VRCodes : embedding unobtrusive data for new devices in visible light

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 97-101).This thesis envisions a public space populated with active visible surfaces which appear different to a camera than to the human eye. Thus, they can act as general digital interfaces that transmit machine-compatible data as well as provide relative orientation without being obtrusive. We introduce a personal transceiver peripheral, and demonstrate this visual environment enables human participants to hear sound only from the location they are looking in, authenticate with proximal surfaces, and gather otherwise imperceptible data from an object in sight. We present a design methodology that assumes the availability of many independent and controllable light transmitters where each individual transmitter produces light at different color wavelengths. Today, controllable light transmitters take the form of digital billboards, signage and overhead lighting built for human use; light-capturing receivers take the form of mobile cameras and personal video camcorders. Following the software-defined approach, we leverage screens and cameras as parameterized hardware peripherals thus allowing flexibility and development of the proposed framework on general-purpose computers in a manner that is unobtrusive to humans. We develop VRCodes which display spatio-temporally modulated metamers on active screens thus conveying digital and positional information to a rolling-shutter camera; and physically-modified optical setups which encode data in a point-spread function thus exploiting the camera's wide-aperture. These techniques exploit how the camera sees something different from the human. We quantify the full potential of the system by characterizing basic bounds of a parameterized transceiver hardware along with the medium in which it operates. Evaluating performance highlights the underutilized temporal, spatial and frequency dimensions available to the interaction designer concerned with human perception. Results suggest that the one-way point-to-point transmission is good enough for extending the techniques toward a two-way bidrectional model with realizable hardware devices. The new visual environment contains a second data layer for machines that is synthetic and quantifiable; human interactions serve as the context.by Grace Woo.Ph.D

Towards the use of visual masking within virtual environments to induce changes in affective cognition

This thesis concerns the use of virtual environments for psychotherapy. It makes use of virtual environment properties that go beyond real-world simulation. The core technique used is based on research found within perception science, an effect known as backwards visual masking. Here, a rapidly displayed target image is rendered explicitly imperceptible via the subsequent display of a masking image. The aim of this thesis was to investigate the potential of visual masking within virtual environments to induce changes in affective cognition. Of particular importance would be changes in a positive direction as this could form the foundation of a psychotherapeutic tool to treat affect disorders and other conditions with an affective component. The initial pair of experiments looked at whether visual masking was possible within virtual environments, whether any measurable behavioural influence could be found and whether there was any evidence that affective cognitions could be influenced. It was found that the technique worked and could influence both behaviour and affective cognition. Following this, two experiments looked further at parameter manipulation of visual masking within virtual environments with the aim of better specifying the parameter values. Results indicated that the form of visual masking used worked better in a virtual environment when the target and mask were both highly textured and that affective effects were modulated by the number of exposures of the target. The final pair of experiments attempted to induce an affect contagion effect and an affect cognition-modification effect. An affect cognition-modification effect was found whereas an affect contagion effect was not. Overall, the results show that using visual masking techniques within virtual environments to induce affect cognition changes has merit. The thesis lays the foundation for further work and supports the use of this technique as basis of an intervention tool