Self-heating compensation in uncooled microbolometer read-out without using IR-shielded (blind) references

In this paper, a self-heating compensation method for uncooled microbolometers is presented. In this method, unlike the conventional use of IR-shielded (blind) references, the current from active sensors adjacent to each other are used to compensate for the undesired self-heating effect. Eliminating the need for IR-shielded references can simplify the fabrication process, resulting in lower costs. Moreover, using the adjacent sensor as the reference makes the read-out circuit insensitive to parameter mismatches in the sensor array. The thermal offset effect due to limited cooling time is also investigated in this paper. It is shown that the proposed structure can completely cancel the thermal offset effect. The proposed read-out has been designed in the standard 0.18-mu m CMOS technology considering an array with 352 x 288 pixels. The simulation results show that the proposed blind-less structure can achieve 25% more compensation than the common differential blind-based circuit in the presence of 20% resistance mismatch and 10% thermal constant mismatch.