| 摘要 |
PURPOSE:To increase an apparent visual field and eye distance and to correct various aberrations excellently by enabling a lens system of three-group constitution, consisting of a cemented lens of a double-concave lens and double-convex lens, a single double-convex lens, and a cemented lens of a double-convex lens and negative meniscus lens from the object side, to meet prescribed requirements. CONSTITUTION:The lens sytem, consisting of the 1st cemented lens group of a double-concave lens and double-convex lens, the 2nd lens group of a double-convex lens, and the 3rd cemented lens group of a double-convex lens and negative meniscus lens from the object side, meets requirements of inequalities (1)-(5). In the inequalities, (f) is the composite focal length of the whole lens system, and R1- R8 are radii of curvature of respective lens surfaces successively from the image side; and d1-d7 are thicknesses and intervals of the lenses, and n1-n5 are refractive indexes. Consequently, the eye distance is >=100% of the focal length in >=45 deg. visual field, which is large, so that the eye piece lens having various aberrations corrected excellently can be obtained. |
