In order to suppress image ripples of the uncooled infrared detector, which is caused by the bias voltage noise bought by the un-uniform characteristic of column channel in the focal plane and changed varying with time, a hardware solution by structure extending is given including the principle and simulation of the design. As a material which is not sensitive to the environmental radiation temperature, the sapphire is used to extend the focal plane as the “background array”, while the readout circuit (ROIC) also extending same pixels. Then the noise value caused by the bias voltage can be calculated by averaging the value of the background pixels, which is subtracted from the sampling value of original array. Simulation results indicate that RMSE of one video image falls from 115 to 10 after 20 frames, while PSNR increases from 30 to 105. It can get expected IR images sustained at a uniformity level and the bias voltage ripples of images are suppressed effectively.