Collimated light

With the invention of the laser in 1960 and the subsequent development of pulsed lasers using Q-switching (Chapter 1), monochromatic and highly-collimated light sources became available with pulse durations in the nanosecond timescale. These Q-switched pulsed lasers allow the study of photo-induced processes that occur some 103 times faster than events measured by flash lamp-based flash photolysis. 

FIGURE 7.6 Schematic of a laser-induced fluorescence detector. A lamp with focusing optics and an appropriate band-pass filter could be used in place of the laser excitation when tightly collimated light is not required. The emitted fluorescence is detected by a PMT that can be operated in current mode or photon counting mode. Inset shows the mutually perpendicular arrangement of excitation, capillary, and detection optics. 

The application of light scattering to the characterisation of colloidal systems has advanced rapidly over the last few decades. This has been made possible by the development of (a) lasers as intense, coherent and well-collimated light sources, (b) sophisticated electronic devices for recording data, and (c) computers for the complex data processing that is involved. 

If a collimated light source is fitted inside the spray chamber, and a photodiode detector is used to measure the amount of light scattered by aerosol droplets inside the spray chamber, it is possible to detect directly changes in aerosol... 

A collimated light beam from the 1R source is directed to the Michelson interferometer where it is divided by the beam splitter. One half of the beam is reflected from a fixed mirror and the other half from a moving mirror. The two light beams recombine after returning from the mirrors and give rise to a reconstructed beam which is optically an interference wave. The interference light beam passes through the sample and is modified by its interaction with the... 

Stark PRH, Halleck AE, Larson DN (2007) Breaking the diffraction barrier outside of the optical near-field with bright, collimated light from nanometric apertures. Proc Natl Acad Sci USA 104 18902-18906... 

LIGHT COLLIMATION LIGHT DECLINATION LIGHT UNIFORMITY ... 

Iv) a light source to illuminate the three-phase contact region from behind. It should be equipped with a heat filter to prevent temperature fluctuations and, hence, convection. The light can be either diffuse or collimated, with different effects. Experience has shown that diffuse illumination (5delding a silhouette) is preferable for closed-circuit television (CCTV) imaging, whereas collimated light is suitable for telescope-type measurements. 

For example, a standard 200 W short-arc, high-P Hg lamp mounted on an optical bench will generate a collimated light beam of 10 to 10 quanta min after passing a standard bandpass filter to isolate a specific Hg emission line in the visible-UV region. 

We consider the case of an aerosol illuminated by a collimated light source of a given wavelength. The experimental arrangement is shown schematically in Fig, 5.6. A photometer of this type installed in a smoke stack or duct would be suitable for measuring the attenuation... 

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