Manufacture of diffraction gratings

Claim 1

IN PRECISIOIN APPARATUS FOR MARKING A MULTIPLICITY OF FINE CLOSELY SPACED PARALLEL LINES ON A FLAT WORKPIECE BY MEANS OF A MARKING TOOL, THE IMPROVEMENT WHICH COMPRISES: (A) A SUBSTANTIALLY VERTICAL CYLINDER AND AXIALLY TRANSLATABLE PISTON DEFINING A CHAMBER FOR CONTAINING FLUID, (B) A PORTION OF SAID PISTON EXTENDING FROM SAID CYLINDER AND SUPPORTING ONE OF SAID TOOL AND WORKPIECE, (C) A FRAME SUPPORTING THE OTHER OF SAID TOOL AND WORKPIECE, (D) THE FLAT OF SAID WORKPIECE BEING VERTICAL, (E) A MOVABLE TOOL DEFINING A STRAIGHT KNIFE EDGE TRANSVERSE TO THE PISTON AXIS IN OPPOSITION TO THE FLAT OF SAID WORKPIECE, (F) DISPLACEMENT MEANS FOR EFFECTING RELATIVE MOVEMENT OF SAID KNIFE EDGE INTO AND OUT OF MARKINGS ENGAGEMENT WITH THE WORKPIECE FLAT WITHOUT RELATIVE SLIDING THEREBETWEEN, (G) PISTON INDEXING MEANS FOR PERIODICALLY CHANGING THE VOLUME OF FLUID IN SAID CHAMBER TO EFFECT A PREDETERMINED AXIAL DISPLACEMENT OF SAID PISTON, WHEREBY SAID WORKPIECE IS RELATIVELY DISPLACED TRANSVERSE TO THE EDGE OF SAID TOOL, AND (B) SYNCHRONIZED DRIVING MEANS FOR ACTUATING SAID DISPLACEMENT AND INDEXING MEANS TO EFFECT ENGAGEMENT OF THE TOOL KNIFE EDGE AND WORKPIECE FLAT AT A TIME WHEN SAID PISTON IS STATIONARY.