Exploiting thermal reflection for interactive systems

Abstract

a) Aluminum (b) Glass (c) MDF (d) Tile Figure 1: We explored the thermal reflectivity of different surfaces for interaction with projected surfaces. The thermal reflectivity allows to sense users that perform in-air gestures inside and outside the thermal camera's direct field-of-view. Four of the eight surfaces we analyzed and which can be found in normal office environments are presented above. ABSTRACTThermal cameras have recently drawn the attention of HCI researchers as a new sensory system enabling novel interactive systems. They are robust to illumination changes and make it easy to separate human bodies from the image background. Far-infrared radiation, however, has another characteristic that distinguishes thermal cameras from their RGB or depth counterparts, namely thermal reflection. Common surfaces reflect thermal radiation differently than visual light and can be perfect thermal mirrors. In this paper, we show that through thermal reflection, thermal cameras can sense the space beyond their direct field-of-view. A thermal camera can sense areas besides and even behind its field-of-view through thermal reflection. We investigate how thermal reflection can increase the interaction space of projected surfaces using camera-projection systems. We moreover discuss the reflection characteristics of common surfaces in our vicinity in both the visual and thermal radiation bands. Using a proof-of-concept prototype, we demonstrate the increased interaction space for hand-held camera-projection system. Furthermore, we depict a number of promising application examples that can benefit from the thermal reflection characteristics of surfaces.

Investigation of Material Properties for Thermal Imaging-Based Interaction

“…In this paper, we present a study that assesses the recognition accuracy of mid-air gestures sensed through thermal reflection using different surfaces in indoor and outdoor setups to complement the work presented by Sahami Shirazi et al [12]. Further, we provide holistic insights on the surfaces' properties that should be considered when it comes to sense interactions on the surface and/or mid-air using a thermal camera.…”

“…The second property is thermal reflectivity which is the result of radiations' reflection when striking a surface. Sahami Shirazi et al [12] propose to use specular reflectivity for extending the mid-air interaction space behind the camera's direct fieldof-view and detecting mid-air gestures. However, they did not report the recognition accuracy of mid-air gestures in the extended space.…”

“…We replicated the system reported in [12]. We recruited 30 participants (11 female, with an average age of 26 years, SD=3.8) using our university's mailing lists.…”

“…No special light source or illumination conditions were requisite as the thermal camera operates independent of illumination. We considered four common surfaces, also used in [12], for the experiment: glass, tile, MDF, and aluminum.…”

“…go even further in the light spectrum from near-infrared light to the far-infrared band [7,12]. Thermal cameras are used to sense heat traces that are left behind when a user moves a finger across a surface [7] or to sense mid-air interaction besides and behind a thermal camera's field-of-view (FOV) through thermal reflection [12]. As a novel sensing technology for human-computer interaction, thermal imaging offers exciting opportunities for the development of interactive systems.…”