[en] This patent describes a dynamic focusing device for a penetrating radiation scanner. The device comprises: at least one detector means located in a position to receive, be illuminated by, and respond to penetrating radiation; a source of penetrating radiation; means for moving the source of penetrating radiation toward or away from the detector means; the detector means comprising individual detectors, septa for separating the individual detectors, the septa extending beyond the individual detectors far enough to reduce lateral penetrating radiation scatter and to cat shadows upon the individual detectors responsive to illuminations thereof from the penetrating radiation source; the detector means being in the form of at least one elongated module carrying the septa and individual detector. The elongated module having a pivot point at one end and a cam follower at the opposite end. The device further comprises movable focuser means having a cam surface on which the cam follower rides to swing the detector means about the pivot point in response to movement of the focuser means; and means for moving the movable focuser means in order to dynamically change the position of the module as a function of any change in the distance from the detector means to the source of penetrating radiation in order to reduce substantially to a minimum any shadow cast by the septa upon the detectors