Soft-test/repair of ccd-based digital x-ray instrumentation

Abstract

Absfrncl Modern x-ray imaging systems evolve toward digifindim for reduced eost, foster time-todiagnosis ondimproved diagnostic eonfurmer. For the digitalx-ray systems, CCD (Charge Coupled Device) technology is eommanly used lo ddect and digitize optical x-ray i m g r This p p e r presents n novel sofr-lesUrepoir approach to overcome the defective pirelproblem in CCD (Charge Coupled Device)-based digital x-ray system through theoretical modeling and analysis of the testhepair process. There w e hw possible solulions lo cope with the defectivs pixel problem in CCD; one is the hard-repair approach mdanother is the proposed soJi-lesUrepoir oppronch. Hard-repair approach employs a high-yield, expensive reparable CCD lo minimize the impact of hard-defects on the CCD, which occur in the form of noise propagated through A/D converler lo LheJlome memory. Therefore, less work is neededlofilter andcorrect the image at the end-user level while if maybe exceedingly expensive lo proclice. On the other hand, theproposed sof-tesUrepoir approach is la detect ondtnlerote defective pixels a1 the digitized image level; thereby it is inexpensive lapmetice andon-line repair can be done for nom-interrupted service. I t tests the imnges to detect the deteclive pireis andfilter noire at the frame memory bve< and caches them in B flash memory in the conlroller for fulure repair, The controller cache keeps neeumubting all the nobe coordinates, and preprocesses the incoming image &la from the AID converter by repairing them. The proposed softlesffmpair approach *. pnrlierlarly devired to facilitate hnrdwore level implementalion uUimotdy for real-time telediagnosir. Porometrie simulation results demonslrale lhe speed and vinual yield enhancement by using lhe proposed opprooeh; thereby highly reliable, yet inexpensive sof-tesUmpoir of CCD-baseddigitalx-roy syrlems can be uUimotely realized.