Piezo-electric detectors

Atomic-force microscopy (AFM) is a technique that examines the surface topography of polymer samples. The probe moves across the surface and a piezo-electric detector can... 

K. Schaffner, S.E. Braslavsky and A.R. Hoizwattfa, Photophysics and photochemistry of phytochrome, Adv. Photochem. 15 (1990) 229. Some of these investigations have led to new developments in monitoring see pages 251 seq. of this paper, on the use of time-resolved measurements by a piezo-electric detector of heat emitted during non-radiative decay of excited molecules. 

The application of interference techniques overcomes the limitations exerted by the large optical wavelengths. With commercial phase-measurement interference microscopes (PMIM), a surface resolution of the order of 0.6 nm can be achieved [33, 34]. In a microscope a laser beam is both reflected from the sample surface and from a semitransparent smooth reference surface (Fig. 3). The interference pattern is recorded on an area detector and modulated via the piezo-electric driven reference surface. The modulated interference pattern is fed into a computer to generate a two-dimensional phase map which is converted into a height level contour map of the sample surface. While the lateral resolution (typically of the... 

Figure 6 shows an outline of a PAS instrument designed for fast time-resolved measurements. The excitation light is a laser pulse of some 20 ns duration, at a wavelength which falls within the absorption spectrum of the sample (e.g. 337 nm with a nitrogen laser). Total absorption of this pulse then deposits an energy E in the sample and this will decay in the course of time into heat which will give rise to the pressure sensed by the detector usual microphones have slow response times, so that piezo-electric devices are used to improve the instrument s time resolution [43]. 

The piezo-electric effect of deformations of quartz under alternating current (at a frequency in the order of 10 MHz) is used by coating the crystal with a selectively binding substance, e. g. an antibody. When exposed to the antigen, an antibody-antigen complex will be formed on the surface and shift the resonance frequency of the crystal proportionally to the mass increment which is, in turn, proportional to the antigen concentration. A similar approach is used with surface acoustic wave detectors [142] or with the surface plasmon resonance technology (BIAcore, Pharmacia). 

Section 4 is devoted to multi-pulse methods of removing magneto-acoustic and piezo-electric ringing (MAPER), generated by numerous objects containing metallic, ferrite, ferro- and piezo-electric components, when detecting explosives with NQR landmine detectors and luggage scanners. 

Fig. 1. Experimental setup. PBS, polarizing cubic beam splitters M1-M3, cavity mirrors APD, avalanche photodiode detector PZT, piezo-electric transducer, (b) Three-level A -type atomic system.

The ARES spectrograph is also equipped with an active wavelength stabilization system, which guarantees fixed shape and position of the echelle spectrum pattern relative to the detector. Altogether five micro-positioning units based on piezo-electrical actuators (four active R1- R4 and one passive thermo-mechanical R5) are implemented to control permanently the relative spectrum geometry (see Figure 3.11). 

Figure 7.5 Experimental setup for the overview absorbance measurements with the ARES spectrograph (1) D2 lamp, (2) tungsten halogen lamp, (3) beam combiner, (4) mechanical shutter, (5,9) toroidal mirrors, (6) sample and blank reservoir, (7) magnetic valve, (8) flame atomizer, (10) entrance slit, (11 -14) pre-dispersing illumination optics, (15,18) spherical mirrors, (16) prism, (17) echelle grating, (19) CCD array detector, (20) Ne lamp, (R1-R5) piezo-electrically controlled rotation units...

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