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Zoom lenses (sometimes referred to as "true" zoom) are ideally parfocal, in that focus is maintained as the lens is zoomed (i.e., focal length and magnification changed), which is convenient and has the advantage of allowing more accurate focusing at maximal focal length then zooming back to a shorter focal length to compose the image. [1]
Cone of light behind an achromatic doublet objective lens (A) without (red) and with (green) a Barlow lens optical element (B). The Barlow lens, named after Peter Barlow, is a type of diverging lens which, used in series with other optics in an optical system, increases the effective focal length of an optical system as perceived by all components that are after it in the system.
Among the terms and conditions of 31 cloud-computing services in January-July 2010, operating in England: [5] 27 specified the law to be used (a US state or other country) most specify that consumers can claim against the company only in a particular city in that jurisdiction, though often the company can claim against the consumer anywhere
A scanning acoustic microscope (SAM) is a device which uses focused sound to investigate, measure, or image an object (a process called scanning acoustic tomography). It is commonly used in failure analysis and non-destructive evaluation .
The resolution of a microscope is defined as the minimum separation needed between two objects under examination in order for the microscope to discern them as separate objects. This minimum distance is labelled δ. If two objects are separated by a distance shorter than δ, then they will appear as a single object in the microscope.
The limit of optical resolution in a conventional microscope, the so-called diffraction limit, is in the order of half the wavelength of the light used to image.Thus, when imaging at visible wavelengths, the smallest resolvable features are several hundred nanometers in size (although point-like sources, such as quantum dots, can be resolved quite readily).
A stanhope or stanho-scope is an optical device that enables the viewing of microphotographs without using a microscope. [1] [2] They were invented by René Dagron in 1857. [1] Dagron bypassed the need for an expensive microscope to view the microscopic photographs by attaching the microphotograph at the end of a modified Stanhope lens. [1]
With no modification to the microscope, i.e. with a simple wide field light microscope, the quality of optical sectioning is governed by the same physics as the depth of field effect in photography. For a high numerical aperture lens, equivalent to a wide aperture, the depth of field is small (shallow focus) and gives good optical sectioning.