Future haptic augmented reality systems could transform our interactions within many environments by furnishing haptic feedback that augments touch interactions with physical objects. However, most prior haptic technologies involve controllers, wearables, or devices that either impede free-hand interactions or make it impossible to directly touch physical objects with the skin. This Ph.D. presents several haptic design approaches and findings that can overcome these limitations, and that provide new methods for augmenting free-hand interactions with physical objects.
The first part of the Ph.D. presents a new haptic augmented reality system for the hand. It introduces Tactile Echoes, a finger-wearable system that provides responsive haptic feedback that augments touch interactions with physical surfaces. It renders these effects by capturing touch-elicited vibrations in the skin and processing them in real-time in order to enliven tactile experiences. Using computational and spatial tracking techniques, different haptic effects may be spatially painted onto different objects or surfaces. This chapter presents experiments characterizing how these novel haptic effects are perceived, demonstrations of several applications, and a user study showing how they can enhance augmented or mixed reality applications.
The second part of this Ph.D. was motivated by observations obtained using Tactile Echoes that indicate that the perceived strength of haptic feedback increases when it is supplied tens of milliseconds after a touch event. This observation is consistent with findings from prior perception research on tactile forward masking. However, prior studies of forward masking have been confined to passive conditions rather than active touch, as occurs in Tactile Echoes. This chapter presents research revealing prominent modulatory effects of the timing, amplitude, and perceptual similarity between the feedback and the transient skin oscillations elicited via touch contact. Forward masking produced a greater attenuation of the perceived intensity of feedback as delay time decreased, with the maximum attenuation reaching nearly 10 dB. These findings shed light on the interplay between perception and action in the haptic system and have important implications for the design of haptic interfaces.
The third part of this Ph.D. presents another method for augmenting touch interactions that exploits mechanical wave propagation in the skin. This method, called Beatactile, involves supplying vibrations on the finger and on the surface with slightly different frequencies. When a surface is touched, the two vibration sources interfere, producing beat frequencies between vibrations in the finger that cause a flat surface to feel coarsely textured. The BeaTactile hardware and software system enables parametric control over these novel effects.
The final part of this Ph.D. concerns thermal augmentations of touch interactions, based on the thermal grill illusion. It presents a newly developed thermal grill haptic interface that exploits juxtaposed warm and cool areas to render surprisingly intense thermal sensations. The results revealed perceived intensity to increase, and response time to decrease, monotonically with temperature differences. An augmented reality demonstration highlights potential applications of this technique haptic design and engineering. This research contributes to knowledge about thermal perception and suggests new design approaches for thermal interfaces.
