1,720,983 research outputs found
Projected Augmented Reality to Guide Manual Precision Tasks: An Alternative to Head Mounted Displays
No full textAugmented reality (AR) devices are gaining popularity in industrial development and healthcare as they provide information that would not be accessible in a rapid and intuitive way. Head-mounted displays dominate in this field and are currently being comprehensively tested. Alongside its informative function, AR can be used to steer the user's actions to aid complex or high precision tasks. This is the case in surgery, which is recently seeing the development of ad-hoc head-mounted displays to meet the requirements of safety, ergonomics, and reliability. However, head-mounted displays are subject to perceptual problems that can affect their use in delicate and demanding tasks. This article aims to evaluate projected AR as an alternative to head mounted displays (HMDs) when accurate guidance on the surface is needed. We directly compare them in a user study and evaluate both user accuracy and user perception to assess whether projected AR can be a practical and useful paradigm for precision manual tasks. Ten users performed tracing trajectory tasks under the guidance of an HMD and a projected AR device. Three accuracy levels were quantitatively tested: 0.5, 1, and 2 mm. Statistical analysis showed no significant difference in the accuracy of the two AR visualization modes, whereas the user perception assessment revealed statistical differences in virtual-to-real perception and visual discomfort. The quantitative results of this article proved that both technologies can guide manual precision tasks with the same accuracy, but projected AR features some perceptual advantages
Control of the Cameras Matrix Parameters for Accurate Online Calibration to Perform Precision Tasks with Microsoft HoloLens 2 Headset
No full textThis study explores and preliminarily validates an online calibration method for Augmented Reality Optical See-Through Head-Mounted Displays. One of the major obstacles with those devices concerns the complexity and the unreliability of the calibration procedures for a correct virtual-to-real alignment, a key aspect of medical and industrial settings. Specific simplified procedures calibrate Commercial Optical See-Through devices, but these are mainly based on the adjustment of the single degree of freedom associated with the user's interpupillary distance. The presented work aims to provide a calibration method that can improve the performance and the accuracy of the user with precise control of the rendering cameras intrinsic and extrinsic parameters on the top of the device's default calibration system. The study was carried out using Microsoft HoloLens 2, which is one of the most advanced Optical See-Through Head-Mounted Displays, and we asked users to complete a targeting task within their peripersonal space after calibrating the device. Preliminary results show that the proposed method improves the alignment task by approximately 50 % in terms of mean error and by approximately 35 % in terms of maximum error
Perceptual Limits of Optical See-Through Visors for Augmented Reality Guidance of Manual Tasks
Full text linkThe focal length of available optical see-through (OST) head-mounted displays (HMDs) is at least 2 m therefore, during manual tasks, the user eye cannot keep in focus both the virtual and real content at the same time. Another perceptual limitation is related to the vergence-accommodation conflict (VAC), this latter being present in binocular vision only. This paper investigates the effect of incorrect focus cues on the user performance, visual comfort and workload during the execution of augmented reality (AR) guided manual task with one of the most advanced OST HMD, the Microsoft HoloLens
In situ visualization for 3d ultrasound-guided interventions with augmented reality headset
Full text linkAugmented Reality (AR) headsets have become the most ergonomic and efficient visualization devices to support complex manual tasks performed under direct vision. Their ability to provide hands-free interaction with the augmented scene makes them perfect for manual procedures such as surgery. This study demonstrates the reliability of an AR head-mounted display (HMD), conceived for surgical guidance, in navigating in-depth high-precision manual tasks guided by a 3D ultrasound imaging system. The integration between the AR visualization system and the ultrasound imaging system provides the surgeon with real-time intra-operative information on unexposed soft tissues that are spatially registered with the surrounding anatomic structures. The efficacy of the AR guiding system was quantitatively assessed with an in vitro study simulating a biopsy intervention aimed at determining the level of accuracy achievable. In the experiments, 10 subjects were asked to perform the biopsy on four spherical lesions of decreasing sizes (10, 7, 5, and 3 mm). The experimental results showed that 80% of the subjects were able to successfully perform the biopsy on the 5 mm lesion, with a 2.5 mm system accuracy. The results confirmed that the proposed integrated system can be used for navigation during in-depth high-precision manual tasks
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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