Bogdan B. Kosmowski

Fiber optic quasi-distributed temperature sensor

The subject of this paper is an optical fiber temperature sensor using the techniques of optical time domain reflectometry. The sensor uses the dependence between the refractive index of epoxy resins and temperature and allows us to develop sensors working in transmission as well as in reflective mode.

Milestones on the way to a reconfigurable automotive instrument cluster

Nowadays, the car driver are faced with a rapidly increasing flood of information. In addition to established information systems (car radio, vehicle monitoring, mobile phones), high class vehicles feature navigation systems almost as standard. In the current decade, driver assistance and collision avoidance systems will appear in vehicles. Hence, there is an increasing demand for supplying the driver with more information that help him to drive safer and more economical. The price decline in the computer market and the availability of powerful graphic hard- and software concepts make it possible to enhance the classical functions of the instrument board to an interactive multifunctional information panel - an interface between information systems of the car and the driver. Therefore, the question of additional visual and cognitive stress, and a possible distraction of the driver by the large amount of information, and its complexity becomes predominant. Reconfigurable instruments, based on a microprocessor controlled active matrix color display, provide a powerful alternative to the usual mechanical/electromechanical instrument clusters in vehicles. They will help to strengthen passive safety, they adapt to user and situation requirements, and they are easy to install, to configure, and to maintain. Reconfigurable instruments in future cars will have a high impact on traffic since they can provide the driver with much more information, presenting it in a way that is flexibly matched to the importance of particular data and to the ergonomic properties of the driver. The functions are manifold and span from classical driver information like speed to navigation prompts and ultimately to video and multimedia access.

Interferometric optical fiber sensors with active stabilization of the operating point using a tunable semiconductor laser

Optical fiber force sensors using Michelson interferometer and a tunable external cavity semiconductor lase rsource are investigated in order to develop a sensor whose operating point is actively stabilized by the change of the source wavelength. Two configurations of such sensros are briefly discussed, and their advantages are compared. Based on presented results a sensor was built and tested. The sensor employs an indirect force transducer in which the force acting on it is converted into hydrostatic pressure which is subsequently measured. The sensor exhibits good linearity. Its bandwidth is currently limited by the tuning speed of the laser and can be extended by increasing the tuning speed of the laser.

Application of computer-assisted modified coupled-mode method for the design of polarimetric sensors

A method for modeling of multiply purturbed fibers was developed as an extension to the modified coupled-mode method. Being based on numerical solution of coupled mode equations, the method is not limited in the scope of its applications to the cases in which coupling coefficients are constant along the fiber. Short computation time was achieved as a result of modification to the solved coupled-mode equations. Presented method was developed as a design tool for polarimetric optical fiber sensors. The use of the method is demonstrated on an example of a twisted single-mode elliptic-core fiber subjected to pure bending. Moreover, it was shown that the presented method can be also applied to visibility calculation in polarimetric sensors using polychromatic sources.

Colorimetric evaluation of display performance

The development of information techniques, using new technologies, physical phenomena and coding schemes, enables new application areas to be benefited form the introduction of displays. The full utilization of the visual perception of a human operator, requires the color coding process to be implemented. The evolution of displays, from achromatic (B&W) and monochromatic, to multicolor and full-color, enhances the possibilities of information coding, creating however a need for the quantitative methods of display parameter assessment. Quantitative assessment of color displays, restricted to photometric measurements of their parameters, is an estimate leading to considerable errors. Therefore, the measurements of a displays color properties have to be based on spectral measurements of the display and its elements. The quantitative assessment of the display system parameters should be made using colorimetric systems like CIE1931, CIE1976 LAB or LUV. In the paper, the constraints on the measurement method selection for the color display evaluation are discussed and the relations between their qualitative assessment and the ergonomic conditions of their application are also presented. The paper presents the examples of using LUV colorimetric system and color difference (Delta) E in the optimization of color liquid crystal displays.

Interferometric optical fiber sensor for weigh-in motion of road vehicles

An interferometric optical fiber sensor intended for use in Weigh-in-Motion systems is presented. The sensor uses a modified Michelson interferometer configuration with two sensing arms. To avoid polarization induced fading the force acting on the sensor is measured indirectly, using modulators which convert it to pressure. Operation of such modulators was verified by experiment and based on its results a laboratory model of a sensor was built and tested.

Polarimetric optical fiber sensor for weight-in-motion applications

Stress sensors dedicated for Weigh-in-Motion of road vehicles should exhibit high dynamic range, good accuracy and repeatability, as well as long service life. One of the most promising group of sensors for this application are polarimetric sensors, due to their simplicity and high sensitivity. Preliminary measurements of the optical fiber properties in this application resulted in significant hysteresis being observed even for relatively low stress, which is probably caused by the cladding properties or by the construction of the modulator used in the measurement.

Fiber optic head for spectrophotometric measurements

The requirements for design and construction of fiber optic measuring heads (probes) based on an imaging rigid fiber optic bundle and on flexible fiber optic bundles are presented. The models of the probes and their application in a spectrophotometric measurement system for a medical application are described and discussed. The performed experiments confirmed their usefulness.

Modeling and computer optimization of fiber optic refractometric sensors

The subject of this paper is modelling and optimization of fiber optic refractometric sensors that based on the principle of attenuation caused by bends of the optical fiber. Sensors of this type are meant to measure the refractive index of fluids and, after some modifications, to measure temperature. The model designed allows us to optimize the construction of this type of sensors in order to obtain the highest possible sensitivity and linearity of characteristics in the assumed range of changes of the measured refractive index.

Optimization of color LC displays

The advancement of the liquid crystal display (LCD) technology, and improvements of the optical and electro-optical properties, have enabled the broad expansion of LCDs application field. The rapid development of the multimedia techniques, new applications in automotive, office, medical domain, forced the demand for the color displays--for the information presentation with the color code. The necessity to fulfil many contradictory and extreme conditions caused the development of the optimization procedures of the color LC displays to be a big problem. Most of the LCDs used nowadays are the twisted nematic, super twisted nematic, and active matrix thin film transistor LCD. The characterization of the achromatic black/white LCDs is made by means of photometric measuring methods, and quantitative measures are used: luminance, reflectance, contrast, contrast ration; as a function of a driving voltage, viewing angle, temperature, etc. The characterization of the color LCD is based on the spectral distributions of the transmittance or reflectance. Quantitative measures are chromatic coordinates and luminance factors are defined according to the colorimetric systems--CIE 1931, CIE 1976, CIELUV, CIELAB. The color difference (Delta) E in the CIELUV system is applied as a optimization parameter for the color display module. The spectral properties of all optical elements of the display module are analyzed and their influence on the set of the optical factors of LCD is evaluated. The correlation between technological parameters and optical characteristics of the LCD has been investigated. The choice of the optimization criterion is discussed and the optimization algorithm is proposed. Results of the color displays evaluation for some examples with different preconditions are presented.