| 摘要 |
<p>A method and apparatus for correcting the undeflected resting postion of an electron beam (36) which has been displaced from its previous resting position because of physical or positional changes in elements of the electron gun (32) which is generating the electron beam (36). The electron beam (36) is directed towards a detector (37) which determines the direction and amplitude of the deviation along mutually perpendicular axes (X-X, Y-Y) of the point of impingement of the electron beam (36) from a given reference point. The signals generated by the detector (37), in cooperation with a computer-controlled deflection system of the electron gun (32), cause the beam (36), to be displaced in a series of iterative steps to the reference point. The distance and direction of the beam (36) from its resting position to the reference point is maintained in the memory of the computer.</p> |
