Mold for an optical element

A mold for an optical element, comprising:

• an upper mold including a first neck part;
• an upper-surface forming surface that is provided in a distal end of the first neck part of the upper mold, the upper-surface forming surface being configured to form an upper surface of the optical element;
• a lower mold including a second neck part;
• a lower-surface forming surface that is provided in a distal end of the second neck part of the lower mold, the lower-surface forming surface being configured to form a lower surface of the optical element;
• a side-surface mold having a hole into which the first neck part of the upper mold and the second neck part of the lower mold are inserted, a part of an inner surface of the hole being configured to form a side surface of the optical element;
• and
• a sleeve in which the upper mold, the lower mold and the side-surface mold are housed,
• wherein a relationship in magnitude between a first clearance which is a clearance between the hole and the second neck part and a second clearance which is a clearance between the hole and the first neck part is determined according to a relationship in magnitude between a first distance which is a distance between a center of curvature of the lower-surface forming surface and an outer diameter height line and a second distance which is a distance between a center of curvature of the upper-surface forming surface and the outer diameter height line,
• wherein the outer diameter height line is defined as a line passing the side surface of the optical element at the half height of the side surface and orthogonal to a direction of the hole.