Gamma-rays camera is mainly used in image diagnostics of intense pulse radiation sources. The spatial resolution of the camera was measured on a 60Co gamma-rays source with edge method. The spatial resolution MTF (modulation transfer function) at the 10% intensity was about 2 lp/mm and the maximal single-noise ratio (SNR) of the camera was found to be about 5:1. In addition, the spatial resolution of the camera was measured with pulse X-rays with 0.3 MeV in average energy and exclusion of effects of secondary electrons from consideration. Accordingly, the spatial resolution MTF at the 10% intensity was about 5lp/mm, verifying effects of secondary electrons induced by 1.25MeV gamma-rays in the scintillator upon the spatial resolution. Based on our analysis, dispersion sizes of secondary electrons in the scintillator are about 0.4 mm∼0.6 mm. Comparatively, as indicated by detailed analysis of spatial resolutions of the MCP image intensifier and CCD devices, both have little effect on the camera's spatial resolution and could be well neglected.
The rising demand for digital imagers has resulted in the push to reduce pixel size while increasing imager sensitivity, which in turn, results in an increasing rate of defects that develop in the field. Research has shown that “Hot Pixels” are the most common type of defects in modern digital imagers, with their number in a given imager increasing over time. In our previous studies we had developed an empirical formula to project the growth rate of hot pixel defects in terms of defects/year/mm2. We discovered that hot pixel densities tend to grow via a power law of the inverse of the pixel size raised to the power of about 3. This paper explores the effects on defect growth rate, of reducing pixel sizes even more, specifically in cell phone imagers. Due to lack of noise suppression algorithms in these imagers, we have developed specialized procedures for analyzing the collected dark frame data. We also ensure that hot pixel detections in cell phone cameras are statistically significant within the error margins. Our current results confirm the accelerated growth rate for this small pixel range, emphasizing the need for caution by designers and further study in this area of defect development.