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Illumination & Displays

Ubiquitous computing using monocular mobile displays

Psycho-physiological responses to using head-mounted displays in an outdoor environment reveal differences in performance and workload that depend on the physical setup.
14 December 2009, SPIE Newsroom. DOI: 10.1117/2.1200911.001596

Computers are found everywhere and take many different forms, including as devices that can be worn like clothing. Monocular head-mounted displays (HMDs) are wearable devices that present information as users view their surrounding environment. Such displays are considered ideal for ubiquitous computing. They are small, lightweight, and have high resolution, thus making them potentially practical and effective for a variety of applications in maintenance,1 medical,2 and target-detection tasks.3

However, monocular HMDs have not yet been widely deployed because they are difficult to use in practice, while their effectiveness has not been demonstrated sufficiently. Disadvantages include a lack of significant performance benefits over conventional displays,4 and some laboratory studies have revealed undesirable physiological effects related to image viewing on monocular HMDs. Therefore, demonstrating the practical applicability of these displays in real-world environments is a high priority. We tested their usability in an outdoor environment, the main objective being to obtain basic data on characteristic user experiences.

In a test conducted in Helsinki (Finland), eight participants were asked to view television news broadcasts on monocular HMDs while walking through a large shopping mall, including ascending and descending an escalator, for approximately 10 minutes. We used two different monocular HMDs (Nikon's UP5 and Arisawa's i-bean:6 see Figure 1) as well as a handheld multimedia player (Apple iPod 5G) in the test. The participants' psycho-physiological responses were measured before, after, and during the test. We used NASA's task-load index (TLX), Simulator Sickness Questionnaire (SSQ), and Visual Symptoms Questionnaire (VSQ) to assess the subjective workloads and symptoms. The participants were also asked about their general impressions of the test conditions. The objective indices recorded were heart rate and stride (using a Polar RS800sd), and a video recording of the participant's view (see Figure 2).

Figure 1. Monocular head-mounted displays. (left) UP. (right) i-bean.

Figure 2. Layout of the device's usability test.

The results revealed differences between the performance of monocular HMDs and other setups, as well as between the different types of monocular HMDs. The TLX results showed that monocular HMDs require a higher subjective workload than the handheld multimedia player. The TLX and heart-rate results showed similar tendencies. Differences between the types of monocular HMDs may have been caused by screen vibration, which was considered a major factor in the user experience in terms of the psycho-physiological workload.

In the future, we will carry out usability tests elsewhere, including in Tokyo (Japan), to investigate higher subjective workloads—such as navigating route changes and interactive gaming—to examine the balance between a user's situational awareness of the information presented by monocular HMDs and the external environment.

This study was funded by the bilateral core program of the Academy of Finland and the Japan Society for the Promotion of Science, which supports research in the field of ubiquitous information technology.

Takashi Kawai
Graduate school of Global Information and Telecommunication Studies
Waseda University
Honjo, Japan
Jukka Häkkinen
Nokia Research Center
University of Helsinki
Helsinki, Finland
Takashi Yamazoe, Hiroko Saito, Shinsuke Kishi, Hiroyuki Morikawa
Waseda University
Saitama, Japan
Terhi Mustonen, Jyrki Kaistinen, Gäte Nyman
University of Helsinki
Helsinki, Finland