Single-photon imaging technology involves multiple aspects such as semiconductor processes,optoelectronic devices,and integrated circuit design.Based on single-photon avalanche diodes,single-photon imaging technology offers high dynamic two-dimensional grayscale imaging,high-precision three-dimensional imaging,and fluorescence lifetime imaging capabilities.It has significant application prospects in fields such as security surveillance,autonomous driving,and biomedicine.With the rapid development of semiconductor process technology,single-photon imaging technology is expected to become a widely used next-generation visual perception technology.This article provides a systematic introduction to imaging technology based on single-photon avalanche diodes,including the device structure of single-photon avalanche diodes,key circuits involved in single-photon imaging,and the latest research progress in gray scale and temporal resolution single-photon image sensors.

Three-dimensional (3D) imaging technology based on Time-of-Flight (ToF) belongs to active 3D imaging technology.It calculates the distance information of the target object by measuring the time needed for modulated light to "fly" back and forth between the target object and the sensor.Compared to other 3D imaging methods, ToF-based 3D imaging methods have significant advantages such as miniaturization, simple structure,and low power consumption.With the development of technology,Indirect Time-of-Flight (IToF) image sensor pixel size gradually decreases,resolution increases,and accuracy improves,making it applicable in various scenarios.However,it still faces challenges such as background light interference,multipath interference,and motion artifacts.The working principle of ToF image sensors is introduced in section 1.The parameter indicators of ToF image sensors and their development trends are analyzed in section 2.The challenges faced by ToF image sensors are analyzed and the solutions are proposed in section 3.The image correction and restoration algorithms applied to ToF technology are introduced in section 4.

Aiming at the application requirements of high frame rate CMOS image sensors,a hybrid analog-to-digital converter (ADC) combining successive approximation register (SAR) and single slope (SS) structures is proposed.The resolution of this ADC is 12-bit,with SAR ADC achieving high 6-bit quantization and SS ADC achieving low 6-bit quantization.The ADC adopts a fully differential structure to eliminate fixed misalignment of the sampling switch and reduce nonlinear errors.At the same time,asynchronous logic circuits are used in SAR ADC to further shorten the conversion cycle.The circuit is designed and implemented using 110 nm 1P4M CMOS technology.The post-layout simulation results show that at clock frequency of 20 MHz,the conversion period is only 3.3 μs,the spurious free dynamic range is 77.12 dB,the signal-to-noise distortion ratio is 67.38 dB,and the effective bit is 10.90 bits.

Aiming at the requirement of high-speed and high linearity of CMOS image sensor for high-speed application devices,this paper realizes a Latch-ADC applied to image sensor on the basis of traditional SS ADC (Single-Slope ADC,Single-Slope analog-to-digital converter),with an operating frequency of 600 MHz.Latch-ADC can use multi-column pixels to share a Gray Code Counter,and quickly lock and store data through Latch structure,which realizes the functions of counter and SRAM in SS ADC.In this paper,a high-speed 12bit Latch-ADC is implemented by using 110 nm technology.Through simulation verification,the Latch-ADC in this paper has high linearity,with each conversion period of 7.094 μs,average power of 180.3 μW,and conversion power consumption of 1.279 nJ.

Image sensors,as crucial devices for capturing visual information,convert perceived light signals into electrical outputs.Currently,the manufacturing technology for image sensors based on complementary metal-oxide-semiconductor is quite mature.However,there is still a demand for miniaturized and multifunctional image sensors in certain specific application scenarios.Facing this challenge,image sensors based on two-dimensional (2D) semiconductors,with their rich material systems and excellent photoelectric properties,demonstrate potential in miniaturization and high integration,offering new opportunities for the development of the image sensor field.This paper first discusses the bandgap characteristics of 2D semiconductors and their corresponding spectral response ranges,showcasing single-pixel imaging technology based on 2D semiconductors.It then describes how the in-plane anisotropic properties of atomic arrangements in 2D semiconductors are utilized to successfully construct polarization-sensitive image sensors.Finally,it explores how the ongoing maturation of large-area growth technologies for 2D semiconductor materials can further facilitate the construction of image sensor arrays based on 2D semiconductors.

Terahertz wave is an electromagnetic wave between millimeter wave and infrared light,which has many feature like strong penetration capability,non-ionization and high instantaneous bandwidth.For these qualities,terahertz waves have a wide range of potential applications in non-destructive testing,medical imaging,safety inspection,and other areas.In the imaging system,the detector is an essential part.This paper presents a structure that combines the output of narrow-band detectors with different center frequencies to realize wide-band detection.In order to reduce the area,these narrowband detectors adopt a nested structure,which means that the high-frequency narrowband detectors are placed inside the low-frequency narrowband detectors in turn.Each narrow-band detector includes a loop antenna,a matching network and a field effect transistor (FET) detector circuit.The detector is fabricated in a 65 nm standard CMOS process,and the detection frequency range covers 100 GHz to 1 000 GHz.Based on this broadband detector,we propose a terahertz focal plane imaging system,which mainly consists of a terahertz radiation source,a PTFE lens,a broadband CMOS detector,etc.The measurement results have shown that the focal plane imaging system is capable of stably imaging at frequencies of 100 GHz,220 GHz and 300 GHz.The imaging quality improves significantly with increasing frequency.In order to solve the problem of missing information in measurement images,the morphological closing algorithm is used to process the original image.This algorithm effectively fills in the missing information and enhances the quality of the image.