Rotating collimator for determining the position of an element provided with sensors in an imaging system by X-ray

Device for X-ray imaging comprising a collimator having a rotating opaque region (22) to X-rays, this opaque region is traversed by a first slot (24) and a second slot (26) transparent to X-rays and extending in two different directions, the collimator for determining the position of a member with X-ray sensor in an imaging system