| 摘要 |
A sample or input image (8) of a part to be inspected is precisely aligned (10) with a reference image derived from known good parts, so that the two images may be compared on a point-to-point (pixel) basis. This alignment is performed by matching the two images using correlation and curve fitting, and then shifting one image into alignment with the other using cubic convolution (20). Differences between the two aligned images are potential defects in the sample image. The pixel values in the difference image are reduced with a position varying threshold (53, 55) such that pixels in image areas with high intrinsic intensity variability are not incorrectly classified as defects. The remaining non-zero pixels are modified by morphological techniques (60), and then analyzed (70). The analysis may specify such measures as the size, peak value, mean, etc. of pixel groups (defects). The part is classified as good or bad comparing these measures to allowable tolerances. |
