◦ The holder plate of cage system has two types of addon methods which are side-in type and slide-in type. The side-in type can attach and detach the holder plate while the cage system are built. The slide-in type must be built in the cage system beforehand, but it is possible to firmly fix the holder plate to the cage (rod). ◦ The holder plate can slide through the rod (cage) in the direction of the optical axis. Even without using the stage, it can easily adjust focus on the lens and camera.