Increasing the Resolution of Far
... microscope focuses accelerated electrons rather than light. The de Broglie wavelength of the electrons can be as small as 0.005 nm and is easily controllable by an acceleration voltage of typically 50-100 kV so that the wave nature of the electrons does hardly play a limiting role. Presently, electr ...
... microscope focuses accelerated electrons rather than light. The de Broglie wavelength of the electrons can be as small as 0.005 nm and is easily controllable by an acceleration voltage of typically 50-100 kV so that the wave nature of the electrons does hardly play a limiting role. Presently, electr ...
Assessment of optical systems by means of point
... of the wavelength of the light. Interferometric methods are mostly used for this purpose. Although the achievable precision is very high, these methods need refined and delicate optical set-ups and, in practice, special laser sources to achieve sufficient signal-to-noise ratio. When a measurement at ...
... of the wavelength of the light. Interferometric methods are mostly used for this purpose. Although the achievable precision is very high, these methods need refined and delicate optical set-ups and, in practice, special laser sources to achieve sufficient signal-to-noise ratio. When a measurement at ...
Three-Dimensional Simulation of Vertical-Cavity Surface
... m to 20 km range) due to better yield, less expensive testing, drive electronics and packaging. In the short-haul links comprising mainly multi-mode fibers, light emitting diodes (LEDs), 780 nm CD lasers and multi-mode VCSELs are the candidates as light sources. LEDs are most common, but suffer from l ...
... m to 20 km range) due to better yield, less expensive testing, drive electronics and packaging. In the short-haul links comprising mainly multi-mode fibers, light emitting diodes (LEDs), 780 nm CD lasers and multi-mode VCSELs are the candidates as light sources. LEDs are most common, but suffer from l ...
The Optics of the Spherical Fish Lens
... Sands (1988) measured the entrance and exit apertures of a series of laser beams passing through goldfish lenses. They concluded that the refractive index gradient inside the lens was smooth, with a form similar to the parabola of Mattheissen. Their estimates of core and cortical indices lay in the ...
... Sands (1988) measured the entrance and exit apertures of a series of laser beams passing through goldfish lenses. They concluded that the refractive index gradient inside the lens was smooth, with a form similar to the parabola of Mattheissen. Their estimates of core and cortical indices lay in the ...
Aperture
In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. The aperture determines how collimated the admitted rays are, which is of great importance for the appearance at the image plane. If an aperture is narrow, then highly collimated rays are admitted, resulting in a sharp focus at the image plane. If an aperture is wide, then uncollimated rays are admitted, resulting in a sharp focus only for rays with a certain focal length. This means that a wide aperture results in an image that is sharp for things at the correct distance. The aperture also determines how many of the incoming rays are actually admitted and thus how much light reaches the image plane (the narrower the aperture, the darker the image for a given exposure time). In the human eye, the pupil is the aperture.An optical system typically has many openings, or structures that limit the ray bundles (ray bundles are also known as pencils of light). These structures may be the edge of a lens or mirror, or a ring or other fixture that holds an optical element in place, or may be a special element such as a diaphragm placed in the optical path to limit the light admitted by the system. In general, these structures are called stops, and the aperture stop is the stop that determines the ray cone angle, or equivalently the brightness, at an image point.In some contexts, especially in photography and astronomy, aperture refers to the diameter of the aperture stop rather than the physical stop or the opening itself. For example, in a telescope the aperture stop is typically the edges of the objective lens or mirror (or of the mount that holds it). One then speaks of a telescope as having, for example, a 100 centimeter aperture. Note that the aperture stop is not necessarily the smallest stop in the system. Magnification and demagnification by lenses and other elements can cause a relatively large stop to be the aperture stop for the system.Sometimes stops and diaphragms are called apertures, even when they are not the aperture stop of the system.The word aperture is also used in other contexts to indicate a system which blocks off light outside a certain region. In astronomy for example, a photometric aperture around a star usually corresponds to a circular window around the image of a star within which the light intensity is assumed.