Collimation film

When 45° i 0°, the incident light is refracted once and the exit angle is given by 

When - 15° 0°, the incident light is either totally reflected back or refracted into exit 

When -45° 0, - 15°, the incident light is first totally reflected and then refracted, 

In most LCDs, the liquid crystal only modifies the polarization state of polarized incident light. Because light generated by a backlight is unpolarized, a polarizer must be used ahead of the liquid crystal panel to produce polarized incident light. Also in order to block light a polarizer 

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Compensation film Polarizer Collimation film Diffuser Light guide... 

Figure 15.8 Angular distribution of light intensity produced by the collimation film. Reproduced with permission from Wiley.

Figure 18.5 Schematic view of a diffraction experiment, (a) A narrow beam of x-rays (red) is taken out from the x-ray source through a collimating device. When the primary beam hits the crystal, most of it passes straight through, but some is diffracted by the crystal. These diffracted beams, which leave the crystal in many different directions, are recorded on a detector, either a piece of x-ray film or an area detector, (b) A diffraction pattern from a crystal of the enzyme RuBisCo using monochromatic radiation (compare with Figure 18.2b, the pattern using polychromatic radiation). The crystal was rotated one degree while this pattern was recorded.

The Bra -Brentano geometry is used widely for preferentially and randomly oriented polycrystalline films. In this geometry (Figure 3a), slits collimate the inci-... 

Track-Etched Track-etched membranes (Fig. 20-66) are now made by exposing a thin polymer film to a collimated beam of radiation strong enough to break chemical bonds in the polymer chains. The film is then etched in a bath which selectively attacks the damaged polymer. The technique produces a film with photogenic pores. 

To resolve the problem applying methods of collimated atom beams, equilibrium vapour as well as radioactive isotopes, the Hall effect and measurement of conductivity in thin layers of semiconductor-adsorbents using adsorption of atoms of silver and sodium as an example the relationship between the number of Ag-atoms adsorbed on a film of zinc oxide and the increase in concentration of current carriers in the film caused by a partial ionization of atoms in adsorbed layer were examined. 

Otherwise commercially interesting proteins, which are not readily crystallizable. The high intensity and collimation of the SR is currently allowing data to be collected and several structures to be studied where samples as small as 100 x 100 x 15 pm and 200 x 50 x 50 pm (Ealick, Helliwell and Cook, unpublished) with unit cell volumes in the range of 10 A or so.. Sample volumes as small as (20 pm) have yielded very strong diffraction patterns with the white SR beam, (Fig. 6) (Hedman et al. 1985). In this application area efforts to reduce the X-ray background at the detector include replacement of traditional glass capillaries in the sample with thin film capillaries. 

Digital Radiography. In this technique, the traditional film is replaced by a linear array of detectors and the X-ray beam is Collimated into a fan beam. The object is moved perpendicularly to the detector array, and the attenuated radiation is sampled digitally by the detectors. Data are processed by stored infoimation in the computer s memory to yield a two-dimensional image of the part being inspected. 

A stretched fiber containing many poly-L-alanine molecules is suspended vertically and exposed to a collimated monochromatic beam of CuKa x-rays, as shown in figure 1(a). Only a small percentage of the x-ray beam is diffracted most of the beam travels through the specimen with no change in direction. A photographic film is held in back of the specimen. A hole in the center of the film allows the incident undiffracted beam to pass through. 

Some materials (for example, certain muscle proteins) form fibers spontaneously or are naturally found in fibrous form. Many other polymeric substances, like DNA, can be induced into fibers by pulling them from an amorphous gel with tweezers or a glass rod. For data collection, the fiber is simply suspended between a well-collimated X-ray source and a detector, such as film (Fig. 9.1). 

The single prism technique has the advantage that ordinary sources with a monochromator can be used. The two prism technique requires an extremely well collimated beam, and only lasers are satisfactory as sources. However, the two prism technique is more sensitive to absorption in the thin film. We shall give some examples of data obtained using each method. It must be admitted that much of the wdrk to date has been of an exploratory nature, designed to demonstrate the utility of spectroscopy using surface waves. 

The program, AXIS, was specifically designed to analyse fibre diffraction patterns similar to that shown in Figure 1, although some of the methods described in this chapter may be extended to other types of pattern if required. The fibre patterns are recorded on flat film using pinhole collimated, nickel-filtered CuKor radiation, and finely powdered calcite is dusted onto the specimen to provide a calibration ring of spacing 0.3035 nm. 

The examples of application presented were taken from the authors personal experience. They concerned a microbeam technique in which the collimators and camera are adapted respectively to produce X-ray beams down to about 10 microns diameter and registration of the diffraction on flat film 10 mm diameter at distances down to 1 mm from the specimen (l, 2). This enabled fibre patterns to be obtained from wax coatings on plants (1) and a single starch granule C3) in both instances leading to new insights about the ultrastructure of these objects. 

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