SENSORS, 2002 IEEE

In this paper we discuss laboratory results from solenoidal magnetoelastic measurements performed on a sample of bridge suspension cable. The experiments were designed to answer basic questions regarding the potential effects of inhomogeneous temperature fields and differential thermal errors between sensor and sample on the accuracy of coercive force measurements. The experiments were conducted with a sample of suspension cable installed in a temperature-controlled thermal chamber. Internal cable temperatures were measured with fine thermocouples which did not breach the sheath, permitting knowledge of the temperature field to be obtained without altering heat transfer. Two sets of experiments were conducted. First, magnetic measurements were taken with the sensor/cable in thermal equilibrium at two different temperatures, and at intermediate points when the temperatures of different ferromagnetic components of the system varied. The magnitude of different heat transfer effects were quantified, and correlated with estimates of the coercive force. Secondly, in order to judge the absolute accuracy of the measurements and to obtain data for further optimizing computer simulations, reference magnetic data was measured using two techniques on a single wire sample of the cable steel. These results are an important step in quantifying the overall accuracy of these sensors.

Design, fabrication and characterization of silicon-based stress-free self-aligned quad beam accelerometer is presented. Standard total internal reflection waveguides have been replaced by ARROW structures, enhancing the sensitivity to >4dB/g at the wavelength visible range (633nm) Moreover, as the waveguide core has approximately the same size as the input fiber optic, insertion losses have been reduced to 2.5dB. Attenuation in ARROW waveguides is 0.3dB/cm.

In this paper, we study a simple angle-sensitive detector for sensing optical beam deflections. This type of device is sought to replace position sensitive detectors commonly used with optical beam deflection techniques in a variety of applications. The main advantage is that the sensitivity is independent of the distance from the deflection point to the detector. To our knowledge this is the first practical design that approaches closely the diffraction limit to the sensitivity when sensing micro-deflections of a laser beam. The detector is based on reflection/transmission of the optical beam near the critical angle and uses a single antireflection layer. The sensitivity is nearly polarization independent. The temperature dependence of the device is discussed and a possible fabrication procedure of the device is analyzed.

Traditionally the acquisition of real time panoramic images has been performed by the usage of lenses or mirrors coupled with standard image sensors, which give distorted images. In this paper we will present a system composed of a mirror and a log polar sensor, which is able to provide directly understandable images.

The method of direct field-strength determination, in combination with the method of conformal mapping, explained in this paper, is elegantly applied for precise analytical calculation of the capacitances of complex-shaped systems of electrodes. Because of the analogy of mathematical formulations, this method can be also applied for calculation of stationary magnetic, electrical and thermal fields. In this paper we will indicate for which geometries of sensor-elements the method can be used to design capacitive sensors The procedure of calculation, novel example and some applications of this method are presented.

Tissue pH is a regional measure of anaerobic metabolism and low blood flow state that can be measured using near infrared (NIR) spectroscopy (700 - 1100 nm). NIR light passes through the skin to probe muscle and tissue at depths of 5 - 10 mm. We have used a fiber optic probe to collect light both through skin and directly from internal organs during surgical procedures, to investigate the measurement of tissue pH in a number of settings. We have demonstrated the successful optical measurement of tissue pH during complete blood flow cessation (vessel occlusion) and during reduced blood flow conditions such as hemorrhagic shock. We have shown, in a series of animal studies, that optically measured tissue pH is accurate under conditions of variable blood flow, temperature, hematocrit and oxygen saturation.

Fast collection of three-dimensional (3D) data sets is required in a growing number of applications like robotic guidance, security and automotive. Scannerless time-of-flight (TOF) based active 3D vision systems are capable of collecting depth profiles of entire scenes in fractions of seconds but have the disadvantage of using high voltage and expensive electronic components. In this contribution we describe the design and test of an integrated smart pixel with 3D vision capability, which attempts to address this kind of problem. The pixel, fabricated in standard 0.6 /spl mu/m CMOS technology, is suitable to be used in scannerless ranging systems. By means of a pulsed laser source, distance estimation is obtained by integrating the back-reflected signal in successive time windows.

In this work we present recent results regarding the activation of sensors with high power density light with energy in the range of the energy gap of the semiconductor. We report the measurements registered for tin oxide RGTO deposited layers using CO as a target gas. The influence of the doping on the activated gas sensing properties has been investigated. We have found the value of the incident power corresponding to the best gas sensing performances (response enhancement and kinetics). The comparison between dark and irradiation condition is presented for the different kinds of layers tested.

Novel semitransparent optoelectronic position sensors, the 'ALMY sensors,' have been developed for high-precision multi-point position and angle measurements of collimated laser beams over a large measurement range. The sensors consist of a thin film of amorphous silicon deposited on a glass substrate between two transparent layers of crossed strip electrodes. They provide a position resolution on the order of a micrometer over sensitive areas of several square centimeters. A transmittance of 80-90% has been achieved for 780 nm laser light produced by diode lasers. We report on recent optimizations of the sensor performance and tests of the long-term stability under laser illumination and of the radiation tolerance at high neutron doses. As expected, the radiation hardness of the amorphous silicon sensors exceeds the that of crystalline silicon devices. The custom designed readout electronics allows for operation at sufficiently low laser intensities in order to prevent significant degradation of the performance of the amorphous silicon sensors under illumination with laser light.

To localize a robot in an indoor environment, ultrasonic sensors are used. Our aim is to show we can classify targets into four classes (edges, corner, plane, small cylinder) using the whole information in the received echo. However, to classify received echoes we need to extract features from raw data. The extracted features must be discriminant to improve the classifier results. The selection of features is an important step of the pattern recognition. In this paper decomposition on wavelet best basis and optimized wavelets are used to extract relevant features from an ultrasonic signal and is compared to other feature extractors.