[Introduction]High-sensitivity detection imaging is an important technical field in space remote sensing applications, such as all-day earth observation, space dim target tracking and recognition and other applications, the demand for very high-sensitivity image sensors is increasing. With the continuous improvement of the technical level of solid-state image sensors, especially the breakthrough of back-illuminated and buried channel processes, the sensitivity of solid-state image sensors has been greatly improved.
Solid-state high-sensitivity image sensors, especially scientific-grade CMOS image sensors, have emerged in the field of high-sensitivity imaging applications due to their small size, high integration, and low power consumption. Although scientific-grade CMOS image sensors can achieve low-light and high-sensitivity imaging, they are far from reaching the radiometric resolution capability of single-photon detection. The emergence of quantum CMOS image sensors is of great significance for broadening the application field of high-sensitivity imaging in space remote sensing and improving the corresponding application level.
According to Memes Consulting, researcher Pan Weijun’s research group from Beijing Institute of Space Mechatronics published an article on “Next Generation Very High Sensitivity Image Sensor Technology Based on Quantum Imaging” in the journal “Space Return and Remote Sensing”. Researcher Pan Weijun is mainly engaged in the research of image sensor design and application.
This research focuses on the quantum CMOS image sensor with single-photon resolution, a new type of very high-sensitivity image sensor. Starting from the noise characteristics of single-photon detection and the high-sensitivity technical mechanism of solid-state image sensors, the key technologies for realizing very-high-sensitivity performance are discussed. On this basis, the technology development history of quantum CMOS image sensor is discussed in detail, the performance of quantum CMOS image sensor and other mainstream single-photon detection sensors are compared, and the future technology of quantum CMOS image sensor technology is summarized and analyzed. Finally, according to different application requirements of aerospace remote sensing, the application mode and application characteristics of quantum CMOS image sensor are analyzed and prospected.
Detection Mechanism of Image Sensors
To achieve the very high sensitivity requirements of single-photon detection, there are strict requirements on the magnitude of the equivalent input readout noise. A very high sensitivity image sensor is similar to a “microscope” used to observe radiation intensity, and its own noise can only achieve the resolution of a single photon when it reaches the deep sub-electron level. Therefore, very high sensitivity means very low noise. The technical approaches to reduce noise mainly include: (1) increase the signal gain; (2) reduce the noise at all levels; (3) achieve a sufficiently small dark current, because the shot noise introduced by the dark current cannot be increased by increasing the signal. If the gain is suppressed, the dark current can only be reduced by process optimization, thereby reducing the influence of the dark current shot noise. In addition, according to different methods of increasing the signal gain, two different mainstream technologies of very high sensitivity image sensors have been formed. , and the other is a technology that realizes high gain amplification by increasing the charge-voltage conversion gain or the transconductance integral gain, represented by scientific-grade CMOS and quantum CMOS image sensors.
In the field of solid-state image sensors, the development of CMOS image sensor technology has roughly undergone three technological leaps: the first is the development of passive pixels to active pixels; the second is the development of scientific-grade CMOS image sensors; the third is quantum The development of CMOS image sensors. The key technologies of quantum CMOS image sensors mainly include deep-flying low-floating diffusion (FD) capacitor technology, transconductance variable integral amplification technology, and column-level correlated multi-sampling (CMS) technology.
Shen Yafei Fa-level small capacitor technology
At present, the mainstream very high-sensitivity image sensors with single-photon detection capability include single-photon avalanche diode (SPAD), EMCCD, scientific-grade CMOS and quantum CMOS image sensors. The six dimensions of dark current and read noise are compared.
Performance comparison of mainstream single-photon image sensors
The future development trend of quantum CMOS image sensors will continue to advance towards lower noise and more flexible and intelligent imaging modes. With the continuous deepening of aerospace remote sensing application levels and the continuous expansion of application fields, the application requirements of very high-sensitivity image sensors will become more and more extensive. How to give full play to its highly sensitive characteristics requires in-depth analysis in combination with different remote sensing applications. The main applications are: all-day earth observation, space situational awareness, and quantitative inversion. In addition to the above application fields, quantum CMOS image sensors can also be applied to star-sensitive sensor design, exoplanet detection and other fields due to their excellent ultra-low noise performance. It is foreseeable that with the further development of quantum CMOS image sensor technology, it is bound to be more widely promoted and applied in more fields.
The major breakthrough in quantum CMOS image sensor technology has brought significant changes to the application pattern of high-sensitivity image sensors in the field of aerospace remote sensing applications. Therefore, it is necessary to actively make arrangements in advance. On the one hand, the technical characteristics of quantum CMOS image sensors should be studied in depth. It is suitable to realize the leap-forward development of my country’s aerospace optical remote sensor technology level.
This project is supported by the National Major Science and Technology Special Project.
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