For applications involving the control of moving vehicles, the recovery of relative motion between a camera and its environment is of high utility. This thesis describes the design and testing of a real-time analog vlsi chip which estimates the focus of expansion (foe) from measured time-varying images. Our approach assumes a camera moving through a fixed world with translational velocity; the foe is the projection of the translation vector onto the image plane. This location is the point towards which the camera is moving, and other points appear to be expanding outward from. By way of the camera imaging parameters, the location of the foe gives the direction of 3-D translation. The algorithm we use for estimating the foe minimizes the sum of squares of the differences at every pixel between the observed time variation of brightness and the predicted variation given the assumed position of the foe. This minimization is not straightforward, because the relationship between the brightn...

this paper a few more important concepts and discussions were uncovered that warrant mentioning. Martin Glasband has written a series of articles on balanced AC systems [3], [4]. Glasband applies the same balanced concepts used in audio inter-

A photon-counting system based on an appropriate microcontroller has been developed. This system controls, acquires, processes and stores the data from a high-resolution multi-channel gas analyzer and provides accurate photon-counting measurements using suitable Photomultiplier Tubes (PMTs) as detectors of the Raman scattering signals. The implemented system ensures low power consumption (90 W for the overall system), low cost, increased reliability and high sensitivity. Also the entire unit allows auto-calibration and drift compensation. Finally, the present photoncounting system can be used in a broad field of applications, in medical electronics (e.g. confocal microscopy), air pollution optical measurements, laser sounding of the atmosphere, and electrooptical systems, provided that PMTs are used in the pulse-counting mode.

In this thesis we report on a new micromachined floating-element shear-stress sensor for turbulent boundary layer research. Applications in low shear-stress environments such as turbulent boundary layers require extremely high sensitivity to detect the small forces (O(nN)) and correspondingly small displacements (O()) of the floating-element. In addition, unsteady measurements in turbulent flows require sensors with high operating bandwidth (~20 kHz). These requirements render most of the existing shear-stress measurement techniques inadequate for this application. In response to the limitations of the existing devices, we have developed a sensor based on a new transduction scheme (optical position sensing by integrated photodiodes). The sensors developed in this thesis have a measured resolution of 0.003 Pa, with a measured range of 133 Pa and the dynamic response of the sensor has been measured to 10 kHz.

Impedance is the AC (alternating current) version of the DC (direct current) term resistance, which is the opposition to electron current flow in a circuit and is expressed in ohms. Impedance (often abbreviated as “Z”) includes capactive reactance and inductive reactance in addition to simple DC resistance. Reactance depends upon the frequency of the signal flowing in the circuit. Capactive reactance increases as frequency decreases: inductive reactance increases as frequency increases. Because of this frequency dependence, impedance is not directly measurable with a multimeter as DC resistance is. What are the differences between high- and low-impedance microphones? To answer this requires a little historical background. High-impedance microphones are capable of producing higher output voltages than low-impedance types. Until recently, “consumer ” audio gear (small P.A. systems, home and semi-pro recording equipment, etc.) was always designed for high-Z mics because their relatively high output level required less amplification or gain. The lower output of low-Z mics required the equipment manufacturer to use input transformers in front of the mic preamplifiers to step up the strength of the signal, which substantially increased the cost of the circuitry. Hence, low-Z mics were rare outside of professional recording and broadcast studios. In these “big-budget ” facilities, low impedance lines offered several big advantages. A high-Z mic’s high

Bridging. They are available in 2, 3, and 4 winding versions and are generally used to provide additional, isolated outputs from a single microphone. The microphone is directly connected to the first preamp input, which provides "phantom power " if required, and also connected to the primary winding of the MB transformer, which now "bridges " the mic to first preamp line. The direct output is the ONLY output which will pass phantom power to the mic. The MB transformer secondary windings are then connected to additional preamp inputs. Since the transformer magnetically couples the signal to each winding, each preamp now "sees " the microphone's output signal while having no problematic direct connection to the other preamps. To a preamp, each isolated MB transformer output "looks like " a normal floating (ungrounded) microphone.

Abstract not found