CMOS analog-to-digital conversion for uncooled bolometer infrared detector arrays

Bias and signal conditioning techniques for uncooled resistance bolometer infrared detectors employ dc bias or various ac modulation and readout techniques. This paper describes a novel method of converting the absorbed incident radiation into digital signals by use of 0.8 micrometers CMOS oscillators in each pixel. Incoming radiation causes a resistance change in the bolometer which in turn results in a frequency shift. A concept of accurately readout out the digital signals from each pixel in the array is presented. Pixelwise A/D conversion and readout is demonstrated using a thin film semiconductor bolometer detector array. An NETD (Noise Equivalent Temperature Difference) of 0.1 K has been measured.