| 摘要 |
PURPOSE:To accurately perform focusing and astigmatic correction with a simple device, by providing a small lens between an objective lens and intermediate lens and fixing a focus current value and astigmatic correction current value of the objective lens. CONSTITUTION:An objective lens 1, small lens 4, intermediate lens 2 and projecting lens 3 are arranged on the same axis from the side of a sample (a) in said order and respectively provided with coils 1a, 4a, 2a, 3a and yokes 1b, 4b, 2b, 3b. The lens 1 is controlled to a fixed current value to align an image face to an object face b1 of the lens 2 in case of maximum magnification and fix a position of the image face. Then in case of imaging at maximum magnification, an electric current is not conducted in the lens 4 but the image of the lens 1 is imaged in a position of the image b1 and the lens 2 is adjusted to a maximum current value and imaged. Then to decrease the magnification from this condition, the current value of the lens 1 is left as fixed, and the current value of the lens 2 is decreased, interlocking to this decrease, the current value of the lens 4 is increased to correctively image the image of the lens 1 to a position b2 by lens action of the lens 4. |
