Ph.D Thesis

Ph.D StudentKatz Alexander
SubjectSensors and 2-D Imagers Based on the CMOS SPAD Detectors
DepartmentDepartment of Electrical and Computer Engineering
Supervisors PROFESSOR EMERITUS Yael Nemirovsky
DR. Amos Fenigstein
Full Thesis textFull thesis text - English Version


The need for high frame rate and low light imaging for medical, military, and civil purposes has increased significantly in recent years. Moreover, photography is undergoing a paradigm shift to high resolution three-dimensional imaging. This gives rise to the need to develop a very fast and sensitive sensor to meet these requirements simultaneously. Key requirements for this sensor are low-cost manufacturing and integration in systems on chip. Thus, it requires a low-cost, mature CMOS process. Achieving a very fast and sensitive imager using CMOS technology requires novel architectures and circuit designs. Our goal in this thesis is to develop a cutting-edge sensor with accompanying novel CMOS architectures and circuit designs to make modern imaging a common-day reality.

This research focuses on a CMOS Single Photon Avalanche Diode (SPAD) sensor with near infra-red enhanced performance. This sensor offers many advantages in terms of single photon response, high gain, read-out noise immunity, and fast timing response. It is the best candidate for high-resolution Light Direction and Range (LiDAR), which is required today in every advanced driver-assistance system.

In fact, a goal of this research is to adapt the above sensor to two-dimensional imager and LiDAR, working in sunlight. In these applications, high background conditions (clutter) require correct electrooptical design as well as the sensor optimization in terms of signal-to-noise ratio and saturation level.

The main contributions of this research are:

A novel, monolithic, small-area, and low-power active-reset approach for near infra-red single ended SPAD. This approach provides a dramatic reduction in the SPAD’s dead time, achieving an enhancement in saturation photon rate for this type of SPAD. The higher-saturation photon rate increases the imager’s immunity to high solar background. Such high background is particularly problematic in sunny days.

A worldwide, pioneering, 15 kfps, 64 x 64, passive, two-dimensional gun muzzle flash detection imager, based on CMOS SPAD pixels was developed and tested in a real firing experiment on a sunny day. A novel imager pixel architecture, equipped by integrated 8-bit memory, enables parallel processing and global shutter readout.

A novel, long-range, time-of-flight LiDAR architecture, based on silicon photo multiplier with simultaneous photon-counting (intensity) and photon-timing (distance) abilities was developed and taped-out. The LiDAR was implemented as a single chip with integrated 500 psec resolution time to digital converter.