Coherent illumination

Enloe, Noise-like structure in the image of diffusely reflecting objets in coherent illumination . Bell Syst. Tech. I., vol. 46, p.1479(1967). 

Frank J 1973 The envelope of electron microscopic transfer functions for partially coherent Illumination Optik ZS 519-27... 

The point of observation is at a large distance compared with the dimensions of any coherently illuminated scattering volume. 

Conditions (2) and (3) are equivalent to the Fraunhofer or far-field approximations in ordinary optics. The coherently illuminated region with usual laboratory X-ray sotuces is a few micrometres across. We therefore expect this theory to be useful in the cases of weak scattering but to be seriously awry for strong scattering. 

Higher contrast can be obtained for relatively large linewidths by using partially coherent illumination that is by arranging that the image of the... 

The beam size in NED can be further reduced by weakening the condenser II and placing the crossover at the front focal plane of the condenser HI lens. This results in a focused probe with the sample close to the back of the focal plane of the pre-objective lens. The probe size formed with coherent illumination can be as small as a few angstroms. The diffraction patterns recorded in this case consists of small disks, which are the same as those recorded in the nanodiffraction mode in STEM. This technique is useful for probing local stmctme variations. ... 

R /f is the numerical aperture (N.A.) and is marked on all objective lenses, together with the magnification. For example, a x25 objective with N.A. = 0.5 is expected to resolve detail of the order of 2X 1 m, ideally. Equation (2.1) has been derived by considering diffraction by a coherently illuminated periodic object. Rayleigh s well-known criterion of resolution, derived for a nonperiodic object incoherently illuminated, gives nearly the same limit of resolution as that determined from the Abbe approach and need not be considered here (see, e.g., Giancoli 1984). 

A source of high intensity, coherent illumination that can be focused to a small beam diameter (approximately 1pm) to excite a wide variety of fluorescent probes. Most analytical systems employ an Argon or Krypton laser to provide illumination between 360nm and 600nm. 

The previous few examples show that, under coherent illumination, one can no longer consider observed spectral intensities as purely characteristic of the atom, since the properties of the Autler-Townes doublet depend on the laser intensity, and the profile of a laser-excited autoionising line will in general possess a shape unrelated to that of an atom excited by a weak source. 

Figure 13.27 Diffraction pattern of a coherently illuminated mask opening at near (Fresnel) and far (Fraunhofer) distances. (Reprinted with permission from Taylor Francis Group LLC. )...

Figure 13.32 The diffraction orders associated with coherent illumination of a grating mask, illustrating the condition for minimum diffraction-limited resolution. (Reprinted...

A notable effect of partial coherence on imaging is the spreading of each diffraction order about their discrete coherent frequencies, as illustrated in Fig. 13.33, which shows the diffraction orders for a rectangular wave mask pattern illuminated with cr values greater than zero. In this situation, the zeroth order is centered on axis but with a width >0, a result of the extent of partially coherent illumination angles. In like manner, each higher diffraction order also has a width >0, an effective spreading of the discrete orders. ... 

The objective of this chapter is to investigate the intensity and polarization fluctuations that appear in the hght scattering by a coherently illuminated two-particle system. We want to obtain information about the geometry and/or optical properties of the system from the statistical knowledge of the scattered... 

Soft X-ray transmission scanning microscope Scanning transmission X-ray microscopes (STXRM) for soft X-rays use Fresnel zone plates as high-resolution objectives to form a focused spot. Scanning microscopes require coherent illumination and are... 

For A5r > A./2, the phase difference A0 of the partial amplitudes in Si and S2 exceeds n. With random emission from the different surface elements df of the source, the time-averaged interference pattern in the plane B will be washed out. The condition for coherent illumination of Si and S2 from a light source with the dimension b is therefore... 

The arguments above may be summarized as follows the coherence surface 5c, i.e., that maximum area Ac that can be coherently illuminated at a distance r from an extended quasi-monochromatic light source with the area As emitting at a wavelength A is determined by... 

For coherent illumination of the slits, the following condition holds ... 

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