Viewing optics for external-mount electron beam welders

In an electron beam welding machine consisting of:

• a vacuum chamber;
• an electron beam gun mounted upon said vacuum chamber;
• a means for directing an electron beam along a path from said electron beam gun to the inside of said chamber;
• a carriage mounted within said chamber and movable along two mutually perpendicular axes;
• a means for mounting on said carriage, workpieces to be welded along a seam by said electron beam;
• and an optical system mounted on said machine for viewing, from outside the chamber, the area to be welded on said workpieces, the said optical system comprising:
• a telescope including an objective and a focusing lens system, arranged along an optical axis which is perpendicular to the path of said electron beam and passes through the center of the said lens system;
• a pentaprism for bending the optic axis by 90 degrees mounted along the said optic axis, between the said objective lens and the path of the said electron beam;
• a means for supporting and rotating the said pentaprism in a plane perpendicular to said optic axis;
• a coherent fiber optics bundle having one end centered along the optic path and adjacent to the said focusing lens;
• a means for moving said focusing lens along the optic path so as to project the image of a desired area on a workpiece upon which the said electron beam can impinge;
• a means cooperating with the said means for moving said focusing lens for automatically rotating the said pentaprism in said plane so that it views an area on the workpiece upon which the said electron beam impinges, and which area is projected in sharp focus onto the said first end of the fiber optics bundle;
• and means for viewing the image which is transmitted to the opposite end of the fiber optics bundle.