An optical system projects an enlargement of an image of an object surface on a screen inclined relative to the object surface. The optical system includes an afocal first lens unit including a diaphragm and at least a second lens unit. The optical axis of the afocal system is not collinear with...http://www.google.es/patents/US5709445?utm_source=gb-gplus-sharePatente US5709445 - Oblique projection optical system
