Year
2005
Abstract
The StepScan software was developed by our group at Los Alamos National Laboratory to acquire digital radiographs using a Varian 3040 amorphous silicon detector array. The basic image size with this detector is approx. 30 cm by 40 cm. With the detector mounted on an X-Y scanner, StepScan is able to move the detector through a mosaic pattern and acquire larger composite images up to approx. 120 cm x 90 cm. We recently added upgrades to the StepScan software to allow stereo radiograph pairs to be acquired, analyzed, and viewed. To acquire a stereo pair, mosaic images are created using a fixed sample-detector geometry with the x-ray source in two different positions. These can be viewed as anaglyphs to give a stereo viewing effect with an ordinary monitor. More importantly, the coordinates of any identifiable point in both images can be extracted. One or more points can be combined to define primitive geometric shapes. A method for using free standing calibration fiducials to compute the two source positions in the detector's coordinate system is presented. This allows the source positions to be determined in a field setup without external measurements. The error in measured spatial positions has been estimated for an example geometry using a Monte Carlo technique and was found to be comparable to that obtainable using transits to measure the source positions. StepScan can be used to analyze TIF file image pairs acquired by any method, including scanned radiographic film.