| 摘要 |
PURPOSE:To contrive compactness of constitution by arranging the 1st group which includes a negative lens, the 2nd group consisting of one or two positive lenses, the 3rd group consisting of a positive single lens having its convex surface on an object field side, and the 4th group consisting of three or four lenses in order from the object field side. CONSTITUTION:The 1st group including the negative lens, the 2rd group consisting of one or two positive lenses, the 3rd group consisting of the positive single lens having its convex surface on the object field side, and the 4th group consisting of three or four lenses are arranged in order from the object side. The 1st group produces large negative distortion to secure f.theta property. The 2nd group compensates a spherical aberration and astigmatism generated by the 1st group to some extent and form an f.theta lens with a large F value along with the 1st group. the 3rd group is for forming a telecentric system and forms a nearly telecentric f.theta lens with a large F value along with the 1st and the 2nd group. The 4th group attains F value = 3.0 and compensates a comatic aberration and curvature of field principally.
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