The present invention relates to an X-ray detector (10) comprising two or more scintillator layers, comprising: a first scintillator layer (20); a second scintillator layer (30); a first photodiode array (40); a second photodiode array (50); and at least one light emitting layer (60). The first scintillator layer is configured to absorb X-rays from an X-ray pulse and emit light. The first photodiode array is positioned adjacent to the first scintillators layer. The first photodiode array is configured to detect at least some of the light emitted by the first scintillator layer. The second scintillator layer is configured to absorb X-rays from the X-ray pulse and emit light. The second photodiode array is positioned adjacent to the second scintillator layer. The second photodiode array is configured to detect at least some of the light emitted by the second scintillator layer. The at least one light emitting layer is 10 configured to emit radiation such that at least some of the emitted radiation irradiates the first photodiode array and at least some of the emitted radiation irradiates the second photodiode array.