Sven G. Kratz

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We conducted a series of user studies to understand and clarify the fundamental characteristics of pressure in user interfaces for mobile devices. We seek to provide insight to clarify a longstanding discussion on mapping functions for pressure input. Previous literature is conflicted about the correct transfer function to optimize user performance. Our(More)
In this paper we explore the design space of around-device interaction (ADI). This approach seeks to expand the interaction possibilities of mobile and wearable devices beyond the confines of the physical device itself to include the space around it. This enables rich 3D input, comprising coarse movement-based gestures, as well as static position-based(More)
We present the $3 Gesture Recognizer, a simple but robust gesture recognition system for input devices featuring 3D acceleration sensors. The algorithm is designed to be implemented quickly in prototyping environments, is intended to be device-independent and does not require any special toolkits or frameworks. It relies solely on simple trigonometric and(More)
When the user is engaged with a real-world task it can be inappropriate or difficult to use a smartphone. To address this concern, we developed ShoeSense, a wearable system consisting in part of a shoe-mounted depth sensor pointing upward at the wearer. ShoeSense recognizes relaxed and discreet as well as large and demonstrative hand gestures. In(More)
Protractor 3D is a gesture recognizer that extends the 2D touch screen gesture recognizer Protractor to 3D gestures. It inherits many of Protractor's desirable properties, such as high recognition rate, low computational and low memory requirements, ease of implementation, ease of customization, and low number of required training samples. Protractor 3D is(More)
We present CapWidgets, passive tangible controls for capacitive touch screens. CapWidgets bring back physical controls to off-the-shelf multi-touch surfaces as found in mobile phones and tablet computers. While the user touches the widget, the surface detects the capacitive marker on the widget's underside. We study the relative performance of this tangible(More)
Secure authentication with devices or services that store sensitive and personal information is highly important. However, traditional password and pin-based authentication methods compromise between the level of security and user experience. <i>AirAuth</i> is a biometric authentication technique that uses in-air gesture input to authenticate users. We(More)
Mobile phones seem to present the perfect user interface for interacting with smart environments, e.g. smart-home systems, as they are nowadays ubiquitous and equipped with an increasing amount of sensors and interface components, such as multi-touch screens. After giving an overview on related work this paper presents the adapted design methodology(More)
By equipping a mobile device with distance sensing capabilities, we aim to expand the interaction possibilities of mobile and wearable devices beyond the confines of the physical device itself to include the space immediately around it. Our prototype, an Apple iPhone equipped with six IR distance sensors, allows for rich 3D input, comprising coarse(More)
Even with the rise of the World Wide Web, TV has remained the most pervasive entertainment medium and is nowadays often used together with other media, which allow for active participation. The idea of connecting non-collocated TV viewers via telecommunication technologies, referred to as Social TV, has recently received considerable attention. Such systems(More)