of the disclosure A method and a device for the control of a joint between a first element and a second element. The first element preferably is an end element of a container and is inserted in an opening in said container such that a rim is formed around the opening and includes a joint. The rim allows the placement of a radiation or wave energy transmitting source at one side thereof and a detector device at the other side. The radiation or wave energy source has a capacity of penetrating, preferably fully, the rim and illuminating said rim by a small dot, which is scanned crosswise the width of the joint by a scanner device. The container is rotated around an axis and the detector device registers the characteristics of the radiation that passes the joint and/or is reflected at the joint and which originates from a repeated "point illumination of the joint". By placing the detector device at a sufficient distance from the rim there is obtained a magnifying effect in the detector, which allows the detection
