D-MAX DMC-20SEC Manual de usuario descargar pdf (Pagina 26)

Evolver software uses finite element analysis to calculate the surface profile at certain points

on the surface. In areas with a greater radius of curvature, where the energies are closer to each

other in terms of magnitude (in other words none are dominant in comparison to any others)

the software uses more measurement points, that is a denser grid, for displaying the graphic

representation.

Figure 16. Example of a graphic representation generated using the Surface Evolver software

Of the models that use a formula based on the Bi-directional Reflectance Distribution Function

(BRDF), which is based on a physical approach, the most widely used is the Cook-Torrance

model, which has surface roughness as one of its input parameters and is also capable of

handling Fresnel distribution. During our simulation we used this, in a Direct3D environment,

so when generating the rendered graphics we were able to use the measured roughness values

as input parameters.

The majority of optical microscopes – including the Olympus BX51 microscope used by me at

the department – are capable of operating in bright field (BF) and dark field (DF) imaging

mode.

In bright field imaging, both the incident and reflected light fall almost perpendicularly onto

the sample, naturally through a focusing lens. Dark field microscopes, on the other hand,

collect beams of light that arrive not perpendicularly but from the side, from below a given

angle, through a lens, in the direction of the observer; in other words the beams of light travel

in the opposite direction but along the same path as would the beams of light that enter

perpendicularly but are diffracted, not reflected.

Dark field microscopy gives a good resolution and microscopes with this capability are usually

more expensive, but they are eminently suitable for the detection of phase boundaries or the

examination of surface irregularities highlighted by the side illumination. In the case of metals,

in which the proportion of diffuse components is smaller and the incident light is reflected

much more in accordance with the principle of optical reflection, bright field microscopy

Materials Science - Advanced Topics

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D-MAX DMC-20SEC Manual de usuario Pagina 26