Abstract: An inspection machine for inspecting the outer surface of a vertically standing container comprising a transparent convey for conveying a vertically standing container through an inspection location. The support conveyor includes a diffuser plate located to be beneath a conveyed container at the inspection location. A beam of collimated light is directed vertically downwardly towards the diffuser plate, and a two-dimensional camera axially views the bottom of the container above the diffuser plate, and the image is processed to evaluate the circumference of the container.