achromatism การใช้

• This artifice is specially adopted in objectives for astronomical photography ( " pure actinic achromatism " ).
• The qualitatively divided retina ( color ) is thus reunited in full activity, resulting in achromatism ( the absence of color ).
• Newton failed to perceive the existence of media of different dispersive powers required by achromatism; consequently he constructed large reflectors instead of refractors.
• According to Schopenhauer, achromatism results when refraction occurs in one direction in the concave lens and in another direction in the convex lens.
• Dollond was aware of the conditions necessary for the attainment of achromatism in refracting telescopes, but relied on the accuracy of experiments made by Newton.
• A derivative of this design, named a " Barlow lens ", is widely used in modern astronomy and photography as an optical element to increase both achromatism and magnification.
• In uniting three colors an " achromatism of a higher order " is derived; there is yet a residual " tertiary spectrum, " but it can always be neglected.
• For example, the condition for achromatism ( 4 ) for two thin lenses in contact is fulfilled in only one part of the spectrum, since dn _ 2 / dn _ 1 varies within the spectrum.
• If all three constants of reproduction be achromatized, then the Gaussian image for all distances of objects is the same for the two colors, and the system is said to be in " stable achromatism ."
• James Gregory and Leonhard Euler arrived at the correct view from a false conception of the achromatism of the eye; this was determined by Chester More Hall in 1728, Klingenstierna in 1754 and by Dollond in 1757, who constructed the celebrated achromatic telescopes . ( See telescope .)
• For infinitely distant objects the radius Of the chromatic disk of confusion is proportional to the linear aperture, and independent of the focal length ( " vide supra ", " Monochromatic Aberration of the Axis Point " ); and since this disk becomes the less harmful with an increasing image of a given object, or with increasing focal length, it follows that the deterioration of the image is proportional to the ratio of the aperture to the focal length, i . e . the " relative aperture . " ( This explains the gigantic focal lengths in vogue before the discovery of achromatism .)