Radiation source displacement measurement based on spatial resolution characteristics of active pixel sensors

In this paper, we leverage the high spatial resolution and strong sensitivity to charged particles of CMOS sensors by employing the weighted centroid method to determine the displacement direction and position of radiation sources, and we evaluate its effectiveness in locating moving radiation sources. Additionally, we investigated the morphological characteristics of α-particle response signals and analyzed the response uniformity and sensitivity of different sensor regions under the influence of a collimating structure. The results indicate that the α-particle response signal is characterized by a concentration of high pixel value pixels, with 3–8 pixels having pixel values between 150 and 255. The sensor regions demonstrated highly consistent responses during irradiation, indicating high sensitivity to changes in the radiation source position. The peak non-uniformity value in the irradiated central region did not exceed 0.125, the non-uniformity difference between regions at the same distance was less than 0.025, and the non-uniformity of each region gradually decreased with increasing distance from the irradiated center. Compared to the classical centroid localization method, the weighted centroid method significantly improved localization accuracy and stability. Localization error gradually converged as the number of accumulated frames increased, reaching approximately 8 pixels when the number of accumulated frames reached 100. Furthermore, when tracking the continuously moving radiation source, the predicted path closely matched the actual path, with the error in the predicted centroid displacement speed being less than 5% compared to the actual speed.