A facility for measuring the thickness of the wall of containers includes an optical system for collecting and focusing on the detection plane of a light sensor and light beams reflected by the outer and inner surfaces of the wall. An optical collecting and focusing system includes a first objective having is object plane located in the vicinity of the impact of the incident light beam with the wall, an at least translucent diffusing screen located in the image plane of the first objective, so as to physically represent the light beams collected by the first objective as hot spots (Ti), and a second objective including, the diffusing screen as an object plane and the light sensor as an image plane.