Patent ID: 7118295

Claim:
An interchangeable lens which is the following second interchangeable lens used in a camera system including a first interchangeable lens, the second interchangeable lens, a first camera and a second camera, the interchangeable lens comprising: a protruding portion protruding from a mount reference surface toward an image plane, the protruding amount of the protruding portion being larger than that of the first interchangeable lens, and the second interchangeable lens having the same flange back as that of the first interchangeable lens, wherein the first camera includes a first wall portion inside its mount, the first interchangeable lens is mounted on the first camera through bayonet coupling, and the first camera prevents mounting on the second interchangeable lens by the protruding portion of the second interchangeable lens contacting the first wall portion, and the second camera includes a second wall portion provided at a position retreated from the protruding portion of the second interchangeable lens inside its mount, the second camera includes a bayonet lug are having the same shape and dimensions as a bayonet lug of the first camera, and the first and second interchangeable lenses are mounted on the second camera through bayonet coupling, wherein the protruding amount of the protruding portion of the second interchangeable lens is set, in a case where the second interchangeable lens has a specific phase relationship with the first camera, so that the protruding portion contacts the first wall portion, and the protruding amount of the protruding portion of the second interchangeable lens is set, in a case where the second interchangeable lens has a phase relationship other than the specific phase relationship with the first camera and an image plane side surface of a bayonet lug of the second interchangeable lens is in contact with the bayonet lug of the first camera, so that the protruding portion is away from the first wall portion.