Image-formation optical system, and imaging system incorporating the same

Abstract

The invention relates to an image-formation optical system that meets both demands for high performance and compactness, and an imaging system that incorporates the same. The imaging system is built up of an image-formation optical system comprises, in order from its object side, an aperture stop S, a first positive single lens L 1 wherein the absolute value of the axial radius curvature of its image side-surface is smaller than that of its object side-surface, a second negative single lens L 2 wherein the absolute value of the axial radius curvature of its image side-surface is smaller than that of its object side-surface and a third positive single lens L 3 , three single lenses in all, and an image pickup device located on the image plane I of the image-formation optical system.

1 - 20 . (canceled)  
   
   
       21 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive lens that is convex on an image side thereof, a second negative lens that is concave on an image side thereof and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens elements, and there is provided a lens barrel for holding said image-formation optical system and said image pickup device, wherein said lens barrel is integrally molded of the same resin material of which said aperture stop is formed.  
   
   
       22 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive lens that is convex on an image side thereof, a second negative lens that is concave on an image side thereof and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens elements, and there is provided a lens barrel for holding said image-formation optical system, wherein a rim of each of at least the first positive lens and the third positive lens is inclined down in such a way as to come closer to an optical axis of the image-formation optical system on an object side thereof, and an inclined rim is in engagement with said lens barrel.  
   
   
       23 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive lens that is convex on an image side thereof, a second negative lens that is concave on an image side thereof and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens elements, and there is provided a lens barrel for holding said image-formation optical system, wherein as viewed from an entrance side of the image-formation optical system, said first positive lens looks as a circle and, as viewed from the entrance side, said third positive lens is in such a shape that a length of a direction corresponding to a short-side direction of an effective image pickup area of the image pickup device is shorter than a length of a direction corresponding to a long-side direction of the image pickup area.  
   
   
       24 - 31 . (canceled)  
   
   
       32 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive meniscus lens that is convex on an image side thereof, a second negative lens and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens element, and there is provided a lens barrel for holding said image-formation optical system and said image pickup device, wherein said lens barrel is integrally molded of the same resin material of which said aperture stop is formed.  
   
   
       33 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive meniscus lens that is convex on an image side thereof, a second negative lens and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens elements, and there is provided a lens barrel for holding said image-formation optical system, wherein a rim of each of at least the first positive lens and the third positive lens is inclined down in such a way as to come closer to an optical axis of the image-formation optical system on an object side thereof, and an inclined rim is in engagement with said lens barrel.  
   
   
       34 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive meniscus lens that is convex on an image side thereof, a second negative lens and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens elements, and there is a lens barrel for holding said image-formation optical system, wherein as viewed from an entrance side of the image-formation optical system, said first positive lens looks as a circle and, as viewed from the entrance side, said third positive lens is in such a shape that a length of a direction corresponding to a short-side direction of an effective image pickup area of the image pickup device is shorter than a length of a direction corresponding to a long-side direction of the image pickup area.  
   
   
       35 - 41 . (canceled)  
   
   
       42 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive meniscus lens that is convex on an image side thereof, a second negative lens and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens elements, and there is provided a lens barrel for holding said image-formation optical system and said image pickup device, wherein said lens barrel is integrally molded of the same resin material of which said aperture stop is formed.  
   
   
       43 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive meniscus lens that is convex on an image side thereof, a second negative lens and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens elements, and there is provided a lens barrel for holding said image-formation optical system, wherein a rim of each of at least the first positive lens and the third positive lens is inclined down in such a way as to come closer to an optical axis of the image-formation optical system on an object side thereof, and an inclined rim is in engagement with said lens barrel.  
   
   
       44 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive meniscus lens that is convex on an image side thereof, a second negative lens and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens elements, and there is a lens barrel for holding said image-formation optical system, wherein as viewed from an entrance side of the image-formation optical system, said first positive lens looks as a circle and, as viewed from the entrance side, said third positive lens is in such a shape that a length of a direction corresponding to a short-side direction of an effective image pickup area of the image pickup device is shorter than a length of a direction corresponding to a long-side direction of the image pickup area.  
   
   
       45 - 47 . (canceled)  
   
   
       48 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive lens that is convex on an image side thereof, a second negative lens and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens element, and there is provided a lens barrel for holding said image-formation optical system and said image pickup device, wherein said lens barrel is integrally molded of the same resin material of which said aperture stop is formed.  
   
   
       49 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive lens that is convex on an image side thereof, a second negative lens and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens elements, and there is provided a lens barrel for holding said image-formation optical system, wherein a rim of each of at least the first positive lens and the third positive lens is inclined down in such a way as to come closer to an optical axis of the image-formation optical system on an object side thereof, and an inclined rim is in engagement with said lens barrel.  
   
   
       50 . An imaging system, characterized by comprising an image-formation optical system comprising, in order from an object side thereof, an aperture stop, a first positive lens that is convex on an image side thereof, a second negative lens and a third positive lens, and an image pickup device located on an image side of the image-formation optical system, wherein said image-formation optical system comprises a total of three lens elements, and there is a lens barrel for holding said image-formation optical system, wherein as viewed from an entrance side of the image-formation optical system, said first positive lens looks as a circle and, as viewed from the entrance side, said third positive lens is in such a shape that a length of a direction corresponding to a short-side direction of an effective image pickup area of the image pickup device is shorter than a length of a direction corresponding to a long-side direction of the image pickup area.