Search results for "Contrast transfer function"
showing 2 items of 2 documents
Reduction of the spherical aberration effect in high-numerical-aperture optical scanning instruments.
2006
In modern high-numerical-aperture (NA) optical scanning instruments, such as scanning microscopes, optical data storage systems, or laser trapping technology, the beam emerging from the high-NA objective focuses deeply through an interface between two media of different refractive index. Such a refractive index mismatch introduces an important amount of spherical aberration, which increases dynamically when scanning at increasing depths. This effect strongly degrades the instrument performance. Although in the past few years many different techniques have been reported to reduce the spherical aberration effect, no optimum solution has been found. Here we concentrate on a technique whose mai…
New Analytical Tools for Evaluation of Spherical Aberration in Optical Microscopy
2010
The required tightly focused spots in three-dimensional (3D) scanning optical techniques are usually achieved by high-NA immersion lenses. The refractive index mismatch between the sample and the immersion medium introduces an important amount of spherical aberration when imaging deep inside the specimen, spreading out the focusing response. Since this aberration depends on the focalization depth, it is not possible to simultaneously achieve a global compensation for the whole scanned sample. In this way, the design of pupil elements that increase the tolerance to this aberration is of great interest. We present a new formalism for the evaluation and the design of filters that decrease the …