| 摘要 |
PURPOSE:To obtain a small-sized and light in weight zoom lens having a high performance and a high magnification, by containing an iris diaphragm in the fourth lens group, and using a refractive index distribution type lens consisting of a heterogeneous medium, for at least one lens being adjacent to the iris diaphragm. CONSTITUTION:At least one piece of refractive index distribution type lens of a co-axial system is used for the fourth lens group. The figure shows an optical system which uses one piece of refractive index distribution lens instead of three pieces of the front group, and the lens has a distribution in which a refractive index decreases gradually in the direction orthogonal to the optical axis. When it is tried to constitute a correction of a spherical aberration, an axial chromatic aberration and a comatic aberration of the periphery of the both faces, by one piece of homogeneous lens, the Petzval sum is generated greatly by a negative value from a zoom part, therefore, it is necessary to use a nitric material of a low refractive index, but when the refractive index distribution type lens is used, the Petzval sum and a spherical aberration can be corrected satisfactorily. Also, as for the lens, not only the number of pieces can be curtailed, but also the optical overall length can be shortened.
|
