Wide angle optical system and image pickup apparatus using the same

摘要

A wide angle optical system includes: a first lens group of negative refractive power; and a second lens group of positive refractive power; the first lens group and the second lens group being arranged in the above-mentioned order from the object side; the second lens group including: a cemented doublet SU21; an aperture diaphragm; a lens SU22; and a biconvex lens L25; the cemented doublet, the aperture diaphragm, the lens and the biconvex lens being arranged in the above-mentioned order from the object side; the largest ones of the air spaces on the axis being the front and rear spaces of the aperture diaphragm except the back focal length; the wide angle optical system being divided into the first lens group and the second lens group at the second largest air space operating as a boundary.