YD: OLED-on-Silicon is a mature technology but has long been affiliated with specific applications like electronic viewfinders, sports optics and defense. What are the advantages of this technology compared to the other incumbent ones?

Gunther Haas (GH): First of all, one main differentiator of OLED-on-Silicon technology compared to other established microdisplay technologies like LCoS is the excellent contrast and overall picture quality. Especially for near-to-the-eye applications, users are very sensitive to this as there is no light from the external environment affecting the display image. We developed an OLED technology with excellent uniformity. The gap between the pixels is so small that it is invisible. In addition, our pixel structure has even smaller sub-elements due to our quad pixel arrangement. Compared to LCOS or LCD microdisplays, the difference in picture quality is very visible in an electronic viewfinder. This is key for digital cameras, but also for defense applications because it relates to the distance of detection. In addition, for head-up or AR-type applications, where the display image is optically laid over the user’s natural view, we can provide extremely high contrast, meaning a black level close to zero, which is mandatory in order not to get parasitic light in the user’s view.

Secondly, our OLED-on-silicon technology has a much better power efficiency compared to our competitors, and to the other technologies mentioned. The display, with its optical system, has a very compact footprint as it does not require external illumination.  All near-to-eye applications are portable and battery-operated, so a power-efficient and compact technology really make the difference. This is especially key for eyewear VR/AR applications.

Last but not least, the wider temperature range and faster response times compared to LCD and LCOS have been one of the main drivers for defense and sport optics applications, where LCOS or LCD are now rarely used.

YD: AR has been promised for many years. Given the need for a microdisplay technology, OLED-on-Silicon products have tried to make a push for this application in wearables and headsets. What would be the advantages of using OLED-on-Silicon?

GH: In the AR space, initially LCOS-based systems were dominating because they can provide very high brightness, but it was at the cost of a bulky and power-hungry system with low picture quality. As explained before, AR glasses require compact and power-efficient displays with very high contrast. As of today, only OLED microdisplays can deliver this. In the past, the limited brightness of OLED microdisplays has been the main limitation. However, advances in OLED materials as well as new device architectures we developed, have allowed us to overcome this issue. As the first products based on our ActiveLook platform impressively demonstrate, OLED microdisplays can be used in full optical see-through systems, even in the  brightest sunlight. These first products are based on a monochrome display, but a two-primaries red and green microdisplay is used by another customer in an AR system for outdoor applications. We currently have full-colorr versions of high brightness OLED microdisplays under development and sampling to our customers.

YD: You very recently raised 8M€ to accelerate the deployment of your ActiveLook Smartglass Platform. What is this platform?

Eric Marcellin Dibon (EMD): ActiveLook is a compact module for AR sunglasses, which connects to various devices, such as mobile phones and smartwatches. The overall system weighs less than 7g with over 12-hour autonomy, including battery, optics, microdisplay and full electronics.

Our first target was the sports eyewear market, and we wanted to do it differently from all the other techie smartglasses. Everything is built around our core technology, our ultra-efficient high brightness microdisplay, with only 1mW power consumption. We designed the system to be very lightweight and to enable stylish good-looking sport sunglasses that are indistinguishable from regular eyewear, and are designed to project data directly in the lens without obstructing and obscuring your vision. Julbo, the extreme sport sunglass maker, recently introduced the EVAD-1digital sports glasses this year. They did a fantastic job integrating our ActiveLook module. We are very proud of this collaboration. The design is amazing. The glasses are very comfortabl, and include photochromic lenses. When you wear them, nobody can guess it includes a real heads-up-display. The Julbo EVAD-1 comes with an ActiveLook sport application, which is available on the Apple App Store, Google Play, and Connect IQ from Garmin.ActiveLook is an open platform. It includes a Software Development Kit, which enables partners to develop their own custom-designed applications. We are working with many partners who see a unique opportunity to extend their market access by making their data available directly in the ActiveLook module. Examples include coaching applications and performance monitoring. Thanks to its low weight, long-duration autonomy, and form factor, ActiveLook will also be an excellent platform for industrial applications, such as connected safety glasses. We have many projects in the pipeline. This is a very exciting time for us.

YD: Why have you decided to go towards developing more than a display, and producing a complete platform? Was it an internal effort or a pull from your clients and partners?

EMD: We have always been a very customer-focused company. Step by step it became obvious that our customer base and new markets were looking for solutions rather than just a microdisplay. It is especially true for new use cases and augmented reality. The consumer brands are very strong in marketing, product design, and retail, but they do not necessarily have a good understanding of the technology. Many have tried to assemble technology parts together but for a poor result. This is where we have a key role to play.

We were convinced that by taking into account the requirements of the customer’s product, from an end-user point of view, we could do things differently, by optimizing the technology all along the chain, from the optics to the microdisplay and the electronics.

At the beginning, it was fully an internal effort, we had to grow the team, integrating many forms of expertise, including mechanical, system engineering, optics, and firmware. Our deep understanding of microdisplays, video, and optics technologies helped us to develop a module that meets market demand.  Very quickly customers approached us and started collaborating on projects together. We provided the expertise and technology they did not have. We have many partners working with us to develop new products and use cases. Julbo’s EVAD-1 sunglasses are the first of these projects. We will extend ActiveLook to many customers and partners but also to other AR applications.

YD: A long-talked but still prototype early-phase technology has been around for a few years now, namely microLEDs. There is lots of promise but no product yet. Do you see this technology as a threat?

GH: The display industries always went through major technology changes, from cathode ray tubes to liquid crystal displays, to OLEDs. For sure new technologies will arise. However, some did not succeed or had very limited market access such as field emission displays, plasma, and DLP, because their key features only matched niche market requirements.

We have so far seen early prototypes of monochrome microLED based microdisplays with very high brightness. However, the samples show many defects and it is not really possible to evaluate picture quality. There are numerous technical hurdles that would have to be overcome for microLEDs before becoming a competitive microdisplay technology even for monochrome displays.

In contrast to OLED-on-Silicon, microLED-on-Silicon is a heterogeneous technology. This means that millions of interconnects at pixel level are required in order to connect the individual pixel circuits to the corresponding microLED element. It is not clear how a reasonable manufacturing yield can be achieved for these interconnects as only very few or sometimes zero-defect pixels can be tolerated in a display. Also, the overall manufacturing process is very complex and includes further steps for pixelization and common connection of the LEDs as well as steps like substrate release. Overall, the cost of manufacturing will be very high.

The efficiency of microLEDs drastically decreases with pixel size, and from available data, we can see that power consumption will be significantly higher compared to OLED, at equal brightness.

MicroLEDs require pixel-to-pixel homogeneity calibration including full-frame memory, which increases both cost and power consumption.

In addition, for AR and other near-the-eye applications, there is no real advantage. The required brightness for monochrome applications is easily met already by our OLED-based microdisplays. However, I think it is in principle possible to realize such monochrome microdisplays that could be used for projection applications where really high brightness is required and where power efficiency and cost are not essential.

When it comes to color, as of today there is no realistic solution how to make full-color microLED-based microdisplays. Full-color direct view microLED displays using color conversion via red and green Quantum Dots has been demonstrated, however with a quite low resolution of 100-200ppi, and with rather low brightness. In microdisplays, we typically have resolutions between 2000 and 4000ppi which correspond to pixel sizes down to 6µm, which is impossible to realize with quantum dots.

Many efforts in microLED today target larger size, relatively low-resolution direct view displays, using mass transfer techniques from red, green, and blue microLED wafers to large glass substrates. I cannot comment on how successful this might be, however, I do not see how microLED technology for very high-resolution displays like microdisplays could become a reality.

On the other hand, OLED materials and devices, in general, are still making significant progress. There is a large critical mass of material and technology developers behind. One example is the recent progress in highly efficient blue emitters.  For microdisplays, we are currently making great progress in terms of efficiency and light output, as well as for optical systems for AR applications which are becoming more efficient as well. Only few applications like projection or some HUD-type applications really require extremely high brightness. Therefore, there will be only a very small space for an expensive and very capital-intensive technology to breakthrough. It is not obvious that even if all the technical and cost-related problems could be solved that this technology will reach the market.

Read more