| 摘要 |
PURPOSE:To detect height amount highly accurately with reduced number of imaging by predicting the wire signal strength of an image signal at an actual focus point and then correcting the quantity of illuminating light based on thus predicted wire signal strength. CONSTITUTION:A bonding wire 1 is imaged 22 at three focal points F1-F3, i.e., unfocused point, focused point, and most focused point, and the images are converted into digital signals 23 which are stored in an image memory 24. A wire image gradation predicting circuit 31 predicts the image signal strength at the focal point F3 of the wire image based on the wire image imaged at the focal point F1. The circuit 31 predicts 32 an optimal wire image profile having no saturable prediction value and corrects 14 the quantity of illuminating light of an illuminator 11 thus imaging the wire image again. Since the wire signal at the position F3 having highest wire signal strength is optimized not to be saturated, the wire images are not saturated at the positions F1-F3. This constitution prevents saturation of wire strength signal, minimizes the number of retry, and prevents erroneous detection of height due to saturation. |
