Keystone distortion correction system for use in multimedia projectors

Not Applicable A multimedia projector () includes an image processor () that forms an image on an image forming device (). Illumination reflecting off the image, propagates through a projection lens (), along a projection axis (), and lands on a projection surface () as a projected image (). An elevator mechanism () tilts the projection axis to position the projected image on the projection surface, which tilting causes keystoning of the projected image. In a first embodiment, an inclinometer () generates angle data indicative of a projection axis angle (). A controller () receives the angle data and coacts with the image processor to predistort the image to compensate for the keystoning. In a second embodiment, the elevator mechanism includes an elevator shaft () having teeth () that alternately pass and obscure light as the elevator shaft undergoes movement. An optical sensor () generates angle data proportional to a distance moved by the elevator shaft. The angle data are processed by the controller and image processor to predistort the image to compensate for the keystoning. In a third embodiment, the teeth are replaced by a rotary encoder wheel () that is rotatably coupled to the elevator shaft.