[en] The collimator consists of a base body ending in a cylindrical adapter on the rear side, with a bayonet closure groove. The adapter houses a safety catch with a pin and a flexible element, fitted to the rear side of the radiation source holder. The holder is inserted in the shielded part of the duct, in the cylindrical base body axis. The front part of the base body features a lined opening for a rotary closure with a collimation orifice, normal to the duct. The rotary closure is provided with pins and a safety catch. The lined opening is covered with a removable lid with securing stops. The front side of the cylindrical casing houses a membrane. The rear side of the casing features a cylindrical guide surface with pins for filling cover attachment. The cylindrical casing adapter is covered with a dust guard. The collimator is designed for level inspection but can also be used where safe beam collimation in undesirable directions is necessary. (M.D.). 2 figs