Diffraction effects

Note Conversely, it is important to emphasize that a lack of phase inversion between the signals of two superimposed echoes along the depth axis is not necessarily an evidence that the defect is volumetric (diffraction effect on a planar defect could miss if the geometry of the tips are not favorable). 

The estimated VSS and EPD allow for the observation of the tip diffraction effects (phase inversion - Atp = 180° - for the direct and mirror diffraction echoes) for all selected Ascan signals. This proves the plane nature of the OSD and confirm our initial hypothesis. 

Takayanagi K 1990 Surface structure analysis by transmission electron diffraction—effects of the phases of structure factors Acta. Crystalloger A 46 83-6... 

This expression is the main tool used in describing diffraction effects associated with Fourier optics. Holographic techniques and effects can, likewise, be approached similarly by describing first the plane wave case which can then be generalized to address more complex distribution problems by using the same superposition principle. 

When a eutectoid steel is slowly cooled from the austenite range, the ferrite and cementite form in alternate layers of microscopic thickness. Under the microscope at low magnification, the diffraction effects from this mixture of ferrite and cementite give an appearance similar to that of a pearl, hence the material is called peadite. 

From shock compression of LiF to 13 GPa [68] these results demonstrate that X-ray diffraction can be applied to the study of shock-compressed solids, since diffraction effects can be observed. The fact that diffraction takes place at all implies that crystalline order can exist behind the shock front and the required readjustment to the shocked lattice configuration takes place on a time scale less than 20 ns. Another important experimental result is that the location of (200) reflection implies that the compression is isotropic i.e., shock compression moves atoms closer together in all directions, not just in the direction of shock propoagation. Similar conclusions are reached for shock-compressed single crystals of LiF, aluminum, and graphite [70]. Application of these experimental techniques to pyrolytic BN [71] result in a diffraction pattern (during compression) like that of wurtzite. 

Segment edges add to diffraction effects and thermal background effects... 

Segment edges will introduce diffractive effects in the image that are in addition to the diffractive effects caused by the total aperture itself. 

Figure 2. Spectral photometric variation versus source position (1-3/im and 3-5/rm ranges). Upper surfaces are only affected by the geometrical effect of the slit geometry, and lower surfaces include the diffraction effects.

Due to diffraction effects of micron-sized mirrors in a regular array, commonly used techniques for surface characterization based on interferometry are inefficient. To overcome the diffraction effects we have developed a novel surface characterization method with an incoherent light source, based on the Foucault s knife-edge test (Zamkotsian and Dohlen, 1999). Since Leon Foucault introduced the knife-edge test in the last century (Foucault, 1859), it has been widely used for testing optical surfaces (see Ch. 3). The test offers a simple way of obtaining easily understandable, qualitative information of the surface shape. 

Contrast enhancement lithography is a clever procedure which uses a bleachable contrast enhancing layer to restore the distorted aerial image of the mask which has been blurred by diffraction effects into a sharp image at the underlying photoresist surface. The process is too complicated to explain in detail here and the interested reader is referred to the cited literature (60,61). Suffice it to say that the large extinction coefficients of most polysilane derivatives coupled with their ready bleachability make them ideally suited for such purposes and we have demonstrated this application at 313 nm (16,18). 

Figure 4 Demonstration of diffraction effect of an aperture The spectra 1-6 were recorded sequentially by moving the sample stage under the 15 pm x 50 pm aperture.

The IR microscopy sampling technique is the ultimate sampling technique since only one particle is required for analysis. Due to the restrictions of diffraction effects, typically, the particles of interest must be greater in size than 10 x 10 /xm. Once the sample of interest is placed upon an IR optical window,... 

When a polychromatic beam reaches the grating, diffraction effects take place, so that the angle at which each spectral component is reflected depends on its particular... 

Figure 5. (a) Deconvoluted image after correction of the dynamical diffraction effect (b) the same as (a) but showing the atomic arrangement schematically (c) result of deconvolution without dynamical diffraction correction and (d) simulated image based on (b). 

S. Bing-Dong, F. Hai-Fu, L. Fang-Hua, Correction for the Dynamical Electron Diffraction Effect in Crystal Structure Analysis, Acta Crystallogr., A49,877-880,1993. 

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