| 摘要 |
PURPOSE:To obtain an F12.8 lens for a compact camera which has short overall length without increasing the diameter of the image-side lens element by using a cemented lens as at least one of four groups, and specifying the conditions of radii of curvature of object-side surfaces and cemented surface of the 1st- the 3rd groups. CONSTITUTION:This lens consists of the 1st group lens of a positive meniscus lens element having a convex surface on the object side, the 2nd group lens of a biconcave lens element, the 3rd group of a biconvex lens element, and the 4th group of a negative meniscus lens element having a convex surface on the image side, and at least one of them uses the cemented lens. Then, the lens system meets requirements shown by inequalites. In the inequalities, r1 is the radius of curvature of the object-side surface of the 1st group lens, ra the radius of curvature of the object-side surface of the 2nd lens, rb the radius of curvature of the image-side surface of the 3rd lens, rci the radius of curvature of the cemented surface of said cemented lens, and (f) the focal length of the whole system.
|
