System of Measuring the Sub-pixel Edge of Linear CCD Based on Auto Focusing

In order to improve the precision, speed, integration and reliability of the linear CCD system, which was used to detect the sub-pixel edge of picture, a new digital system based on auto focusing was designed. The system captures the image of the tested work piece through a CCD, puts the image data into computer, gathers coordinate of tested edge of work by the method of digital image processing and auto focusing. In order to meet the need of rapid and efficient measurement, the author studies the extraction technique of the moving edge. Depending on the feature of system, suitable space gradient operator and time gradient operator of the extraction of the moving edge are chosen. The experimental results demonstrated that defects within 40 μm~1000 μm were inspected effectively by the CCD scanning defects inspection instrument, and Good agreement was shown between defects images real-time reconstructed and optical microscopic images not only in shape but also in gray.