A low-power digital readout integrated circuit (DROIC) for silicon diode uncooled infrared focal plane arrays (IRFPAs) is presented. The DROIC adopts a 14-bit column-level extended-counting analog-to-digital converter (ADC) based on a cascade of a coarse continuous-time Σ-ADC and a fine single-slope ADC. While the weak detector signal is integrated, the coarse conversion is implemented by a feedback current-steering digital-to-analog converter (IDAC), which shortens the signal chain and reduces the bandwidth requirement for the op-amp, to reduce power consumption. Besides, the ramp signal of the fine conversion is generated locally by an additional column-level IDAC, which matches the coarse conversion IDAC to decrease the DNL. Also, a low-power non-uniformity calibration circuit is adopted to compensate the non-uniformity of the IRFPA and adjust the ADCfs input signal range. The DROIC with 1024 ×768 pixel array is fabricated in a 0.18μm CMOS process. The experimental results demonstrate the DROIC consumes 109mW. The noise is 1.7LSB and the equivalent input noise voltage of the column circuit is about 2.1μVrms. The INL and DNL are less than +6.1LSB/.4.4LSB and +0.40LSB/.0.38LSB, respectively.

This article establishes a behavior model for analyzing the temperature-dependent fixed pattern noise (TD-FPN) induced by pixel passive and active resistance for uncooled bolometric thermal imagers. A model-based two-point correction method is also proposed to compensate for the TD-FPN by using the ratio of passive and active resistance. An infrared imaging system based on a $640\times512$ readout chip is implemented to verify the proposed model and the model-based correction method. The comparison between the simulation and measurement results shows the model’s accuracy. The residuals after the model-based correction are within ±25 LSBs, which is considerably lower than the traditional method’s residuals. Due to the low residuals, the spatial noise equivalent temperature difference (S-NETD) is less than 100 mK within the temperature range of [−40 °C to 80 °C]. The proposed model and the correction method enable uncooled bolometric thermal imagers to achieve low-cost and wide-temperature-range shutter-less operation.

This paper presents an uncooled infrared imager with flicker noise reduction, which is realized by the proposed phase difference modulation (PDM) method. The PDM method makes noise transfer function (NTF) generate a series of notches to reduce flicker noise. To realize PDM, a high-speed sub-frame readout circuit is proposed. The readout circuit has been manufactured and the output data is processed with FPGA. The measurement results show that the flicker noise power in the frequency range above 10Hz is reduced by 42% compared with traditional method at 60fps full image output rate, and the noise equivalent temperature difference (NETD) is reduced from 40mK to 34mK.

TEC-less bolometric imagers have the advantages of size, weight, power, and cost (SWaP-C). However, the imagerfs responsivity drifts dramatically with the substrate temperature, resulting in scene dynamic range (DR) degradation. This brief presents a 120∘C operating range TEC-less bolometric imager with ultra-low responsivity drift. The proposed imagerfs low responsivity temperature coefficient is obtained by summing the positive and negative temperature coefficients. In the readout circuit, a poly resistor and a bolometer resistor are used in series as the feedback resistor of the pre-amplifier to accomplish the above summing. The proposed readout circuit is a low-cost improvement and hardly increases the complexity. A 12 μm pixel pitch 640×512 resolution vanadium oxide (VOx) bolometric imager is implemented for verification. Measurement results show that the responsivity drift is less than 20% within the 120∘ temperature range, while the drift is higher than 90% without compensation. The proposed imagerfs measurement noise equivalent temperature difference (NETD) is 45 mK, demonstrating good NETD performance. The proposed imager is suitable for TEC-less wide temperature range low SWaP-C applications.