In optical see-through augmented reality (AR), information is often distributed between real and virtual contexts, and often appears at different distances from the user. To integrate information, users must repeatedly switch context and change focal distance. If the user's task is conducted under time pressure, they may attempt to integrate information while their eye is still changing focal distance, a phenomenon we term transient focal blur. Previously, Gabbard, Mehra, and Swan (2018) examined these issues, using a text-based visual search task on a one-eye optical see-through AR display. This paper reports an experiment that partially replicates and extends this task on a custom-built AR Haploscope. The experiment examined the effects of context switching, focal switching distance, binocular and monocular viewing, and transient focal blur on task performance and eye fatigue. Context switching increased eye fatigue but did not decrease performance. Increasing focal switching distance increased eye fatigue and decreased performance. Monocular viewing also increased eye fatigue and decreased performance. The transient focal blur effect resulted in additional performance decrements, and is an addition to knowledge about AR user interface design issues.

For optical see-through augmented reality (AR), a new method for measuring the perceived three-dimensional location of virtual objects is presented, where participants verbally report a virtual object’s location relative to both a vertical and horizontal grid. The method is tested with a small (1.95 × 1.95 × 1.95 cm) virtual object at distances of 50 to 80 cm, viewed through a Microsoft HoloLens 1stgeneration AR display. Two experiments examine two different virtual object designs, whether turning in a circle between reported object locations disrupts HoloLens tracking, and whether accuracy errors, including a rightward bias and underestimated depth, might be due to systematic errors that are restricted to a particular display. Turning in a circle did not disrupt HoloLens tracking, and testing with a second display did not suggest systematic errors restricted to a particular display. Instead, the experiments are consistent with the hypothesis that, when looking downwards at a horizontal plane, HoloLens 1stgeneration displays exhibit a systematic rightward perceptual bias. Precision analysis suggests that the method could measure the perceived location of a virtual object within an accuracy of less than 1 mm.

A haploscope is an optical system which produces a carefully controlled virtual image. Since the development of Wheatstone's original stereoscope in 1838, haploscopes have been used to measure perceptual properties of human stereoscopic vision. This paper presents an augmented reality (AR) haploscope, which allows the viewing of virtual objects superimposed against the real world. Our lab has used generations of this device to make a careful series of perceptual measurements of AR phenomena, which have been described in publications over the previous 8 years. This paper systematically describes the design, assembly, calibration, and measurement of our AR haploscope. These methods have been developed and improved in our lab over the past 10 years. Despite the fact that 180 years have elapsed since the original report of Wheatstone's stereoscope, we have not previously found a paper that describes these kinds of details.

For optical see-through head-mounted displays, the mismatch between a display's focal length and the real world scene inadvertently prevents users from simultaneously focusing on the presented virtual content and the scene. It has been shown that it is possible to ameliorate the out-of-focus blur for images with a known focus distance, by applying an algorithm called Sharp View. However, it remains unclear if Sharp View also improves the readability and clarity of text rendered on the display. In this study, we investigate whether users reported increased text clarity when Sharp View was applied to a text label, and how the focal demand of the display, the focal distance to real world content, and gaze condition affect the result. Our results indicate that, in non-fixated viewing, there is a significant user preference for Sharp View-enhanced text strings.

In previous papers, a novel haploscope-based AR environment was implemented [1, 3]. In that system, a participant looks through a set of reflective lenses onto a real-world environment. However, at the same time, there are monitors to the side displaying a virtual object. This object is reflected onto the lenses and is thus, from the viewpoint of the participant, overlaid onto the real environment. In Hua [1], some initial work was done designing a calibration procedure for this haploscope-based AR environment. The current work seeks to modify and expand Hua's original calibration procedure to make it both more effective and more efficient. As part of developing this new calibration procedure, this paper examines potential sources of error and recommends processes and steps for reducing or eliminating these potential error sources.