Spatial filtering with a photographic replica of the Fourier transform of a half-tone picture

Spatial filtering of the Fourier transform of a newspaper picture is achieved using a photographic negative of the Fourier transform generated by illumination of a small portion of the object. The results show improvement over those of simple pinhole spatial filtering. Also described is the use of photographically reduced array of dots as a spatial filter, giving slightly inferior results but greater flexibility of use. The optical system used incorporates a 2 mW He-Ne laser as the source.