Dynamic compensation of non-linear electron beam landing angle in variable axis lenses

A method for correcting deviations from telecentric deflection in an electron beam projection/deflection system, comprising the steps of

• establishing values for coefficients A, B and C in the equation:
• .DELTA.I.sub.x,y =(I.sub.x.sup.2 +I.sub.y.sup.2)[Ax(I.sub.y -I.sub.x)-(I.sub.x.sup.2 +I.sub.y.sup.2)(BI.sub.x,y +CI.sub.y,x)],
• wherein .DELTA.I.sub.x,y is a correction current at address x, y and I.sub.x, I.sub.y, I.sub.x,y and I.sub.y,x are current values corresponding to x and y addresses,
• determining correction values for deflection currents corresponding to an address and said values of A, B and C, and
• correcting said deflection currents by the amount of said correction current values.

An electron beam projection/deflection system including

• a deflection means for deflecting said electron beam in response to at least one deflection current applied thereto,
• a means for developing said at least one deflection current in response to an address,
• a means for providing correction values in response to said address, said correction values being approximately defined by a solution of the equation:
• .DELTA.I.sub.x,y =(I.sub.x.sup.2 +I.sub.y.sup.2)[Ax(I.sub.y -I.sub.x)-(I.sub.x.sup.2 +I.sub.y.sup.2)(BI.sub.x,y +CI.sub.y,x)],
• wherein .DELTA.I.sub.x,y is a correction current at address x, y and I.sub.x, I.sub.y, I.sub.x,y and I.sub.y,x are current values corresponding to x and y addresses,
• means for correcting said at least one deflection current in accordance with said correction value to derive a corrected deflection current, and
• means for applying said corrected deflection current to said deflection means.