Off-axis electron holography without Fresnel fringes

A new method for forming an electron hologram without Fresnel fringes caused by an electron biprism is presented. Adding a fine filament to the ordinary setup for off-axis electron holography directly prevented Fresnel diffraction at the electron biprism and eliminated 70% of the phase error due to the Fresnel diffraction. This made it possible to obtain a hologram having uniform interference fringes, and to reconstruct a clear phase image of a weak electric-field.