| 摘要 |
PURPOSE:To obtain a lens which is incorporated in a small-sized camera and has an excellent spherical aberration on a short-wavelength side by using two negative and positive combined lenses for the 2nd group of the rear converter lens, and specifying the refractive index and Abbe number of the lens, the radius of curvature of the joint surface, etc. CONSTITUTION:The rear converter lens consists of the 1st group of a positive single lens and the 2nd group of two positive and negative, or negative and positive combined single lenses, and its joint surface has a positive refracting power; and inequalities I -IV hold, where (f) is the focal length of the whole lens system including a main lens, Ni and nui are the refractive index and Abbe number of the (i)th lens from the object side about a line (d), and R4 is the radius of curvature of the joint surface. Consequently, the aberrations of the converter lens whose main lens focal length is increased by about one and half times are compensated excellently to incorporate the lens in a small-sized camera body. |
