Pattern scanning device for copying machines

The pattern scanning projection device for copying machines of the type in which a pattern is projected in a strip-like manner on an image recording support by means of a pattern scanning unit which is movable in guiding grooves and includes a plurality of scanning lens plates. The lens plates for the sake of uniform projection of partial images cooperate with aperture and/or image field diaphragms and with separating diaphragms. The lens plates are individually insertable into an objective housing which is detachable from the copying machine. The housing is assembled of two parts, one housing part being provided with mounting longitudinal grooves engaging one longitudinal edge of respective lens plates and the lens plates being centered in the longitudinal grooves by separate centering grooves and being secured in central position at one point only so as to permit longitudinal displacement due to mechanical or thermal stresses. The other longitudinal edges of the plates are covered by the other housing part which is preferably made of a plastic material. The entrance and the discharge ports of the objective housing are hermetically sealed by glass panes.