Achromatic lens A lens that is designed to produce a view or image that is free of the fringe of rainbow colours that surrounds the images produced by simpler lenses.
ACHROMATIC LENS.
Two lenses made from different glasses, reducing, but not eliminating, the problem of chromatic aberration. The colour defect can be further reduced by using more lenses to produce an apochromatic lens.
ACTIVE GALAXY.
Achromatic Lens
A telescope lens composed of two lenses ground from different types of glass and designed to bring two selected colors to the same focus and correct for chromatic aberration
Active Galaxy ...
achromatic lens
a two-element lens, or doublet, that significantly reduces chromatic aberration
active galactic nuclei ...
Achromatic Lens
(a) Lens (or combination of lenses) that brings different wavelenghts within a ray of light to a single focus, thus overcoming chromatic aberration. It was first successfully made by Joseph von Fraunhofer.
An achromatic lens. [DC99]
Achromatic Color
A color that has no hue; i.e. black, white, or gray. [DC99]
Achromatic Lens ...
The achromatic lens, which greatly reduced color aberrations in objective lenses and allowed for shorter and more functional telescopes, first appeared in a 1733 telescope made by Chester Moore Hall, who did not publicize it.
An achromatic lens that increases the effective focal length of the objective lens or primary mirror and doubles or triples eyepiece magnification. Hence, a 30mm eyepiece becomes a 15mm eyepiece when used with a 2x barlow.
1733 - Chester Moor Hall invents the achromatic lens refracting telescope
1734 - Indian observatory of Sawai Jai Singh at Jaipur
1753 - Real Observatorio de Cádiz (Spain)
1753 - Vilnius observatory at Vilnius University, Lithuania ...
Two achromatic lenses are matched together to act as a precision magnifier of what the telescope brings into view.
For most of the next century, telescopes of speculum metal provided the greatest apertures, though telescopes using achromatic lenses were also in wide use.
While achromatic lenses bring two primary colors (red and blue) into focus at the same point, they leave some uncorrected chromatic aberration at wavelengths in between.
(Later, when glasses with a variety of refractive properties became available, achromatic lenses became possible.) In 1671 the Royal Society asked for a demonstration of his reflecting telescope.
He designed his reflector, which used a concave objective and a smaller "diagonal" mirror, in order to solve the problem of chromatic aberration, a serious degradation in all refracting telescopes before the perfection of achromatic lenses.
 See also: Telescope, Element, Light, Planet, Star
  
|
RSS
