16.09.11

Fraunhofer Institute paves way for 4-camera 3D shooting

For 3D to be watched comfortably without glasses a new way of shooting and processing is needed, according to The Fraunhofer Institute for Telecommunications. The German organisation is working on a four-camera system that will be able to handle live transmissions. Calibrating four cameras can take days but the Fraunhofer research scientists are developing a system that can slash the time to between 30 and 60 minutes.

When the boundaries merge between the action and the viewer, television becomes a special experience. Fraunhofer research scientists are optimizing the technologies that make it possible to watch TV in 3D without technical aids such as 3D glasses. A new four-camera system will even be able to handle live transmissions.

“The breakthrough for 3D television will only come when you don’t need glasses, argues Frederik Zilly from the Fraunhofer Institute for Telecommunications, Heinrich Hertz Institute HHI in Berlin. “Wearing them is just too uncomfortable and tiresome.”

Research scientists at HHI are working with twelve partners in the MUSCADE project on technologies which will make glasses-free 3D TV viewing better.

This relies on autostereoscopic displays, which are coated with special optical foils. They create two different images for the left and the right eye, which is the basic principle of three-dimensional vision. To allow different viewing positions – for instance, when the viewer moves his head – these displays use five to ten different views of an image. In the future this number will be considerably higher. As conventional stereo productions only have two views, however, the captured images have to be converted before transmission, for which purpose depth information is extracted from them.

HHI researchers believe that to reliably determine depth information more than two cameras must be used. The MUSCADE project partners use four cameras, but this makes the already complex stereo production extremely intricate and expensive. “It can take days to calibrate four cameras to each other,” explains Zilly.

A four-camera assistance system is claimed to reduce this timeframe to about 30 to 60 minutes. “The development is based on our STAN assistance system, which has already proved its value in conventional stereo productions. But with four cameras calibration is much more complicated,” explains Zilly.

This is because all positions and angles of the cameras must be set exactly the same so that the optical axes are parallel, all lenses have the same focal length and all focal points are on a common stereo basis.

Therefore, the scientists have developed a feature detector, which recognizes identical objects in the image on all cameras. Using their position, the assistance system then calibrates the individual cameras to each other. But even after calibration small inaccuracies remain. These occur if lenses with fixed focal lengths are used, which in most cases are subject to small fluctuations. Such residual faults can only be corrected electronically, e.g. using a digital zoom. This last correction stage is carried out by the new assistance system in real time – making even live transmissions possible.

The HHI research scientists are currently working on an efficient video encoding system for compressing the huge volume of data that arises when four cameras are used so that the content can be transmitted on the existing broadcasting infrastructure.