Patent ID: 7414665

Claim:
An imaging system comprising: a zoom lens comprising a plurality of lens groups wherein a spacing between individual lens groups is varied to vary a focal length and an aperture stop located in an optical path for limiting at least an axial light beam diameter, and an electronic image pickup device located on an image side of the zoom lens, wherein: the aperture stop has a fixed shape, and a filter for performing light quantity control by varying transmittance is located on an optical axis of a space located at a position different from that of a space in which the aperture stop is located, the zoom lens comprises at least a first lens group having negative refracting power and a second lens group having positive refracting power, located just after the first lens group, a spacing between the first lens group having negative refracting power and the second lens group having positive refracting power becomes narrower at a telephoto end than at a wide-angle end of the zoom lens, the aperture stop is located between a surface in the first lens group having negative refracting power, said surface being located nearest to an image side of the zoom lens, and an image side-surface in the second lens group having positive refracting power, the light quantity control filter is located on an image plane side with respect to the aperture stop, when the focal length is varied, the aperture stop is moved with the second lens group, and when 1.5×10 3 ×a/1 mm<F where F is a full-aperture F-number at a telephoto end and a is a minimum pixel pitch in mm of the electronic image pickup device, a length of the aperture stop in a vertical or horizontal direction of an image pickup plane is longer than the length of the aperture stop in a diagonal direction of the image pickup plane, or when 1.5×10 3 a/1 mm>F, the length of the aperture stop in the vertical or horizontal direction of the image pickup plane is shorter than the length of the aperture stop in a diagonal direction of the image pickup plane.