Pixel Dark Current Calibration Method to Reduce Dark Fixed Pattern Noise in Amorphous Silicon Bolometer-type Uncooled Infrared Image Sensor

In this paper, we propose a pixel dark current calibration method to reduce dark fixed pattern noise in an amorphous silicon bolometer-type uncooled infrared image sensor. This dark current calibration method utilizes an active pixel, a reference pixel, and a calibration circuit. The active and reference pixels were fabricated entirely from amorphous silicon. Even if amorphous silicon components with the same resistance are manufactured, there may be variations in resistance owing to process deviations during the manufacture of the amorphous silicon pixels. Dark fixed pattern noise due to resistance variations causes non-uniformity among the output voltages of the pixels. The operating principle of the pixel dark current calibration method to reduce dark fixed pattern noise is thus based on the subtraction of the averaged dark current of the active pixel from that of the reference pixel. The proposed pixel dark current calibration method is implemented by a chip consisting of an amorphous silicon bolometer pixel array, a calibration circuit, and column readout circuits. The entire chip was fabricated using a 0.11 μm CMOS image sensor process and its performance was evaluated.