|Thesis abstract: |
In my Ph.D. major research I developed, characterized, validated, and tested a complete system able to acquire combined 2D and 3D images and movies at the single photon level. The sensor relies on Single-Photon Avalanche Diode (SPAD) detectors and on Time-of-Flight (TOF) measurements in order to obtain 3D information from each photon sent toward the target objects in the scene and then reflected back to the camera and detected by each pixel of the imager.
The activity was developed within the European project ¿MiSPIA¿ (Microelectronic Single-Photon 2D and 3D Imaging Arrays for Safety and Security applications), which aimed at designing 2D imaging cameras and 3D ranging cameras for safety and security applications. Beyond these applications the developed system will be employed in Near Infra-Red Spectroscopy (NIRS), Fluorescence Lifetime Imaging (FLIM), Diffuse Optical Tomography (DOT) and other measurements based on the Time-Correlated Single-Photon Counting (TCSPC) technique.
The core of the entire project has been the design of the sensor chip, which is an array of SPADs integrated together with TDCs into each pixel and both photon-counting and photon-timing modes have been implemented within the same sensor. The integrated SPADs present the best-in-class performance among CMOS SPAD detectors, having 120 cps median DCR, with less than 5% hot-pixels, and 55% peak efficiency at 450 nm. The 1024 TDCs have 250 ps resolution and present negligible cross-talk even when all of them work in parallel.
The developed compact module, with an FPGA for data readout and preprocessing, is controlled through USB 2.0 by means of a Matlab GUI interface, and it has been used for acquiring 2D fast movies (100,000 fps) and 3D scenes.