OPTICAL SYSTEM FOR CONVERTING ASPECT RATIO AND IMAGE PROCESSOR CAPABLE OF CONVERTING ASPECT RATIO

摘要

PROBLEM TO BE SOLVED: To easily change an aspect ratio to an optional value by providing a positive lens group which is arranged to be opposed on both sides by putting a diaphragm in between and whose middle part is afocal and an anamorphic lens which is arranged at the middle part and which is afocal. ;SOLUTION: This optical system for converting an aspect ratio 1 is constituted of symmetric positive lenses 3 and 4 arranged to be opposed by putting the diaphragm 2 in between and an anamorphic lens system 5 arranged at the middle part of the positive lenses 3 and 4. The lens system 5 is constituted of an anamorphic negative lens 6 and an anamorphic positive lens 7 arranged by putting the diaphragm 2 in between. Therefore, a focal distance f1 on an object side and a focal distance on an image side are the same in a Z-axis direction, so that unmagification is attained. Meanwhile, a focal distance on the image surface side becomes the focal distance f3 shorter than the above focal distance in a Y-axis direction, so that the magnification(f3/f1) becomes smaller than 1. Thus, the image having the different aspect ratio in longitudinal/ lateral directions, that is, horizontal/vertical directions is obtained.;COPYRIGHT: (C)1998,JPO