As infrared (IR) imaging systems are being used more often in military fields, the importance of IR sensor evaluation system has emerged. Owing to their non-destructiveness and cost effectiveness, hardware-in-the-loop (HWIL) systems with IR scene projectors (IRSPs) are now being widely used. IRSPs generate virtual IR scenes to evaluate IR imaging systems, which has two performance parameters: thermal range and thermal resolution. Specifically, IR scene quality is determined by the thermal resolution performance and the input digital depth increment can provide a suitable solution to improve resolution. However, the input digital depth increment is limited by system noise and setting a sufficient thermal resolution with wide thermal range is difficult. In this paper, a mode-selective read-in integrated circuit (RIIC) with native transistor is proposed. The native transistor having almost zero threshold voltage, increases the input range, which helps to improve noise margin. A prototype of the RIIC was fabricated using a 0.18-μm 1-poly 6-metal CMOS process and its performance was estimated from measured data. Thermal resolution below 325 K was less than 30 mK and was 185 mK above 325 K in high-current mode; with 14-bit digital resolution, the thermal range varied from 270-325 K to 270-990 K.
This paper proposes a read-in integrated circuit (RIIC) for infrared scene projectors, which compensates for the voltage drops in ground lines in order to improve the uniformity of the emitter current. A current output digital-to-analog converter is utilized to convert digital scene data into scene data currents. The unit cells in the array receive the scene data current and convert it into data voltage, which simultaneously self-adjusts to account for the voltage drop in the ground line in order to generate the desired emitter current independently of variations in the ground voltage. A 32 × 32 RIIC unit cell array was designed and fabricated using a 0.18-μm CMOS process. The experimental results demonstrate that the proposed RIIC can output a maximum emitter current of 150 μA and compensate for a voltage drop in the ground line of up to 500 mV under a 3.3-V supply. The uniformity of the emitter current is significantly improved compared to that of a conventional RIIC.
The infrared scene projector (IRSP) is a tool for evaluating infrared sensors by producing infrared images. Because sensor testing with IRSPs is safer than field testing, the usefulness of IRSPs is widely recognized at present. The important performance characteristics of IRSPs are the thermal resolution and the thermal dynamic range. However, due to an existing trade-off between these requirements, it is often difficult to find a workable balance between them. The conventional read-in integrated circuit (RIIC) can be classified into two types: voltage-mode and current-mode types. An IR emitter driven by a voltage-mode RIIC offers a fine thermal resolution. On the other hand, an emitter driven by the current-mode RIIC has the advantage of a wide thermal dynamic range. In order to provide various scenes, i.e., from highresolution scenes to high-temperature scenes, both of the aforementioned advantages are required. In this paper, a hybridmode RIIC which is selectively operated in two modes is proposed. The mode-selective characteristic of the proposed RIIC allows users to generate high-fidelity scenes regardless of the scene content. A prototype of the hybrid-mode RIIC was fabricated using a 0.18-μm 1-poly 6-metal CMOS process. The thermal range and the thermal resolution of the IR emitter driven by the proposed circuit were calculated based on measured data. The estimated thermal dynamic range of the current mode was from 261K to 790K, and the estimated thermal resolution of the voltage mode at 300K was 23 mK with a 12-bit gray-scale resolution.