Abstract: A metal mold including: a first inner metal mold which forms a first lens surface and a first flat surface portion of a lens; a first outer metal mold which forms a second flat surface portion; a second inner metal mold which forms a second lens surface and a third flat surface portion; and a second outer metal mold which forms a fourth flat surface portion, and wherein a first protruded portion which forms a first concaved portion on the lens is formed all around an outer periphery of the first inner metal mold, the first concaved portion serving as clearance for a burr, and a second protruded portion which forms a second concaved portion on the lens is formed all around an outer periphery of the second inner metal mold, the second concaved portion serving as clearance for a burr.

Abstract: A metal mold including: a first inner metal mold which forms a first lens surface and a first flat surface portion of a lens; a first outer metal mold which forms a second flat surface portion; a second inner metal mold which forms a second lens surface and a third flat surface portion; and a second outer metal mold which forms a fourth flat surface portion, and wherein a first protruded portion which forms a first concaved portion on the lens is formed all around an outer periphery of the first inner metal mold, the first concaved portion serving as clearance for a burr, and a second protruded portion which forms a second concaved portion on the lens is formed all around an outer periphery of the second inner metal mold, the second concaved portion serving as clearance for a burr.

Abstract: A lens including: a lens body having first and second surfaces; a flange part formed to protrude from a periphery of the lens body and to have a cylindrical outer circumferential surface; a lens installation surface formed at an outer edge part of the flange part; a recessed part formed as a part of the flange part such that a part of the cylindrical outer circumferential surface is recessed toward the optical axis; and a gate root part located at a central part of the recessed part. The gate root part has a flat surface which is in a same level with respect to the lens installation surface. The gate root part lies on an optical axis side with respect to a virtual curved surface formed by extending the cylindrical outer circumferential surface through the recessed part.

Abstract: A lens including: a lens body having first and second surfaces; a flange part formed to protrude from a periphery of the lens body and to have a cylindrical outer circumferential surface; a lens installation surface formed at an outer edge part of the flange part; a recessed part formed as a part of the flange part such that a part of the cylindrical outer circumferential surface is recessed toward the optical axis; and a gate root part located at a central part of the recessed part. The gate root part has a flat surface which is in a same level with respect to the lens installation surface. The gate root part lies on an optical axis side with respect to a virtual curved surface formed by extending the cylindrical outer circumferential surface through the recessed part.

Abstract: A lens for an optical pick-up formed by injection molding, the lens including a lens body having a first surface on an optical disc side and a second surface on a light source side, and a flange part formed to protrude from a periphery of the lens body outward in a radial direction of the lens body, and wherein a part of the flange part has been cut off along a cylindrical outer circumferential surface of the flange part to remove a gate part of the lens, and when D denotes a cutting depth of the flange part, R denotes a radius of the lens and WG denotes a width of the gate part, the lens satisfies a condition: D < R - R 2 - ( W G 2 ) 2 .

Abstract: A metal mold including: a first inner metal mold which forms a first lens surface and a first flat surface portion of a lens; a first outer metal mold which forms a second flat surface portion; a second inner metal mold which forms a second lens surface and a third flat surface portion; and a second outer metal mold which forms a fourth flat surface portion, and wherein a first protruded portion which forms a first concaved portion on the lens is formed all around an outer periphery of the first inner metal mold, the first concaved portion serving as clearance for a burr, and a second protruded portion which forms a second concaved portion on the lens is formed all around an outer periphery of the second inner metal mold, the second concaved portion serving as clearance for a burr.

Abstract: A lens forming metal mold comprising: a first metal mold portion that forms a first lens surface of a lens; and a second metal mold portion that forms a second lens surface of the lens. An air vent groove is formed on at least one contacting surface of a contacting surface of the first metal mold portion contacting with the second metal mold portion and a contacting surface of the second metal mold portion contacting with the first metal mold portion. A convex surface serving to form a concaved portion on the lens for accommodating a burr caused by the air vent groove is formed at least around the air vent groove on an outer circumference forming surface of the at least one contacting surface on which the air vent groove is formed, the outer circumference forming surface serving to from a tubular surface of the lens.