Ultra fast imaging for LiDAR applications

About this Session
By the monolithic combination of CMOS and CCD, incredible things are possible. A prerequisite for this is a perfect integration of the CCD functionality in the (standard) CMOS process. For example, CMOS is not suitable for achieving very small leakage cur- rents in transistors. This is also not necessary for most CMOS circuits. However, leakage currents are fatal in imaging. CMOS imaging also suffers from the weakness of low quantum efficiency in the near infrared due to thin EPI layers. But there are also advantages of CMOS. In addition to low costs, these are to be found in the fact that both the drivers of the CCD gates and the conversion of the charge into voltage or into digitized values can be placed in close proximity on the same substrate. This enables clock frequencies with the CCD structures up to the gigahertz range to be achieved. This is the prerequisite for ultra-fast gated imaging, which enables applications such as TOF, LiDAR, FLIM, etc. In ad- dition, CCD allow mathematical operations in the charge domain such as addition, subtraction, multiplication or binning. These operations in the charge domain are not generating additional noise components, such as the kTC noise generated in the voltage or current domain. The presentation talks about the imaging requirements for the said applications and the technological challenges of the implementation of CCD in a standard CMOS process. In addition, some realized examples are presented which show the achieved results.

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