Fraunhofer FEP Presents Anti-Reflective Coatings

At SID Display Week, June 2-4, 2015, in San Jose, CA (German Pavilion, booth no. 222) the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP will present a coating that is required to expand the diameter of a laser beam by more than factor of one hundred. With this coating, backlighting for holographic displays can be realized in the future.
 
SeeReal Technologies in Dresden works on holographic displays. Holographic displays use certain properties of laser light for the complete three-dimensional display of images. Therefore, an expansion of the laser beam to the display size is necessary. One can easily imagine that a laser beam with a diameter of a television display is difficult to realize. A conventional option would be large lens systems, but these are clunky and can only be manufactured complexly and at very high costs.
 
In a joint project with SeeReal Technologies, the scientists of Fraunhofer FEP have now developed coatings that enable usage of low power lasers for illumination. The laser is directed in at a very flat angle into a glass plate. Similarly to the shadow of a person which is extending in the setting sun and whose projected area on the earth also extends, the diameter of the laser beam increases. A small spot becomes an elongated ellipse.
 
In a second step, the elongated ellipse impinges again on a second glass plate, whereby the second direction of the ellipse, the “short axis,” is elongated. Thus the laser spot is expanded to a circle, that is large enough in order to illuminate the entire display.
 
“We have developed an anti-reflective coating which increases the part of the transmitted light significantly,” said Dr. Daniel Gloss, head of the Dynamic Coatings department of the Precision Coatings division at FEP. “By means of magnetron sputtering, thin layers are deposited on glass. These layers consist of two different materials with varying optical density. Even complicated optical functions can be achieved via multilayer systems, which, for instance, let only certain colors of the light pass through and reflect the others.”
 
The anti-reflective coatings, which were manufactured at Fraunhofer FEP, were installed into the demonstrator of SeeReal Technologies. There, holography has already become reality.