| 摘要 |
PURPOSE:To increase the spherical and the chromatic aberration coefficients of an objective in which a sample is inserted in lateral direction by specifying the dameters of the holes and the diameters of the top surfaces of an upper and a lower pole piece to be different under the practical conditions of the distance between the pole pieces, the position of the sample and the taper angles of the pole pieces. CONSTITUTION:A side-entry-type objective in which a sample 6 is inserted in lateral direction, is constituted by installing pole pieces 4 and 5 integrated with a spacer 3 above a yoke 1 in which an excitation coil 2 is installed. The distance (S) between the pole pieces 4 and 5 is adjusted to not less than 5mm., the sample 5 is located Z0 over the center of the distance (S), and the taper angle (theta1) of the pole piece 4 is made larger than the taper angle (theta2) of the pole piece 5. In addition, when the diameters of the holes of the pole pieces 4 and 5 are (b1) and (b2) and the diameters of their top surfaces are (D1) and (D2), they are adjusted to satisfy the formulas of D1<D2 and b1<=b2<S. As a result, the spherical and the chromatic aberration coefficients of the lens can be decreased without increasing the diameter of the top surface of the pole piece, thereby enabling image observation of high resolution to be realized. |
