METHOD FOR SCANNING LINEAR FOCUS CURVE

PURPOSE:To shorten a measuring time by scanning a position on which the existence of a defect is supposed like a band with a certain width along an optional curve passing the position by means of a linearly focused optical beam. CONSTITUTION:An optical beam 1 is expanded to uniform light flux 2a having a fixed diameter parallel with the optical axis by a beam expander 2. An optical beam 3a passing a cylindrical lens 3 is linearly focused on the surface of a sample 6 to be measured as a straight projection image 20. When a rotation stage 7 and an X-Y stage 4 are controlled and driven by a microcomputer, the projection image 20 of the linearly focused optical beam 3a scans the surface of the sample 6 along an optional curve 21 so that the image 20 is always vertical to the tangent 22 of the curve 21. Consequently, the object can be scanned like the band with the prescribed width only by one scanning operation.