Resolution and Noise Properties of CMOS and CR Digital Radiography Systems

Due to development of computer technology and image processing, conventional industrial radiography has changed to digital radiography system. In this study, two types of industrial digital radiography (IDR) modules for non destructive testing (NDT), namely complimentary metal oxide semiconductor (CMOS) with 50 μm pixel pitch and computed radiography (CR) with 25 μm pixel pitch have been evaluated for NDT applications. The modulation transfer function (MTF) and noise power spectrum (NPS) measurement and calculation were adapted in order to evaluate the image quality of IDR images. From the measurement and calculation, the averaged MTF for CR and CMOS at 20% modulation are 4.48 cycles/mm and 2.83 cycles/mm, respectively. NPS measurement and calculation show that CMOS produced higher noise than CR. The CR system has lower and more stable NPS but has lower modulating capability at 20% compared to the CMOS system. The study shows that in order to perform NDT by using the evaluated modules, the user must know the true capability of system and how it is designed for specific application and discontinuity ditection.