Jérémy Picot-Clémente, EPIC’s Photonics Technologies Program Manager, talks with Jürgen Zosel, division manager of engineering at Orafol Fresnel Optics, a manufacturer of microstructured polymer optics
Early career
In 1991, after graduating with a Bachelor’s of Science in Electrical Engineering, which focused on electro-forming, Zosel joined Fresnel Optics, based in Apolda, Germany. Since its foundation in 1972, Fresnel had specialised in the manufacture of compression mouldings for OHP lenses for overhead projectors. But, at the end of the 1980s, this came to a halt because the required tools became unavailable. As a result, he was taken on as Technical Manager to develop new technologies, particularly galvano-forming processes to form or grow metal parts.
Company development
In the 1990s, Fresnel became a subsidiary of the US company Reflexite, a developer of OHP lenses, and Zosel oversaw the introduction of compression moulding and injection moulding technology and galvanic treatments into Fresnel’s production processes.
Over the next 10 years, Fresnel refined its vario-thermal injection moulding processes and focused with this technology on microstructured polymer optics. But, when the LCD projector emerged, the demand for OHP lenses fell and so there was a need to broaden Fresnel‘s portfolio in 2003. Accordingly, they introduced silicone-on-glass lenses, and focused more on the solar market, that is until 2014, when the European solar market collapsed – forcing the company to downsize from a workforce of 125 to around 80.
In 2011, Reflexite was bought by Orafol Europe, and the company became known as Orafol Fresnel Optics. Over the next few years, Fresnel continued to develop optics, including for a reduced CPV (concentrating photovoltaic systems) market. But, by 2013, the solar market had broken down completely, so they shifted towards a more flexible approach with a focus on products for the emerging markets like machine vision, sensors, lighting and the display sector.
In 2016, Zosel’s friend and Fresnel’s Managing Director suddenly died, which was a shock and challenge for the whole company. Zosel accepted the offer from Orafol for him to take over as MD, as he saw it as a way to maintain continuity for the employees – and avoid the possibility of someone coming in from the outside who may not understand the technology.
Fresnel Optics today
Fresnel currently offers custom fabrication of plastic micro- and nanostructured optical components based on a complete chain of optical design, tool fabrication, precision polymer replication, and custom finishing. Its main markets are lighting and solar along with machine vision, sensors and display, which have seen spectacular growth. Machine vision is particularly important due to the wide range of polymer optics required for image processing applications. Their products, both standard and customised, include Fresnel lenses – whose surface is divided into a number of concentric grooves – cylindrical Fresnel lenses and also reflective corner cube retro-reflectors.
Fresnel’s polymer optical components are also ideally suitable for use in sensor applications as the company’s range of polymer processing technologies enable them to fabricate optics of high precision, excellent contour accuracy and low stress birefringence. For display applications, the company offers the customised development and fabrication of light guides for uniform illumination with a high lumen yield. For decoupling light, they use different scattering patterns such as fine surface structures or printed dot patterns, and they can manufacture plano components as well as wedge-shaped parts.
Fresnel’s core capabilities include optical design using specialised software, and master tools manufactured by ultra-precision machining (UP) using technologies, such as UP-diamond turning, UP-fly-cutting and UP-linear ruling.
Additionally, different manufacturing processes are available for precision polymer replication, i.e., compression moulding, a special injection-compression moulding process, and a casting process for the fabrication of hybrid optics (silicone-on-glass).
Also available are standard and custom anti-reflective and reflective coatings as well as interference layers that can be applied on polymer substrates of plano, structured or continuous surfaces.
Fresnel’s polymer optical components are suitable for use in sensor applications
For Zosel, one of Fresnel’s most important core capabilities is custom finishing, which is achieved by CNC milling that can cut parts to virtually any shape in close tolerances. The other is quality assurance.
As he explains, although the company has been certified according to ISO 9001 since 1996, it has taken a lot of time and money to ensure the ultra-high levels of quality control required for customers.
Every component, big or small, has to be inspected before it leaves their facilities and the first inspections are now fully automated – except for larger parts that are still inspected manually as they are too difficult to handle in an automatic process.
But the main challenge has been inspecting microstructures because of the difficulty in finding inspection systems on the market that can handle such special components. After unsuccessfully trying for several years to find a suitable system, Fresnel finally took matters into its own hands and, 18 months ago, in collaboration with a partner, designed and implemented its own microstructure inspection system.
Every component has to be inspected before it leaves the premises
The future
For Zosel, Fresnel has a bright future, particularly in the machine vision and lighting markets. His strategy will be to continue as they have done over the previous five years: developing and producing optical components in cooperation with customers, and to introduce new standard micro and nanostructured components as new market needs emerge. To this end, Fresnel has a number of advantages over its competitors. As he explains, microstructured lenses must have absolutely precise surfaces, which are not possible to achieve with standard injection moulding machines. To meet this challenge, the company has successfully implemented vario-thermal injection moulding to provide the level of accuracy that will be required by next generation applications and this capability has become one of their unique selling points.
Furthermore, the master tools, which are the starting point for any production, are all original and in-house. The master tool is the basis for the so-called ‘tooling tree’, whereby, for example, in an electroforming process, several copies of the master tool are created from which stampers are created for the actual fabrication of the components themselves. In parallel to having the master tools in-house there is good option to offer prototyping to enable customers to quickly evaluate a lens design.
These factors mean the company is well-placed to consolidate and enhance its position as a leader in microstructured polymer optics.
When asked about his advice for the next generation of entrepreneurs, Zosel says the most important thing is to be able to motivate your team and employees to work together on interesting projects – and to motivate them to stay in the company.
