Jeffhs...
Here is an article describing DLP projectors. Both front and rear DLP units use essentially the same types of imaging components. The light path in a rear projector is "folded" by the use of mirrors, so that it "fits" into a small box behind the screen, rather than projecting across the viewing room. They do not use CRTs or "tubes".
http://en.wikipedia.org/wiki/DLP_projector
jr