A measurement system (1) has robotic system (3) mounted over a base plate (2) which provides a vertical height reference. In the optical head (8), a CCD camera (17) is adjustable to be pre-set in height. The optical head (8) also has an upper light source (18) comprising LEDs and a lower light source (25) comprising a white fluorescent lamp (26) for lateral component illumination. An air flow system (45) directs cooling air in a swirling motion around the tube. An image analysis computer (10) automatically performs various tests to co-ordinate optical and mechanical operation.