subject to go from the front table 6 to the rear table 8 during scanning as will be further described below the housing 4 includes a well 9 having a bottom at which the opening 10 is disposed the well 9 advantageously allows the user to observe the test subject as it progresses toward the rear table 8 the scanner 2 is placed within a light tight enclosure 12 to prevent room light from contaminating the light transmitted through the test subject by the scanner the enclosure 12 is provided with light tight door 14 to provide access to the scanner 2 video cameras 16 are provided within the enclosure 12 to provide remote monitoring of the test subject during the scanning period light fixtures 18 provide illumination within the enclosure 12 not detectable by the scanner such as yellow or red light the enclosure 12 is advantageously small for example about 400 mm cube so as to not occupy so much space in a crowded laboratory where space is a premium a light tight access port 13 for cables and other lines is provided referring to fig4 and 5 the scanner 2 comprises a vertically rotating scanning head 20 comprising a rotating plate 22 mounted on a ball bearing 24 which mounts on a stationary hub 26 supported by a vertical structure 28 laser diode 30 and its controller 32 are carried by the rotating plate 22 the output of the laser diode 30 may be connected.