Aperture numerical

The magnification is rather chosen to be about 500 to 1000 where is the numerical aperture of the objective (see the next section) The eyepiece is then necessary to magnify the real image so that it can conveniently be inspected. 

The abihty of a waveguide to collect light is determined by the numerical aperture (NA) which defines the maximum angle at which light entering the fiber can be guided. 

The theoretical limit to an instrument s resolving power is determined by the wavelength of light used, and the numerical aperture of the system ... 

Run-of-the-mill instruments can achieve a resolution of 5-10 nm, while the best reach 1 nm. The remarkable depth of focus derives from the fact that a very small numerical aperture is used, and yet this feature does not spoil the resolution, which is not limited by dilfraction as it is in an optical microscope but rather by various forms of aberration. Scanning electron microscopes can undertake compositional analysis (but with much less accuracy than the instruments treated in the next section) and there is also a way of arranging image formation that allows atomic-number contrast, so that elements of different atomic number show up in various degrees of brightness on the image of a polished surface. 

The risk of distortion on firing is greater if the design calls for numerous apertures in the vessel or its cover. 

By deriving or computing the Maxwell equation in the frame of a cylindrical geometry, it is possible to determine the modal structure for any refractive index shape. In this paragraph we are going to give a more intuitive model to determine the number of modes to be propagated. The refractive index profile allows to determine w and the numerical aperture NA = sin (3), as dehned in equation 2. The near held (hber output) and far field (diffracted beam) are related by a Fourier transform relationship Far field = TF(Near field). 

Consequently the outlines of the far field are characteristies of the smallest detail in the near field. Due to the diffraction laws it is possible to link the speckle substructure typical dimension to the numerical aperture ... 

The resolution of an acoustic lens is determined by diffraction limitations, and is 7 = 0.51 /N.A [95], where is the wavelength of sound in liquid, and N.A is the numerical aperture of the acoustic lens. For smaller (high-frequency) lenses, N.A can be about 1, and this would give a resolution of 0.5 Kyj. Thus a well designed lens can obtain a diameter of the focal spot approaching an acoustic wavelength (about 0.4 /Ltm at 2.0 GHz in water). In this case, the acoustic microscope can achieve a resolution comparable to that of the optical microscope. 

C. P. J., Wilson, K. R., Muller, M. and Brakenhoff, G. J. (1998) Characterization of femtosecond pulses focused with high numerical aperture optics using interferometric surface-third-harmonic generation. Opt. Commun., 147, 153-156. 

Laser trapping is a technique to manipulate small sized materials, which was developed by Ashkin in 1970 [20, 21]. In this experiment, a laser beam is tightly focused by an objective lens with high numerical aperture (NA), and a dielectric... 

The advantage of Raman spectromicroscopy is that very small specimens can be studied while still allowing the determination of the second and fourth moments of the ODF. However, the expressions for the Raman intensities are more complex since the optical effects induced by the microscope objective have to be considered. Although the corrections may be small, they are not necessarily negligible [59]. This problem was first treated by Turrell [59-61] and later by Sourisseau and coworkers [5]. Turrell has mathematically quantified the depolarization of the incident electric field in the focal plane of the objective and the collection efficiency of the scattered light by high numerical aperture objectives. For brevity, only the main results of the calculations will be presented. Readers interested in more details are referred to book chapters and reviews of Turrell or Sourisseau [5,59,61]. The intensity in Raman spectromicroscopy is given by [59-61]... 

The constants Aohi and Boh characterize the collection efficiency of the objective and originate from the integration over Q. They are related to the numerical aperture NA of the objective so that... 

The upgrade of a frequency-domain fluorescence lifetime imaging microscope (FLIM) to a prismless objective-based total internal reflection-FLIM (TIR-FLIM) system is described. By off-axis coupling of the intensity-modulated laser from a fiber and using a high numerical aperture oil objective, TIR-FLIM can be readily achieved. The usefulness of the technique is demonstrated by a fluorescence resonance energy transfer study of Annexin A4 relocation and two-dimensional crystal formation near the plasma membrane of cultured mammalian cells. Possible future applications and comparison to other techniques are discussed. 

The primary requirement for making any connection is to minimise the optical power that is lost in it. Intrinsic losses result from technological variations of the fibres to be connected i.e. core area mismatch, numerical aperture mismatch, and profile mismatch. These obvious errors can only be omitted by proper matching of connected fibres or additional optical elements should be used. Contrary to the intrinsic losses, extrinsic ones can be corrected by a mechanical alignment. Extrinsic losses are caused if ends of the fibres are in some distance and the light from the input fibre cannot be collected by the sink fibre. A similar situation with power losses occurs in lateral displacement and angular misalignment. 

The incoming light reflects from the end surface of a fibre, which is caused by the difference in refractive indexes of a fibre, a light source and a gap between them. Such losses are usually small as compared with other losses occurring in the system. The losses caused by different numerical apertures cannot be avoided. As higher NA of the fibre, as lower losses of... 

Important parameters, characterizing fibre properties, are the attenuation a and numerical aperture NA. The attenuation (Equation 1) represents optical losses caused by absorption or scattering of the light guided through the unit fibre length. It is given by ... 

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