High dynamic range infrared image sensor based on flexibly adjustable per-pixel integration time

The growing demand for high dynamic range (HDR) imaging in modern intelligent security systems and industrial inspection has revealed a fundamental limitation of conventional infrared focal plane arrays (IRFPAs): their global-shutter-based integration time configurations fails to simultaneously resolve high-intensity and low-intensity regions within a single frame, leading to persistent highlight saturation and low-light invisibility. Although conventional HDR algorithms merge multi-frame images with varied integration times to extend dynamic range, such methods suffer from inherent latency. The inter-frame temporal disparities induce motion blur/ghosting artifacts and constrain the peak frame rate of the detector. To address the critical trade-off between dynamic range and real-time imaging performance in single-exposure infrared imaging, this work proposes a novel image sensor design featuring per-pixel adjustable integration time, implemented through a direct-injection pixel architecture with embedded functional modules. Each pixel integrates in-pixel memory cells, timing counters, and digital comparator, enabling individual exposure configuration during a single integration cycle via SPI interface. Fabricated in a standard 0.13 μm CMOS process, the readout integrated circuit (ROIC) incorporates a 640×512 pixel array with 15-μm pixel pitch. Experimental characterization demonstrates: (1) linear correlation between output response and integration time across a wide range of irradiation intensities; (2) a 47.2 dB dynamic range enhancement versus conventional infrared detectors when employing multi-tiered integration time configurations with image fusion algorithms. The proposed circuit preserves both highlight and shadow details under extremely high illumination conditions. Moreover, its per-pixel programmability supports on-chip real-time reconfiguration for adaptive optimization of imaging quality based on incident radiation intensity, significantly advancing applications requiring simultaneous high dynamic range and instantaneous response.