Spatial resolution and image processing for pinhole camera-based X-ray fluorescence imaging: a simulation study

Spatial resolution and image-processing methods for full-field X-ray fluorescence (FF-XRF) imaging using X-ray pinhole cameras were studied using Geant4 simulations with different geometries and algorithms for image reconstruction. The main objectives were: (1) calculating the quantum efficiency curves of specific cameras, (2) studying the relationships between the spatial resolution and the pinhole diameter, magnification, and camera binning value, and (3) comparing image-processing methods for pinhole camera systems. Several results were obtained using a point and plane source as the X-ray fluorescence emitter and an array of 100 × 100 silicon pixel detectors as the X-ray camera. The quantum efficiency of a back-illuminated deep depletion (BI-DD) structure was above 30% for the XRF energies in the 0.8–9 keV range, with the maximum of 93.7% at 4 keV. The best spatial resolution of the pinhole camera was 24.7 μm and 31.3 lp/mm when measured using the profile function of the point source, with the diameter of 20 μm, magnification of 3.16, and camera bin of 1. A blind deconvolution algorithm with Gaussian filtering performed better than the Wiener filter and Richardson iterative methods on FF-XRF images, with the signal-to-noise ratio of 7.81 dB and improved signal-to-noise ratio of 7.24 dB at the diameter of 120 μm, magnification of 1.0, and camera bin of 1.