Distance estimation with mixed real and virtual targets in stereoscopic displays Chiuhsiang Joe Lin a,⇑ , Bereket Haile Woldegiorgis a , Dino Caesaron b , Lai-Yu Cheng a a Department of Industrial Management, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Da‘an Dist., Taipei City 10607, Taiwan, ROC b Industrial Engineering Department, Bunda Mulia University, Lodan Raya Street No. 2 North Jakarta – 14430, Jakarta, Indonesia article info Article history: Received 17 September 2014 Received in revised form 5 November 2014 Accepted 18 November 2014 Available online 3 December 2014 Keywords: Augmented reality Stereoscopic displays Exocentric distance Near field Distance perception abstract In this paper we investigated the accuracy of center-to-center distance perception in near field augmented reality visual targets viewed by stereoscopic glasses. One real and one virtual targets were presented in four layout or target orientations (two horizontal and two vertical, by altering the relative positions of real and virtual targets) at three different parallax conditions (on screen, 5 cm from screen and 10 cm from screen) and four levels of scaled between targets’ distance (10–20 cm, 20–30 cm, 30–40 cm and 40–50 cm). The result revealed overall underestimation with an accuracy of about 84%. Interestingly, it was noticed that the main effects of layout, parallax and center-to-center distance were significant. Generally, accuracy improves when targets put vertical, close to observers’ position and smaller separation of targets. Significant interactions among the three main factors were also reported. The results are of great importance as it provides guide for the developers to decide where to present targets depending on the need for relative accuracy of judgment. Some engineering implications of the result are also discussed in this paper. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction In the spectrum of 3D stereoscopic vision, augmented reality (AR) lies between viewing completely real and completely virtual objects. In completely immersive virtual environment, the real object is completely replaced by the virtual 3D image and observ- ers could not see their physical environment around. Whereas, in augmented reality the virtual 3D image will be integrated into the physical environment so that both can coexist and can be cre- ated by combining the virtual and real world environment using either the optical or video approaches [1,2]. Unlike virtual reality, AR aims at supplementing reality instead of completely replacing it [2]. For Nicolau et al., [3] any AR would fall in one of the four systems; video-based, see-through, projection-based or tracking; depending on the display technology employed. In optical systems, synthetic images are overlaid on the real object while in videos approaches the real object’s real-time image is recorded and displayed to the user after mixed with the virtual image. Displays, trackers, and haptic and force feedback are basic hardware components required to realize the augmented environment. Head mounted displays (HMDs) are the oldest and most commonly used display devices. Different types of HMDs are commercially available. Some models provide cameras embed with sensors that continuously track head movement and update scenes accordingly. Other commercially available displays that can also support aug- mented reality are see-through optical (OST) or video (VST) HMDs [4]. Handheld display devices (HHD) are also used where mobility is required as recent applications sees promises of broad users [5]. Integrating augmented environment on physical elements report- edly improve performance of operators in many of applications such as medical [2,4], manufacturing [2,4], maintenance [2,6], annotation and visualization [2], robot routing [2,4], military [2,4] and entertainments [2,4]. The current advances in mobile devices such as smart phones and tablets gave another dimension to AR applications such as tourism and entertainment [1,5,7]. Together with security and privacy issues as in Google Glass, enhancing felt realism and brain and sensory perceptions remained to be challenges of the current technology in building augmented reality [1]. The aim of this study is to explore the accuracy of exocentric distance perception which is an important component of interaction in near field synthetic environment. 2. Background and related work Kurkovsky et al., identified three major challenges in recent AR, especially for handheld devices [5]. These are accuracy of naviga- tion and tracking, where the user’s location should continuously http://dx.doi.org/10.1016/j.displa.2014.11.006 0141-9382/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +886 2 2737 6352. E-mail address: chiuhsiangjoelin@gmail.com (C.J. Lin). Displays 36 (2015) 41–48 Contents lists available at ScienceDirect Displays journal homepage: www.elsevier.com/locate/displa