Method for photographically producing light balanced dial indicators

Claim 1

FOR AN INTEGRALLY ILLUMINATED INSTRUMENT OF THE KIND INCLUDING (I) A FACE ELEMENT OF SUNSTANTIALLY PLANE ASPECT, (II) A BIOCK ELEMENT IN SPACED RELATION TO SAID FACE ELEMENT AND HAVING A PLANE SURFACE ADJACENT SAID FACE ELEMENT AND SUBSTANTIALLY PARALLEL THERETO, AND (III) AT LEAST ONE SUBSTANTIALLY POINT-TYPE SOURCE OF ILLUMINATION MOUNTED ON SAID BLOCK ELEMENT AND DIRECTED TOWARD SAID FACE ELEMENT, THE METHOD OF PRODUCING A FACE ELEMENT HAVING LIGHT TRANSMISSION CHARACTERISTICS ADJUSTED TO COMPENSATE FOR IRREGULARITES IN ILLUMINATION SO THAT SAID FACE ELEMENT HAS A SUBSTANTIALLY CONSTANT LIGHT TRANSMISSION OVER THE ENTIRE ILLUMINATED SURFACE THEREOF, SAID METHOD COMPRISING THE STEPS OF (1) PHOTOGRAPHING SAID PLANE SURFACE OF SAID BLOCK ELEMENTAND SAID POINT-TYPE SOURCE OF ILLUMINATION THROUGH A DIFFUSION FILTER TO PRODUCE A PHOTOGRAPHIC NEGATIVE OF THE AREA OF ILLUMINATION, SAID SOURCE OF ILLUMATION BEING LIT; (2) MAKING A HALF-TONE POSITIVE FROM SAID NEGATIVE; (3) APPLYING A FILMLIKE LAYER OF OPAQUE MATERIAL TO ONE BROAD SURFACE OF A PIECE OF FACE ELEMENT BLANK MATERIAL, SAID BLANK MATERIAL ITSELF BEING A MATERIAL PERMITTING LIGHT RAYS TO PASS THERETHROUGH; (4) APPLYING A LAYER OF PHOTOSENSITIVE MATERIAL TO SAID LAYER OF OPAQUE MATERIAL; (5) EXPOSING SAID LAYER OF PHOTOSENSITIVE MATERIAL THROUGH SAID HALF-TONE POSITIVE; (6) DEVELOPING AND WASHING SAID PHOTOSENSITIVE MATERIAL TO LEAVE UNPROTECTED THOSE PORTIONS OF SAID LAYER OF OPAQUE MATERIAL PREVIOUSLY POSITIONED BENEATH UNEXPOSED PORTIONS OF SAID LAYER OF PHOTOSENSITIVE MATERIAL; (7) ETCHING SAID LAYER OF OPAQUE MATERIAL TO REMOVE ONLY THE UNPROTECTED PORTIONS THEREOF; (8) APPLYING A THIN LAYER OF TRANSLUCENT WHITE PAIONT TO SAID BROAD SURFACE OF SAID PIECE OF FACE ELEMENT BLANK MATERIAL, AND (9) APPLYING A BLACK COATING OVER SAID LAYER OF TRANSLUCENT WHITE PAINT TO COVER ALL AREAS THEREOF EXCEPT THOSE CONSTITUTING THE INDICIA OF SAID INSTRUMENT FACE ELEMENT, SAID DIFFUSION FILTER IN STEP (1) BEING POSITIONED WITH RESPECT TO SAID POINT-TYPE SOURCE OF ILLUMINATION IN APPROXIMATELY THE SAME LOCATION AS THAT TO BE OCCUPIED BY SAID LAYER OF TRANSLUCENT WHITE PAINT UPON ASSEMBLY OF SAID INSTRUMENT.