Zoom Lens

DEFINITION:

A lens capable of changing focal length continuously, without changing position of the image point, by moving a part of the lens system along the optical axis.

DESCRIPTION:

For zoom lenses, it is important that the focal length can be changed continuously and that the position of the image point and aberration do not change. To be more precise, mechanical or optical compensation is made to minimize movements of the image point. Optical compensation simplifies the mechanism because movements of the lens are simple, but the dimensions increase. With mechanical compensation, movements of the lens are changed by means of a cam, but the mechanism is complicated.