Useful field of view

Indeed, the processing of visual information has been shown to be a problem in older adults (Merat et al., 2005). For example, performance deficits on assessments such as the useful field of view (UFOV), which examines visual processing and attentional control functions that may be symptomatic of numerous neurological and visual disorders, are consistently and significantly associated with crash risk... 

But there is a lot more to vision than (sensitivity to a stimulus that) meets the eye. We have essentially two mechanisms to distribute our visual attention beyond the narrow 5 degree field that is projected on our fovea. The first mechanism involves an increase in awareness of objects or events in the peripheral visual field while we are attending to events in the center of the field, and the second mechanism (which is linked to the first) involves moving our eyes from fixating on one area of the visual field to fixating on another area. The first mechanism, of distributed visual attention is most commonly referred to as the useful field of view (Ball and Owsley, 1991), but has also been called by other names, such as the functional field of view (Crundall et al., 1999), and the effective visual field (Shinar and Schieber, 1991). 

Ball, K, and C. Owsley (1993) The useful field of view test a new technique for evaluating age related declines in visual function. J. Am. Optom. Ass. 64, 71-80. 

Ball, K., D. Roenker, J. Bruni, C. Owsley, M. Sloane, D. Ball and K. O Connor (1991) Driving and visual search expanding the Useful Field of View. Invest Ophthalmol. Vis. Sci. Supp. 32,1041. 

Reliability and Validity of Useful Field of View Test Scores as Administered by Personal Computer. J. Clinic. Exp. Neuropsychol, 27(5), 529-543. 

Useful field of view (width of visual field over which information can be acquired in a quick glance). Decline in spatial and peripheral vision Difficulty in detecting events that develop at the sides of the visual field (merging cars etc.) Charman (1997) Haegerstrom-Portnoy et al. (1999) Owsley and McGwin (1999) Sekuler et al. (2000)... 

On the basis of current research there seem to be two possible exceptions to tiie generalization that drivers can adjust to their limitations by self-regulation of their driving. The first concerns contrast sensitivity and the second concerns the useful or effective field of view (in which peripheral target detection is measured in the presence of attentional load in the center of the field). The weight of the evidence - reviewed in Chapter 4 - suggests that they are both moderately associated with crash involvement. Furthermore, with respect to the attentional field of view, such as the Useful Field of View (UFOV), West et a/. s (2003) results also indicate that drivers with impaired attentional field did not report any self restrictions. This insensitivity may be the underlying reason why this measure, is associated with overinvolvement in crashes. 

Dewar or test chamber installation information Mounting configuration Valve type and pumping required Cooling method to be used 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. 

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... 

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. 

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. 

The main consequence of isoplanatism is to reduce the sky coverage of AO systems. In addition, the PSF is not constant inside the field of view, a fact which complicates the analysis of images obtained using AO. For example, astronomical photometry is usually performed by comparing objects in the field to a known point spread function which is considered constant over the field. 

The idea of optimal conjugation can be extended by using multiple deformable mirrors-this is referred to as multi-conjugate AO or MCAO. Again, the question arises as to the optimal altitudes of the deformable mirrors. Toko-vinin et al. (2000) showed that if the turbulence in the volume defined by fhe field of view and fhe felescope aperfure is perfectly known, then the isoplanatic error in an MCAO system with M deformable mirrors is given by... 

Figure 10. Results of numerical simulations to obtain the Strehl ratio at 2.2 pm over the field of view for a held of diameter 1 arcminute (left) and 1.5 arcminute (right) when using three natural guide stars.

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