Traditionally, optical devices have served to enhance the capability of human eyes to see smaller or distant objects better, to improve the precision of some measurements or to make other kinds of measurement possible. More recently, new optical and opto-electronic devices, sometimes in conjunction with computers, have made possible optical systems that function without the intervention of human beings. They are capable of executing the key step of drawing conclusions from "scenes" automatically, often without a conventional "image" even being formed. This kind of automation adds increased speed and reliability to the advantage that optical techniques usually have in being non-contacting (not to mention non-destructive). These factors now make optical techniques suitable for use directly on the production line. 100% on-line inspection for quality control is one such use. Making pertinent measurements further upstream - to control the process - can be even more useful than automated quality control at the end of the line, which only sorts scrap from good production without affecting the amount of scrap made.