Imaging system having an improved electrostatic yoke and method of making same

In an electron tube of the type comprising:

• an evacuated envelope having oppositely disposed ends and a longitudinal axis;
• a faceplate closing one end of said envelope;
• a target adjacent to said faceplate and disposed in a plane perpendicular to said longitudinal axis;
• an electron gun disposed within said envelope for generating and directing an electron beam;
• and
• an electrostatic yoke within said envelope for generating a variable substantially uniform electric field within said envelope to deflect said electron beam along two coordinates, the improvement wherein
• said electrostatic yoke comprising a first conductive layer bonded to an interior surface of said envelope and a second conductive layer overlying said first layer and being in contact therewith, said first layer having a thickness within the range of about 500 to 1000 .ANG. and said second layer having a thickness within the range of about 800 to 1500 .ANG., said first and second layer including two pairs of interleaved electrodes.

A method for forming an electrostatic yoke on an interior surface of a glass envelope comprising

• (a) providing a substantially uniform first layer of a first conductive material which is bonded to said interior surface,
• (b) providing a substantially uniform second layer of a second conductive material over said first layer,
• (c) forming a photoresist film on said second layer
• (d) exposing to light portions of said photoresist film,
• (e) removing said exposed portions of said photoresist film by means of an aqueous solution of a photoresist developer to expose portions of said second layer, and
• (f) removing said exposed portions of said second layer and said underlying first layer.