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Feasibility Of An Optical Beam Attenuator (OBA) For Optical Equalization In Camera-Based X-Ray Imaging Systems

We have investigated the feasibility of an optical beam attenuator (OBA) for image equalization in the optical light path of a camera-based x-ray imaging system. In our OBA design, a liquid crystal device (LCD) operated in transmissive mode is used to equalize low spatial frequencies. In most camera systems, compression of image dynamic range will result in improved performance. The advantages of optical equalization include bit compression for digital applications, video-rate equalization, detective quantum efficiency (DQE) improvement at high dose rates, and high-pass frequency filtration for film-based applications. A prototype OBA system has been constructed and installed in our DSA imaging laboratory. Equalized phantom images have been obtained which demonstrate improved visualization of structures in the darker regions of the image. The effect of the OBA on system limiting spatial resolution and system noise performance has also been investigated.