| 摘要 |
PURPOSE: To detect the defects of a low contrast on a sample without receiving the influence of unequal lighting, etc., by determining differential values between the average of plural proximate pixels and a notice point from the television image signals formed by picking up the image of an object to be inspected and comparing these differential values and reference values. CONSTITUTION: A halogen lamp is used for an illuminating light source 37. Illuminating light turns back at a half mirror 38 via a condenser lens and illuminates the sample 34, for example, a magnetic head, on a stage 36 by Kohler's illumination. The reflected light from the sample 34 passes an objective lens 34 then the half mirror 38. This light is detected by a detector 42, for example, a TV camera. The respective focal lengths at the three points at which an arbitrary triangle shape is formable or the four points at which a rectangular shape is formable on the magnetic head are detected by a focus detector 33 when the sample 34 is mounted at a spring-like head arm as with the magnetic head. The magnetic head is leveled by moving a shifting stage towardθx andθy directions according to the deviation rates of the respective points to the focal positions. The deviation rates in the X, Y direction by the shifting are determined from the shifting rates and the distances between the focus detection positions of the sample and are corrected by moving the X-Y stage. Next, the detected image data are subjected to image processing by an image processing section 31.
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