Varifocal lens with an element with vera, this part of the refractive power of

摘要

PURPOSE:To make the constitution of a zoom lens compact and suitable for electronic control, by constituting the zoom lens of a fixed lens group and another lens group which changes the power of the zoom when moving in the coaxial direction and providing a variable refracting power element to one of the lens groups. CONSTITUTION:The zoom lens of this invention is composed of an unmovable front lens F, variator V which changes the power of the zoom lens when moving in the coaxial direction, unmovable relay lens R, and unmovable compensator C' equipped with available refracting power element which changes the refrac tive index by changing the shape of the lens surface. To an infinite object, the compensator C' is set to a negative value at the wide angle and telephoto ends and to a near object, the refracting power of the compensator C' is further made smaller. Therefore, the image surface of the entire system can always be maintained constantly irrespectively of the change in the variable power and object distance by the movement of the variator V by changing the refract ing power of the variable refracting power element in such a way, and high- speed auto-focus control can be performed with a small-sized and simple constitu tion.