Abstract: A telecentric lens optical system includes: a front lens group; a rear lens group having a front focal point coinciding with a rear focal point of the front lens unit; and diaphragm mechanisms, each of which is disposed at a position where the rear focal point of the front lens unit and the front focal point of the rear lens unit coincide with each other. One of the front lens group and the rear lens group is provided by a plurality of variable magnification lens groups. The diaphragm mechanisms are provided corresponding to the variable magnification lens groups, respectively. A magnification switching mechanism is provided to selectively move a pair of one of the variable lens groups and one of the corresponding diaphragm mechanisms to be disposed on an optical axis of the other of the front lens group and the rear lens group.

Abstract: A telecentric lens optical system includes: a front lens group; a rear lens group having a front focal point coinciding with a rear focal point of the front lens unit; and diaphragm mechanisms, each of which is disposed at a position where the rear focal point of the front lens unit and the front focal point of the rear lens unit coincide with each other. One of the front lens group and the rear lens group is provided by a plurality of variable magnification lens groups. The diaphragm mechanisms are provided corresponding to the variable magnification lens groups, respectively. A magnification switching mechanism is provided to selectively move a pair of one of the variable lens groups and one of the corresponding diaphragm mechanisms to be disposed on an optical axis of the other of the front lens group and the rear lens group.

Abstract: In order to provide an objective lens which can reduce the generation of flare light, an objective lens including a front-group lens, a rear-group lens arranged on an optic axis of the front-group lens with the front-group lens interposed between an object plane and the rear-group lens, and a semitransparent mirror arranged between the front-group lens and the rear-group lens for reflecting illumination into the front-group lens, transmitting reflected light from the object plane and entering the transmitted light into the rear-group lens is provided. The front-group lens is a single lens or a cemented lens formed by sticking two lenses together.

Abstract: A double telecentric objective lens includes a front group and a rear group each having a positive refracting power as a whole. The front group includes a first unit and a second unit. The first unit is formed of a cemented lens composed of a convex lens and a concave lens. The second unit includes a convex lens or a cemented lens composed of a convex lens and a concave lens, and a concave lens. The rear group includes a third unit and a fourth unit. The third unit includes a concave lens and a cemented lens composed of a convex lens and a concave lens. The fourth unit is formed of a cemented lens composed of a convex lens and a concave lens. In the above configuration, the optical constants of the lenses are determined so as to satisfy the following conditions: n1n−n1p>0.1  (1) &ngr;1p−&ngr;1n>25  (2) 0.3 fF−r2n<0.5 fF  (3) 1.4<(r2p/r2n)<2.

Abstract: A double telecentric objective lens includes a front group having and a rear group each having a positive refracting power as a whole. The front group includes a first unit formed of a cemented lens composed of a convex lens and a concave lens, and a second unit including a convex lens or a cemented lens composed of a convex lens and a concave lens, and a concave lens. The rear group includes a third unit including a concave lens and a cemented lens composed of a convex lens and a concave lens, and a fourth unit formed of a cemented lens composed of a convex lens and a concave lens.

Abstract: An objective lens for a microscope including a first lens group and a second lens group. The first lens group is positioned far from a surface of an object and has a negative refractive power as a whole. The second lens group is disposed between the object and the first lens group and has a positive refractive power as a whole. The first lens group includes two compound lenses, each with a convex lens and a concave lens, and the second lens group has a single convex lens and compound lenses. The objective lens is composed to satisfy the following conditions:5F<D<15F (1)F<.vertline.F1.vertline.<2.5F (2)25<.nu.2p-.nu.2n<60 (3)0.01F<1/r<0.06F (4)1.6<n (5)where D is the distance between the first lens group and the second lens group, F is the focal length of the objective lens, F1 is the focal length of the first lens group, .nu.2p is the average Abbe number of the convex lenses of the second lens group, .nu.

Abstract: An illuminating device for slit lamp microscopes wherein rays reaching an objective through a slit from a light source are so made as to be able to be directed to a position deflected from the optical axis of the objective by displacing or replacing a part of elements forming an illuminating optical system, in order that the illuminating rays may be incident upon an eyeball diagonally from above or below.