As a result, we achieved an accuracy of over 92% for a position-invariant differentiation between left and right thumbs.
We focused on combinations that involve the thumb and index finger as these are mainly used for interaction. We collected a dataset of low-resolution fingerprints and trained convolutional neural networks that classify touches from eight combinations of fingers. While these approaches are based on external sensors which are inconvenient, we use capacitive images from mobile touchscreens to investigate the feasibility of finger identification.
Previous work presented a wide range of approaches to provide secondary actions by identifying which finger touched the display. However, touch input is limited to 2D touch locations which makes it challenging to provide shortcuts and secondary actions similar to hardware keyboards and mice. Touchscreens enable intuitive mobile interaction. We derive three design implications for BoD input to help designers considering reachability and unintended input. We identified comfortable areas on the back in which no unintended inputs occur and found that the least unintended inputs occurred on 5" devices. We recorded finger movements with a motion capture system and analyzed the unintended inputs. Participants performed common tasks on four smartphones which they held in the prevalent single-handed grip while sitting and walking. In this paper, we study the BoD areas in which unintended inputs occur during interaction with the touchscreen. However, there is no understanding of unintended BoD inputs which frustrate users and lead to embarrassing mistakes. Researchers investigated all fingers' comfortable areas to avoid grip changes. While previous work showed the benefits of input beyond the touchscreen, unfavorably designed input controls force detrimental grip changes and increase the likelihood of unintended inputs. Additional input controls such as fingerprint scanners, physical buttons, and Back-of-Device (BoD) touch panels improve the input capabilities on smartphones.