an apparatus for controlling the position of a screen pointer for an electronic device having a display screen includes a light source for illuminating an imaging surface , thereby generating reflected images . the apparatus includes a motion transducer . a lens receives the reflected images and directs the reflected images onto the motion transducer . the motion transducer includes an electronic shutter for controlling the amount of time that light is collected for image frames . the motion transducer is configured to generate digital representations of the reflected images . the motion transducer is configured to generate movement data based on the digital representations of the reflected images . the movement data is indicative of relative motion between the imaging surface and the motion transducer . a controller coupled to the light source turns the light source on only during the time that light is being collected for an image frame .