Nanostylus: Enhancing Input on Ultra-Small Displays with a Finger
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NanoStylus: Enhancing Input on Ultra-Small Displays with a Finger-Mounted Stylus Haijun Xia1,2, Tovi Grossman1, George Fitzmaurice1 1Autodesk Research 2University of Toronto {firstname.lastname}@autodesk.com [email protected] ;63<21 !"#$%& NanoStylus 9 : /'( .'( -'( ,'( 60%4700$%828 31%4700$%828 16%4700$%828 0 +'( *'( !012234500$%&673 )'( '( Figure 1. a) The NanoStylus is a finger-mounted stylus which improves touch precision on ultra-small devices (wrist-mounted circuit board and wires not shown). b) Compared to direct touch and a traditional stylus, the NanoStylus significantly reduces occlusion. c) The heat maps show the estimated percentage of occluded area when pointing at each coordinate on the display. ABSTRACT One approach to address this issue is to displace the Due to their limited input area, ultra-small devices, such as interaction away from the watch face using hardware smartwatches, are even more prone to occlusion or the fat augmentations [28, 41]. Unfortunately, this negates the direct finger problem, than their larger counterparts, such as smart interaction paradigm that users have become accustomed to. phones, tablets, and tabletop displays. We present Alternatively, designers can adapt the user interface for NanoStylus – a finger-mounted fine-tip stylus that enables lower-precision input, such as supporting swipes [13], or fast and accurate pointing on a smartwatch with almost no multi-level taps [30]. However, such interactions limit the occlusion. The NanoStylus is built from the circuitry of an tasks and interfaces that can be presented. active capacitive stylus, and mounted within a custom 3D- printed thimble-shaped housing unit. A sensor strip is We present the NanoStylus, a finger-mounted stylus that mounted on each side of the device to enable additional enables high precision direct input on smartwatches. The gestures. A user study shows that NanoStylus reduces error device is built from the circuitry of an active capacitive stylus, rate by 80%, compared to traditional touch interaction and by mounted within a custom 3D-printed thimble-shaped housing 45%, compared to a traditional stylus. This high precision unit (Figure 1a). An ultra-thin nib effectively eliminates pointing capability, coupled with the implemented gesture occlusion and enables high-precision input on a smartwatch sensing, gives us the opportunity to explore a rich set of (Figure 1b, c). Additional touch sensors are used to turn the interactive applications on a smartwatch form factor. sides of the NanoStylus into 1D touchpads. Tapping, holding, and swiping are detected on both sides independently, INTRODUCTION yielding a rich set of gestures. Smartwatches have become increasingly popular in recent years, bringing convenience to basic tasks, such as checking In the following sections, we detail our exploration of the a calendar and setting an alarm. These devices typically rely possible form factors of a finger-mounted stylus, and then on touch as their primary input modality. While the fat finger describe our implementation of the NanoStylus. A target problem [36] occurs on any touch device, the problem is acquisition study shows that the NanoStylus is 80% more exacerbated by the ultra-small display size of a smartwatch, accurate than touch, and 45% more accurate than traditional where a single finger can easily occlude more than half of the stylus, while maintaining similar acquisition times. We then display (Figure 1b, c). describe the set of gestures enabled by the NanoStylus and demonstrate sample interaction scenarios which they enable. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed It is important to note that our current prototype may be for profit or commercial advantage and that copies bear this notice and the full cumbersome for everyday use, and is not intended as to be a citation on the first page. Copyrights for components of this work owned by others than ACM must be honored. Abstracting with credit is permitted. To copy otherwise, market-ready product. Our main contribution is the or republish, to post on servers or to redistribute to lists, requires prior specific investigation and resulting knowledge of using the use of a permission and/or a fee. Request permissions from [email protected]. miniature stylus form factor for interaction with very small UIST '15, November 08-11, 2015, Charlotte, NC, USA. © 2015 ACM. ISBN 978-1-4503-3779-3/15/11…$15.00 devices. In our Discussion and Future Work section we DOI: http://dx.doi.org/10.1145/2807442.2807500 discuss several potential technical implementations to reduce work, the NailDisplay [35] explores precise pointing on a the form factors and designs to support convenient access to smartwatch by simulating a transparent finger using a display the NanoStylus without affecting manual activities. worn on the fingernail. While participants found the RELATED WORK technique useful, the vertical separation between the display Our research draws from several areas of related work: and touch surface was reported as being problematic. Our interaction for wrist-worn devices, finger-mounted work also augments the finger to support precise touch, but wearables, stylus interaction, and small target acquisition. still supports direct interaction with the display. Interaction Techniques for Wrist-worn Devices Stylus Interaction Despite the ultra-small form factor of wrist-worn devices, Since Fitts’ early work on human motor control [15] the touch is still the primary input modality on most commercial performance of stylus input has been widely examined [14, devices, exacerbating the fat finger problem [36]. One 27, 32], and shown to be an accurate alternative to touch approach to addressing this problem is modifying the input [14]. Vogel et al. showed that stylus interaction can interface. For example, ZoomBoard [30] and Swipeboard cause significant occlusion [39], and developed occlusion [13] use iterative zooming and swiping on the touch screen to aware interfaces [40]. Research in pen-based computing has enable text entry on ultra-small devices. also demonstrated how additional input channels can be used to enable novel interactions, such as pressure [31], Utilizing other available space on wrist-worn devices is orientation [37] roll, [8], and hover [16]. Other works [19,34] another possible solution. EdgeTouch [28] enables a set of explore the interaction possibilities enabled by sensing hand grasp gestures by bringing touch sensing to the edge of the grips and touch gestures on the barrel of a stylus. device. Xiao et al. [41] propose using the watch face as a mechanical interface to support navigation on a smartwatch. While such techniques provide inspiration for our work, their implications to smart watch interaction have not been Facet, consisting of multiple touch-sensitive displays, enables explored. We build upon these techniques and adapt them to touch interaction to span across multiple segments [26]. an interactive finger-worn form factor, to enable interaction NanoTouch [6] uses touch on the backside of the device to avoid finger occlusion. with ultra-small devices. Small Target Acquisition Space around the watch has also been explored for input. Small target acquisition is a well-explored problem in the Skin buttons [25] are icons projected onto the skin around the research literature [11]. A number of works have explored watch. Abracadabra [18] enables finger tacking and gesturing the limit of the human motor system with different input above the watch with a finger-worn magnet. Similarly, techniques [14, 27]. The stylus has been shown to be more Gesture Watch [23] senses hand gesture made over the accurate for selection, especially for target sizes close to device with an array of infrared proximity sensors. 5mm, where touch becomes unreliable [9, 14]. Holz et al. The above review shows promising input techniques for showed how specialized hardware could be used to improve wrist-worn devices. However, many require the watch to be touch accuracy by sensing fingerprints [21]. augmented with additional hardware, and most act as indirect Numerous software techniques have also been proposed to control to the graphical interface on the screen. Our work support ultra-small target acquisition [3, 7, 38, 43]. Although attempts to enable high precision and direct touch input, by promising, most software techniques require additional input enhancing the finger, and not the watch. or display space, which is rarely available on an ultra-small Interaction Techniques of Finger-mounted Wearables device. NanoStylus is a straightforward approach for Prior work has explored different input and output acquiring small targets that does not require software capabilities of finger-mounted devices. The use of a ring enhancements or additional screen real-estate. form-factor has been a common approach. The Nenya ring Commercial Finger Styluses [5], made from a magnet, can be tracked by a magnetometer It is important to acknowledge that a variety of passive on the wrist. iRing [29] uses infrared reflection sensor to finger-based styluses have been developed commercially12. sense the physical force on it. LigthRing [22] senses the fine- However, these passive devices need to be almost as large as grained fingertip movements on a 2D surface. the finger itself to be sensed properly on a smart watch. Sensing devices have also been instrumented on other Furthermore, there is no academic literature discussing their positions of hand. uTrack [12] converts the user’s thumb and implementation or reporting their performance. Our work finger into a 3D input system with magnetic field sensing. investigates an active finger-based stylus, specifically FingerPad [10] uses a similar technique to turn the tip of the designed for high precision, which also enables interactive index finger into a touchpad. The Magic Finger [42], worn on gestures through side-mounted touch pads. the tip of the index finger, enables touch input on physical surfaces and can sense the surface’s texture.