| 摘要 |
1,044,056. Electron-beam apparatus. UNITED AIRCRAFT CORPORATION. March 18, 1964 [March 23, 1963], No. 11336/64. Heading H1D. [Also in Division G1] In electron beam apparatus for working material, e.g. for milling, cutting, soldering, brazing or drilling, the current flowing through the focusing lens is adjusted automatically to obtain an optimum focusing position for the beam relative to the workpiece by measuring the working distance between the lens and the surface of the workpiece continuously and adjusting the focusing current accordingly. As shown, an electron beam from a gun 1 is focused by a magnetic lens 14 on to a workpiece 16, the optical bright spot thus formed by the beam being viewed by a pair of photo-cells 27, 28 through an optical system consisting of lenses 22, 29 and a mirror 26, a coinciding double image being produced in the plane of the photocells. A motor 24 controls the axial displacement of lens 22 and also the control member 32 which controls the lens current supply. A filter 30 placed in the path of one of the beams ensures that when the two images deviate from the central line between cells 27, 28, one cell is illuminated more than another, thus actuating the control system. |
