Attributive and (now rare) in the genitive. Designating an eyepiece consisting of two planoconvex lenses of equal focal length with their convex surfaces towards each other and a separation less than their focal length.
Origin
Late 18th century; earliest use found in Philosophical Transactions of the Royal Society of London. From the name of Jesse Ramsden, English instrument-maker, who described the eyepiece in 1783 (Philos. Trans. (Royal Soc.) 73 94).
Definition of Ramsden in US English:
Ramsden
nounˈramzdən
Optics
Attributive and (now rare) in the genitive. Designating an eyepiece consisting of two planoconvex lenses of equal focal length with their convex surfaces towards each other and a separation less than their focal length.
Origin
Late 18th century; earliest use found in Philosophical Transactions of the Royal Society of London. From the name of Jesse Ramsden, English instrument-maker, who described the eyepiece in 1783 ( Philos. Trans (Royal Soc.) 73 94).