ontrolled by the control apparatus (for example, the Z, X and Y movers 15 to 17, the coarse Z positioner 20 and the detector 10) to enable the processor 25 to control operation of these components, the user input 31 consisting, in this example of a keyboard 31 a and a pointing device 31 b, and the user output 36 consisting, in this example, of a display such as a CRT or LCD display 36 a and a prin