Illumination oblique incidence

Illumination by an infinite plane wave corresponds to the uniform beam in the limit Pj- 00. We can then repeat the calculation of Section 20-7 for oblique incidence at angle... 

Resolution and image brightness are maximized if a cone of illuminating rays is incident on the specimen. The contrast of fine detail can be enhanced by artificially and selectively operating on the characterizable properties of the oblique illumination, relative to the normally incident component. 

Here, d//dA denotes the spectral intensity distribution of the incident X-ray beam V is the volume of sample illuminated V0 is the sample unit cell volume 0 is the Bragg angle for the reflection h P is the polarisation factor A is an absorption correction for the sample in its capillaiy and D is a detector sensitivity and obliquity factor. Quantities such as P, A and D vary with any or all of A, 0 and x, the position of the diffracted beam on the detector the spectral intensity distribution is, in general, not precisely known in advance and the detector may suffer from spatial distortion and non-uniformity. Thus equation (7.17) may be written as... 

The effect of M on the reflected light intensity is known as the Kerr effect. The polar Kerr effect refers to a situation in which the sample has a component of M normal to the surface and normal incidence illumination is used. The longitudinal Kerr effect is used when M is parallel to the surface and the illumination is oblique. 

Uniform aperture illumination using simple harness with T connectors. Absorbs everything at broadside and for some oblique angles of incidence... 

An elegant approach which overcomes these difficulties was suggested in the group of Sackmann et al.. A parallel polarized laser beam was focused to an off axis spot in the back focal plane of a microscope objective of high numerical aperture. The sample which is located in the front plane is then illuminated by a parallel polarized beam of light incident on the SEimple under an oblique angle. The exact angle of incidence is controlled by the... 

In both bright-field and oblique illumination, the undeviated incident beam, after passing through the sample, falls within the limits of the objective lens. 

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