Imaging with lenses

For the periodic boundary conditions described below, the cutoff distance is fixed by the nearest image approximation to be less th an h alf th e sm allest box len gth. With a cutoff an y larger, m ore than nearest images would be included. 

In image mode, the post-specimen lenses are set to examine the information in the transmitted signal at the image plane of the objective lens. Here, the scattered electron waves finally recombine, forming an image with recognizable details related to the sample microstructure (or atomic structure). 

A lens images the diffracted light onto a wafer with the amount of information collected from the mask by the lens being related to the numerical aperture of the lens with higher NA lenses having higher resolution capability. 

As an example of the application of this result, the minimum aberration for acoustic imaging with a wavelength of 25 fan at a depth of 0.5 mm below the surface of a material of refractive index n = 0.25 would be given by h/sb = 0.7, so that the optimum lens angle would be 0opt = 8.3°. This result depends rather weakly on Sb, so that halving the depth would increase the optimum angle by less than 1 °. 

Near-field Raman imaging with a scanned probe has been reported [18, 19]. However, the technique is painfully slow (5-10 h, even for strong scatterers) and it has found very little use. Acquisition time can be decreased by using a polystyrene bead as a very high numerical aperture immersion lens. Working at 532 nm, Kasim et al. used a 60x/1.2 immersion aperture as an optical tweezer to simultaneously position the bead and operate it as a high NA lens [20]. They obtained a spatial resolution of about 80 nm on doped silicon with a few minutes scan time (Fig. 5.1). However, because of the need for a relatively smooth surface and a very intense scatterer, this technique is not likely to find much application in biomedical or pharmaceutical applications [21, 22],... 

To acquire this information, the two displaced continuum beams are imaged with a cylindrical and a spherical lens onto different positions along the length of the entrance slit of a low dispersion spectrograph (Instruments SA, model UFS-200). The two resulting parallel dispersed spectra are fully separated from each other at the focal plane, where they are detected by the model 1254 SIT detector head of an EG + G Princeton Applied Research Corporation optical multichannel analyzer system. In conjunction with a model 1216 detector controller and model 1215 console, this detector is programmed with a two dimensional... 

Figure 1.16 Engraved markings on the barrel of an objective lens. (Reproduced with permission from D.B. Murphy, Fundamentals of Light Microscopy and Electronic Imaging, Wiley-Liss. 2001 John Wiley Sons Inc.)...

Q.29.3 If the lens in Q.29.2 were to be used in a compound microscope as the objective lens along with an eyepiece lens that has a magnification of 10 X, what will the size of the image formed on the retina be What is the magnification of this instrument ... 

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