| 摘要 |
PURPOSE:To obtain a lens used for a compact copier, etc., which has corrected its various aberrations satisfactorily, has a high contrast, and is 100% in its opening efficiency, by satisfying its prescribed conditions, in a lens system consisting of a positive biconvex lens and a negative meniscus lens in order from the side of an object. CONSTITUTION:In a reflection objective lens holding an object space and an image space in common, the first positive biconvex lens 1 and a negative meniscus lens 2 are placed from the common object and image side, and as for the second lens 2, its concave surface is directed to the common object and image side, and the second surface of the second lens is formed as a reflection surface 2a. In this lens system constituted of 2 groups and 2 pieces, the condition of 1.3<f/f1<1.7, 3.126f<fM<3.4f is satisfied, provided that f, f1 and fM denote a composite focal distance, a focal distance of the first lens and a focal distance of the reflection surface 2a, respectively. In this way, it is possible to obtain a compact reflection objective lens which has corrected its various aberrations satisfactorily, has a high contrast, and is 100% in its opening efficiency. |
