JPS6474516A - Gaussian lens - Google Patents

Abstract

PURPOSE:To realize a Gaussian lens for correcting satisfactorily an aberration by providing first and second positive lenses, third and fourth negative lenses, and fifth, sixth and seventh positive lenses, placing the fourth lens and the sixth lens by cementing them, and also, satisfying specific conditions. CONSTITUTION:The first lens and the second lens are positive lenses whose convex faces are turned to an object side, and the third lens is a negative lens. The fourth negative lens and the fifth positive lens are cemented and constitute the fourth and the fifth meniscus lenses which have negative refracting power as a whole and whose convex faces are turned to an image face side. The fixed lens is a positive lens whose convex face has been turned to the image face side, and the seventh lens consists of both convex lens faces, and also, a diaphragm is placed between the third lens and the fourth and the fifth lenses. By satisfying the conditional expressions among a focal distance, a radius of curvature, an air internal, a refraction, etc. of each of these constitution lenses, various aberrations which are generated when a back-focal distance whose diaphragm diameter is small are lengthened is corrected satisfactorily.