Lens body tube

A lens body tube including at least one component to be fixed therein, comprising:

• at least one first recessed portion, each of which is recessed outward along the radial direction of the lens body tube on a part of the inner circumferential surface of the lens body tube, the at least one first recessed portion being arranged in the circumferential direction of the lens body tube;
• at least one second recessed portion, each of which is recessed inward along the radial direction of the lens body tube on a part of the outer circumferential surface of a corresponding one of the at least one component which is located such that the outer circumferential surface thereof faces the inner circumferential surface of the lens body tube, the at least one second recessed portion being arranged in the circumferential direction of the lens body tube;
• at least one insertion member;
• and
• at least one ring member, each of which is configured to be attached to the inner circumferential surface of the lens body tube to grip a corresponding one of the at least one component in the axial direction of the lens body tube inside the lens body tube,
• wherein each of the at least one first recessed portion is formed to have substantially a semicircular cross section,
• wherein each of the at least one second recessed portion is formed to have substantially a semicircular cross section,
• wherein each pair of the at least one first recessed portion and the at least one second recessed portion forms substantially a circular opening recessed along the axial direction of the lens body tube,
• wherein each of the at least one insertion member is formed of substantially a cylinder solid.
• wherein a corresponding one of the at least one insertion member is inserted into the circular opening along the axial direction of the lens body tube,
• wherein the lens body tube has a female screw portion on the inner circumferential surface thereof,
• wherein each of the at least one ring member is configured to be screwed together with the female screw portion on the inner circumferential surface of the lens body tube, and
• wherein each of the at least one ring member is configured to have contact with a corresponding one of the at least one insertion member in the axial direction of the lens body tube to prevent the one of the at least one insertion member from dropping out of the opening into which the one of the at least one insertion member is inserted.