Variable shaped spot electron beam pattern generator
AssigneeU.S. Philips Corporation
InventorJames P. Beasley
Life of this patent
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Abstract
The electron beam 2 of the generator illuminates a first rectangular aperture 4 which is then imaged on a second rectangular aperture 10 by a magnetic lens 7 having reversible flux. The flux of the lens is chosen so that the focused image of the first aperture is rotated by 22.5+45n degrees where n=0,1,2 etc. One flux direction places the aperture image sides 8 parallel to the second aperture sides so that a rectangular shaped beam emerges. The other flux direction places the aperture image sides 8' at 45 degrees to the second aperture sides so that a triangular shaped beam emerges. A beam deflector 6 between the apertures allows rectangles or 45 degree isoceles triangles of a range of sizes to be produced. Thus triangles are produced without further generator components being needed.
Claims5
An electron beam pattern generator comprising an electron gun for emitting an electron beam, a first rectangular aperture for shaping the cross-section of the electron beam into a rectangular shape, an electron-optic lens focusing an image of the first rectangular aperture on the plane of a second rectangular aperture, a beam shaper deflection system for deflecting the image over the plane of the second rectangular aperture, means for projecting the electron beam emerging from the second aperture onto a target plane to form a shaped beam spot by overlap of the image of the first aperture on the second aperture, and means for scanning the shaped beam spot on the target plane to generate a pattern, characterised in that the electron-optic lens is a magnetic lens having reversible magnetic flux, in that the magnetic flux of the lens produces a rotation of the focused image of 22.5+45 n degrees where n=0, 1, 2, etc., in that one flux direction places the sides of the focused image of the first rectangular aperture parallel to the sides of the second rectangular aperture, the beam shaper deflection system being energisable so that the overlap of the images defines a rectangle, and in that the other flux direction places the sides of the focused image of the first rectangular aperture at 45 degrees to the sides of the second rectangular aperture, the beam shaper deflection system being energisable so that the overlap of the images defines a 45 degree right angled triangle.
Dependencies are inferred from the claim text.