Military missions often require drivers to maneuver across hazardous, off-road terrain using visual displays rather than direct vision. When soldiers use 2D displays, significantly more mobility errors occur than when soldiers use 3D displays that provide a stereoscopic view of the terrain. The purposes of the present experiment were to quantify the visual forewarning of a drop-off provided by a stereoscopic 3D display compared to a 2D display, and to measure the potential of increased camera separation (i.e., hyperstereo) for enhancing the benefit of 3D for the detection of terrain drop-offs. This experiment consisted of four viewing conditions: 0X (the 2D condition), 1X (stereo with the normal interpupillary distance [IPD] between the viewpoints provided to the two eyes), 2X (stereo with twice the normal IPD), and 3X (stereo with three times the normal IPD). Thirty-two participants viewed 80 video clips, each clip depicting an approach to a terrain drop-off as would be seen in a daytime driving situation. As soon as the drop-off became apparent, he or she pressed a brake pedal. As expected, the average detection time for drop-offs viewed with 1X (stereo display) was significantly better than when drop-offs were viewed with the 0X (2D) display. The failure to observe further improvements in task performance with 2X and 3X IPD suggests follow-on research to determine whether these unexpected hyperstereo results may be attributable to adverse side effects of hyperstereo: increased mismatch between accommodation and convergence, the minification effect, and increased stereoscopic "frame violation."

This paper discusses the depth acuity research conducted in support of the development of a Modular Multi-Spectral Stereoscopic (M 2 S 2 ) night vision goggle (NVG), a customizable goggle that lets the user select one of five goggle configurations: monocular thermal, monocular image intensifier (I 2 ), binocular I 2 , binocular thermal, and binocular dualwaveband (thermal imagery to one eye and I 2 imagery to the other eye). The motives for the development of this type of customizable goggle were (1) the need for an NVG that allows the simultaneous use of two wavebands, (2) the need for an alternative sensor fusion method to avoid the potential image degradation that may accompany digitally fused images, (3) a requirement to provide the observer with stereoscopic, dual spectrum views of a scene, and (4) the need to handle individual user preferences for sensor types and ocular configurations employed in various military operations. Among the increases in functionality that the user will have with this system is the ability to convert from a binocular I 2 device (needed for detailed terrain analysis during off-road mobility) to a monocular thermal device (for increased situational awareness in the unaided eye during nights with full moon illumination). Results of the present research revealed potential depth acuity advantages that may apply to off-road terrain hazard detection for the binocular thermal configuration. The results also indicated that additional studies are needed to address ways to minimize binocular incompatibility for the dual waveband configuration.