| 摘要 |
PURPOSE:To realize magnification variation without spoiling the compactness of a lens system by varying the focal length of a main lens by adding one transmission lens element and satisfying specific conditions when conjugate length is made constant. CONSTITUTION:This system consists of a convex lens and a concave lens having a reflecting surface on one side. A comparator lens added in front of the main reflecting lens which forms an image on the same side with an object consists of at least one transmission lens element and the focal length of the main lens is varied by the addition; when the conjugate length is made constant, inequalities I and II for about 0.707 magnification or an inequality III for about 1.154 magnifications hold. In the inequalities, r1 is the radius of curvature of the 1st surface of the added lens, fm is the focal length of the main reflecting surface, and fc is the focal length of the added lens. |
