The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology (FEP) in Germany has integrated its bidirectional OLED microdisplays for the first time into multifunction data glasses, enabling new applications in the areas of augmented and virtual realties and 2D and 3D content.
Fraunhofer FEPs had previously developed the bidirectional OLED microdisplays, which comprise an OLED microdisplay with an additional image sensor. The imager can be used for detection. “In the new glasses, this sensor is used to capture the eye scene, which allows eye tracking and, thus, an interaction with the system,” says developer Judith Baumgarten, Fraunhofer FEP. “As an advantage, compared with external eye tracking cameras, the image sensor of the bidirectional microdisplay captures images with almost no distortion, as it is virtually mounted on the same axis as the eye by use of a special optic.”
Fraunhofer FEP has been developing OLED microdisplays for more than 10 years. So Baumgarten says the fundamental technology is ready to use for customer and application-specific products. “To demonstrate this, Fraunhofer FEP has developed this initial demo to show the impact and TRL (technology readiness level) of the technology,” the expert says.
Best solution for VR/AR
“In general, OLED microdisplays are the best solution for VR/AR because they provide best-in-class contrast and image performance with rather low power consumption — caused by the self-emission of the organic layer,” Baumgarten says, adding that compared with liquid crystal on silicon (LCOS), the system does not require additional components, such as an external light source. “With the integration of the image sensor, even more functions are moved to the microdisplay, resulting in a high-end SoC (system on chip).”
Applications for bidirectional OLED microdisplays
According to Baumgarten, interactive data glasses are the primary application for this new kind of bidirectional OLED microdisplays, but she adds that bidirectional microdisplays can be used in other applications requiring a light source and an imager. An optical fingerprint sensor Fraunhofer FEP has already presented is one example.
Challenges in developing the bidirectional OLED microdisplays
Her team's biggest challenge in developing these new bidirectional OLED microdisplays, according to Baumgarten, was controlling the image sensor without impacting the display function. “To solve this, we included different modes to the silicon chip to control light emission and detection.” These modes fall into two categories: parallel mode, where exposure and illumination/display function run in parallel, and sequential mode, where those two phases occur time-sequentially. Each modes has its advantages, depending on the application.
“The demo of the bidirectional OLED microdisplay in data glasses is one application of the technology,” Baumgarten says. “We are currently working on many other fields of applications.”
Baumgarten and her Fraunhofer colleagues are now working on achieving higher resolution and lower power consumption with the microdisplays, even at high frame rates. “In the field of data glasses and electronics, we intend to minimize the overall system size,” she says. “Using this, we want to roll out the technology to other applications, including smart systems, sensors, etc.”
Written by Sandra Henderson, Research Editor, Novus Light Technologies Today