A readout apparatus and method for processing spatially distributed signals is disclosed. The readout apparatus and method may reduce/eliminate the impact gain variations among a plurality of sensing channels. This is done by continuously varying the dispersion properties of a signal distribution device, which may induce a spatial shift of the signal distribution during data acquisition, allowing the distributed signals to move across the sensor area. Shifting of the distributed signals may occur multiple times, hence eliminating the impact of gain variation across the sensor array. The accumulated data may be re-assembled subsequently to complete the readout operation.