| 摘要 |
PROBLEM TO BE SOLVED: To provide an intermediate lens barrel for microscope whose number of times of image formation is one, has no change in the direction of an image in the case of returning it to the original optical path and does not generate an aberration of a pupil. SOLUTION: A circulating optical path is formed by N (N is an even number >=4) reflection surfaces, an intermediate image 7 is formed once in the circulating optical path and, by representing an angle formed by both normals N1 , N2 when a normal N1 to a reflection surface R1 and a normal N2 to a second reflection surface R2 are projected on a plane orthogonal to an optical axis X1 reflected by the first reflection surface R1 byα1 , similarly, an angle formed by both normals NN-1 , NN when a normal NN-1 to a reflection surface RN-1 and a normal NN to a reflection surface RN are projected on a plane orthogonal to an optical axis XN-1 reflected by the reflection surface RN-1 byαN-1 and an angle formed by both normals NN, N1 when the normal NN to the reflection surface RN and the normal N1 to the reflection surface R1 are projected on a plane orthogonal to the optical axis XN reflected by the reflection surface RN byαN, the lens barrel is formed so that (α1 +α3 +...+αN-1 )--(α2 +α4 +...+αN)=180 deg.+360 deg.×n (n is integer).
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