C. Bichlmeier, N. Navab Virtual Window for Improved Depth Perception in Medical AR International Workshop on Augmented Reality environments for Medical Imaging and Computer-aided Surgery (AMI-ARCS 2006), Copenhagen, Denmark, October 2006 (bib)
	Real-time in-situ visualization has been a subject of intensive research and development during the last decade. Besides accuracy and speed of the systems one of the challenges to improve acceptance of medical AR is to overcome the misleading depth perception caused by superimposed virtual entities of the AR scene onto real imagery, e.g. virtual tissue and bones occlude real skin. Occlusion is the most effective depth cue and let e.g. the visualized spinal column appear in front of the real skin. We present a technique to tackle this problem. A virtual window overlaid onto the real skin of the patient creates the feeling of getting a view on the inside of the patient. This view is restricted by the frame of the window, however, due to motion of the observer the frame covers and uncovers fragments of the visualized bones and tissue and enables the depth cues motion parallax and occlusion, which rectify the perceptive misinformation. An earlier experiment has shown the perceptive advantage of the window. Therefore seven different visualization modes for the spinal column were evaluated regarding depth perception. This paper describes the technical realization of the window.
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