Zhenyu Liu, Xiaowei Lyu, Zizhuo Liu, Hao Xu
Charge-coupled device (CCD) image sensors stand out for their high sensitivity, low noise, and strong radiation tolerance, which have established them as core components in high-end imaging fields such as astronomical observation, remote sensing, and defense and security. With increasingly stringent requirements for imaging system performance in emerging applications, including ultra-high resolution, intelligent sensing, and multimodal information fusion, CCD technology continues to evolve toward higher levels of integration and improved performance. Within a fixed sensor area, one of the most straightforward ways to raise image resolution is to shrink pixel size, that is, CCD pixel miniaturization. In this review, we provide a systematic survey of the major advances in CCD pixel miniaturization achieved in recent years. We first detail four mainstream CCD architectures-linear-array, full-frame, frame-transfer, and interline-transfer-along with several newly developed architectures, and compare their performance characteristics and application constraints. We then summarize the key technologies that enable pixel miniaturization and examine several closely related technological directions. Finally, we look at the current state of CCD pixel miniaturization and discuss its future development trends.