Laser welding of an electron gun

A method for laser beam welding a strap conductor to an electrode of an electrode gun, the strap conductor for applying a voltage to a predetermined portion of the electrode, comprising the steps of:

• disposing a strap conductor at a predetermined position along a surface of the electrodes to be laser beam welded to the electrodes;
• providing a laser beam generator for generating, upon actuation, a laser beam for welding, the laser beam having a predetermined optical axis;
• providing a positioning light source for generating a positioning light beam having an optical axis bearing a fixed predetermined relationship to the optical axis of the laser beam;
• causing relative movement of the electrodes and strap conductor relative to the optical axes of the laser and positioning beams;
• causing said positioning beam to be incident on an edge of the surface of the electrode, the positioning beam being at least partially reflected therefrom;
• detecting reflected light obtained when said positioning light beam is reflected by the edge of the electrode from the point to be welded, light reflected from portions of the electrode other than the edge being stopped by a pin hole aperture;
• stopping said relative movement in response to the detection of the reflected light;
• and
• actuating the laser beam generator so as to expose a welding point of the strap conductor to the laser beam for welding in response to the detection of said reflected light so as to effect welding of the electrode and strap conductor together.