Current clinical mammographic imaging has been limited to screen/film, but advances in photodetector and x-ray converter technology has opened up the possibility of significantly improving mammographic screening with digital imagers. One limitation of some recently developed in direct detection imagers is a limited optical fill factor in the photodetector. A small fill factor reduces the amount of light collected from individual x-ray interactions in the screen. It can also lead to an overall reduction in the number of x-ray quanta detected. In addition, the fill factor usually decreases with an increase in photodetector resolution. To reduce these effects, we propose a technique for improving the effective fill factor of any indirect detection imager by incorporating focusing microlens arrays between the phosphor screen and the photodetector. In this investigation, we evaluate the light collection efficiencies of our proposed imager/microlens combination using Monte Carlo simulation and optical ray tracing.
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