| 释义 |
Ramsden|ˈræmzdən|
The name of Jesse Ramsden (1735–1800), English instrument-maker, used attrib. and in the possessive to designate an eyepiece commonly used in astronomical telescopes (see quot. 1847) which he described in 1783 (Phil. Trans. R. Soc. LXXIII. 94).
1787Phil. Trans. R. Soc. LXXVII. 55 The telescope..was an achromatic object-glass of Dollond, of 16 inches focal length, and 2 inches aperture; with a Ramsden's eye⁓glass, magnifying about 25 times. 1847R. Potter Elem. Treat. Optics I. vii. 117 Ramsden's eyepiece is formed of a plano-convex and a convexo-plane lens of equal focal lengths, set at a distance of about two-thirds of the focal length of either. 1900R. A. Herman Treat Geom. Optics vi. 137 Both Huyghens' and Ramsden's eye-pieces have convergent powers, and the image appears inverted. 1923Glazebrook Dict. Appl. Physics IV. 77/1 When a Ramsden eyepiece is employed even pronounced apparent distortion is of no importance for exact measurements. 1971Smith & Thomson Optics viii. 133 The focal plane of eyepieces of the Ramsden type is close to the first lens. |