高光谱成像用高帧频CMOS图像传感器

High Frame-rate CMOS Image Sensor for Hyperspectral Imaging

摘要:

针对高帧频、全局曝光和光谱平坦等成像应用需求,设计了一款高光谱成像用CMOS图像传感器。其光敏元采用PN型光电二极管,读出电路采用5T像素结构。采用列读出电路以及高速多通道模拟信号并行读出的设计方案来获得低像素固定图像噪声(FPN)和非均匀性抑制。芯片采用ASMC 0.35μm三层金属两层多晶硅标准CMOS工艺流片,为了抑制光电二极管的光谱干涉效应,后续进行了光谱平坦化VAE特殊工艺,并对器件的光电性能进行了测试评估。电路测试结果符合理论设计预期,成像效果良好,像素具备积分可调和全局快门功能,最终实现的像素规模为512×256,像元尺寸为30μm×30μm,最大满阱电子为400ke-,FPN小于0.2%,动态范围为72dB,帧频为450f/s,相邻10nm波段范围内量子效率相差小于10%,可满足高光谱成像系统对CMOS成像器件的要求。

Abstract:

For the imaging requirements such as high frame rate, global shutter and flat spectral response characteristics, a kind of high-frame rate CMOS image sensor for hyperspectral imaging was designed. The circuit employed 5T (5-transistor) photodiode pixel for global shutter operation. And high-speed readout and signal processing circuits were designed to achieve low fixed pattern noise (FPN) and non-uniformity. The sensor was fabricated in ASMC 0.35μm standard CMOS process. In order to suppress the spectral interference of the photodiode, back-end spectral flatness process was implemented, and the photoelectric response of the device was tested and evaluated. The test results indicate that the circuit has met the design expectation, resulting in pixel array size of 512×256, pixel size of 30μm×30μm, high full well capacity of 400ke-, wide dynamic range of 72dB and frame rate of 450f/s. The quantum efficiency difference between neighboring 10nm spectral band is less than 10%, being able to meet the general requirements of a hyperspectral imaging system.