| 摘要 |
Atmospheric scanning electron microscope achieves a wide field of view at low magnifications in a broad range of gaseous pressure, acceleration voltage and image resolution. This is based on the use of a reduced size pressure limiting aperture together with a scanning beam pivot point located at the small aperture at the end of electron optics column. A second aperture is located at the principal plane of the objective lens. Double deflection elements scan and rock the beam at a pivot point first at or near the principal plane of the lens while post-lens deflection means scan and rock the beam at a second pivot point at or near aperture at the end of the optics column. The aperture at the first pivot may act also as beam limiting aperture. In the alternative, with no beam limiting aperture at the principal plane, maximum amount of beam rays passes through the lens and with no post-lens deflection means, the beam is formed (limited) by a very small aperture at or near-and-below the final lens while the aperture skims a shifting portion of the wide beam, which is physically rocked with a pivot on the principal plane but with an apparent pivot point close and above the aperture, all of which result in a wide field of view on the examined specimen. |
