Phase-contrast electron microscope and phase plate therefor

A phase plate disposed in a substantially optical-axis position in the vicinity of a back focal plane of an objective lens of an electron microscope, comprising:

• a thin-wire shaped electrode covered with conductors adapted to expose portions lying in a region through which electrons corresponding to a focused electron beam of a direct wave lying in said substantially optical-axis position and to wrap said electrode therein with insulators interposed therebetween.

A phase-contrast electron microscope having a phase plate disposed in the vicinity of a focused electron beam of a direct wave formed on an optical axis adjacent to a back focal plane of an objective lens, said phase plate comprising a microelectrode covered with conductors adapted so as to expose portions through which electrons corresponding to the focused electron beam of the direct wave pass and to interpose said microelectrode between said conductors with insulators interposed therebetween, and a conductor for introducing an external potential into said microelectrode, said phase-contrast electron microscope comprising:

• an electric source for supplying the external potential to said microelectrode, and
• said conductors interposing said electrode therebetween being grounded.

A phase-contrast electron microscope having a phase plate disposed in the vicinity of a focused electron beam of a direct wave formed on an optical axis adjacent to a back focal plane of an objective lens, said phase plate comprising a ring-shaped microelectrode covered with conductors adapted so as to expose a ring inner surface through which electrons corresponding to the focused electron beam of the direct wave pass and to interpose said microelectrode between said conductors with insulators interposed therebetween, and a conductor for introducing an external potential into said microelectrode, said phase-contrast electron microscope comprising:

• an electric source for supplying the external potential to said microelectrode, and
• said conductors interposing said microelectrode therebetween being grounded.

A phase-contrast electron microscope having a phase plate disposed in the vicinity of a focused electron beam of a direct wave formed on an optical axis near a back focal plane of an objective lens and a biprism provided behind said phase plate, said phase plate comprising an electrode covered with conductors adapted so as to expose portions in a region through which electrons corresponding to the focused electron beam of the direct wave pass and to wrap said electrode therein with insulators interposed between said conductors, said phase-contrast electron microscope comprising:

• an electric source for supplying an external potential to said electrode,
• said conductors interposing said electrode therebetween being grounded, and
• said biprism being used to evaluate the effects of said phase plate prior to the observation of a specimen.

A phase-contrast electron microscope having a phase plate disposed in the vicinity of a focused electron beam of a direct wave formed on an optical axis near a back focal plane of an objective lens and a biprism provided behind said phase plate, said phase plate comprising an electrode covered with conductors adapted so as to expose portions in a region through which electrons corresponding to the focused electron beam of the direct wave pass and to wrap said electrode therein with insulators interposed between said conductors, said phase-contrast electron microscope comprising:

• an electric source for supplying an external potential to said electrode,
• said conductors interposing said electrode therebetween being grounded,
• said biprism being used to evaluate the effects of said phase plate prior to the observation of a specimen, said evaluation being carried out based on a change in image at the time that an electric potential for supplying a diffraction image focused onto an observing surface to said biprism is changed.