A method, device, and inspection line for optically reading portions in relief on a side wall of a container, includes using a light source to light a portion of interest with a peripheral incident light beam comprising non-parallel radial light rays and using specular reflection of the beam on the portion of interest and on the portions in relief through an optical element to form a plane image in the field of view of a two-dimensional photoelectric sensor. The image received by the sensor is processed in order to detect the portions in relief to cause the light source that provides the peripheral incident light beam to move relative to the optical element in translation along the direction of a theoretical central axis to modify the contrast of the image received by the sensor between zones of the image that correspond to the portions in relief and adjacent zones.