| 摘要 |
PURPOSE:To obtain a lens for copying which is bright with an F number of 4 and vignetting factor of about 100% and corrected in various aberrations, with the coma flare being specially suppressed to a small value, by constituting the optical system of the lens of fix pieces of lenses of six groups so as to satisfy specific conditions. CONSTITUTION:The lens system of this lens is constituted of the 1st to 6th lens groups arranged in the order from the object side and a diaphragm is provided between the 3rd and 4th groups. The 1st and 6th groups are respectively constituted of convex meniscus lenses 10 and 20 having the same form and the 2nd and 5th groups are constituted of concave meniscus lenses 12 and 18 having the same form. The 3rd and 4th groups are constituted of convex meniscus lenses 14 and 16 having the same form. Then nonspherical surfaces are adopted to the object-side surfaces of the 1st- and 5th-group lenses and image- side surfaces of the 6th- and 2nd-group lenses and the lens system is caused to satisfy conditions of -0.039<K1<0.023 and 0.03<K4<0.091, where the K1 and K4 respectively represent the cone constants of the nonspherical surfaces of the 1st- and 6th-group lenses and 2nd- and 5th-group lenses. |
