Wide-field eyepiece

Claim 2

A wide-field eyepiece comprising a first, second and third lens components wherein said first lens component is a positive cemented doublet consisting of a negative lens and a positive lens, said second lens component is a negative cemented doublet consisting of a negative lens and a positive lens, and said third lens component comprises at least two lens elements and has positive refractive power as a whole, the lens element located on the eye side in said third lens component being a positive meniscus lens arranged to be concave toward the eye side, said wide-field eyepiece being arranged to fulfill the following conditions: (1) n 6 ≧1.75 (2) (n 3 -n 4 )≧0.1 (3) -0.8f≧r 4 ≧-1.2f (4) 52≧ν 2 ≧36 wherein reference symbols n 3 and n 4 respectively represent refractive indices of respective lens elements constituting the second lens component, reference symbol n 6 represents the refractive index of the lens element arranged on the eye side in the third lens component, reference symbol r 4 represents the radius of curvature of the lens surface located on the first lens component side in the second lens component, reference symbol ν 2 represents Abbe's number of the lens element arranged on the second lens component side in the first lens component, and reference symbol f represents the focal length of the lens system as a whole.

Claim 3

A wide-field eyepiece according to claim 1 wherein said third lens component comprises a biconvex lens and a positive meniscus lens arranged to be concave toward the eye side.

Claim 4

A wide-field eyepiece according to claim 2, in which said wide-field eyepiece has the following numerical data: ______________________________________ r.sub.1 = -139.822 d.sub.1 = 2.30 n.sub.1 = 1.56873 ν.sub.1 = 63.16 r.sub.2 = 22.850 d.sub.2 = 7.20 n.sub.2 = 1.70154 ν.sub.2 = 41.24 r.sub.3 = -64.729 d.sub.3 = 21.29 r.sub.4 = -29.247 d.sub.4 = 3.00 n.sub.3 = 1.76182 ν.sub.3 = 26.52 r.sub.5 = 21.633 d.sub.5 = 9.80 n.sub.4 = 1.56873 ν.sub.4 = 63.16 r.sub.6 = -28.463 d.sub.6 = 1.30 r.sub.7 = 47.518 d.sub.7 = 4.00 n.sub.5 = 1.64000 ν.sub.5 = 60.09 r.sub.8 = -74.266 d.sub.8 = 0.20 r.sub.9 = 21.330 d.sub.9 = 4.51 n.sub.6 = 1.80400 ν.sub.6 = 46.57 r.sub.10 = 49.878 f = 25 mm, field number = 26.5 magnification = 10X, eye point distance = 19.44 mm ______________________________________ wherein reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 5

A wide-field eyepiece according to claim 2, in which said wide-field eyepiece has the following numerical data: ______________________________________ r.sub.1 = -147.686 d.sub.1 = 2.91 n.sub.1 = 1.56873 ν.sub.1 = 63.16 r.sub.2 = 24.261 d.sub.2 = 5.81 n.sub.2 = 1.70154 ν.sub.2 = 41.24 r.sub.3 = -56.213 d.sub.3 = 20.78 r.sub.4 = -23.628 d.sub.4 = 3.11 n.sub.3 = 1.72825 ν.sub.3 = 28.46 r.sub.5 = 21.514 d.sub.5 = 8.94 n.sub.4 = 1.56873 ν.sub.4 = 63.16 r.sub.6 = -25.885 d.sub.6 = 0.90 r.sub.7 = 60.934 d.sub.7 = 3.95 n.sub.5 = 1.64000 ν.sub.5 = 60.09 r.sub.8 = -63.816 d.sub.8 = 0.20 r.sub.9 = 20.705 d.sub.9 = 3.80 n.sub.6 = 1.75700 ν.sub.6 = 47.87 r.sub.10 = 61.245 f = 25 mm, field number = 26.5 magnification = 10X, eye point distance = 20 mm ______________________________________ wherein reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 6

A wide-field eyepiece according to claim 2, in which said wide-field eyepiece has the following numerical data: ______________________________________ r.sub.1 = -134.440 d.sub.1 = 2.30 n.sub.1 = 1.56873 ν.sub.1 = 63.16 r.sub.2 = 24.592 d.sub.2 = 7.00 n.sub.2 = 1.72000 ν.sub.2 = 46.03 r.sub.3 = -55.879 d.sub.3 = 20.80 r.sub.4 = -21.374 d.sub.4 = 3.00 n.sub.3 = 1.76182 ν.sub.3 = 26.52 r.sub.5 = 24.274 d.sub.5 = 8.90 n.sub.4 = 1.56873 ν.sub.4 = 63.16 r.sub.6 = -23.606 d.sub.6 = 0.80 r.sub.7 = 58.802 d.sub.7 = 4.00 n.sub.5 = 1.64000 ν.sub.5 = 60.09 r.sub.8 = -57.535 d.sub.8 = 0.20 r.sub.9 = 21.194 d.sub.9 = 3.80 n.sub.6 = 1.80400 ν.sub.6 = 46.57 r.sub.10 = 55.138 f = 25 mm, field number = 26.5 magnification = 10X, eye point distance = 20 mm ______________________________________ wherein reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 7

A wide-field eyepiece according to claim 2, in which said wide-field eyepiece has the following numerical data: ______________________________________ r.sub.1 = -171.991 d.sub.1 = 2.89 n.sub.1 = 1.56873 ν.sub.1 = 63.16 r.sub.2 = 27.122 d.sub.2 = 7.09 n.sub.2 = 1.70154 ν.sub.2 = 41.24 r.sub.3 = -53.937 d.sub.3 = 20.76 r.sub.4 = -22.543 d.sub.4 = 3.12 n.sub.3 = 1.76182 ν.sub.3 = 26.52 r.sub.5 = 25.059 d.sub.5 = 8.93 n.sub.4 = 1.56873 ν.sub.4 = 63.16 r.sub.6 = -25.059 d.sub.6 = 0.20 r.sub.7 = 62.252 d.sub.7 = 4.23 n.sub.5 = 1.69680 ν.sub.5 = 55.52 r.sub.8 = -62.252 d.sub.8 = 0.20 r.sub.9 = 21.123 d.sub.9 = 3.80 n.sub.6 = 1.80400 ν.sub.6 = 46.57 r.sub.10 = 53.228 f = 25 mm, field number = 26.5 magnification = 10X, eye point distance = 19.44 mm ______________________________________ wherein reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.