Effect of outside view on attentiveness in using see-through type augmented reality device

When a viewer watches a virtual image through a see-through augmented reality (AR) device and an outside view simultaneously, the viewer's attentiveness is affected. In this study, the authors examined the relationship between the viewer's attentiveness and viewing distance of the outside view. The virtual image in the see-through AR device was at a fixed distance of 2.5 m, while a TV at distances of 0.33, 1, 2.5 and 5 m was considered as the outside view. In this experiment, thirty participants viewed a movie on an AR device and ten target images of pictures and words were sequentially displayed on the TV by overlapping them onto the virtual image. The participants were then asked to identify these target images from examples of sixty images. A correct answer (CA) ratio was used to measure the participant's attentiveness. Results demonstrated that CA ratios at distances of 0.33 and 1 m was better than CA ratios at distances of 2.5 and 5 m. Further, the CA ratio of target images of pictures was better than that of words. When the virtual and target images were located at similar distances, these images were sharply focused on the retina. However, when the distances of these images were different, the participant's eyes focused on one image causing a defocus on the other. A better CA ratio at different distances implied that the difference of sharpness in overlapped virtual and target images helped the participants in identifying the virtual or target image rather than two overlapped images of similar sharpness. Thus, sharply focused virtual and target images at the same distance did not guarantee better identification of two distinct images.