Objective lenses medium

Considering that TIRFM illumination has a depth of penetration of 150nm and the depth of focus on the objective lens is about 100 nm, the large clusters of seeds formed at first in solution and were not in contact with the substrate. The hazy areas observed at the initial stages, as indicated by the arrows in Fig. 15.4, may represent the clustered seeds or aggregated intermediates formed in solution. Since the thickness of the water medium... 

A 6-inch, f/3.8 objective lens with coated optics was used in conjunction with a 4V2-inch extension tube. Three No. 5 medium peak flash bulbs connected in series provided the proper background lighting. The Dynafax capping shutter is equipped with a synchromatic delay which provided synchronization for this type of lamp. 

Figure 16.19 shows the spatial-frequency distributions of bit data recorded with focused laser beam and coherent optical transfer function (CTF) of reflection type confocal microscopeFigure 16.19a shows a spatial-frequency distribution of bit datum recorded in very thick medium. This distribution coincides with the spatial-frequency distribution of the focused light to record the bit datum, because the bit is recorded with the focused beam. It is assumed that the NA of the objective lens is given by n sin a and k =l ulk, where A denotes the wavelength. 

An alternative readout system is a scanning differential phase-contrast microscope with a split detector as shown in Figure 16.5. The optical configuration is compact and easy to align. The memory medium, in which the data bits have been recorded, is located at the focus of an objective lens. The band limit of the optical transfer function (OTF) is the same as that of a conventional microscope with incoherent illumination. The resolution, especially the axial resolution of the phase-contrast microscope, is similar to that obtained by Zemike s phase-contrast microscope. The contrast of the image is much improved compared to that of Zernike s phase-contrast microscope, however, because the nondiffracted components are completely eliminated by the subtraction of signals between two detectors. The readout system is therefore sensitive to small phase changes. 

The threshold of the pulse energy to induce the laser tsunami is relatively low for a femtosecond laser compared with nanosecond and picosecond lasers. The laser tsunami expands to a volume of (sub pm)3 around the focal point, when an intense laser pulse is focused into an aqueous solution by a high numerical aperture objective lens. When a culture medium containing living animal cells is irradiated, they could be manipulated by laser tsunami. Mouse NIH 3T3 cells cultured on a substrate can be detached and patterned arbitrarily on substrates [36]. We have also demonstrated that the laser tsunami is strong enough to transfer objects with size of a few 100 pm [37], which is impossible by conventional optical tweezers because the force due to the optical pressure is too weak. In addition we demonstrated for the first time the crystallization of organic molecules and proteins in their super-saturated solution by laser tsunami [38-40]. 

A,/a . The expression n sin a can be called the numerical aperture of the diffracted beam of first order which, for microscopes, is identical to the numerical aperture A - of the objective lens. The numerical aperture of a lens is the product of the refractive index of the medium in front of the objective and of the sine of half of the angle whose vertex is located on the optical axis and being the starting point of a light cone of angle a which is just collected by the lens. 

Figure 4 The effect on numerical aperture of the refractive index, n, of the medium between the object and the objective lens. In the examples shown, in (A), where the medium is air, the most oblique rays accepted by the objective leave the object at 39° with oil-immersion (B), rays leaving at up to 60° are collected.

Immersion objectives are designed such that spherical aberrations are minimized when the appropriate medium (oil, water, or glycerin) lies between the front element of the objective lens and the coverslip. Immersion objectives may therefore be used equally for covered and uncovered (reflected-light) specimens. 

The NA is calculated as the product of the refractive index of the medium between the objective lens and the specimen multiplied by the sine of the half angle of the cone of light entering the objective. This cone becomes narrower (and therefore the NA smaller) as the working distance increases (4). 

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