Anamorphic lenses are used to capture the Cinemascope image with an aspect ration of 2.35:1 or 2.38:1 on regular 35mm film material. It was invented in the 1950s. A single cylindrical lens element squeezes the image horizontally, there as the vertical image size remains unchanged. At the projector the opposite lens un-squeezes the image again to the proper image width.

real and projected image	squeezed image on film

image captured on film with anamorphic lens	image projected with anamorphic lens