The present invention is a projection device for a photocopying machine in which the original documents are moved during the photocopying process and which permits photocopying both of thick and of thin original documents. The projection means includes a focussing means which has a short focal length and is positioned to correctly focus the image of thin original documents which are brought to an exposure station and are only separated space-wise from the focussing means onto a photosensitive material, and a transparent block which, when a thick original document is copied, is automatically interposed between the focussing means and the exposure station and compensates the deviation in the path of image-wise light caused by the transparent carrier on which the thick original document is supported, whereby good resolution is achieved in photocopies of all types of original documents.