Condensers with a numerical aperture of 0.95 or less are designed to be used without oil or other fluid on the top lens and are termed dry condensers.
42.
In this sense, the traditional thin-lens definition and illustration of f-number is misleading, and defining it in terms of numerical aperture may be more meaningful.
43.
It works because numerical aperture is a function of the maximum angle of light that can enter the lens and the refractive index of the medium through which the light passes.
44.
The distance between the axes as seen in the field of the microscope depends partly on the axial angle of the crystal and partly on the numerical aperture of the objective.
45.
Assuming quality ( diffraction-limited ) optics, lenses with larger numerical apertures collect more light and will generally provide a brighter image, but will provide shallower depth of field.
46.
The size of this diffraction pattern and the focal volume it defines is controlled by the numerical aperture of the system's objective lens and the wavelength of the laser used.
47.
The LBR uses a laser to write the information, with a wavelength and final lens NA ( numerical aperture ) chosen to produce the required pit size on the master blank.
48.
Made of optical layers on an opaque or transparent substrate, these supports do not modify the light polarization after reflection even if the numerical aperture of the incident source is important.
49.
Where n is the index of refraction of the medium in which the lens is working and ? is the angle of light that can enter the lens ( see numerical aperture ).
50.
By decreasing the wavelength, using a higher numerical aperture ( 0.85, compared with 0.575 for MO ), the laser beam can be focused much more tightly.
