An arrangement for illuminating documents in a document-processing system wherein a large number of documents are rapidly and continuously transported past one or more imaging stations, each station having, for illumination, an integrating structure which houses one or more cylindrical, integrating Lambertian reflecting/diffusing cavities, each cavity having one or more like light sources, so that each cavity generates and projects a highly intense, highly uniform and highly diffuse beam of illumination, while incorporating imaging camera means and optical guide means to couple the illumination beam to the face of the documents at the imaging station and to couple the image of the document to the imaging camera.