We are developing an embedded vision system for the humanoid robot iCub, inspired by the biology of the mammalian visual system, including concepts such as stimulusdriven, asynchronous signal sensing and processing. It comprises stimulus-driven sensors, a dedicated embedded processor and an event-based software infrastructure for processing visual stimuli. These components are integrated with the existing standard machine vision modules currently implemented on the robot, in a configuration that exploits the best features of both: the high resolution, color, framebased vision and the neuromorphic low redundancy, wide dynamic range and high temporal resolution event-based sensors. This approach seeks to combine various styles of vision hardware with sensorimotor systems to complement and extend the current state-of-the art.

Double Schottky barriers in ZnO are modified piezotronically by the application of mechanical stresses. New effects such as the enhancement of the potential barrier height and the increase or decrease of the natural barrier asymmetry are presented. Also, an extended model for the piezotronic modification of double Schottky barriers is given.

Conventional clocked line sensors generate large amounts of data when employed in high-speed short-latency machine vision applications because they read out data of all pixels at a fixed rate. For various problems such as measurement tasks, shape detection, object orientation extraction etc., a substantial fraction of the image data produced does not provide any information necessary to accomplish the function or to increase reliability or precision. One way to suppress image data redundancy is to use a self-timed data-driven sensor architecture.The optical line sensor presented here combines an asynchronous pixel circuit with on-chip precision time-stamping and a synchronous bus arbiter. The temporal resolution of this new sensor is 100ns (compared to line rates on the order of 100kHz for the fastest clocked line sensors [1][2][3][4]) and is beneficial for various high-speed machine vision applications that do not rely on conventional image data. The output data volume depends on the dynamic contents of the scene and is typically orders of magnitude lower than equivalent data output produced by clocked line sensors in this type of applications.Each pixel operates autonomously and responds with low latency to relative illumination changes by generating asynchronous events [5]. Pixels that are not stimulated do not produce outputs. The circuit combines an active continuous-time logarithmic photo-sensor with a self-timed differentiating switched-capacitor amplifier, threshold comparators and handshake logic. It generates two types of events, which represent a fractional increase or decrease in intensity that exceeds a tunable threshold. Combined with the pixel address, these events are referred to as 'address-events' (AE) [6]. The pixel is able to detect contrast changes of a few percent over a dynamic range of >120dB. The wide dynamic range arises from the logarithmic compression in the front-end photoreceptor circuit and the local (pixel intrinsic) event-based differentiation operation [5]. The 28T3C pixels measure 15µm×165µm in a standard 0.35µm CMOS process and are arranged in a 2×256 dual-line configuration with 15µm pixel pitch and 250µm line separation.Time-stamps are traditionally assigned to asynchronous addressevent data by a post-processor after arbitration of a shared communication channel, e.g. [6]. Depending on data rate and arbitration strategy, a non-deterministic variable latency affects the timing precision of the data [7-8]. The architecture presented here performs the time-stamp assignment at the pixel level. Time-stamps are combined with the corresponding address events to compose a synchronous stream of data packets. Events occurring during the same time-stamp period are interpreted as concurrent and are arbitrated in the order of their addresses. Pixel addresses and time-stamps are read out via a 3-stage pipelined synchronous bus arbiter. A single set of output data from the sensor is referred to as a 'timed addressevent' (TAE).A block diagram of the chip is shown in Fig. 28.1.1. Pixels signa...

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The piezoelectric effect of ZnO has been investigated recently with the goal to modify metal/semiconductor Schottky-barriers and p-n-junctions by application of mechanical stress. This research area called “piezotronics” is so far focused on nano structured ZnO wires. At the same time, ZnO varistor materials are already widely utilized and may benefit from a piezotronic approach. In this instance, the grain boundary potential barriers in the ceramic can be tuned by mechanical stress. Polycrystalline varistors exhibit huge changes of resistivity upon applied electrical and mechanical fields and therefore offer descriptive model systems to study the piezotronic effect. If the influence of temperature is contemplated, our current mechanistic understanding can be interrogated and corroborated. In this paper, we present a physical model based on parallel conducting pathways. This affords qualitative and semi-quantitative rationalization of temperature dependent electrical properties. The investigations demonstrate that narrow conductive pathways contribute to the overall current, which becomes increasingly conductive with application of mechanical stress due to lowering of the barrier height. Rising temperature increases the thermionic current through the rest of the material with higher average potential barriers, which are hardly affected by the piezoelectric effect. Hence, relative changes in resistance due to application of stress are higher at low temperature.