DC-controlled solid-state X-ray image converter

A thin solid-state X-ray panel of sandwich-type structure using photoconductive (PC) and semiconducting electroluminescent (EL) powder layers has been developed. The PC layer and the semiconducting EL layer are connected electrically in series. Both ac and dc voltages are applied across the combination. The X-ray sensitivity of the converter depends on the dc voltage drop across the PC powder layer and on input X-ray intensity. Gamma and input latitude of the converter performance are widely controllable by adjusting the dc voltage applied across the panel. The ac supplies excitation for the EL phosphor. The light output intensity at a low X-ray intensity level is substantially improved without deteriorating the picture resolution. For X-ray intensity of 30 mR/min, 80 kV peak, the converter produces light output about 800 times as bright as a conventional fluoroscope screen does, and Mo wire of 200-µm diameter is observed. However, seconds are required for image buildup and cutoff. Converted X-ray images using an experimental converter are also shown.