Point-scanning technique

The point-scanning technique can be extended by using an approach described as line-scan imaging [12,13]. This method employs cylindrical optics or scanning mechanisms to distribute a laser beam in one dimension, whereas the other dimension maintains the size... 

Speckle shearing interferometry, or shearography, is a full field optical inspection teclmique that may be used for the nondestructive detection of surface and, sometimes, subsurface defects. Whilst being more sensitive in the detection of surface defects, it may also be considered for pipe inspection and the monitoring of internal conoslon. In contrast, laser ultrasound and other forms of ultrasound, are point by point measurement techniques, so that scanning facilities and significant data processing is required before information on local defects is extracted from any examination of extensive areas [1 - 3]. 

Both TCSPC and TG benefit from operation in SPC mode. SPC results in little or no noise and a high photon-economy [10]. Therefore, TCSPC and TG are ideal for high spatial and lifetime resolution imaging [24], Both techniques offer high image contrast also on dim samples. However, the dead-time of the detectors and the point scanning character limit the throughput of these systems. 

In principle, lifetime imaging is possible by combination of the single-photon timing technique with scanning techniques. However, the long measurement time required for collecting photons at each point is problematic. 

The isotope dilution results in Table II are on fuel source samples obtained from NBS which were considered homogeneous. The results in Table III are from the sampling points indicated in Figure 4. These summarized results are mostly by the SSMS general scan technique which has an estimated accuracy of better than 50%. The isotope dilution measurements are limited by the emulsion detector to 3-5%. The results are in grams of metal flow per minute. The mass balance for the various elements was computed by the following equations ... 

Since crystal and film are fixed, only a small part of reciprocal space can be observed at a time, but a reciprocal point of the diffracting volume scatters during the whole exposure time. By contrast, scanning techniques such as Weissenberg or precession cameras see a larger part of reciprocal space, but each reciprocal point stays only a short time on the Ewald sphere. 

The static technique able to re.solve reactions on the second-time scale is easie.st to perform and a good point to start with. The reaction can be slowed down by variation of external parameters. The rapid. scan technique can resolve already millisecond reactions and has the broadest applicability. A time resolution of microseconds is most easily... 

Fdlner-Feldegg, using a multiple scanning technique incon)orating the three-point method of Nicolson and Ross (Figure 10), has recently demonstrated thin-sample t.d.s. by didectric measurements on alcohols. Figure 17 shows the data for butan-l-ol at 298 K plotted on the con l ... 

Boyd, A. Tarmarin, A. (1984) Improvement to critical point drying technique for SEM. Scanning 6, 30-35. 

A very important point occurs in the transmission of acoustic power into a liquid which is termed the cavitation threshold. When very low power ultrasound is passed through a liquid and the power is gradually increased, a point is reached at which the intensity of sonication is sufficient to cause cavitation in the fluid. It is only at powers above the cavitation threshold that the majority of sonochemical effects occur because only then can the great energies associated with cavitational collapse be released into the fluid. In the medical profession, where the use of ultrasonic scanning techniques is widespread, keeping scanning intensities below the cavitation threshold is of vital importance. As soon as the irradiation power used in the medical scan rises above this critical value, cavitation is induced and, as a consequence, unwanted even possibly hazardous chemical reactions may occur in the body. Thus, for both chemical and medical reasons there is a considerable drive towards the determination of the exact point at which cavitation occurs in liquid media, particularly in aqueous systems. Historically, therefore, the determination of the cavitation threshold was one of the major drives in dosimetry. 

Both the frequency-domain and the time-domain techniques can be classified into camera, or direct imaging techniques, and scanning, or point-detector techniques. There are considerable differences between the ways the two detection principles interact with laser scanning. Figure 5.72 shows the excitation of a sample in the focus of a one-photon microscope (left) and a two-photon microscope (right). 

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