Rear conversion lens for astronomical telescope

Abstract

Abstract PURPOSE:To obtain a rear conversion lens of simple constitution for a large-diameter astronomical telescope having small aberrations, by making a lens system, consisting of three negative, positive and negative lenses successively from an objective lens side, meet prescribed requirements. CONSTITUTION:A lens system, consisting of three negative, positive and negative lenses successively from an objective lens side and having three-group three-element two-group three-element or one-group three-element constitution by cementing the lenses, meet requirements as shown by inequalities (1)-(4). In the inequalities, fi, ni, and nui are the focal length, refractive index to a line (d), and Abbe number of the (i)-th lens, and (f) is the composite focal length of the entire lens system. Consequently, the rear conversion lens, when equipped to the objective lens of an about 1:12 aperture ratio astronomical telescope, provides about two magnifications of the focal length.

Inventors

• 👤 Yasunori Arai

Bibliographic Details