Augmented reality (AR) display characteristics have the potential to either enhance or impair users' spatial abilities and performance. While previous work included studies of spatial performance with various display factors, evidence for objective performance differences is limited due to compensatory behaviors employed by users and overall behavioral differences. In general, it is challenging to document the effects of display factors on task performance as they depend on users' task behaviors, which in turn depend on users' reliance and trust in the technology, which are also affected by the display factors. In this paper, we present two within-subjects experiments (each N = 20) in which we aim to elucidate some of the interrelations between two AR display factors (field of view and visual contrast) with objective task performance and subjective assessments of reliance and trust, while controlling for different behaviors. Participants performed a $360^\circ$360∘ search-and-selection task in a unique hybrid setup, in which we simulated a controlled task environment by having participants stand inside an immersive CAVE-like space while at the same time wearing a head-worn display that overlaid AR tags over the simulated environment. Specifically, we evaluated three fields of view ($43^\circ$43∘, $93^\circ$93∘, and $143^\circ$143∘) and three visual contrasts (0.05, 0.25, and 0.5). We controlled for four different behaviors: AR-Only (only relying on AR), AR-First (prioritizing AR over real world), Real-First (prioritizing real world over AR), and Real-Only (only relying on real world). By controlling for these behaviors, we were able to show objective and subjective benefits of larger fields of view and visual contrast. We illustrate how the controlled behaviors relate to users' subjective reliance and trust in an AR system, and why it is important for researchers and practitioners to understand these subjective and behavioral aspects.

Real-world augmented reality (AR) systems are increasingly network connected in order to succeed in operational spaces dependent on cutting edge sensor and computing technologies, all connected together via the network. This dependency inevitably introduces new sources of error to the AR system through instability in network performance. These errors create familiar problems, such as registration errors, on scales unfamiliar to modern AR systems. The effects of these problems on user performance are difficult to investigate as user performance involves many interrelated factors, some of which are difficult to measure. In this work, we control for user behavior to reduce the complexity of investigating the effects of real-world scale latency and signal dropouts on users’ objective task performance and subjective assessments of the AR system. Behavior was controlled by instructing participants to adopt specific behaviors based on different levels of trust and reliance on AR tags and environmental visual cues. We found significant negative effects of both network error sources on subjective assessments of both the AR system and task, as well as objective task completion time and errors committed. Participants’ subjective assessments and objective task also varied unexpectedly with increasing network error levels, suggesting that human perception of the effects of network errors are not well calibrated to the actual effects on performance. We also found significant interaction between behavior and network errors on task performance, drawing implications not just for AR system design, but also for AR system operation guidelines.

Augmented Reality (AR) head-worn display (HWD) technologies for warfighters have seen various advances over the last decade that make them attractive for simulations, training, and operations. In particular, optical see-through (OST) AR displays are becoming more used on the battlefield as they do not reduce warfighters' visual acuity of the real world. Unfortunately, these displays are still limited in terms of the field of view (FOV) and luminance of the display, the latter of which competes with the luminance in the warfighter's environment. The objective of this work is to evaluate how these two AR HWD factors impact participants' spatial task performance and perception. Specifically, this paper presents an experiment, performed inside a novel hybrid experimental space in which both the FOV and the luminance contrast of the HWD were varied compared to the simulated environment. Participants performed a spatial task involving simulated humans arranged in the 360-degree space around them, augmented with red or blue team member tags on the AR display. The results show that a FOV of 45 degrees or wider as well as a luminance contrast of 0.1 or higher were required for participants to reach a task performance that matched or exceeded that which could be reached without the use of AR. Implications for warfighter AR HWD systems are discussed, especially as they pertain to a warfighter's willingness to trust an AR HWD system and how that trust impacts performance.

The information presented by augmented reality (AR) systems may not appear exactly like information perceived in the "real" world. Shortfalls in AR technology give rise to anomalies like tracker errors, lack of opacity compared to the background, and reduced field of view (FOV) compared to the human visual system's field of view. These anomalies can make users feel like the information presented in an AR training system is not believable. This lack of belief can lead to negative training, where trainees adjust how they train due to flaws in the training system and are therefore less prepared for actual battlefield situations. We have completed an experiment to investigate trust, reliance, and human task performance in an augmented reality three-dimensional experimental scenario. Specifically, we used a methodology in which simulated real (complex) entities were supplemented by abstract (basic) cues presented as overlays in an AR headworn display (HWD) for a visual search and awareness task. We simulated shortfalls of different AR display systems to determine which of the properties most affect training efficacy. Results from our experiment will feed directly into the design of training systems that use AR displays and will help increase the efficacy of training.

This research paper explores the impact of augmented reality (AR) tracking characteristics, specifically an AR head-worn display’s tracking registration accuracy and precision, on users’ spatial abilities and subjective perceptions of trust in and reliance on the technology. Our study aims to clarify the relationships between user performance and the different behaviors users may employ based on varying degrees of trust in and reliance on AR. Our controlled experimental setup used a 360° field-of-regard search-and-selection task and combines the immersive aspects of a CAVE-like environment with AR overlays viewed with a head-worn display.We investigated three levels of simulated AR tracking errors in terms of both accuracy and precision (+0°, +1°, +2°). We controlled for four user task behaviors that correspond to different levels of trust in and reliance on an AR system: AR-Only (only relying on AR), AR-First (prioritizing AR over real world), Real-Only (only relying on real world), and Real-First (prioritizing real world over AR). By controlling for these behaviors, our results showed that even small amounts of AR tracking errors had noticeable effects on users’ task performance, especially if they relied completely on the AR cues (AR-Only). Our results link AR tracking characteristics with user behavior, highlighting the importance of understanding these elements to improve AR technology and user satisfaction.

Light-on-dark color schemes, so-called “Dark Mode,” are becoming more and more popular over a wide range of display technologies and application fields. Many people who have to look at computer screens for hours at a time, such as computer programmers and computer graphics artists, indicate a preference for switching colors on a computer screen from dark text on a light background to light text on a dark background due to perceived advantages related to visual comfort and acuity, specifically when working in low-light environments. In this article, we investigate the effects of dark mode color schemes in the field of optical see-through head-mounted displays (OST-HMDs), where the characteristic “additive” light model implies that bright graphics are visible but dark graphics are transparent . We describe two human-subject studies in which we evaluated a normal and inverted color mode in front of different physical backgrounds and different lighting conditions. Our results indicate that dark mode graphics displayed on the HoloLens have significant benefits for visual acuity and usability, while user preferences depend largely on the lighting in the physical environment. We discuss the implications of these effects on user interfaces and applications.

SA Photonics and SL Process have developed a new type of electronic see-through augmented reality head mounted display. Our display utilizes a very compact freeform prism eyepiece that has almost no peripheral obscuration. This provides the wearer with the advantages of an electronic see-through system (occlusion, operation in high ambient environments, high contrast imagery, image enhancement, image export) but in a system that also allows natural vision of the real world outside the field of view of the eyepiece. As such, the user sees a seamless view of the entire real world, with augmentation in the central 62-degree diagonal field of view. The cameras for the see-through imagery are “hidden” behind the eyepieces, so they do not block the view of the real world, providing less than a 10% obscuration of the total visual field, much less than any other electronic see-through system and even less than many optical see-through systems. In addition to providing the see-through imagery, these cameras and SL Process’ innovative video processing architecture provide six degrees of freedom head tracking as well as hand tracking.

The color blue is problematic for inclusion in a symbology color set for use by operators with head-up and helmet-mounted displays (HUDs and HMDs), as well as with augmented reality (AR) displays. The distinguishing feature of these see-through displays is the optical combiner that presents color-coded symbology combined with the forward real-world scene. Unlike head-down displays that can use color fills, see-through displays are limited to lines and text. The presence of high-ambient daylight can desaturate symbol colors and make them difficult to recognize. This is especially true for blue symbols that become faint and colorless in moderate daylight as well as when mixed with green night-vision imagery. We propose the alternative color blue prime (blue')—a mix of 100% blue and 50% green that lies between blue and cyan—as an alternative to blue. The color blue’ is more resistant to daylight than blue, yet still retains the color name “blue.” Blue' lags other colors such as green and white in visibility, and its use needs to be moderated. We present experimental data to support the use of blue’ as a basic color code.

Color-coded symbology has the potential to enhance the performance of people using head-up and head-mounted displays (HUDs and HMDs). The distinguishing feature of these displays is the optical combiner that presents symbology combined with the forward real-world scene. The presence of high-ambient daylight can desaturate the symbol colors, making them difficult to recognize. We defined a set of colors for testing based on color-coding conventions, color symbology research, and results from our previous testing. We then conducted a series of experiments to test the visibility and naming of color symbols and the legibility of color text mixed with daylight. Results were statistically analyzed and also modeled using color-difference formulae. Specific attention was given the symbol color blue, and an alternative blue color was proposed that had much higher visibility.

A dichoptic HMD vision system can provide an expansive and highly detailed visual experience by presenting a large FOV, lower quality image to one eye and a small FOV, higher quality image to the other. We compared a benchtop dichoptic vision system (DiVS) to a reference binocular system (RBS) using both subjective ratings and a performance test. Subjective ratings were directed at questions involving image quality, viewing comfort and presence or immersion. The performance test required observers to scan the scene to locate a target and then make an identification. Response times were collected for each component of this task. Target acquisition times were found to be much shorter for the DiVS condition while target identification times were longer. Total time to acquire and identify a target was found to be significantly shorter for a dichoptic system.

SA Photonics and Vision Systems International (VSI) are developing an innovative wide field of view digital night vision head mounted display (HMD). This HMD has an 80 degree field of view and has been designed to minimize weight, peripheral obscuration and forward projection. Digital night vision sensors enable electronic image enhancement and VSI's Zero A/C Integration enables the HMD to be integrated with legacy aircraft and provide symbology overlay and recording without the need for an expensive drive electronics box.

Many existing flight simulators employ faceted displays, with multiple panels of “out the window” visual information presented at different angles and with multiple vertices. Using a head-mounted display (HMD) in a faceted simulator can present visual artifacts not seen in the cockpit, including HMD imagery which appears slanted and with a distorted perspective compared to the imagery presented on the faceted simulator displays. Users viewing information presented across the vertices of the simulator display may notice anomalies due to the HMD imagery being “flat” while the vertex represents a “fold” in the displayed simulator imagery. Binocular HMDs present issues with vergence mismatch when integrated with faceted displays, where the vergence distance (the distance at which the user’s eyes converge) to the HMD imagery stays constant while the vergence distance to the simulator imagery varies with head position. These effects could potentially lead to double-imaging (diplopia) and discomfort, and could also diminish the feeling of immersion. In our previous research, adaptive vergence clearly led to improved comfort and utility compared to fixed vergence, and also led to increased performance on a targeting task. However, some users complained about the distorted perspective, and this may have also affected targeting performance. We have expanded upon those earlier results and examined the effects of mitigating these artifacts using a combination of image perspective warping, rotation and bending. We evaluated both adaptive vergence mitigation only, as well as adaptive vergence mitigation with image warping, rotation, and bending. For each experimental condition, we asked the users to report diplopia/comfort and we also measured their timed performance in a simulated targeting task. We conducted this experiment in a simplified two-facet display system with viewing distance ranging from 36 – 45 inches. Our results show that attempting to mitigate slant and vertex effects have no measureable increase in operator comfort and actually decrease operator performance. In addition, many subjects did not like the fact that the symbology bent into the vertex and moved in space to become coplanar with the out the window displays. Given our previous positive results from adaptive vergence alone, we would recommend not implementing slant and vertex mitigation, but instead just using adaptive vergence mitigation.

One of our previous studies examining the integration of a head-mounted visual display with a faceted flight simulator display showed that a monocular condition was the most uncomfortable and it also resulted in poorer operator performance. In the present study, we investigated whether this reduction in performance was dependent on eye dominance and whether it could be reduced or eliminated through training. Our performance measure was the amount of time it took operators to make correct decisions on a simplified targeting task using a see-through monocular head-mounted display and a large-screen display upon which was presented an out-the-window view of a desert scene. A binocular on-screen viewing condition served as baseline. The results revealed that response time significantly decreased with training but that eye dominance did not exert a significant effect. These results are interpreted within the context of training regimes for using HMDs with sparse symbology.

Faceted simulator displays are widely used because they are relatively compact and economical. One drawback, however, is that viewing distance changes depending on where users are looking. This variation creates a challenge for the integration of binocular head mounted displays (HMDs), because confusing imagery and visual fatigue can result when the user views symbology presented by the HMD at one distance and simulator imagery at different distances. Understanding the best approach to presenting symbology with a binocular HMD in a faceted simulator has become an important issue, with the deployment of the F-35 Joint Strike Fighter and its binocular HMD. Successful integration of a binocular HMD would not only allow current faceted simulators to be retrofit with the F35 simulator HMD, but would also allow future simulators to have either a dome or faceted design, thus affording acquisition agencies greater flexibility. Binocular HMDs are becoming more prevalent, so solving this integration issue will likely become important for multiple platforms. We performed an experiment to quantify the best method of presenting symbology on a binocular HMD when used with a faceted simulator display. Five viewing conditions were tested: 1) HMD converged to 36”, 2) HMD converged to 42”, 3) dynamic HMD vergence, 4) monocular presentation on the HMD, and 5) on-screen presentation. Screen distances ranging from 36” to 54” were tested. Our results suggest that adaptive vergence is the preferred solution. Both static vergence conditions and the monocular condition resulted in lower comfort scores and poorer performance. The on-screen condition, although rated comfortable, does not represent the real-world flight condition where symbology is displayed using an HMD. Although additional evaluations under more operational conditions remain to be completed, these results indicate that adaptive vergence is a viable solution for the integration of binocular HMDs into faceted flight simulator displays.