An event-detection high dynamic range CMOS image sensor

A novel CMOS image sensor is proposed to overcome the analog design limitations in Active Pixel Sensors - APS and large area overcome in Digital Pixel Sensors - DPS for use in bio-medical applications. The design includes a pixel level event generation mechanism by using a binary search technique. A ramp voltage generated by a combined block of 10-bit counter and DAC Digital to Analog Converter is compared with the pixel integrated voltage at each clock cycle at the same time allowing a fixed exposure time interval. The proposed design arrives to a total pixel array area of 1505.62μm × 4566μm for a pixel array size of 160(Zf) × 120(V). The photo-active area in each pixel is considered as the N-well area in a p002B;/n-well/p-sub type photo-transistor corresponding to a size of 11.24μm × 10.76μm. The overall pixel array reaches a fill factor of %34.

Characterization of Standard CMOS Compatible Photodiodes and Pixels for Lab-on-Chip Devices

Sandro Carrara, Giovanni De Micheli, Gözen Köklü, Yusuf Leblebici

High quality CMOS image sensors are of great importance for LoC - Lab-on-Chip devices based on optical measurements. The main target in these devices is to minimize the cost and area while achieving a good resolution. The performance parameters of image sensor pixels and CMOS compatible photodiodes depend on the size, type and the geometry of the photodiode layout and varies for each technology. In this study, we present a comparative analysis of CMOS compatible photodiode types at different areas. The results have shown n-well/p-sub type photodiode with 5 x5 um2 diffusion area achieves the highest sensitivity (69.81 x 10^12 V.s^-1.cm^-2) / W x cm^-2) and with 40x40 um^2 diffusion area, highest SNR - Signal-to-Noise Ratio (72.26dB) at 630 nm, while the p+/n-well/p-sub type photodiode with 40x40 um^2 diffusion area results in highest responsivity (0.466 A.cm^-2 / W.cm^-2) at the same wavelength.

2013

SPADnet: a fully digital, scalable and networked photonic component for time-of-flight PET applications

Claudio Bruschini, Edoardo Charbon, Gabor Nemeth, John Richard Walker

The SPADnet FP7 European project is aimed at a new generation of fully digital, scalable and networked photonic components to enable large area image sensors, with primary target gamma-ray and coincidence detection in (Time-of-Flight) Positron Emission Tomography (PET). SPADnet relies on standard CMOS technology, therefore allowing for MRI compatibility. SPADnet innovates in several areas of PET systems, from optical coupling to single-photon sensor architectures, from intelligent ring networks to reconstruction algorithms. It is built around a natively digital, intelligent SPAD (Single-Photon Avalanche Diode)-based sensor device which comprises an array of 8x16 pixels, each composed of 4 mini-SiPMs with in situ time-to-digital conversion, a multi-ring network to filter, carry, and process data produced by the sensors at 2Gbps, and a 130nm CMOS process enabling mass-production of photonic modules that are optically interfaced to scintillator crystals. A few tens of sensor devices are tightly abutted on a single PCB to form a so-called sensor tile, thanks to TSV (Through Silicon Via) connections to their backside (replacing conventional wire bonding). The sensor tile is in turn interfaced to an FPGA-based PCB on its back. The resulting photonic module acts as an autonomous sensing and computing unit, individually detecting gamma photons as well as thermal and Compton events. It determines in real time basic information for each scintillation event, such as exact time of arrival, position and energy, and communicates it to its peers in the field of view. Coincidence detection does therefore occur directly in the ring itself, in a differed and distributed manner to ensure scalability. The selected true coincidence events are then collected by a snooper module, from which they are transferred to an external reconstruction computer using Gigabit Ethernet. We will detail the SPADnet core technologies as well as the latest project achievements in all project areas.

Spie-Int Soc Optical Engineering2014

SPADnet: a fully digital, scalable and networked photonic component for time-of-flight PET applications

Claudio Bruschini, Edoardo Charbon, Gabor Nemeth, John Richard Walker

Spie-Int Soc Optical Engineering2014