“Holography is as promising as electronics was in the 1950s and 1960s”

Mr. Cedra and Dr. Schütz, how did your companies come to collaborate on the development of holographic display elements for the windows of buses and trains?

Ingolf Cedra: Our cooperation began ten years ago when HÜBNER, together with the Fraunhofer Institute for Physical Measurement Techniques IPM in Freiburg, received a PRISM Award for the tunable laser “C-WAVE” a continuously emitting optical parametric oscillator that emits laser light over the entire visible spectral range. We have continued to develop this principle further and created a new laser platform that is ideally suited for holographic applications in various wavelength ranges of the RGB (red-green-blue) spectrum due to its high performance in CW mode. Together with ZEISS Microoptics, we have worked out the technical requirements of an industrialized application in holography and incorporated them into the further development.

Our new “HoloTUNE” laser platform is now available in three versions for the different wavelength ranges. In the course of the partnership, we started talking about how we could use our respective laser technology and holographic expertise to create innovative products that are relevant for customers in our core market of public transportation, in other words, for rail companies and public transport providers. We had already had the idea of developing innovative displays and lighting options before and had pursued several approaches. But it was only with ZEISS that we found a partner who placed very specific, high demands on our lasers for its holography development and had a clear idea of how holography could be industrialized. That decisively advanced our laser development. Now that ZEISS has integrated our lasers into their holography systems, we are working together to integrate its holographic display modules into our window systems for trains and buses. We built a demonstrator and recently presented it at Innotrans, the world’s largest trade fair for the rail industry. The feedback was outstanding. There is obviously great interest in the public transportation sector in new display solutions for passenger information and infotainment.

Dr. Viktor Schütz: ZEISS is pursuing the strategic goal of industrializing holography. To achieve that, we need to develop value-adding products. To that end, we have solved a host of technological issues both internally and externally with partners as part of the development process. Within the design of the replication technology, we have reached an agreement with Hübner in the field of laser technology and have entered into a strategic partnership for this purpose. Since Hübner, like Zeiss, serves various markets and offers different products, it made sense to exchange ideas about potential applications and cooperation opportunities and thus combine our expertise in optics and optics production with HÜBNER’s specific industry knowledge in the train and bus sector. In general, we define the optical systems and set up the corresponding production steps so that we can implement the holographic products for the mobility, consumer and home tech markets together with partners. Cooperation with strategic partners is a guiding principle for ZEISS. With the reliable and industry-compatible “HoloTune” lasers, we can also bring holographic displays for different markets into series production. Transparent displays for buses and trains are a very promising future field. We see this as just the beginning and have many more application ideas for the public transportation market that we want to drive forward together.

What are the main advantages of holography over OLED or LCD displays?

Cedra: They are technically simpler (but only at first glance), require less energy and less installation space in the vehicle, can be retrofitted at any time as no complex technology is required for output media, and on top of that offer a high image resolution. If you look around in today’s buses and trains, you will find a few displays that take up a lot of space and are also expensive. They are also not visible from all seats. Holographic displays, on the other hand, can be integrated into any window, offer unbeatable imaging quality even in backlit conditions and are easy to install. All that is needed is the holographic film, which is integrated directly into new windows and applied and protected on the window in retrofit solutions. The projector can be installed above the windows in the smallest of spaces. The technology also offers options for interactive operation or for the flexible division of window surfaces to provide customized information. And the holographic displays show the information where passengers can see it immediately, in other words, directly at the point of interest. We will now test with the first pilot customers how passengers accept this solution and to what extent scaling it makes sense. We see the scaling and flexible division of the window areas as a major advantage of holographic displays. Every public transport provider can follow its own philosophy here—and retrofit its existing fleets with passenger information and infotainment systems. We are talking about several million vehicles worldwide.

Are window surfaces needed to integrate holographic display elements like these?

Schütz: A quick addendum on energy efficiency: A typical television needs up to 200 watts for a 55-inch screen diagonal. Depending on the projection surface used and the defined eyebox, a holographic display manages with a x10 watt projector and provides information at the point of interest within the eyebox exactly when it is needed—Otherwise this surface is almost completely transparent and does not obstruct the view. However, it is also possible to use much larger display areas with more powerful projection systems. But back to your question: Basically, we can transform any surface—whether transparent or opaque—into a display-on-demand using our holography systems. All that’s needed is the holographic film, the projector, the holograms and the corresponding know-how for their optimal integration ...

Cedra: ...we have this expertise in window systems for buses and trains. For HÜBNER, the project is a bridge between the photonics enabled technologies of our HÜBNER Photonics division and our traditional core business of mobility. It is an answer to the question we often hear internally as to what photonics and mobility have to do with each other and how the two areas belong together in our company. I have long been convinced that photonics as a platform technology will sooner or later gain a foothold in every living space and every industry. With ZEISS, we are bringing our respective ecosystems together to harness the best of both worlds for the industrialization of holographic displays. Whether in buses and trains ...

Schütz: ... or in cars, public spaces or retail—we see huge potential.

The purpose of windows is to let light in and let people see out. Is this original function impaired by the integration of holographic display elements?

Cedra: The naked eye cannot see whether a holographic film is integrated into the window. Information only appears when the projector projects the image onto the hologram film. Otherwise, the pane is completely transparent.

Do all passengers see the same thing or do the viewing direction and angle play a role in what can be depicted holographically?

Schütz: With holography, we implement displays on demand. In other words, information can be displayed in specific areas that is relevant to the passengers sitting there or that advertisers have paid for, for example, such as information about museum exhibitions or places to eat near the next stop. Who gets to see this and other information and in what form will have to be clarified in future use case analyses and derived business models. In this context, your question points to an important difference compared to conventional displays: Depending on the viewing angle, information can be selectively provided for a few or even a large number of passengers. Thanks to holography, there are virtually no limits.

Can you outline the hardware structure of holographic displays and explain your companies’ respective contributions?

Cedra: In principle, all you need is the holographic film and (if desired) a high-resolution LED-based projector that projects the image information onto the film. Our tunable lasers are used for mastering and replication, in other words, duplicating the holograms. This is a major advantage in terms of the system costs for the display modules.

Schütz: The complexity of this display technology lies in the hologram. This is the crucial difference compared to LED, LCD or OLED displays, which are manufactured in high-tech factories with highly complex processes. A display factory is an investment worth billions. Semiconductor materials are also a valuable, energy-intensive resource, of which, by comparison, only tiny quantities are required for holographic displays. The hologram itself is created by the interaction between a photosensitive material and special laser technology, which inscribes the corresponding information into the volume of this material. This is where ZEISS’ expertise lies, which we have built up in recent years and secured with several hundred patents for various aspects of holography technology. To sum up, we have developed built up with partners an industrial, purely photonic production chain requires no physical forming, casting, grinding, embossing or the like ...

Cedra: ...and is absolutely fascinating! As a result, the manufacturing costs for a hologram are far lower than the current state of the art in the display market. We see better quality, and higher energy and resource efficiency at lower costs. These are the prerequisites for rapid, possibly even disruptive market penetration.

What strategic role does photonics play for a group of companies like HÜBNER, which—at least from an external viewpoint—has a clear focus on the mobility sector?

Cedra: We are a family-run group of companies with around 3500 employees worldwide and a turnover of around 500 million euros. HÜBNER has been active in photonics for quite some time. Shortly before I joined the management team here in 2014, the company had won two PRISM awards with Fraunhofer IPM. In addition to our tunable laser “C-WAVE”, our terahertz spectrometer “T-Cognition” was also honored. For me, this was proof of the potential of these technologies, which were recognized and rewarded accordingly by the industry. I see our photonics business as a strategic growth area that we are consistently boosting by recruiting outstanding specialists and making targeted strategic acquisitions. Opening up new target markets and strengthening our sales organization play a central role in this. Since 2016, HÜBNER Photonics has been our third independent business area alongside Mobility and Material Solutions and a separate corporate division. It has a steep growth curve behind it—and, in my opinion, even more so ahead of it. In the future, the HÜBNER Group will be a foundation company. The basis for that was laid years ago. We take a very long-term view and see technological diversification and a focus on sustainability as the key to remaining successful and independent in the long term.

What is your focus in photonics?

Cedra: We address four core markets: Life science, where we maintain strategic cooperations with instrument developers for diagnostics in addition to our strong laser portfolio. Metrology with a focus on spectroscopy and microscopy. A third field is quantum technologies, in which a variety of our highly customized lasers are in great demand. And the fourth field is interferometry and holography. We have been active here since 2016 and have cooperated closely in the past with various North American start-ups that wanted to establish holography in the automotive industry. In these projects, we have learned that good technology is not everything. True to our slogan “Coherence matters”, our high-performance lasers have the necessary high coherence length. However, market access is complex, and industrialization is complicated and requires vast and very special know-how. That requires the right partners, which is why we feel like we are in very good hands in our cooperation with ZEISS.

Buses and trains are probably the exception for ZEISS. To what extent have you recently experienced an increased diversification of photonic target markets, Dr. Schütz?

Schütz: Diversification is inherent in holography. We don’t have to implement photonic systems with glass or plastic optics. It is also possible to inscribe a great deal of optical information in a hologram in order to implement much more compact systems. This is the basis for a large number of new products that were simply not possible to produce in the past. In our view, holography is just as promising as electronics was in the 1950s and 1960s. Just as the first silicon chips were on a completely different scale to those of today, optical systems based on holography and integrated optics will become increasingly miniaturized—and take up less and less space for ever more complex functions. When I look at the progress made in electronics in recent decades, I look forward to the development of optics, photonics and holography—and to playing an active role in shaping it! ZEISS recognized these opportunities early on and is investing strategically in this field of technology.