Arrays of Single Photon Avalanche Diodes in CMOS Technology: Picosecond Timing Resolution for Range Imaging (INVITED)

A solid-state imager fabricated in CMOS technology is presented for depth information capture of arbitrary 3D objects with millimeter resolution. The system is based on an array of 32x32 pixels that independently measure the time-of-flight of a ray of light as it is reflected back from the objects in a scene. A single cone of pulsed laser light illuminates the scene, thus no complex mechanical scanning is required. Millimetric depth accuracies can be reached thanks to the rangefinder’s optical detectors that enable picosecond time discrimination. The detectors, based on a single photon avalanche diode operating in Geiger mode, utilize avalanche multiplication to enhance light detection. Optical power requirements on the light source can therefore be significantly relaxed. A number of standard performance measurements, conducted on the imager, are discussed in this paper. The 3D imaging system was also tested on real 3D subjects demonstrating the suitability of the approach.

Design and characterization of a CMOS 3-D image sensor based on single photon avalanche diodes

Pierre-André Besse, Edoardo Charbon, Cristiano Niclass, Alexis Rochas

The design and characterization of an imaging system is presented for depth information capture of arbitrary three-dimensional (3-D) objects. The core of the system is an array of 32 × 32 rangefinding pixels that independently measure the time-of-flight of a ray of light as it is reflected back from the objects in a scene. A single cone of pulsed laser light illuminates the scene, thus no complex mechanical scanning or expensive optical equipment are needed. Millimetric depth accuracies can be reached thanks to the rangefinder's optical detectors that enable picosecond time discrimination. The detectors, based on a single photon avalanche diode operating in Geiger mode, utilize avalanche multiplication to enhance light detection. On-pixel high-speed electrical amplification can therefore be eliminated, thus greatly simplifying the array and potentially reducing its power dissipation. Optical power requirements on the light source can also be significantly relaxed, due to the array's sensitivity to single photon events. A number of standard performance measurements, conducted on the imager, are discussed in the paper. The 3-D imaging system was also tested on real 3-D subjects, including human facial models, demonstrating the suitability of the approach.

2005

Single-Photon Techniques for Standard CMOS Digital ICs

Claudio Favi

The advent of single-photon detectors known as Single-Photon Avalanche Diodes in standard CMOS technology opened the way to new perspectives in integrating these ultra sensitive light sensors with digital logic. Light has some interesting properties that attracted researchers in computer and electronics for a long time. Its weightlessness nature makes it a candidate to replace electrons when it didn't already do so. This is particularly true for long distance data transfers. However a new trend can be observed. Researchers are looking into photonics, the science of light, for short distance communications as well. Power efficiency is one of the reasons of this trend. In fact, photons, the elementary particles of light, don't suffer of resistive, capacitive, or inductive effects like electrons do. The wavelike nature of light can also free designers from problems such as cross-talk and side-channel noise injection while taking advantage of interference. However photonics is still not the panacea and we don't believe it will ever completely replace electronics. Most certainly a combination of the two will be adopted to take advantage of both worlds. CMOS digital Integrated Circuit (IC) design faces many challenges and it is not clear whether technology will still provide small footprints, high performance, and low power in the future. Photonics with SPADs can answer some of these questions. In this work, we present three investigations where SPAD photonics is integrated within digital CMOS technology. The main contributions of this thesis are threefold: single-photon CMOS communication paradigms, single-photon processing and readout techniques, single-photon clocking and synchronization methods. Single-photon communication was achieved using a combination of SPADs and ultra-fast TDCs in a pulse position modulation scheme. In this context, theoretical channel capacity limits in the presence of noise and other non-idealities typical of SPADs were derived; a TDC with a resolution of 17 ps was demonstrated in a standard FPGA fabric. To the best of our knowledge, at the time of this writing, this is the highest reported resolution for a TDC of this kind. Single-photon processing and readout was achieved in several technologies, focusing on image sensor design, whereby massive parallel architectures were studied and implemented in CMOS. Single-photon clocking and synchronization was demonstrated allowing potentially zero skew systems irrespective of the chip area. The power benefits of this approach in embedded systems with instruction set extensions are particularly interesting. The thesis makes use of SPAD technology implemented in CMOS for a number of applications creating a bridge between digital design and high performance photonics. We believe that this is the first attempt in this direction focused on CMOS technology.

EPFL2011

Single-Photon Synchronous Detection

Edoardo Charbon, Claudio Favi, Ties Jan Henderikus Kluter, Frédéric Monnier, Cristiano Niclass

Phase and intensity of light are detected simultaneously using a fully digital imaging technique: single-photon synchronous detection. This approach has been theoretically and experimentally investigated in this paper. We designed a fully integrated camera implementing the new technique that was fabricated in a 0.35 mu m CMOS technology. The camera demonstrator features a modulated light source, so as to independently capture the time-of-flight of the photons reflected by a target, thereby reconstructing a depth map of the scene. The camera also enables image enhancement of 2D scenes when used in passive mode, where differential maps of the reflection patterns are the basis for advanced image processing algorithms. Extensive testing has shown the suitability of the technique and confirmed phase accuracy predictions. Experimental results showed that the proposed rangefinder method is effective. Distance measurement performance was characterized with a maximum nonlinearity error lower than 12 cm within a range of a few meters. In the same range, the maximum repeatability error was 3.8 cm.

2009

Single-Photon Techniques for Standard CMOS Digital ICs

Claudio Favi

EPFL2011