Patent ID: 7136229

Claim:
A stereoscopic microscope objective comprising, in order from the object plane, a first lens (L 1 ) with negative focal length (f 1 ), wherein the ratio of the focal length (f 1 ) to the total focal length (f) of the microscope objective is at least −2.11 and at most −1.20, and the proportion of refractive power of the image-side surface of the first lens (L 1 ) is at least 80%, a second lens (L 2 ) with positive focal length (f 2 ), wherein the ratio of the focal length (f 2 ) to the total focal length (f) is at least 1.30 and at most 1.45, and the proportion of refractive power of the image-side surface of the second lens (L 2 ) is at least 60%, a third lens (L 3 ) with positive focal length (f 3 ), wherein the ratio of the focal length (f 3 ) to the total focal length (f) is at least 1.15 and at most 1.37, and the proportion of refractive power of the object-side surface of the third lens (L 3 ) is at least 60%, a fourth lens (L 4 ) with positive focal length (f 4 ), wherein the ratio of the focal length (f 4 ) to the total focal length (f) is at least 0.65 and at most 1.70, and the proportion of refractive power of the object-side surface of the fourth lens (L 4 ) is at least 70%, and a fifth lens (L 5 ) with negative focal length (f 5 ), wherein the ratio of the focal length (f 5 ) to the total focal length (f) is at least −0.96 and at most −0.48, and the proportion of refractive power of the image-side surface of the fifth lens (L 5 ) is at least 80%, wherein the amount of refractive power of the fourth lens (L 4 ) and fifth lens (L 5 ) combined is less than 0.31-times the total refractive power of the microscope objective, and wherein the first lens (L 1 ) and fifth lens (L 5 ) have a partial dispersion of a first type, and the second lens (L 2 ), third lens (L 3 ) and fourth lens (L 4 ) are made of materials having a partial dispersion of a second type.