Patent Number: 
Section: claims

1. An electron column comprising:an electron emission source, anda single lens for performing functions of a source lens, a focusing lens, and a deflector simultaneously,wherein the lens consists of:an upper lens layer configured to function as an extractor for inducing emission of electrons from the electron emission source;a central lens layer configured to perform functions for focusing and deflecting electrons from the electron emission source; anda lower lens layer configured to perform a focusing function that causes electron beam focused on a sample and limits electrons from the electron emission source so as to form an effective electron beam. 2. The electron column as set forth in claim 1, wherein the electron column is a multiple electron column. 3. The electron column as set forth in claim 2, wherein the multiple electron column is monolithically fabricated. 4. The electron column as set forth in claim 3, wherein the electron column is a multiple electron column. 5. The electron column as set forth in claim 4, wherein the multiple electron column is monolithically fabricated. 6. The electron column as set forth in claim 1, wherein the central lens layer of the single lens comprises one deflector-type lens layer, and the deflector-type lens layer is located between the upper and lower lens layers. 7. The electron column as set forth in claim 6, wherein the deflector-type lens layer comprises a plurality of regions all of which are bordering an electron-passing-through hole, and separate voltages are applied to each of the regions which are insulated from each other by insulating portions. 8. The electron column as set forth in claim 7, wherein the electron column is a multiple electron column.