Collimated illumination

The Case of Collimated Illumination Separation of Ballistic and Diffusive Contributions... 

It can appear to those not completely familiar with geometrical optics that diffuse illumination will produce a different measurement result than collimated illumination because so many more incident rays and angles are transmitted through the sample. This is not true. The collimated viewing system with hemispherical illumination only accepts the incident rays that are reciprocal to the radiation pattern produced by an identically collimated incident beam. 

Transmissive mode displays in which orientation effects are utilized, are located between two crossed polarizer films (Fig. 13c). The illuminating source can mostly be situated immediately behind the liquid crystal display. Colored liquid crystal displays which, for example, exploit the DAP effect (Deformation of Aligned Phases), must be illuminated by collimated light to avoid dependence of the color on the viewing angle. Moreover the front electrode must be a scattering disc. Collimated illumination is not required for color displays with homogeneously oriented liquid crystal layers, for example when the depolarization effect is used. 

The sensor concept with a collimated illumination beam in the measurement volume (Fig. 12.12) differs from the SE-F-Sensor only by a different collimator which collimates an illumination beam with an approximately constant e diameter in the measurement volume. The divergence of the light beam along its propagation direction is significantly lower than with the focused light beam. For... 

Fig. 12.12 Optical design of a SE-C-Sensor with collimated illumination beam...

Another optical technique, called the back-light scattering (Kossel-diffraction) method can also be used to investigate structure in food emulsions and foams. In this method, the emulsion (or foam) in a transparent vessel is illuminated by a collimated laser beam (See... 

Fig. 1 Schematic drawing of a wide-field single-particle tracking fluorescence microscope equipped. Several lasers are used as excitation source for different fluorophores with fast selection hy an acousto-optical tunable filter (AOTF). The collimated laser light is coupled into the objective such that only the observed area is illuminated. The emission light is separated from the excitation light by a dichroic mirror. In the case of multi-color imaging, the emission light is separated by...

Once a diffraction-limited excitation spot is achieved, the same microscope objective that is used for illumination can also be used to collect light from the sample similar to the case of SNOM. If the incoming beam of light is collimated, the beam of collected light is also collimated for a chromatically corrected microscope objective. The use of collimated beams... 

The technique used to (effectively) overcome the VBE is to reduce the effective spatial coherence of the light source used for the development exposure by rotating the sample. Alternatively, the sample could be illuminated simultaneously from many different directions, but it is more convenient to use a moderately collimated beam striking the sample surface at a shallow angle while rotating the sample about an axis perpendicular to that surface. The time constants involved in the polymerization process are typically of the order of minutes, so that rotation rates of the order of 1 rps are usually more than sufficient. 

---