Tangible user interfaces and social interaction in children with autism

Tangible User Interfaces (TUIs) offer the potential for new modes of social interaction for children with Autism Spectrum Conditions (ASC). Familiar objects that are embedded with digital technology may help children with autism understand the actions of others by providing feedback that is logical and predictable. Objects that move, playback sound or create sound – thus repeating programmed effects – offer an exciting way for children to investigate objects and their effects. This thesis presents three studies of children with autism interacting with objects augmented with digital technology. Study one looked at Topobo, a construction toy augmented with kinetic memory. Children played with Topobo in groups of three of either Typically Developing (TD) or ASC children. The children were given a construction task, and were also allowed to play with the construction sets with no task. Topobo in the task condition showed an overall significant effect for more onlooker, cooperative, parallel, and less solitary behaviour. For ASC children significantly less solitary and more parallel behaviour was recorded than other play states. In study two, an Augmented Knights Castle (AKC) playset was presented to children with ASC. The task condition was extended to allow children to configure the playset with sound. A significant effect in a small sample was found for configuration of the AKC, leading to less solitary behaviour, and more cooperative behaviour. Compared to non-digital play, the AKC showed reduction of solitary behaviour because of augmentation. Qualitative analysis showed further differences in learning phase, user content, behaviour oriented to other children, and system responsiveness. Tangible musical blocks (‘d-touch’) in study three focused on the task. TD and ASC children were presented with a guided/non-guided task in pairs, to isolate effects of augmentation. Significant effects were found for an increase in cooperative symbolic play in the guided condition, and more solitary functional play was found in the unguided condition. Qualitative analysis highlighted differences in understanding blocks and block representation, exploratory and expressive play, understanding of shared space and understanding of the system. These studies suggest that the structure of the task conducted with TUIs may be an important factor for children’s use. When the task is undefined, play tends to lose structure and the benefits of TUIs decline. Tangible technology needs to be used in an appropriately structured manner with close coupling (the distance between digital housing and digital effect), and works best when objects are presented in familiar form

Optical Communication Systems

A receiver, transmitter, and photon counting detector for use in an optical communication link are disclosed. Also disclosed are methods of communicating using the transmitter, the receiver, and the photon detector

Electro-Optical Modulator Bias Control Using Bipolar Pulses

An improved method has been devised for controlling the DC bias applied to an electro-optical crystal that is part of a Mach-Zehnder modulator that generates low-duty-cycle optical pulses for a pulse-position modulation (PPM) optical data-communication system. In such a system, it is desirable to minimize the transmission of light during the intervals between pulses, and for this purpose, it is necessary to maximize the extinction ratio of the modulator (the ratio between the power transmitted during an "on" period and the power transmitted during an "off" period). The present method is related to prior dither error feedback methods, but unlike in those methods, there is no need for an auxiliary modulation subsystem to generate a dithering signal. Instead, as described below, dither is effected through alternation of the polarity of the modulation signal. The upper part of Figure 1 schematically depicts a Mach-Zehnder modulator. The signal applied to the electro-optical crystal consists of a radio-frequency modulating pulse signal, VRF, superimposed on a DC bias Vbias. Maximum extinction occurs during the off (VRF = 0) period if Vbias is set at a value that makes the two optical paths differ by an odd integer multiple of a half wavelength so that the beams traveling along the two paths interfere destructively at the output beam splitter. Assuming that the modulating pulse signal VRF has a rectangular waveform, maximum transmission occurs during the "on" period if the amplitude of VRF is set to a value, V , that shifts the length of the affected optical path by a half wavelength so that now the two beams interfere constructively at the output beam splitter. The modulating pulse signal is AC-coupled from an amplifier to the electro-optical crystal. Sometimes, two successive pulses occur so close in time that the operating point of the amplifier drifts, one result being that there is not enough time for the signal level to return to ground between pulses. Also, the difference between the optical-path lengths can drift with changes in temperature and other spurious effects. The effects of both types of drift are suppressed in the present method, in which one takes advantage of the fact that when Vbias is set at the value for maximum extinction, equal-magnitude positive and negative pulses applied to the electro-optical crystal produce equal output light pulses