| 摘要 |
PURPOSE:To detect surface deficiency accurately by automatically detecting a reference value for each object to be inspected and adding several levels for detection of defects thereto to set the threshold level. CONSTITUTION:An output voltage from a photoelectric converter 14 while one cycle is made at the position of radius r is converted into digital from anaglog to be written into a memory section 24. Then, a CPU section 25 determines the mean VA of all data (X1, X2... and Xn) and adds certain levels L1, L2 and L3 set thereby to the mean VA to set threshold levels T1, T2 and T3. All data are compared with the threshold level T1(=VA+L1) to detect the smallest defect (less than 1.0mum) and the data larger than the threshold level T1 is determined to be deficiency data. Furthermore, the data are compared with the threshold levels T2 and T3 and the data larger than these threshold levels T2 and T3 are determined to be deficiency data. Thus, the data are classified by the sizes. |
