Patent ID: 6320701
Filing Date: 2001-11-20
Classification: G02B

Abstract:
A rear-focus-type zoom lens comprising four lens groups of positive, negative, positive and positive refractive power, respectively, the first lens group and the third lens group being fixed relative to an image surface of the zoom lens, zooming is accomplished by moving the second lens group and the fourth lens group along the optical axis, and focusing is accomplished by moving the fourth lens group along the optical axis, wherein:the first lens group is formed of, in sequential order from the most object side, a first lens formed of a negative lens element and a positive lens element that are joined, and a second lens which consists of a single lens element of positive refractive power;the second lens group is formed of, in sequential order from the object side, a third lens which consists of a single lens element of negative refractive power, and a fourth lens formed of, in order from the object side, a negative lens element joined with a positive lens element; andthe third lens group consists of a single lens element; andthe fourth lens group is formed of, in sequential order from the object side, a lens element of positive refractive power, a lens element of negative refractive power, a lens element of positive refractive power, and a lens element of positive refractive power.