Read-in IC with Current-programming Scheme for Improved Image Quality of Infrared Scene Projectors

Abstract

In this thesis, read-in integrated circuits (RIICs) with a current-programming scheme are proposed in order to improve the quality of the infrared (IR) images projected by infrared scene projectors. The unit cells in the array are designed to minimize the non-uniformity of the emitter current by compensating for voltage drops along the ground line and to circumvent fluctuations in the emitter current in the snapshot mode regardless of the matching properties of the sampling capacitors and MOS switches. A current output digital-to-analog converter (DAC) that converts the digital scene data to analog data currents is integrated on the same chip as the unit cell array for improved noise immunity. The current sample-and-hold array receives the output current of the DAC and delivers the scene data current to the unit cell array on a row-by-row basis. The RIIC is designed to provide both raster and snapshot modes of operation for users to select from depending on the operation mode of the detector under test. Two RIICs with a spatial resolution of 32 × 32 are implemented using a 0.18 $\mu m$ CMOS process. The experimental results demonstrate that the fabricated RIIC can output a maximum emitter current of 150 $\mu m$ A and compensate for a voltage drop in the ground line of up to 500 mV under a 3.3 V supply. The operations in the raster and snapshot modes at a frame rate of 200 Hz are verified by simulations. When the resistive emitter with a resistance of 15 kΩ is driven by the proposed RIIC, the IR images can be projected with an apparent temperature range from 271.78 K to 565.93 K and a thermal resolution of 46.4 mK near 300 K in the mid-wavelength IR band.