| 摘要 |
PURPOSE:To obtain an eyepiece of less movement quantity for visibility correction, by moving only a positive lens group in the eyepiece consisting of the positive lens group and an afocal system which has magnifications not smaller than unmagnification to satisfy a prescribed condition. CONSTITUTION:An eyepiece consists of an afocal system A and a positive lens group B provided movably in the direction of the optical axis, and the focal length of the positive lens system B is obtained by dividing a prescribed focal length by magnifications of the afocal system A for the purpose of equalizing the focal length of the combined system between the afocal system A and the positive lens system B to the prescribed focal length of the eyepiece lens. As the afocal system, a Galileo system consisting of a meniscus lens whose convex face faces toward the object lens is the simplest, and expressions (1) and (2) are satisfied when radiuses of curvatures of the convex face and the concave face of the meniscus lens and the center thickness are denoted as r1, r2, and d1 respectively. |
