Spatial correction of solid-state semiconductor imaging detectors in x-ray range (abstract)

Abstract

The images which are obtained using solid-state semiconductor detectors (charge-coupled devices and photodiode arrays) in the x-ray region in the regime of integrating detectors with the accumulation of the charges of plural events in cells, have specific distortions caused by a diffusive propagation of photogenerated minority carriers. Due to the peculiarity in the corresponding point-spread function, these distortions do not worsen the geometrical resolution (i.e., at a sufficiently high frequency of the spatial discretization, any images, however close, of delta functions are distinguishable), but they turn out to be very significant for the determination of the configurations, sizes, and brightnesses of the objects. Thus, the elaboration of techniques for reconstruction of the initial undistorted images becomes an urgent problem. In this work we describe experimental results on the correction of the images obtained under various conditions. The correction was performed in digital form by a microcomputer using a fast Fourier transformation of the data of the image being processed and the measured point-spread function. In a series of cases, nonlinear adaptive filtering was performed to limit high-frequency noise. A comparative analysis has been made of the registration of x-ray images by detectors with a flat (epitaxial devices) and with tilted (the devices on the single-crystal substrate), but being corrected, modulation transfer function. A linear model with an additive noise and a theoretical Fourier transfer function is used. In addition, the feasibility of an on-line reconstruction of the images in the case of degeneracy of the transfer function at a grazing incidence of the radiation has been investigated.