| 摘要 |
PROBLEM TO BE SOLVED: To realize an image-forming optical device equipped with a rod lens array and having optimum refractive index distribution for obtaining high resolving power. SOLUTION: When a distance in a radial direction measured from the optical axis of a rod lens is (r), a refractive index on the optical axis of the rod lens is n0, refractive index distribution coefficients are g, h4, h6 and h8, the refractive index distribution of the rod lens is expressed by an expression 45. Then, the refractive index distribution coefficients h4, h6 and h8 are set on the ellipsoidal solid of revolution in an orthogonal coordinate where h4 is shown on x-axis, h6 is shown on a y-axis, and h8 is shown on z-axis. When a vector from the origin of the orthogonal coordinate to the center of the ellipsoidal solid of revolution is O*, vectors in the major axis direction, middle axis direction and minor axis direction of the ellipsoidal solid of revolution are A*, B* and C* respectively, the ellipsoidal solid of revolution is defined by a vector X* expressed by an expression 46.
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