| 摘要 |
PURPOSE:To obtain a compact varifocal lens which facilitates assembly adjustments and has high performance and high power by arranging a negative and a positive lens group and using a distributed index lens as at least one element of the positive lens group. CONSTITUTION:The lens system consists of the negative lens group A and positive lens group B successively from an object side; and the object-side lens of the group B which has curved surfaces R7 and R8 decreases in refractive index from the optical axis to the outer periphery and distribution coefficients N1 and N2 are both negative, thereby compensating a spherical aberration. The lens which has curved surfaces R9 and R10 increases in refractive index from the optical axis to the outer periphery and distribution coefficients N1 and N2 are both positive, thereby compensating a distortion aberration and astigmatism. The positive lens group B, therefore, consists of two lens element and is lightweight and compact, and assembly adjustments are facilitated; and the spherical aberration at the telephoto end, distortion aberration at the wide-angle end, and astigmatism over the entire range are easily compensated. |
