6.4 A 400×400 3.24µm 117dB-Dynamic-Range 3-Layer Stacked Digital Pixel Sensor

In recent years, digital pixel sensors (DPS) have been developed for augmented reality (AR) glasses and virtual reality (VR) headsets. Thanks to a 2-layer stacked process, DPS provides low power consumption, high dynamic range (HDR) and global shutter in a small pixel size [1], [2]. To meet the increasingly important form factor and performance requirements of these devices, a 3-layer stacked DPS with a $3.24\cup \mathrm{m}$ pixel is developed to reduce the chip size while incorporating a frame averaging unit (FAU), image signal processing (ISP), and sparse transmission (ST) functionalities. The $3.24\mu\mathrm{m}$ pixel is achieved with a single-ended comparator, optimized control logic and a 10b in-pixel SRAM memory to offer single-exposure HDR capture. The sensor significantly improves noise performance by correcting the fixed-pattern noise (FPN) with FAU and ISP, and ST enables various artificial intelligence (AI) and computer vision (CV) use cases with a low power consumption. The sensor has a die size of $2.47\times 1.85\text{mm}^{2}$, suitable for AR and VR devices where small cameras are demanded.