Abstract: Line-scanning equipment, especially for aerial photography of terrestrial scenes, has an infra red scanner which causes the scanning beam to sweep repeatedly across the scene in the direction at right angles to the direction of travel of the aerial vehicle. As the angle of departure of the scanning beam from the vertical increases the strip of the scene being viewed in any one scanning cycle widens progressively so that the total strip has the shape of a `bow-tie`. A mechanically-actuated shutter is provided to restrict the recorded image to only that part of the recording beam information which is derived from a parallel-sided ground area within the `bow-tie`; and a correcting lens is employed to ensure that the final image is parallel-sided.