Hardware and software corrections of the spatial distortions of position-sensitive detectors

Abstract

Possible causes of the spatial distortion encountered when using pierced resistive anodes for position-sensitive detection are discussed. An accurate map of the spatial distortion around a circular hole in a resistive anode is presented, which shows that the hole's effect is felt at distances up to three times its radius. The effect of load conditions on the detector's spatial linearity, as well as the distortions induced near the center of the detector due to penetrating electrostatic fields, are also discussed. In response to these points, alternative methods are described-in hardware and software-for the correction of distorted images. The hardware approach, which makes use of electrically programmable readonly memories, has the advantage of allowing real-time operation albeit with some loss in the precision of the intensities of the features within an image. One benefit of the software approach, beside the fact that it provides the best possible correction of the intensities, lies in the fact that all the information contained in the raw data is kept intact, which gives some latitude for future recalibration of the detector, or for emulation of a detector of another shape.

Using Powder Diffraction Patterns to Calibrate the Module Geometry of a Pixel Detector

“…Previous efforts to measure strains accurately using a 2D area detector showed that good calibration of the experimental geometry and distortion are essential [10]. The conventional methods [11][12][13][14][15] for calibration of earlier CCD detectors generally fitted smooth functions (splines or polynomials) to images of grid-like targets. The production of an accurate calibration artifact is problematic because machining tolerances are difficult to reduce below about 10 µm for a >150-mm-sized object.…”