TW200620145A - Imaging systems for image acquisition and for defect detection, location, and analysis - Google Patents

Abstract

Described are autofocusing algorithms and system implementations for machine inspection applications. The disclosed algorithms depend neither on the type of image (visual, infrared, spectrometric, scanning, etc.) nor on the type of image detector. Disclosed image filtering techniques, image focus measure functions and adaptive velocity control methods can be used in computer-based inspection systems for many different types of cameras and detectors as well as for a variety of magnification levels. The proposed autofocusing system can utilize the existing imaging hardware of the inspection system and does not require any additional components. In some embodiments that employ infrared thermography, test vectors heat features of a device under test to produce thermal characteristics useful in identifying defects. The test vectors may be timed to. enhance the thermal contrast between defects and the surrounding features, enabling IR imaging equipment to acquire improved thermographic images. Mathematical transformations applied to the images acquired using the aforementioned autofocus algorithms provide enhanced defect detection and analysis. Some defects produce image artifacts, or "defect artifacts," that obscure, the defects, rendering difficult the task of defect location. Some embodiments employ defect-location algorithms that analyze defect artifacts to precisely locate corresponding defects.