| 摘要 |
PURPOSE:To improve the accuracy of determining the roughness of the surface of a material without exerting any adverse influence thereon, by projecting the light passed through or reflected on a fine pattern on the surface of the material to form an image of the pattern thereon, moving the material so as to set an image of the pattern, formed on a pickup unit, in agreement with the image of the pattern formed on the surface of the material, and measuring the amount of displacement of the material thus moved. CONSTITUTION:An image of a projection object 2 formed on a material 4 to be measured is also formed on a pickup surface 61 of a pickup unit 6. A projection optical system 3 and a pickup optical system 5 is arranged such that the image formed on the material 4 and the image on the pickup surface 61 agree with each other. A detection circuit 7 receives a pickup signal from the pickup unit to determine the position of the material 4 with respect to a focal point of the images referred to above. A focusing fine adjustment means 94 is driven by a drive circuit 8 on the basis of a signal of determination from the detection circuit 7, to bring the material 4 to a focal point. At this time, the number of pulses from a motor for use in driving a stage 10 is counted in the drive circuit 8. Thus, the amount of vertical displacement of the stage 10 is calculated. The stage 10 is moved at a low speed in the horizontal direction as well. Variations in roughness of the surface of the material 4 can be determined with reference to the above calculated value. |
