WIDE-ANGLE LENS OF LONG FOCAL LENGTH WITH OUTSIDE ENTRANCE PUPIL Russian patent published in 1999 - IPC

FIELD: optical. SUBSTANCE: proposed wide-angle lens includes three lens groups. First group is manufactured in the form of positive meniscus facing space of objects with concavity and biconvex lens. Second lens group has one biconvex lens. Third lens group is made of two positive meniscuses and biconvex lens placed between them. One of its meniscuses faces space of objects with concavity and the other one - with convexity. Positive meniscuses of first and third lens groups can be cemented from biconcave and biconvex lenses. Relation of sum of thickness along axis of first lens group and distance to entrance pupil to thickness along axis of third lens group lies within limits of 1.02 to 1.5 and values of air gaps between lens groups has following relation 2.0 <DB2/DB1 < 2.5, where DB1 and DB2 are values of air gap correspondingly between first and second and second and third lens groups. EFFECT: enlarged angle of field of vision, increased quality of image and increased relative aperture with preservation of sufficiently large length of lens. 17 cl, 9 dwg, 2 tbl