| 摘要 |
PURPOSE:To compensate the coma aberration, curvature of field, etc., of a telecentric f.theta lens optical system consisting of five elements in five groups by satisfying four specific conditional expressions. CONSTITUTION:The optical system consists of the 1st group of a negative meniscus lens having a concave surface on an object side, the 2nd group of a positive meniscus having a concave surface on the object side, and the 3rd group of a positive lens, the 4th group of a positive lens, and the 5th group of a meniscus lens having a concave surface on the image side successively from the object side, and four conditional inequalities shown by I hold, where (f) is the focal length of the whole system, f234 is the composite focal length of the 2nd - the 4th group, and ri is the radius of curvature of the (i) th surface. The refractive index of the 1st group lens and the mean refractive index of the 2nd - the 4th positive lens groups are preferably <=1.75 and >=1.65. |
