| 摘要 |
1,006,389. Electric beam focusing apparatus. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. June 16, 1964 [June 19, 1963], No. 24914/64. Heading H1D. An electron-optical system for focusing a hollow, conical electron beam includes two rotationally symmetric coaxial lenses arranged one behind the other, and means for producing in the aperture of each lens a radial electric or radical magnetic field, for minimizing the spherical aberration of the system. The symmetrical arrangement of Fig. 7 consists of two similar magnetic lenses, each with an electrostatic radial field. The magnetic sheath 55 surrounding the coil 41 is interrupted by a non-magnetic ring 55, the polepieces of the lens being formed by cylinders 47 and 48 of magnetic material. Insulating ceramic ring 58 supports an annular electrode 57 having an insulated lead 59, and a central electrode 61 is supported by wires 62 and stops the centre of the lens aperture. The system may be used, e.g. in X-ray shadow microscopy, microanalysis, electronic drilling and welding, and oscillography, to reproduce an inaccessible image at an accessible position. Alternatively, a non- symmetrical arrangement, consisting of two dissimilar lenses, may be employed, to provide magnification or diminution, and instead of the electrostatic radial field, a magnetic radial field may be employed by the use of an axial rod of ferromagnetic material. The use of two systems of the above type, arranged in series along a common axis, is also referred to. |
