M et hod o f A d ju st ment s v ersu s M et hod o f Co nst ant St imu li in t he Qu ant i cat io n o f A ccu racy and Precision of R end ered Dep t h in Head -Mou nt ed Disp lay s A b st r a ctThe utilization of head-mounted displays (HMDs) in high-end applications such as medical, engineering, and scienti c visualization necessitates that the position of objects be rendered accurately and precisely. Accuracy and precision of rendered depth for near-eld visualization were measured in a custom-designed bench prototype HMD. Experimental results were compared to theoretical predictions established from a computational model for rendering and presenting virtual images by Robinett and Rolland (1992). Such a theoretical model provided the necessary graphics transformations required so that rendered virtual objects be perceived at the rendered depth in binocular HMDs. Three object shapes of various sizes were investigated under two methodologies: the method of constant stimuli modi ed for random size presentation and the method of adjustments. Results show a 2 mm and an 8 mm performance for the accuracy and the precision of rendered depth in HMDs, respectively. Results of the assessment of rendered depth in HMDs for near-eld visualization support employing the method of adjustments over the method of constant stimuli whether or not the method of constant stimuli is modied for random size presentation.
Head-mounted display design is an iterative process. As such, a standardized usercentered assessment protocol of head-mounted performance during each phase of prototype development should be employed. In this paper, we first describe a methodology for assessing prototype head-mounted displays and virtual environments using visual performance metrics. We then present an application of the methodology using a prototype of a projection head-mounted display and the first module of our assessment: resolution visual acuity as a function of contrast. To evaluate the total system, we also used three different light levels and two different types of projection materials. Results from both studies indicate that the visual acuity metric resolution accurately identified reductions in user visual acuity caused by parameters of the projection display and those of the phase conjugate material. Results further support the need for benchmark metrics that allow comparison of prototype head-mounted performance through each stage of design.
Visualizing information in three dimensions provides an increased understanding of the data presented. Furthermore, the ability to manipulate or interact with data visualized in three dimensions is superior. Within the medical community, augmented reality is being used for interactive, three-dimensional (3D) visualization. This type of visualization, which enhances the real world with computer generated information, requires a display device, a computer to generate the 3D data, and a system to track the user. In addition to these requirements, however, the hardware must be properly integrated to insure correct visualization. To this end, we present components of an integrated augmented reality system consisting of a novel head-mounted projective display, a Linux-based PC, and a commercially available optical tracking system. We demonstrate the system with the visualization of anatomical airways superimposed on a human patient simulator.
Augmented reality is often used for medical training systems in which the user visualizes 3D information superimposed on the real world. In this context, we introduce a augmented reality tool to train the medical practitioner handeye coordination in performing critical procedures such as endotracheal intubation.
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