Arthur Tang

Comparative effectiveness of augmented reality in object assembly

Although there has been much speculation about the potential of Augmented Reality (AR), there are very few empirical studies about its effectiveness. This paper describes an experiment that tested the relative effectiveness of AR instructions in an assembly task. Task information was displayed in users field of view and registered with the workspace as 3D objects to explicitly demonstrate the exact execution of a procedure step. Three instructional media were compared with the AR system: a printed manual, computer assisted instruction (CAI) using a monitor-based display, and CAI utilizing a head-mounted display. Results indicate that overlaying 3D instructions on the actual work pieces reduced the error rate for an assembly task by 82%, particularly diminishing cumulative errors - errors due to previous assembly mistakes. Measurement of mental effort indicated decreased mental effort in the AR condition, suggesting some of the mental calculation of the assembly task is offloaded to the system.

Display-relative calibration for optical see-through head-mounted displays

Optical see-through head-mounted displays (OSTHMDs) have many advantages in augmented reality application, but their utility in practical applications has been limited by the complexity of calibration. Because the human subject is an inseparable part of the eye-display system, previous methods for OSTHMD calibration have required extensive manual data collection using either instrumentation or manual point correspondences and are highly dependent on operator skill. This paper describes display-relative calibration (DRC) for OSTHMDs, a new two phase calibration method that minimizes the human element in the calibration process and ensures reliable calibration. Phase I of the calibration captures the parameters of the display system relative to a normalized reference frame and is performed in a jig with no human factors issues. The second phase optimizes the display for a specific user and the placement of the display on the head. Several phase II alternatives provide flexibility in a variety of applications including applications involving untrained users.

Attention Issues in Spatial Information Systems: Directing Mobile Users' Visual Attention Using Augmented Reality

Knowledge of objects, situations, or locations in the environment can be productive, useful, or even life-critical for mobile augmented reality (AR) users. Users may need assistance with (1) dangers, obstacles, or situations requiring attention; (2) visual search; (3) task sequencing; and (4) spatial navigation. The omnidirectional attention funnel is a general purpose AR interface technique that rapidly guides attention to any tracked object, person, or place in the space. The attention funnel dynamically directs user attention with strong bottom-up spatial attention cues. In a study comparing the attention funnel to other attentional techniques such as highlighting and audio cueing, search speed increased by over 50 percent, and perceived cognitive load decreased by 18 percent. The technique is a general three-dimensional cursor in a wide array of applications requiring visual search, emergency warning, and alerts to specific objects or obstacles, or for three-dimensional navigation to objects in space.

Evaluation of calibration procedures for optical see-through head-mounted displays

Optical see-through head-mounted displays (HMDs) are less commonly used because they are difficult to accurately calibrate. In this article, we report a user study to compare the accuracy of 4 variants of the SPAAM calibration method. Among the 4 variants, Stylus-marker calibration, where the user aligns a crosshair projected in the HMD with a tracked stylus tip, achieved the most accurate result. A decomposition and analysis of the calibration matrices from the trials is performed and the characteristics of the computed calibration matrices are examined. A physiological engineering point of view is also discussed to explain why calibrating optical see-through HMD is so difficult for users.

Experimental evaluation of augmented reality in object assembly task

This study evaluated the effectiveness of spatially overlaid instructions using augmented reality (AR) in an assembly task compared with other traditional media. Results indicate that overlaying 3D instructions on the workspace reduce error rate by 82%, particularly cumulative errors. Measurement of mental effort also suggests some of the mental workload is offloaded to the computer.

Performance Evaluation of Augmented Reality for Directed Assembly

Although there has been great speculation about the potential of augmented reality (AR) in manufacturing applications, there have been very few empirical studies that assess the effectiveness of the technology. This chapter describes an experiment that tested the relative effectiveness of AR instructions in computer-assisted assembly. The AR solution displayed task information in the user’s field of view (FOV) as 3D objects registered with the workspace. The presentation demonstrates the exact execution of a procedural step. Three traditional instructional media approaches were compared with the AR system: a printed manual, computer-assisted instruction (CAI) using a monitor-based display, and CAI utilizing a head-mounted display (HMD). Results indicate that overlaying 3D instructions on the actual work pieces reduced the error rate for an assembly task by 82%, particularly diminishing cumulative errors, errors due to previous assembly mistakes. Measurement of the mental effort indicated decreased mental effort in the AR condition, suggesting some of the mental calculation of the assembly task is offloaded to the system. The results indicate that an AR system for computer-assisted assembly can improve worker performance.

Suicide Notes in Hong Kong in 2000

Suicide notes have been regarded as one of the most informative data sources to understand the reasons why people commit suicide. However, there is a paucity of suicide note studies, leaving researchers with an assumption that this phenomenon remains static over time. This study examines this assumption by comparing the characteristics of note-leavers of the same population at 2 different points in time. The authors investigated the characteristics of 316 note-leavers in 2000 in Hong Kong and compared them to note-leavers in 1992. The proportion of people who left suicide notes increased from 20% to 35% between 1992 and 2000, a change that may be related to changes in suicide methods. Note-leavers in 2000 were characterized as individuals aged 25–59 years old, employed, with no physical illness, no psychiatric illness, and died as a result of charcoal-burning. Present data suggest that reasons for leaving suicide notes may have changed over the 8 years from 1992 to 2000.

Effects of the number of hidden nodes used in a structured-based neural network on the reliability of image classification

A structured-based neural network (NN) with backpropagation through structure (BPTS) algorithm is conducted for image classification in organizing a large image database, which is a challenging problem under investigation. Many factors can affect the results of image classification. One of the most important factors is the architecture of a NN, which consists of input layer, hidden layer and output layer. In this study, only the numbers of nodes in hidden layer (hidden nodes) of a NN are considered. Other factors are kept unchanged. Two groups of experiments including 2,940 images in each group are used for the analysis. The assessment of the effects for the first group is carried out with features described by image intensities, and, the second group uses features described by wavelet coefficients. Experimental results demonstrate that the effects of the numbers of hidden nodes on the reliability of classification are significant and non-linear. When the number of hidden nodes is 17, the classification rate on training set is up to 95%, and arrives at 90% on the testing set. The results indicate that 17 is an appropriate choice for the number of hidden nodes for the image classification when a structured-based NN with BPTS algorithm is applied.

The Omnidirectional Attention Funnel: A Dynamic 3D Cursor for Mobile Augmented Reality Systems

Knowledge of objects, situations, or locations in the environment may be productivity enhancing, generally useful, or even life-critical for mobile augmented reality (AR) users. Users may need assistance with: (1) dangers, obstacles, or situations requiring attention, (2) visual search, (3) task sequencing, and (4) spatial navigation. The omnidirectional attention funnel is a general purpose AR interface technique that rapidly guides attention to any object, person, or place in the space. The attention funnel dynamically draws user attention with a set of strong bottom-up spatial attention cues. In a study comparing the attention funnel to other attention directing techniques such as highlighting and audio cueing, we found that the attention funnel increased search speed by over 50%, and decreased perceived cognitive load by 18%. The technique has applicability as a general 3D cursor or cue in a wide array of AR applications that require visual search, emergency warning and alerts to specific objects or obstacles, or as a method for 3D navigation to objects in a room or guidance through space.

An egocentric augmented reality interface for spatial information management in crisis response situations

In emergency operations centers, operators are challenged with managing and analyzing massive amounts of information in a timely manner. With the advent of motion tracking systems and low-cost, high-performance graphics workstations, novel spatial augmented reality (AR) interfaces are becoming technologically feasible. AR interfaces have very unique characteristics as compared to other media and computer interfaces: users interact with the computer system through body motion in a volumetric space, instead of via a two-dimensional surface. We have created three prototype immersive AR computing interfaces for emergency operation center. User interacts with the information using a pair of motion tracked pinch gloves, and information is displayed through a head-tracked optical see-though head mounted display. The emergency operator uses intuitive grab and release gesture to move and manipulate the digital information in the environment analogous to interaction of everyday life objects.