Abstract: This invention concerns an apparatus for detecting the presence of faults in a translucent container of the kind comprising a scanning zone in which a translucent container is rotated while being repeatedly scanned by a spot beam of light in a direction parallel to the axis of rotation of the container, a light collection apparatus being arranged to receive light from the beam after passing through the container.The light collection apparatus comprises a rectangular matrix of photosensitive devices disposed behind a light-diffusing screen upon whose front surface the light from the scanning beam falls after passing through the container. A rectangular grid of thin white walls is sandwiched between the screen and the photosensitive devices so as to define a plurality of boxes with a respective device being located at the rear of each box.