| 摘要 |
A method and apparatus for identifying the probable existence and location of defects within a workpiece. The workpiece is preferably wood exhibiting natural variations not the result of defects in the workpiece. The method takes into account the natural variations by segmenting the workpiece into a series of zones. Scanning of the workpiece is performed by an energy source and a detector array. The energy source can be an x-ray source to identify areas of high and low density within the workpiece. For each zone scanned, a long-term average of density is determined. Then for each zone a moving average is determined for localized positions, the moving average being a function of the average of density at the localized position and the long-term average. In this way, regional natural variations in the density of the workpiece bias the long-term average of the workpiece. The method can further include the step of smoothing the raw data with a low pass spatial filter to remove noise and natural variation from the energy source and the detector array. The apparatus includes an energy source, a detector array, and a computer configured to implement the method. The apparatus preferably includes an x-ray device having a plurality of calibration shutters which can be used to perform multi-stage calibration of the detectors and the energy source. The x-ray apparatus further includes collimators having chamfered edges in the apertures. |
