PURPOSE: To make the overall length of a lens not a little shorter than conventional lens and to obtain high performance by giving the 1st lens group negative refracting power and the 2nd lens group positive refracting power successively from an object side and providing at least one distributed refraction index type lens.
CONSTITUTION: This zoom lens system consists of two lens groups, i.e. the 1st negative lens group 11 and the 2nd positive lens group 12 from the object side and varies in power from the wide-angle end to the telephoto end by reducing the gap between the 1st negative lens group 11 and the 2nd positive lens group 12. In this case, the 2nd positive lens group 12 consists of two lens elements, a positive-power distributed index lens having such a refractive index distribution that the refractive index decreases from the optical axis to the outer periphery at right angles to the optical axis and a negative-power distributed index lens which has such a refractive index distribution that the refractive index increases from the optical axis to the outer periphery at right angles to the optical. Consequently, the overall optical length of the whose system is shortened.
NAKAYAMA HIROKI
SUDA SHIGEYUKI
HATTORI JUN
HORIUCHI AKINAGA
