Bernhard Schurian/ Fraunhofer FOKUS

Projector Auto-Alignment for Arbitrary Shaped Screens

A multi-projector system is often necessary when projecting content on curved screens, such as panoramic or dome projections. The challenge lies in calibrating the projectors with reasonable expenditures of time and effort in such a way that a homogeneous image is created.

Fraunhofer FOKUS has developed an automatic camera-based projector calibration procedure that stands out with its great flexibility and speed. Test patterns are projected onto the screen and automatically captured by digital cameras.

Using imaging processing algorithms, the image parts sent by each projector are then distorted and adapted to the screen in such a way that a high-resolution, seamless image emerges. The projectors' partial images are accurately adapted to one another in the areas of overlap. Automatic projector re-calibration can easily and quickly be run whenever the position or the parameters of one or more projectors change. The projection screens can be of any shape: domes, spheres, cylinders, and curved screens are just some examples.

The system thus covers all necessary functions for an automatic multi-projector calibration: geometry correction (warping), automatic softedge blending, brightness correction and projector auto-alignment. Fraunhofer FOKUS holds several patents on camera-based projector autocalibration.

Fraunhofer FOKUS is licensing the software (warping, blending, and projector auto-calibration) and integrates it in existing and new systems, such as media servers, warping boxes and projectors.

In the last ten years, more than 130 multi-projector installations with more than 600 projectors in 13 different countries worldwide have been created using the Fraunhofer FOKUS software for projector autoalignment, warping and edgeblending. Most of the installations are planetarium domes, amusement parks, flight simulators and 3D dome cinemas.

In 2013, Fraunhofer FOKUS disclosed the details of their automatic projector calibration technology in the book “Fullspace-Projektion. Mit dem 360°Lab zum Holodeck” that was published by Springer Publishing.