PROBLEM TO BE SOLVED: To provide a radiation image detector which detects X-ray exposure by itself and reflects all the signal charge obtained by the exposed X-ray, on an X-ray image.SOLUTION: An electronic cassette comprises an FPD 21. The FPD 21 is provided with: an imaging panel 21a in which pixels 39 are arrayed in matrix a gate driver 51, serving as drive means to turn a TFT 42 on and off, which is for performing three operations including a reset operation of resetting dark charge by turning on the TFT 42, a storage operation of storing signal charge in respective pixels 39, and a readout operation of reading out the signal charge from the respective pixels 39 to signal lines 38 an exposure detection part 59 which detects the start of X-ray exposure according to leak charge leaked to the signal lines 38 while the TFT 42 is off and a control part 52 which controls the exposure detection part 59 to perform the exposure detection before the start of the storage operation and controls the TFT 42 to shift to the storage operation while keeping the TFT 42 in an off state, after the start of the exposure of radiation is detected.COPYRIGHT: (C)2012,JPO&INPIT【課題】X線の照射を自己検出するとともに、照射されたX線によって得られる信号電荷を全てX線画像に反映させる。【解決手段】電子カセッテはFPD21を備える。FPD21は、画素39がマトリクスに配列された撮像パネル21aと、TFT42をオンオフする駆動手段であり、TFT42をオンして暗電荷をリセットするリセット動作と、各画素39に信号電荷を蓄積させる蓄積動作と、各画素39から信号電荷を信号線38に読み出す読み出し動作の3つの動作を行わせるためのゲートドライバ51と、TFT42がオフされた状態で信号線38にリークするリーク電荷に基づいてX線の照射開始を検出する照射検出部59と、蓄積動作を開始する前に照射検出部59による照射検出動作を行わせ、前記放射線の照射開始が検出された後、TFT42をオフ状態のまま蓄積動作へ移行させる制御部52と、を備える。【選択図】図5
