A charged particle filter with an integrated energy filter, in which the charged particle emitter, the focusing electrodes, and the deflection electrodes are arranged round a straight axis. Where most energy filters used have a highly curved optical axis, and thus use parts with forms that are difficult to manufacture, the source according the invention uses electrodes surrounding a straight optical axis. A beam of charged particles can be deflected quite far from the axis showing respectable energy dispersion at an energy selecting slit without introducing coma or astigmatism that cannot be corrected, provided that some of the are formed as 120°/60°/120°/60°. Such electrodes can be attached to each other by gluing or brazing of ceramic, and then series of a highly concentric bores can be formed by, e.g., spark erosion.