A light source, suitable for use in a high-speed, continuous transport microfilm imaging system, includes an LED emitter element thermally coupled to a heat sink and is mounted within a light source housing. A light output opening in the light source housing, further defined by a narrow width light transfer channel, defines a narrow width active illumination area on the microfilm media. An optical diffusion plate, providing for a randomized directional distribution of light emitted by the LED emitter element, is mounted within the light source housing in an optical path extending between the light output opening and the LED emitter element. A switched current source is coupled to the LED emitter element to enable strobed operation synchronous with the periodic operation of a line imaging camera. The LED emitter element can be construed as a linear micro-strip array of LED elements. A cylindrical lens can be place in the optical path between the LED emitter element and diffusion plate to narrow and increase the intensity of light incident on and transmitted through the diffusion plate.