Minimization of the Projector Focal Length of the Double Air Gap Electromagnetic Lenses

An electromagnetic projector lens of double air gap with identical four poles and single coil has been designed. The projector focal length has been minimized to its lowest value, in order to obtain higher magnification and resolution by reducing the air gap width and the axial bore diameter. The single coil was divided in to two coils of equal area and number of turns. It was found that the projector lens properties for the single coil in comparison with that of the double coils were identical. Moreover, the radial and spiral distortions were reduced at the minimum value of the projector focal length when the lens of double air gap was used and the direction of the current was reversed, which led to attaining this lens the best image formation.