HaptiCase: Back-of-Device Tactile Landmarks for Eyes-Free Absolute Indirect Touch
HaptiCase is an interaction technique for eyes-free absolute indirect touch based on back-of-device tactile landmarks and proprioception. It improves tapping accuracy significantly (14% target size reduction) without software modification.
Using a smartphone for touch input to control apps and games mirrored to a distant screen is difficult, as the user cannot see where she is touching while looking at the distant display. We present HaptiCase, an interaction technique that provides back-of-device tactile landmarks that the user senses with her fingers to estimate the location of her finger in relation to the touchscreen. By pinching the thumb resting above the touchscreen to a finger at the back, the finger position is transferred to the front as the thumb touches the screen. In a study, we compared touch performance of different landmark layouts with a regular landmark-free mobile device. Using a landmark design of dots on a 3×5 grid significantly improves eyes-free tapping accuracy and allows targets to be as small as 17.5 mm—a 14% reduction in target size—to cover 99% of all touches. When users can look at the touchscreen, landmarks have no significant effect on performance. HaptiCase is low-cost, requires no electronics, and works with unmodified software.
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