backprojection

Backprojection is a computational technique for reconstructing images from projection data, essential to CT scans and other medical imaging.

The algorithm works backward from measurements taken at multiple angles to build a cross-sectional image of internal structures: The CT scanner uses filtered backprojection to generate detailed brain images.

The term also appears in film and video production, where backprojection means projecting an image onto a screen behind actors to simulate environments—a technique largely replaced by green screens.