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Usability Evaluation of Touchless Mouse Based on Infrared Proximity Sensing

Young Sam Ryu, Do Hyong Koh, Dongseok Ryu, and Dugan Um

Journal of Usability Studies, Volume 7, Issue 1, November 2011, pp. 31 - 39

Article Contents


The following sections discuss a pointing device that uses infrared proximity sensing and standards for evaluating pointing devices.

Pointing Device Using Infrared Proximity Sensing

While the finger-tip touch based user interface has become mainstream in mobile electronics, the conventional mouse, touchpad, and isometric pointing device are the main pointing devices in desktop and laptop computers. However, these input devices cannot be operated by a wet, oily, or dusty hand in environments such as hospital operating rooms, clean rooms, petroleum plants, or combat environments.  An effective touchless interface device would alleviate this limitation, allowing operators under difficult or less-than-tidy circumstances to provide inputs to computers. Although many studies have been conducted on touchless interfaces, a functioning pointing device has yet to be introduced in the market. The delay is primarily due to the high cost and lack of operational reliability.

Currently 3D stereo cameras in conjunction with markers and virtual reality gloves are more typical for touchless Human-Machine Interface (HMI) experiences; nevertheless, cost and reliability issues still remain. Ryu et al. (2010) introduced a novel HMI device to offer a non-contact gesture input capability using finger or palm movements. The enabling technology of the proposed device (Touchless Mouse or T-less Mouse) is the Infrared Proximity Array (IPA) sensor. Using an IPA sensor, real-time, 3-D depth information can be captured for machine control. The uniqueness of the T-less mouse is that it uses only one camera, which reduces the cost significantly, while still providing acceptable operational reliability (Figure 1).

To examine the viability of this novel input device, we conducted a standards-based usability evaluation of the T-less mouse and compared the performance of the T-less mouse with a conventional mouse. The usability evaluation followed the standards and guidelines set for pointing device evaluations by ISO 9241-9 based on Fitts’ Law tasks. Additionally, a subjective questionnaire was administered to assess user satisfaction. Although two input modes were introduced by Ryu et al. (2010), only the finger input mode was evaluated in this study.

Figure 1

Figure 1. T-less: A touchless pointer based on an Infrared Proximity Array sensor

Standards for Evaluating Pointing Devices

ISO 9241-9 (2000) establishes uniform guidelines and testing procedures for evaluating computer pointing devices. The metric for comparison is throughput, in bits per second (bits/s), which includes both the speed and accuracy of the user’s performance. The equation for throughput is Fitts’ Index of Performance using an effective index of difficulty (IDe). Specifically,

Throughput = IDe / MT                (1)

where MT is the mean movement time, in seconds, for all trials within the same condition, and

IDe = log2 (D / We + 1)                (2)

IDe, in bits, is calculated from D, the distance to the target, and We, the effective width of the target. We is calculate as

We = 4.133 × SD                        (3)

where SD is the standard deviation in the selection coordinates measured along the line from the center of the home square to the center of a target.


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