Optical transducers

Based on the definition, device sensitivity is related to the variation of transducing optical parameters, and thus depends on the transducing method. For the resonant wavelength shift scheme, it is expressed as... 

M Brenci, Thermochromic transducer optical fibre temperature sensor, SPIEProc. 515, 155 (1984). 

Linear position Linear motion is typically driven by the use of lead screws, ball screws, or worm drives with ranges from less than a 25 mm to over 6 m. Linear sensors for position feedback in the lower range include LVDTs, magnetic, and optical encoders. For longer strokes, the linear feedback devices include encoders and magnetostrictive position transducers. Optical encoders are practical up to 2 m. Magnetostrictive position transducers can be used up to 20 m. 

The most common principle used in optical biosensors for detection in the real part of the refractive index is evanescent wave detection, where the transducer optics are modified by changes in optical parameters of the medium in contact with the sensor surface via the interaction with the evanescent light wave penetrating into the ambient medium. As the evanescent wave decays exponentially from the surface, the most sensitive detection is just at the transducer surface. 

The number of existing Materials is laige, therefore the examples are restricted to those materials (glass and crystals) used for lenses, prisms, mirrors, filters or other substrates and windows. Polarizing elements, transducers, optically-active devices and modulators are excluded. 

Transducers Optical, Optoelectronic Transducers Piezoelectric Transducers Electrochemical Transducers... 

Eggins BR (1996) Transducers optical methods. In Biosensors an Introduction. Wiley and Teubner 87-120... 

Sensing element Combination of sensing materials (indicators and/or biological compounds) and a transducer (optical fiber). 

Laser Surface acoustic wave Semiconductor Target transducers Optical fiber Radiation Radar Surface acoustic wave Electrophoresis Electrochemical Paramagnetic Chemi/bioluminescence Tunable diode laser absorption... 

A large technological expansion has also occurred in the area of fiber optics. Improvements have been made in the optical quality and mechanical resistance of optical fibers, and they now have many applications in transducers. Optical fibers lend themselves to the construction of biosensors a suitable biological substance is attached to the tip of the fiber and produces an optical signal when it is in contact with the system under study [8]. Optical biosensors exploit a variety of radiation phenomena, for example, absorption, fluorescence, and... 

The first detector for optical spectroscopy was the human eye, which, of course, is limited both by its accuracy and its limited sensitivity to electromagnetic radiation. Modern detectors use a sensitive transducer to convert a signal consisting of photons into an easily measured electrical signal. Ideally the detector s signal, S, should be a linear function of the electromagnetic radiation s power, P,... 

This aspect is not included here, but is related to optical flow diagnostics. It is based again on the principle of the optical Doppler effect. Multifunctional equipment is available for noncontact measurements of flow-induced vibration on surfaces of structural elements, for acoustic measurements, and for calibration of accelerometers and vibration transducers. 

Jerman, J. H., and D. ]. Clift. Miniature Fabry-Perot Interferometers Micromachined in Silicon for the Use in Optical Fiber WDM Systems. Transducers 91 Conference, Digest of Technical Papers (1991), pp. 372-375. 

Fig. 3. Schematic beam path of a phase-measurement interference microscope (PMIM, Fizeau optics). The beam partially reflected at the reference plane and at the sample surface interfere with each other while the reference plane is moved by the piezoelectric transducer for automatic phase determination. A reflectivity of at least 1% is required for the sample surface...

Figure 33. Proposed interface between an electronic component (video camera) and a nerve (optical nerve) that could transduce electronic signals from the equipment to ionic signals that can be understood by dendrites.

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