Using a Projector to project to a very close screen (stage performance)

Im doing a school production of lord of the flies, and i want to use a projector to project certain images onto screens, and i want the projector to be really close to the screens so i dont get any shadows from people walking in front of it, but as we all know, when a projector is very close to a screen the projection itself is very small, how can i keep the projector close but get the video image/projection to be large. Thank You