| 摘要 |
A high speed magnetic focus lens develops a relatively large static magnetic force field which has radial symmetry and which varies along the axis of an electron beam and radially outwardly therefrom so as to focus off-axis electrons to the same focal point on a cathode ray tube screen, thereby producing a visible spot characterized by minimum distortion and aberration and therefor which is very small. The lens also develops a smaller dynamic field component which varies with beam deflection so as to maintain the beam in focus with minimum aberration, even though the beam is deflected through relatively large angles while moving over the screen. The static and dynamic elements of the lens are electrically isolated so as to minimize the time constant associated with dynamic focusing, thereby enabling the lens to focus a beam moving at high speed.
|
