Patent ID: 6104544
Filing Date: 2000-08-15
Classification: G02B,G03F

Abstract:
A projection optical system located between a first object and a second object, for projecting an image of the first object onto the second object, said projection optical system having:a first lens group with positive refracting power, said first lens group being placed between the first and second objects;a second lens group with negative refracting power, said second lens group being placed between said first lens group and the second object;a third lens group with positive refracting power, said third lens group being placed between said second lens group and the second object;a fourth lens group with negative refracting power, said fourth lens group being placed between said third lens group and the second object;a fifth lens group with positive refracting power, said fifth lens group being placed between said fourth lens group and the second object; anda sixth lens group with positive refracting power, said six lens group being placed between said fifth lens group and the second object,wherein said first lens group includes at least two positive lenses, said third lens group includes at least three positive lenses, said fourth lens group includes at least three negative lenses, said fifth lens group includes at least five positive lenses and at least one negative lens, and said sixth lens group includes at least one positive lens,wherein said second lens group comprises a front lens placed as closest to the first object and having negative refracting power with a concave surface to the second object, a rear lens placed as closest to the second object and having negative refracting power with a concave surface to the first object, and an intermediate lens group placed between said front and rear lenses in said second lens group, andwherein said intermediate lens group has a first lens with positive refracting power, a second lens with negative refracting power, a third lens with negative refracting power, and a fourth lens with negative refracting power in the named order from the first object toward the second object.