CALIBRATION AND CORRECTION OF SPATIAL DISTORTIONS IN 2D DETECTOR SYSTEMS

Many photon and other radiation 2D detection systems introduce spatial distortions into recorded data. As long as these distortions are to some degree repeatable it is possible to use a grid of holes of known positions to illuminate the detector and calibrate the distortion. Knowledge of this distortion can be used to correct subsequent images. Aspects of calibration grid design are discussed with the aim of achieving optimum results. Cross-correlation with known hole functions is proposed as a method for estimating grid peak centres giving optimum accuracy and efficiency. Strategies to search efficiently complete grids are also presented. Where a physical model of the distortion process is lacking or inadequate, bi-cubic splines are as suitable interpolating functions for defining approximate spatial distortion functions. Bi-cubic splines allow both adequate flexibility to describe arbitrary distortions and, most importantly, to allow efficient calculation for the correction of data. Calibration and correction algorithms have been developed and applied to 2D detector systems. Sample results are presented.