurately inserted and glued within the piece.

The art of precision aspheric manufacturing is refined with flexible tools, pitch tool patterning, Foucault and Hartman testing and reduction of the air turbulence effects.

Timeline Reosc 1967


1977: Early work for Space and Laser

During this deceny, REOSC is developping two new business:

Space: the company supplies the space telescope optics for the METEOSAT wheather forecast satellite serie initiated by CNES.

Laser: Precision lenses and mirrors are supplied to the Centre d'Etude Atomique (CEA) in Limeil-Brevanes where laser-matter interactions are studied.

In parallel, the engineers and technicians of Matra-Optics are developping the technology of high fluence thin film coating for High Energy laser optics. They will join REOSC in the end of the 90's.

Timeline Reosc 1977_Early Space & Laser


1987: Space optics for defense and export

CNES is developping the various generation of the SPOT satellite and REOSC is key contributor in term of optical design, manufacturing, alignment and testing. The same core optical design delivers 10-m GSD (SPOT-1, 2 & 3).

SPOT-4 is developped by CNES in synergy with HELIOS-1, the first French military high resolution earth observation satelite. REOSC contributes to its optical design and delivers all the optics, along with test collimators.

SPOT-5 is developped in synergy with HELIOS-2. Thanks to improved manufacturing and testing techniques, new sensors and the super-resolution algorithms the refined SPOT instrument delivers now 2.5-m GSD. HELIOS-2 optics is further pushing the technology of mirror lightweighting and mounting, precision aspheric polishing, coating, assembly and testing.

Several contracts are gained for export like the OFEQ-1 telescopes, lens assemblies and first Three Mirror Anastigmat telescopes for the ISRO IRS serie.  

Space science is also booming in this period and the company is contributing to ORFEUS, PRONAOS, ISO, HIPPARCOS, ...



1995: First VLT Mirror delivered

In 1989 REOSC is selected by ESO for polishing the four 8-m giant primary mirrors for the Very Large Telescope observatory installed on the Cerro Paranal in Chili.

Again the company has to move to a new place in order to be able to build the required large optics facility for the project. We come in 1991 to Saint Pierre du Perray, 35 km south of Paris, near the Seine river for easy transportation of the 8-m large giant piece of glass. This unique optical shop is fitted with two robotic lapping and polishing machines and a 30-m high test tower which becomes the new flagship of the company.

Between 1995 to 1999 the four VLT's (plus two 8-m mirrors for the US GEMINI project) are delivered at a rate of about 1 a year. In parallel, our parent company SFIM is delivering the electromechanics actuators implement in the VLT Active Optics support system.

REOSC has also supplied ESO VLT with the lightweight secondaries made from Beryllium, many mirrors for the Coudé train as well as the smaller optics for the Cat's Eye telescopes used to built interferometric fringes between the various telescopes.



2000: Segmented optics for the GTC

In 2000 Reosc is selected by the Gran Telescopio Canarias organization for the supply of the 36 (+ 6 spares) 1.8-m segments of its 10.5 m primary mirror. After the Keck telescopes developped in the US such segmented optics technology is a premiere in Europe.

The challenges are multiple : non rotationnally symmetric optical profile, hexagonal contour, ow edge effects down to a few millimeter only, harder specifications on mid and high spatial frequency residual errors and radius matching between the segments

Thanks to the robotic Computer Controlled Polishing (CCP) technology, Ion Beam Figuring (IBF) deterministic finishing technique and sophisticated Computer Controlled Hologram (CGH) testing technique Reocs doped its productivity and reached a production rate of 2 segments / month, more than 10 times faster than more conventional techniques.



2005: Semiconductor optics

Safran Reosc is proud to have contributed to some developments in the domain of precision optics for the semiconductors. We contributed to several state of the art programs:

     High NA KrF Lithography optical systems. This are several 193 nm litho mask illumination systems and extremely accurate NA 0.75 projection optics.

     ArF Medium NA mask inspection lenses with high fluence level in order to enable fastest possible inspection process.

     Several Extreme UV (EUV) illumination and projection optics requiring ultra-low roughness and high flatness in order to properly handle EUV light at 13,5 nm wavelength. 




2007: Silicon Carbide optics for NIRSpec

Since a few years, under the stimulus of Airbus Defense & Space, Reosc is pushing its polishing technique for Silicon Carbide, a new material for precision optomechanics combining high stiffness to weight and thermal stability, quite the ideal material for aeropsace applications. SiC is tough to polish and we solved this challenge by 2000 with the delivery of the Formosat-2 optics to Airbus.

In 2007 we deliver the first optics for key project of the Near IR Spectrograph (NIRSpec) instrument, one of the few European contributions (with the launch) to the James Webb Space project. NIRSpec included 3 successive Three Mirror Anastigmat (TMA) optics made from SiC material in order to deliver the required imagery under the cryogenic environment at the Lagrange L2 point where JWST will be installed. The mirrors are strong off-axis elements, the specifications are severe, but we deliver in total more than 27 mirror elements and align and assemble them in 9 TMA telescope modules with full success.  

Beside NIRSpec Reosc is also involved in several further SiC space optics

   the GAIA giant primary mirrors of the twin telescopes doing utra-high resolution mapping of the sky

   EarthCare  ATLID lidar telescope optics

   SPOT-6 & 7 and Pleiade NEO new generation of dual-use EO satellites

   the primary mirror of EUCLID, the dark matter hunter of the European Space Agency(ESA)   

   OTOS Large aperture demonstrator for next gen defense EO satellites




2011: Thin glass shell a new type of optical component

Large ground telescopes use more and more Adaptive Optics (AO) mirrors with a large thin sheet of glass actuated by a huge number of actuators to compensate for the atmospheric turbulences.

In 2011 Reosc delivered the first AO thin shell for the VLT M2 AO unit, replacing the solid light Be mirror produced 15 years earlyer by the company. We are proud to have contributed to this major breakthrough

of ESO in ground astronomy with the supply of this 1.1 m diameter aspheric thin shell of only 1.92 mm thickness.

Our technique is based on the thinning after polishing concept, i.e. we first polish the front aspheric surface and then we attach the part to a blocking body and thin it progressively to the 1.92 mm thickness and control its thickness uniformity to the specified 15 µm. The challenge is to preserve the part integrity during the various steps of the process.



2013: Petawatt laser optics & coatings

Laser research laboratories are shifting from nanosecond pulse length to femtosec. This enables completely new physics research to be conducted with peak light power on Petawatts.

Based on its heritage with CEA and Megajoule for ns optics and a PHD work conducted in relation with LULLI-APOLLON new laser lab, Reosc developped new designs and skills in high performances coatings for Petawatt systems. Multi Layer Dielectric (MLD) and later Metal-MLD formula were developped. The tests showed interesting results and Reosc become key partner to LULLI for the equipment of this world leading laser laboraty.

Mirrors, afocal beam expanders, periscope systems, large aperture - high deviation angle Off Axis Parabola, thin sheet mierrors for large AO units correcting the laser beam wavefront deformation, ... are produced in various size in our thin film laboratory.



2015: Advanced IR optics & coatings for MTG

The Meteosat Third Generation (MTG) will be the next satellites collecting data for wheather forecast.

Reosc is a key contributor to MTG thanks to its deep skill in precision IR optom-mechanics and coatings. Beside the entrance scan mirrors and some main telescope optics Reosc is supplying MTG with critical equipment and components :

The Spectral Separator Assembly (SSA) is a compact opto-mechanical equipment splitting the light gathered by the entrance telescope into five spectral sub-bands : the visible channel (0,4 - 0,9 µm), a NIR channel (1,3 - 2,3 µm), the IR1 (3,6 - 7,6 µm), IR2 (8,5 - 9,8 µm) and IR3 (10,1 - 13,6 µm) channels. Relay optics, folding mirrors, beam splitters, diasporameter elements, were designed in the very compact arrangement required, manufactured from various exotic IR materials, coated with a multiplicity of differents coatings adapted to the various spectral bands and functions and finally aligned and integrated in their mechanical barrels.

The various IR filters and windows delivered to Sofradir for integration in the focal plane.

Beside MTG Reosc is also developping the innovative technique of AR coating on the IR detector itself, thus enabling nearly 30 % gain in throughput for the whole system.

More, we have developped a technique to contruct a pixelated AR coating structure on matrix detectors in order to be able to capture dual band imagery with one detector only.




2017: Contract for the ELT M1 segments

May 2017: Contract for the polishing and integration of the 798 (+133 spare) segments constituting the primary mirror of the Extremely Large Telescope.

This major contract is to be associated with other key contracts signed with ESO:

July 2015: Contract for the production of the AO M4 thin glass shells

July 2016: Contract for the polishing of the 4-m aperture M2 convex mirror

Feb 2017: Contract for the polishing of the M3 mirror

March 2019: Contract for design and production of the M5 mirror



2019: First New Space project gained with Norway

In 2019 Reosc is entering in the world of New Space with its selection by the Norvegian Defense Research Organisation (FFI) for the supply of a "Low Light Imager", an EO payload enablig ship detection from durable orbit on-board a nanosatellite plateform of only 20 kg.

In parallel Reosc is maturating its offer of such EO payloads with its Small satEllite instrument for Earth imagING (SEEING) combining top performance optics with COTS 35 mm image sensors:

SEEING 10-m offers 10-m GSD over 60x40 km² from 600 km orbit

SEEING 1.5-m offers 1.5-m GSD over 11x8 km from 500 kmorbit and fits in a 12 to 16-U nanosat. With super-reoslution data processing SEEING 1.5-m is able to deliver down to 0.75-m imagery.

     And more to come ... !



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