Adaptation effects in stereo due to on-line changes in camera configuration

The ability to make on-line adjustments to stereoscopic camera position parameters dynamically, during execution of telemanipulation tasks, allows one to maintain a theoretically `optimal' camera configuration, in response to changing viewing conditions. Associated with this, however, is the problem of the observer's being forced to adapt to a (continuously) changing relationship between perceived inter-object distances in the depth plane and the corresponding real distances. One problem in particular is the potential conflict between varying stereoscopic depth cues and unchanging size cues. Two experiments were performed. In the first we investigated how depth judgement ability varied with unsignalled changes in camera convergence distance. This resulted in significant changes in distance judgement, with overestimation for increases in camera separation and underestimation for decreases. Short- term feedback on judgement error was sufficient to correct the changes. In the second experiment, on-screen calibrated depth cues were added, by means of overlaid stereoscopic computer graphics, causing the significant estimation errors found in the first experiment to disappear. The implication of this is that distance/depth judgement can in principle be rescaled to compensate for perceptual conflicts caused by changing camera configuration, by providing either real or virtual depth scaling cues at the task site.