A compact and light-weighted projection lens system that is capable of projecting
an image at an angle as wide as 75 degrees with sufficient field angle and brightness
as represented by F number of approximately 2.4, that is capable of effectively
correcting chroic aberration of magnification and aberration of distortion and
exhibiting optical stability against environmental variations, and that is suitable
for obtaining an extraordinarily fine image by the magnification and projection.
In the projection lens system that comprises first to third groups of lenses in
the order from the closest a magnified image where the first lens group of negative
refractive power includes one or more aspherical lenses each having an aspherical
plane on one or both of the surfaces, the second lens group of positive refractive
power includes one or more positive lenses, and third lens group of positive refractive
power includes one or more cemented triplet lenses comprised of three lenses of
positive, negative, and positive attributes joined in this order, a projection
lens system is characterized by terms and conditions defined as in the following formulae:
where f is a total focal length throughout the projecting lens system, f1
is a focal length of the first group of lenses, f2 is a focal length
of the second group of lenses, and f3 is a focal length of the third group
of lenses.
