Optics manufacturing 4.0 is in its infancy—but it’s a start!

DIOPTIC in Weinheim, Germany, examines the feasibility of optical systems, develops imaging and illumination optics and produces infrared lenses and ultra-precise measurement and alignment technology. It makes use of extensive expertise in the area of diffractive optics. In the interview, managing director Jean-Michel Asfour talks about Photonics 4.0, augmented reality in industry and recreational sport, and space exploration as a driver for increasingly precise optical systems.

Mr. Asfour, would you like to give us a brief description of your company?

Jean-Michel Asfour: DIOPTIC celebrates its 20th anniversary next year. We are 24 employees, ten of whom have a doctor’s degree in physics. Before the company was established, I worked as a freelancer developing medical diagnostics equipment. It involved non-invasive blood sugar measurement using infrared spectrometry. I noticed that in medical engineering there was a high demand for expertise in the field of optical measurement technology. DIOPTIC took its first steps in this area and gradually acquired customers in the automotive, electronics, and food industries, aerospace, and in overarching future-oriented fields such as virtual and augmented reality. We offer services and our own products in optical measurement technology, optics design, and imaging.

You have a very wide range of products and services. How do you manage that with 24 employees?

Asfour: We focus on five fields: optics design for illumination and imaging optics, development of inline and end-of-line inspection systems, diffractive optics, infrared lenses, and our ARGOS surface inspection systems. In our production facilities, we collaborate closely with suppliers and see ourselves primarily as system developers and integrators. Our diffractive optics are special. We are one of only two providers in the world of asphere measurement technology. We do this with computer-generated holograms (CGHs), which we produce in an ultra-precise lithographic structuring process on precision substrates. Through asphere testing we have customer relationships with all the major optics manufacturers in Europe, North America, and, in-creasingly, Asia. We also develop and produce infrared lenses for industrial thermal imaging cameras that measure accurately in the sub-microkelvin range. And with ARGOS, we are active in the area of automated optical inspection. Each of these product areas is looked after by a small, well-practiced team, each with two experts with doctor’s degrees. The focus, our high level of specialization, and the deliberately low level of vertical integration are the key to getting a lot done with just a few people.

With your ARGOS product family you are advancing automated inspection of optical surfaces in the direction of Photonics 4.0. How do you see development in this area?

Asfour: ARGOS is especially tailored for inspection of optical polished surfaces. A system to inspect optical fibers is also used. To date, inspections are carried out almost exclusively visually. Employees assess the surfaces in a dark room with bright light sources – a very tiring process in the long run. Besides, this type of inspection is not really objective, which frequently leads to conflicts between suppliers and customers. Our system needs two seconds to inspect optics. To do this, they are rotated around their own axis and scanned under a line scan camera. The inspection is extremely reliable and objective and the results are automatically recorded in an inspection report. The documentation creates the necessary data base to track process and product quality with the help of statistical methods. Our customers use this, for example, to compare polishing products and processes. ARGOS is a module for Optics Manufacturing 4.0. Manufacturing processes are still dominant: systematic capturing of characteristic variables, tracking individual optical elements, or automated quality inspection in the process have not been able to gain acceptance to date. Optics manufacturing 4.0 is in its infancy—but it’s a start. Among other things, there have been considerations to mark optics with diffractive optical processes to ensure traceability in the process chain.

DIOPTIC, together with partners, develops head-mounted displays for industry and lei-sure. What technological contributions does your company make?

Asfour: In 2008, we spun off MOMES GmbH (Moving Micro Electronic Solutions). It offers a patented system for cyclists that monitors performance via sensors in the pedal and shows this in a head-mounted display. Its optical unit is from DIOPTIC. Our data glasses were launched on the market in 2010; two years before Google Glass. Our display works solely with ambient light and, as a result, the glasses consume very little power. The coin cell lasts for months. It works on the basis of a fluorescent film that provides the background lighting of the LCD display, adjusted to the ambient light, via a waveguide. It works in bright sunlight and under a full moon. In 2018, we received the Gold Award at the ISPO Sports Fair in Munich for this. ABUS handles the marketing. We are also working on augmented reality glasses for the industrial environment in the research consortium Glass@Service together with Siemens, Uvex, Ubimax, Fraunhofer FEP, and the German Federal Institute of Occupational Safety and Health. We are developing the imaging unit and an optical sensor system for the gesture-based system controls. It allows wearers hands-free interaction with specific data systems.

You have developed an alignment system based on your CGHs with which optical elements of the Euclid space telescope can be aligned extremely accurately. Could you briefly explain your approach?

Asfour: Our approach is based on interferometry. With an in-house designed high-precision CGH we generate several ring zones designed specifically for the lenses that are to be aligned. This process is known from surface inspection of lenses, where the visible shifts in the interferogram are subtracted out. In the alignment process we use these interference strips to check whether the optical element is aligned accurately. Consequently, we offer a highly sensitive measuring systemthat shows accurately the direction in which the respective optical element must shift or tip. Relative alignment of the optical elements to each other is ten times more accurate than the process that was previously used.

You can draw a comparison between medical engineering, astronautics, and other applications. Where are the precision requirements highest?

Asfour: The requirements differ in each case. In medical engineering, the main focus is on system reliability. Diagnosis and treatment devices must work correctly at all times and switch off immediately in case of a fault—just think of eye lasers. On the other hand, thanks to the much higher budget, astronautics can push forward to the limits of what is technically feasible and shift the boundaries bit by bit. The precision that is achieved advances us in other applications. For example, the new CGH alignment method could help align elements in the area of freeform surface optics to each other more accurately. Ultimately, the Euclid project has encouraged us to make our CGH-based measuring technology useful for aligning optical elements. The search for dark matter in space provided the stimulus to implement a space telescope with amazing precision. The technical progress that was achieved brings optical technologies another step forward.