Binocular telepresence systems afford the opportunity of increasing the inter-camera distance (ICD) beyond the normal interocular distance (IOD) which magnifies the magnitude of the disparity information. This improves performance in nulling and matching tasks. Here we examine whether telepresent observers can learn to use enhanced disparities to accurately perform tasks requiring the recovery of Euclidean geometry (a shape task). The design comprised three phases: pre-adaptation (ICD equals 6.5 cm), adaptation (ICD equals 3.25 or 13 cm) and post-adaptation (ICD equals 6.5 cm). Telepresent observers were required to adjust the magnitude of a depth interval (specified by binocular disparity) so that it matched a specified 2D interval specified by two lights (set between 5 and 15 cm) in an otherwise blacked-out scene. In the adaptation phase, the ICD/IOD ratio was changed to 0.5 or 2 and observers adjusted the depth interval repeatedly until a performance criterion was reached. Two forms of feedback were given in the adaptation phase: direct, where another light was shown at the correct disparity; and symbolic, where a signed number indicated the magnitude and direction of the error. Observers were clearly affected by ICD/IOD changes but learned the new ratio rapidly under both feedback conditions.
The experiments reported here were designed to address two aims. Th first was to determine the sufficiency of head- generated motion parallax, when present in isolation, for the control of natural prehensile movements. The second was to assess the consequences of providing enhanced parallax information for prehension. Enhanced parallax was created by changing the spatial extend of the movement of a camera relative to the extend of the teleoperator's head movements. The gain ranged from 0.5 to 4. The scene was viewed for 2 secs before reaches were made in open-loop conditions. Results showed clearly that information from motion parallax is sufficient to support reliable and accurate motor movements. The enhanced information, led to predictable distortions in perceived size and distance and corresponding alterations in the transport and grip components. The results suggest that the provision of parallax information is beneficial for tasks requiring the recovery of metric depth information. However, if enhanced parallax is used, which facilitates performance in a range of perceptual tasks, re-calibration of the relative motion information is necessary to prevent size/distance distortions.
The control of inter-camera distance (ICD) can be used to change the range of binocular disparities available from a visual scene viewed remotely. Binocular disparity is considered pre-eminent in the control of reaching behavior. One reason for this is that once suitably scaled it can specify metrical depth relationships within a scene. Such information is necessary in order to plan the transport and grasped phase of a reaching movement. However whether an observer can take advantage of enhanced disparities to control reaching is unknown. Here we examine the effects of manipulating ICD on reaching movements with ICDs ranging from 6.5cm to 26cm. Typically sized, real world objects were placed in a scene and reaching performance was assessed. An experimental sequence consisted of three blocks. The first and last block used a normal ICD/IOD of 6.5cm whereas the middle block used an increased ICD. Larger than normal ICD were found to disrupt reaching performance, with slower peak velocities and smaller grip apertures being observed. This was more pronounced for unfamiliar objects. Little evidence for learning was found.