Optical viewer and grinding wheel dresser

Claim 1

IN COMBINATION WITH A GRINDING MACHINE HAVING A TABLE, A GRINDING WHEEL, AND WORK-PIECE HOLDING AND ROTATING CENTER POSITIONED ON THE TABLE IN FRONT OF THE GRINDING WHEEL, AN OPTICAL VIEWER, COMPRISING, A FRAME MEMBER MOUNTED ON THE TABLE HAVING A RAIL PORTION EXTENDING LONGITUDINALLY OF THE TABLE AND SPACED VERTICALLY OF THE WORK-PIECE HOLDING AND ROTATING CENTERS; A LIGHT-TIGHT HOUSING SLIDABLY MOUNTED ON THE SAID RAIL PORTION; AN OBJECTIVE LENS SYSTEM MOUNTED IN ASSOCIATION WITH THE HOUSING A DEPENDENT POSITION AND FACED TOWARD THE WORKPIECE HOLDING AND ROTATING CENTERS AND GRINDING WHEEL, THE HOUSING HAVING A VIEWING SCREEN IN ITS FRONT WALL AND AN IMAGE PROJECTING SYSTEM, OPTICALLY ALIGNED WITH THE OBJECTIVE LENS SYSTEM; A REFLECTING MIRROR MOUNTED ON THE TABLE, BELOW THE WORK-PIECE HOLDING AND ROTATING CENTERS, IN OPTICAL ALIGNMENT WITH THE OBJECTIVE LENS SYSTEM AND FACED TOWARD THE REAR OF THE TABLE; AND A LIGHT SOURCE MOUNTED TO THE REAR OF THE TABLE IN OPTICAL ALIGNMENT WITH THE REFLECTING MIRROR, COMPRISING A VERTICALLY ELONGATED HIGH INTENSITY GAS DISCHARGE LAMP, A COLLIMATOR LENS, SPACED FROM SAID LAMP, TWO OPAQUE BLADES, MOVABLE TOWARD AND AWAY FROM EACH OTHER, POSITIONED BETWEEN THE LAMP AND THE COLLIMATOR LENS, THE BLADES HAVING OPPOSED EDGES THAT ARE TAPERED AWAY FROM THE BLADE SURFACE FACE TOWARD THE LAMP SO THAY PRESENT TWO RAZOR THIN PARALLEL STRAIGHT EDGES FACED TOWARD THE LAMP, AND MEANS FOR VARYING THE DISTANCE BETWEEN THE OPPOSED BLADES TO PROVIDE CRITICAL AND COLLIMATION OF THE PROJECTED BEAM IN A VERTICAL PLANE BETWEEN A POINT WHEREIN FRESNEL DIFFRACTION OCCURS ON THE VIEWING SCREEN, AND A POINT WHEREAT THE PERCENTAGE OF COLLIMATION NO LONGER PRODUCES A PENUMBRA-FREE SHADOW IMAGE ON THE VIEWING SCREEN.