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Objective lenses characteristics

High-resolution electron microscopic studies employed a modified JEOL-JEM200CX (8) operated at 200 kV with objective lens characteristics Cs = 0.52 mm, Cc = 1.05 mm leading to a theoretical point resolution as defined by the first zero in the phase contrast transfer function of 1.95 A at the optimum or Scherzer (9) defocus position (400 A underfocus). [Pg.575]

The overall resolution in HRTEM is governed partly by the electron wavelength and partly by the optical characteristics of the objective lens. The most important effect of the latter arises from spherical aberration. This aberration introduces a phase difference into the individual diffracted beams and when the real image is synthesized by the lens from these diffracted beams this can give rise to considerable confusion in the image contrast. [Pg.448]

The characteristics of an objective lens are engraved on the barrel as shown in Figure 1.16. Engraved markings may include the following abbreviations. [Pg.13]

X, Y and Z are the magnitudes of reciprocal vector R, corresponding to the magnitude (x, y and z) of vector r in the real space. Since the electron waves pass the objective lens, the objective lens can affect the wave characteristics. The effect of the objective lens on the wave function can be represented by a transfer function, 7TR). Thus, the actual wave function on the back-focal plane becomes the following function. [Pg.98]

A diffraction pattern is formed on the back-focal plane of the objective lens when an electron beam passes through a crystalline specimen in a TEM. In the diffraction mode, a pattern of selected area diffraction (SAD) can be further enlarged on the screen or recorded by a camera as illustrated in Figure 3.16. Electron diffraction is not only useful to generate images of diffraction contrast, but also for crystal structure analysis, similar to X-ray diffraction methods. SAD in a TEM, however, shows its special characteristics compared with X-ray diffraction, as summarized in Table 3.4. More detailed SAD characteristics are introduced in the following section. [Pg.101]

This basic concept applies to our technique as well. In microsphere nanoscopy, microspheres are in direct contact with objects, which forms a Particle-on-Surface (POS) system, as illustrated in Fig. 8(a). It is this POS system that effectively interacts with the near-field evanescent waves, decouples and turns them into propagating wave that would reach the objective lens in the far-field. Like in NSOM, such interaction are quite complicated and only takes place in the proximity of the interface of particle and substrate, which was indicated by the shadow zone in Fig. 8(a). The characteristic thickness of the evanescent waves scattering zone, dg, could be decided by ... [Pg.205]

The aberration characteristics of the objective lens are determined by the polepiece geometry and magnetic field strength. The diameters of the discs of confusion associated with these aberrations, i.e. the magnitude of the aberration and the associated image resolution limitation, are directly proportional to two lens parameters called the spherical aberration coefficient (Cg) and the chromatic aberration coefficient (C ). [Pg.546]

Until recently, all SEMs used a "pinhole objective lens and single SE detector located below the lens, as shown in fig. 6(a). A characteristic of the "pinhole" lens, in which the polepiece bore diameter closest to the specimen is smaller than the other bore, is that the stray magnetic field below the lens is very low. With the specimen in field-free space, the low energy SEs are readily collected by a SE detector located in the vicinity of the specimen. The other reason for selecting this particular lens design... [Pg.551]

The images produced by the SE detector above the objective lens are strongly influenced by specimen surface characteristics such as topography, composition, and voltage differences. The BSE information content is considerably less than in the case of a conventional SEM. [Pg.559]

The characteristics of the objective lens are crucial because they determine to a large extent the image resolution and the contrast. The other two lenses mainly provide the desired magnification. [Pg.1085]


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See also in sourсe #XX -- [ Pg.49 ]

See also in sourсe #XX -- [ Pg.48 ]




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Objective lens

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