Field of view

Other limitation for the spatial resolution can be found in the detector. A limited number of pixels in the camera array can be a reason for pure resolution in the case of a big field of view. For example, if field of view should be 10 by 10 nun with camera division 512x512 pixels the pixel size will be approximately 20 microns. To improve the relation of the field of view and the spatial resolution a mega-pixel sensor can be used. One more limitation for the spatial resolution is in mechanical movement (rotation) of the object, camera and source. In the case of a mechanical movement all displacements and rotations should be done with accuracy better than the spatial resolution in any tested place of the object. In the case of big-size assemblies and PCB s it is difficult to avoid vibrations, axle play and object non-planarity during testing. 

Figure A3.14.13. Further examples of the various Turing patterns observable in a 2D gel reaetor. (a) and (b) spots, (e) and (d) stripes, (e) and (1) wider field of view showing long-range defeets in basie stnietine. The seale bar alongside eaeh figure represents 1 nnu. (Reprinted with pemrission from [39], The Ameriean Institute of Physios.)...

In practice, the NEP of a room-temperature THz spectrometer is usually limited by fluctuations (shot-noise) in the ambient blackbody radiation. Usmg an optical bandwidth Av = 3 THz (limited by, for example, a polyethylene/diamond dust window), a field of view (at nomial incidence) 0 = 9 and a detecting diameter (using a so-called Winston cone, which condenses the incident radiation onto the detecting element) laboratory applications, the background-limited NEP of a bolometer is given by... 

Figure Bl.14.10. Flow tlirough an KENICS mixer, (a) A schematic drawing of the KENICS mixer in which the slices selected for the experiment are marked. The arrows indicate the flow direction. Maps of the z-component of the velocity at position 1 and position 2 are displayed in (b) and (c), respectively, (d) and (e) Maps of the v- and the y-velocity component at position 1. The FOV (field of view) is 10 nnn. (From [31].)...

From the early 1980s to present, infrared sensitive two dimensional arrays were mated to integrated circuits for signal processing and sensitivity to better than 0.03 K (see Photodetectors). These focal plane arrays of some 500 by 500 elements eliminate the need for scanning and provide good spatial resolution. Some versions have no special cooling requirements. The development trend is to increase the number of pixels to improve resolution, increase the field of view and keep the size and cost of the optics within acceptable bounds. 

Theory and Equipment. Many diseases of the human body can be identified by visual appearance. Tumors in the upper gastrointestinal (GI) tract, for example, possess a characteristic salmon pink color (3). The presence of such a color can be an indication of disease. Endoscopy is the medical imaging tool used to detect such colors in the inside of hoUow internal organs such as the rectum, urethra, urinary bladder, stomach, colon, etc. An endoscope is the instmment used to perform endoscopy. Endoscopic imaging involves the production of a tme color picture of the inside of the human body using lenses and either hoUow pipes, a fiber optic bundle, or a smaU CCD camera. AU three use a large field-of-view, sometimes referred to as a fish eye, lens to aUow a 180° field of view. 

The field of view (FOV) is dependent on the quadrature sampling rate, T, during the appHcation of G and the magnitude of G ... 

The contrast for specimen detail in the field of view is gready enhanced by darkfield illumination (10). The degree of contrast and sensitivity of detection of smaH-object details depend on the relative indices of the specimen and the mounting Hquid and on the intensity of the illumination. Darkfield illumination is not, however, a satisfactory solution for biologists who need direct transmitted light in order to observe specimens, especially stained specimens. It is, however, very usefiil in detecting asbestos fibrils that often exist in door tiles or water and air samples as 20-nm fibers (10 times finer than the resolution of an asbestos analyst s usual microscope) (11). Darkfield illumination yields an uimatural appearance and difficulties in interpretation hence, a need for better contrast methods stiU exists. 

When equation 12 is vaUd, the detector is said to be a background-limited infrared photodetector (BLIP). When this is the case, attempts often are made to improve D by cold shielding which reduces ( ). The ideal D is shown in Figure 3 as a function of wavelength with background photon flux as a parameter. The line of termination in the lower left corner represents TN values for a 180° (27T) detector field of view, 300 K ambient background... 

Fig. 3. Ideal photon detector sensitivity as a function of cutoff wavelength. Lower background flux generates less photon-induced noise giving higher sensitivity. The sensitivity limit for the condition of 300 K background temperature and hemispherical (27T) field of view is shown.

Fig. 9. Spectral sensitivity of detectors where the detector temperatures in K are in parentheses, and the dashed line represents the theoretical limit at 300 K for a 180° field of view, (a) Detectors from near uv to short wavelength infrared (b) lead salt family of detectors and platinum siUcide (c) detectors used for detection in the mid- and long wavelength infrared. The Hg CdTe, InSb, and PbSnTe operate intrinsically, the doped siUcon is photoconductive, and the GaAs/AlGaAs is a stmctured supedattice and (d) extrinsic germanium detectors showing the six most popular dopants.

Elastic scattering is also the basis for Hdar, in which a laser pulse is propagated into a telescope s field of view, and the return signal is collected for detection and in some cases spectral analysis (14,196). The azimuth and elevation of the scatterers (from the orientation of the telescope), their column density (from the intensity), range (from the temporal delay), and velocity (from Doppler shifts) can be deterrnined. Such accurate, rapid three-dimensional spatial information about target species is useful in monitoring air mass movements and plume transport, and for tracking aerosols and pollutants (197). 

To determine the level of electrification on an insulating surface, an elec tric field meter should always be used. There is a direct relationship between the charge density on the surface of an insulator and the elec tric field intensity at the surface. Measurements should be made at locations where the insulating surface is several inches away from other insulating or conduc tive surfaces. The area of the measured surface should be large, compared to the field of view of the meter. In locations where a flammable vapor-air mixture has an MIE greater than 0. 2 mj, field intensities of 500 kV/m or more should be considered unsafe. 

Fig. 3.43. Non-resonant laser-SNMS mapping of a contact test structure on GaAs. Field of view 40 x 40 pm [3.114],...

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