Ojective lens for endoscope
First Claim
1. An objective lens for an endoscope, having a lens system consisting of four single lenses designated as first lens L1, second lens L2, third lens L3 and fourth lens L4 from the object side, wherein:
- said first lens L1 consists of a negative lens having a concave surface on the image side;
said second lens L2 consists of a positive lens having a surface of a smaller radius of curvature on the object side;
said third lens L3 consists of a positive lens having a surface of a smaller radius of curvature on the image side; and
said fourth lens L4 consists of a positive lens;
said first to fourth lenses L1 to L4 of said lens system being arranged to satisfy the following conditions (1) to (4). ##EQU1## where n1, n5 and n7 are refractive indices of said first lens L1, third lens L3 and fourth lens L4 relative to line d, and γ
1, γ
3, γ
5 and V7 are Abbe'"'"'s numbers of said first lens L1, second lens L2, third lens L3 and fourth lens L4, respectively.
1 Assignment
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Accused Products
Abstract
An objective lens particularly suitable for use in endoscope, employing a lens system which is composed of four single lenses, namely, composed of, from the object side, a first lens L1 consisting of a negative lens having the concave surface thereof on the object side, a second lens L2 consisting of a positive lens having a surface of smaller radius of curvature disposed on the object side, a third lens L3 consisting of a positive lens having a surface of smaller radius of curvature on the image side, and a fourth lens L4 consisting of a positive lens. In this lens construction, the respective lenses L1 to L4 are adapted to satisfy the conditions of n1 >1.70, γ1 >40.0, γ3 <42.5, n5 >1.60, γ5 >50.0, n7 >1.60, and γ7 >50.0 (where n1, n5 and n7 are refractive indices of the first lens L1, third lens L3 and fourth lens L4 relative to line d, respectively, and γ 1, γ3, γ5 and γ7 are Abbe'"'"'s numbers of the first to fourth lenses L1 and L4, respectively.)
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Citations
7 Claims
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1. An objective lens for an endoscope, having a lens system consisting of four single lenses designated as first lens L1, second lens L2, third lens L3 and fourth lens L4 from the object side, wherein:
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said first lens L1 consists of a negative lens having a concave surface on the image side; said second lens L2 consists of a positive lens having a surface of a smaller radius of curvature on the object side; said third lens L3 consists of a positive lens having a surface of a smaller radius of curvature on the image side; and said fourth lens L4 consists of a positive lens; said first to fourth lenses L1 to L4 of said lens system being arranged to satisfy the following conditions (1) to (4). ##EQU1## where n1, n5 and n7 are refractive indices of said first lens L1, third lens L3 and fourth lens L4 relative to line d, and γ
1, γ
3, γ
5 and V7 are Abbe'"'"'s numbers of said first lens L1, second lens L2, third lens L3 and fourth lens L4, respectively. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification