Wyniki 1-10 spośród 11 dla zapytania: authorDesc:"Zenon HOTRA"

Temperature sensor on the base of light selective reflection

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The dependence of laser generation frequency from temperature in the distributed feedback laser based on cholesteric liquid crystal (CLC) can be used for creation of primary converter of sensor device for temperature controlling. it is well known [1], that the sensitivity CLC to temperature gives the possibilities to register the temperature with high accuracy (0,01 -0,001C ). The[...]

Powłokowe struktury optyczno-aktywnych materiałów w czujnikach światłowodowych do zastosowań w systemach ekologicznych

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Coraz szybszy rozwój cywilizacyjny i pęd człowieka do wprowadzania nowych technologii pociąga za sobą nieunikniony wpływ na otaczające nas środowisko. W większym, bądź mniejszym stopniu ma to niestety negatywne skutki. Sytuacja taka, co jest obecnie mocno akcentowane, wymaga bardzo wnikliwej oceny stanu naturalnego środowiska i prowadzenia na bieżąco pomiarów jego wielu różnych parametrów, j[...]

Signal transducers of capacitive microelectronic sensors


  Microelectronic sensors state of the art is characterized by wide using of special designs of signal transformation which would improve measurement accuracy including transformation function linearization, temperature compensation, noise reduction etc. [1]. In contrast to digital technique, devices of preliminary analog signal transformation require much more attention with relation to measuring transformation as well as to elemental base. Taking into consideration the fact that outward things show up mainly in analog form, the sensor input signal has an analog form too. Consequently, preliminary analog signal transducers normalizing the signal for its following digitization essentially influence the device parameters in whole [2]. For the last years scientific publications have been focused on actuality of analog signal transducers further development and their compatibility with digital microcontrollers [3-6]. Strong interest in making measurement process more intelligent shows up, particularly in connection with analog sensor nodes [7,8]. Analog signal transducers are particularly actual for microelectronic capacitive transducers (position transducers, chemical analysis sensors, humidity sensors). This actuality can be attributed to the serious difficulty with small capacitance values measurements (a typical value of a microelectronic capacitive sensing device capacitance amounts to several picofarads at all) [9-14]. When analyzing capacitive sensors signal transformation problem one probably would note at least three main methods of measurement. The first method is based on capacitance impedance measurement at certain fixed frequency or several fixed frequencies. The second method assumes capacitance charging time measurement at some fixed charging current. In the simplest case it can be time-domain measurement of RTCX circuit, where CX is transducer measuring capacitance, RT is a resistor, defining the current. The thi[...]

Field characteristic of magnetic sensors on the split hall structures


  Galvanomagnetic sensors are widely used for magnetic field measurement due to their capability to work in a wide range of magnetic flux density (from 10-6 T to several tens of Tesla) and temperature (from 1 K to 400 K), their small sizes (several millimeters) and low cost (in large-scale production) [1, 2]. Hall sensors are a kind of galvanomagnetic sensors. A typical Hall sensor is a rectangular semiconductor slab with two pairs of electrodes: one pair is used for energizing the slab whilst the other is intended for Hall voltage measurement (these two electrodes are referenced to as potential electrodes, they are placed symmetrically along the current-flow line) [3, 4]. One can distinguish two typical variants of probes of Hall sensors - with normal (transverse) and with axial position of a sensor in a probe. Such probes are intended for measuring the only magnetic-field vector’s projection which is normal to the probe’s work surface. This fact causes two problems. The first problem is restricted spatial resolution; the second one is impossibility of simultaneous measurement of three magnetic-field vector’s projections (BX, BY, BZ) in a certain point of space. As shown in Fig. 1a, there no difficulties concerned to measurement of the magnetic-field vector’s projection normal to a certain surface. In order to measure this projection sensor is to be placed immediately on this surface. The distance d between the surface being measured and the effective layer (active region) can be rather short and depends on the width of the effective layer’s substrate. Thinning the substrate appropriately, one can achieve the distance d nearly equal to 0.2…0.3 mm. However if the magnetic-field vector’s projections parallel to the surface are to be measured then the sensor’s structure is to be set vertically (Fig. 1b). This causes the minimal possible distance d between the sensor’s active reg[...]

Simulation of magnetically controlled elements for optoelectronic systems on the basis of liquid crystals


  One of the possible ways of cost reduction of optical networking is the use of multimode optical fibers. However, their application is significantly restricted by dispersion phenomena that lead to distortion of information transmission in telecommunication fiber networks. In addition, in fiber networks there is an issue of coordination of connection in fiber systems [1, 3]. One of possible solutions of these problems is the application of phase compensators which can reduce the effect of dispersion phenomena. Molecular models In this work we review the possibility of development of magnetically controlled cells on the basis of liquid crystals for optical fiber systems. Magnetically controlled liquid crystalline element is alight guide with a radial distribution of the director profile. The application of an external magnetic field with a magnetic induction vector directed along the axis of the fiber leads to the formation in the center of the coaxial liquid crystalline fiber an are a with distribution of liquid crystal director field in the direction of applied magnetic field. In order to analyze the possibility of the development of LC structure with necessary characteristics there was carried out a computer simulation of molecular models by the means of GBMOLDD software [4]. Molecular models considered in classicalmechanical level and are described by force fields. Bounding interactions in the molecule as a following form [2]: where, nb - number of bo[...]

Formation of thin polyaniline films by means of ionic sputtering in crossed electromagnetic field

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Polymers with their own electron conduction constitute one of the most interesting classes of organic semiconductor materials [1]. Such polymers pose semiconductor properties [2] caused by the presence of π-electron bonds. From the practical point of view, polyaniline (PAN) which is the simple nontoxic synthesis of high sensitivity to outer factors and high reproductively of optical pro[...]

Optical properties of vacuum deposited poly(o-toluidine) films in integral and fibre optics to use

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Elements basis of fibre and integral optical devices are mainly based on application of electro-physical effects in solids, semiconductors, thin and thick film materials and waveguides. Latest achievements in technology of polymers with proper electronic conduction as well as the study of electro-physical, electro-chromic effects, photosensitivity and luminescence along with unique propertie[...]

The field stabilization of optic-active medium of harmful substances sensors


  Liquid crystals (LC) can be regarded as a recording medium. Specificity of LC is that they, on the one hand, are an orderly structure, but on the other hand - medium with exceptionally high sensitivity to changes of the regularity under the influence of external factors, what can be easily registered optically due to a large optical anisotropy of the medium. LC output structure can be changed by very weak external factors of different nature: temperature, electric and magnetic fields, radiation of different wavelengths, intermolecular interactions with the substrate and even mechanical or chemical factors that cause changes in optical parameters. Thin films of liquid crystals easily absorb gases and steam from the environment. Gases and steam, absorbed on the surface, significantly alter the optical properties of cholesteric films and, above all, their selective reflection coefficient [1]. Selective properties of cholesteric liquid crystals (CLC) and the ability to change the spiral pitch allow of lasers with tuned frequency. Optical pumping is realized by laser which wavelength falls in the region of dye absorption band. Dye emission wavelength is comparable or equal to cholesteric spiral pith, so a selective light reflection takes place. Therefore cholesteric liquid crystal acts as resonator and selector. The centre wavelength of selective reflection band (SRB) is λmax = nP while the width of the band is Δλ= PΔn, where P is the pitch of the chiral liquid crystal, n = (ne+no)/2 is the average refractive index of the cholesteric planes which have a birefringence of Δn = ne ‑ no, finally ne and no are the extraordinary and ordinary refractive indices respectively [2]. To achieve generation during a pulse laser (solid or gas) excitation into absorpti[...]

Technology development of organic photosensitive structures and study of their electrophysical properties


  The study of electrical properties of photosensitive elements based on organic polymer or low molecular semiconductors (in particular - the current-voltage and capacitance-voltage characteristics and impedance spectroscopy) associated with the study of potential barriers of the metal - semiconductor have been presented in this paper. The good knowledge about mutual dependences of current and voltage gives a possibility to determine the mechanism of charge transport in the developed structures and estimate the effectiveness of the technology of their creation. The main disadvantage of known organic barrier structures is small efficiency due to the small diffusion length of excitons in organic materials, low carrier mobility, small effective surface area of transition, a low concentration of carriers. The results of optimization of technology creation and electrical measurements of organic semiconductor barrier structures have been discussed. The special attention was laid on improving of electrical parameters of devices - in other word - the conductivity of low molecular weight semiconductor materials by doping and increase the active area of structure barriers by introduction of additional transport layers in the anode region of devices. Additionally, the influence of composite coating of low-molecular semiconductors (nickel phthalocyanine) and conjugated polymers (polyaniline) on manufacturing process were also analyzed Structures fabricated on flexible conductive substrate of nickel phthalocyanine films doped with oxygen Most of the phthalocyanines have low intrinsic conduction, which limits their practical application in phototransformator and light-emitting devices [1]. An effective method for increasing the concentration of free charge carriers in them are doping by oxygen molecules. The presence of introduced impurity oxygen leads to a significant increase in the concentration of holes. For example, after exposing of [...]

Sensor systems with optical channel of information transferring

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W artykule zaprezentowano i omówiono charakterystyki przedstawiające zależność długości skoku helisy w cholesterycznych ciekłych kryształach (CLC) oraz anizotropii współczynnika załamania CLC od temperatury, a także zależność długości skoku helisy od stężeń par acetonu, etanolu i amoniaku, pod kątem wykorzystania tych właściwości w sensorowych systemach monitoringu środowiska. Opisano również strukturę światłowodu planarnego, splittera i wzmacniacza optycznego opartą o właściwości warstw ciekłokrystalicznych. (Systemy sensorowe z optycznym kanałem przesyłu informacji). Abstract. In this paper, the temperature characteristics of the helical pitch and the anisotropy of refractive index in cholesteric liquid crystals (CLC) as well as the characteristics: the helical pitch in CLC layers versus the concentrations of vaporous acetone, ethanol and ammonia, are presented. The possibilities of designing devices based on optical properties of liquid crystal planar structures are discussed and an optic planar waveguide, a splitter and an amplifier for a sensor system with optical channel for environment monitoring are proposed. Słowa kluczowe: czujnik optoelektroniczny, długość skoku helisy, falowód planarny. Keywords: optoelectronic sensor, helical pitch length, planar waveguide. Introduction The common usage of liquid crystals (LC) has focused on electro-optical flat panel display devices. Recently, growing interest in employing liquid crystals as well-suited sensing elements in optical sensors of temperature and pressure, as well as in sensors for monitoring the concentrations of vapourous components which have detrimental effect on environment, can be perceived. At present, for these purposes the semiconductor-based sensors are widely used; as the sensing element, different metal oxides, organic semiconductors, or silicon structures are applied. The drawbacks of these sensors are as follows: high operating temperature, low selectivity and p[...]

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