| 摘要 |
PURPOSE:To improve the precision of the adjustment of the optical axis of illumination light by forming a pattern which consists of grooves or projections in a symmetrical step shape on a sample surface, detecting the symmetry of the light quantity distribution of an image formed by the reduced or enlarged projection of an objective, and adjusting the optical axis of the illumination light so that the symmetry is maximum. CONSTITUTION:Light from a lamp 1 illuminates the pattern 12 for optical axis adjustment through a contactor lens 2, light guide 10, intermediate lens 11, half- mirror 3, and objective 4. Its reflected light forms an image on a linear image sensor 14 through the objective 4, half-mirror 3, and a cylindrical lens 13. Light intensity signals regarding respective parts of the sensor 14 are stored in a memory 18 through an AD converter 17 and further processed by an arithmetic circuit 19 to adjust the optical axis of the illumination system so that the symmetry of an image on a monitor 20 corresponding to the symmetry that the pattern 1 has is maximum. Thus, the adjustment precision of the illumination optical axis is improved. |
