Abstract: An imaging lens comprises in order from an object, a first lens group of positive refractive power, a second lens group of positive refractive power, and a third lens group of negative refractive power. In focusing from infinity to a close object, the first lens group is fixed in position, and the second lens group and the third lens group are moved so that the distance between the first lens group and the second lens group is reduced, and the distance between the second lens group and the third lens group is increased. Further, the following conditional expression (1) is satisfied: 1.0<f1/f<2.5??(1) where f1: is the focal length of the first lens group, and f: the focal length of the entire system.

Abstract: An imaging lens comprises in order from an object, a first lens group of positive refractive power, a second lens group of positive refractive power, and a third lens group of negative refractive power. In focusing from infinity to a close object, the first lens group is fixed in position, and the second lens group and the third lens group are moved so that the distance between the first lens group and the second lens group is reduced, and the distance between the second lens group and the third lens group is increased. Further, the following conditional expression (1) is satisfied: 1.0<f1/f<2.5??(1) where f1: is the focal length of the first lens group, and f: the focal length of the entire system.

Abstract: A mold for use in production of a glass optical element includes an upper mold and a lower mold on which a molten glass is dropped, the lower mold being provided with a molding surface for press molding the molten glass with the upper mold. A recess for forming a positioning protrusion on the glass optical element is provided at an outer side of the molding surface. An inclined section is provided at an inner circumferential surface of the recess closer to the molding surface. The inclined section is inclined such that, when the molten glass dropped on the molding surface spreads toward the outer side, the molten glass enters the recess while maintaining contact with the inclined section.

Abstract: A method for manufacturing a glass optical element includes the steps of: feeding molten glass onto a lower mold part; and compression-molding the molten glass using an upper mold part and the lower mold part. The upper mold part is provided with a recess for forming a positioning protrusion of the glass optical element. A surface of the recess includes a first region where a protective film against the molten glass is formed, and a second region where the protective film is not formed and the upper mold part is exposed. In the step of compression-molding the molten glass, after the molten glass enters the recess, the molten glass is compression-molded in a state where a part of the molten glass and the second region do not contact each other, to thereby form the positioning protrusion of the glass optical element.