Lorenzo Gonzo

A CMOS 3-D Imager Based on Single Photon Avalanche Diode

A 64-pixel linear array aimed at 3-D vision applications is implemented in a high-voltage 0.8 mum CMOS technology. The detection of the incident light signals is performed using photodiodes biased above breakdown voltage so that an extremely high sensitivity can be achieved exploiting the intrinsic multiplication effect of the avalanche phenomenon. Each 38times180-mum2 pixel includes, besides the single photon avalanche diode, a dedicated read-out circuit for the arrival-time estimation of incident light pulses. To increase the distance measurement resolution a multiple pulse measurement is used, extracting the mean value of the light pulse arrival-time directly in each pixel; this innovative approach dramatically reduces the dead-time of the pixel read-out, allowing a high frame rate imaging to be achieved. The sensor array provides a range map from 2 m to 5 m with a precision better than plusmn0.75% without any external averaging operation. Moreover, with the same chip, we have explored for the first time the implementation of an indirect time-of-flight measurement by operating the proposed active pixel in the photon counting mode

Novel CMOS image sensor with a 132-dB dynamic range

A CMOS image sensor providing an ultrawide dynamic range with a piecewise linear response is presented. The active pixel is based on a novel architecture which implements a voltage comparator and an analog memory to detect and store the information on the integration time needed to reach saturation, while also maintaining the standard integrated photo-current signal. A 128/spl times/64 pixel array has been designed and fabricated in 0.35-/spl mu/m, 3.3-V CMOS technology. The chip measures 2.67/spl times/4.90 mm/sup 2/ with a pixel size of 24.65/spl times/24.65 /spl mu/m/sup 2/ and a fill factor of about 11%. The sensor has been fully characterized and the measured dynamic range turned out to be 132 dB with a power consumption of 14 mW at video frame rate. The sensor features also good noise performance with a temporal noise of 0.2% (1.7%) and a fixed pattern noise of 0.4% (1.5%) at low (high) irradiance.

Single-Photon Avalanche Diode CMOS Sensor for Time-Resolved Fluorescence Measurements

A single-photon avalanche diode-based pixel array for the analysis of fluorescence phenomena is presented. Each 180 times 150 - mum2 pixel integrates a single photon detector combined with an active quenching circuit and a 17-bit digital events counter. On-chip master logic provides the digital control phases required by the pixel array with a full programmability of the main timing synchronisms. The pixel exhibits an average dark count rate of 3 kcps and a dynamic range of over 120-dB in time uncorrelated operation. A complete characterization of the single photon avalanche diode characteristics is reported. Time-resolved fluorescence measurements have been demonstrated by detecting the fluorescence decay of quantum-dot samples without the aid of any optical filters for excitation laser light cutoff.

CMOS Single-Photon Avalanche Diode Array for Time-Resolved Fluorescence Detection

A single photon avalanche diode detector for the analysis of fluorescence phenomena is presented. The 14-pixels array, fabricated in a conventional high voltage 0.35-mum CMOS technology, allows measuring photon densities as low as 108 photons/cm2s. Each 180times150-mum2 pixel integrates a single photon avalanche diode combined with an active quenching circuit and a 17-bit digital events counter. On chip master logic provides the digital control phases required by the pixel array with a full programmability of the main timing synchronisms. Time-resolved measurements has been demonstrated by detecting a 10ns, 10pW (peak-power on the pixel) light pulse with a typical resolution of 80ps

A Range Image Sensor Based on 10-

This paper presents the design and characterization of a lock-in pixel array based on a buried channel photo-detector aimed at time-of-flight range imaging. The proposed photo-demodulator has been integrated in a 10-μm pixel pitch with a fill factor of 24%, and is capable of a maximum demodulation frequency of 50 MHz with a contrast of 29.5%. The sensor has been fabricated in a 0.18-μm CMOS imaging technology and assembled in a range camera system setup. The system provides a stream of three-dimensional images at 5-20 fps on a 3-6 m range, with a linearity error lower than 0.7% and a repeatability of 5-16 cm, while the best achievable precision is 2.7 cm at a 50-MHz modulation frequency.

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Fast collection of three-dimensional (3D) data sets is required in a growing number of applications like robotic guidance, security and automotive. Scannerless time-of-flight (TOF) based active 3D vision systems are capable of collecting depth profiles of entire scenes in fractions of seconds but have the disadvantage of using high voltage and expensive electronic components. In this contribution we describe the design and test of an integrated smart pixel with 3D vision capability, which attempts to address this kind of problem. The pixel, fabricated in standard 0.6 /spl mu/m CMOS technology, is suitable to be used in scannerless ranging systems. By means of a pulsed laser source, distance estimation is obtained by integrating the back-reflected signal in successive time windows.

Lock-In Pixels in 0.18-

A prototype of a 34 /spl times/ 34 pixel image sensor, implementing real-time analog image processing, is presented. Edge detection, motion detection, image amplification, and dynamic-range boosting are executed at pixel level by means of a highly interconnected pixel architecture based on the absolute value of the difference among neighbor pixels. The analog operations are performed over a kernel of 3 /spl times/ 3 pixels. The square pixel, consisting of 30 transistors, has a pitch of 35 /spl mu/m with a fill-factor of 20%. The chip was fabricated in a 0.35 /spl mu/m CMOS technology, and its power consumption is 6 mW with 3.3 V power supply. The device was fully characterized and achieves a dynamic range of 50 dB with a light power density of 150 nW/mm/sup 2/ and a frame rate of 30 frame/s. The measured fixed pattern noise corresponds to 1.1% of the saturation level. The sensors dynamic range can be extended up to 96 dB using the double-sampling technique.

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This paper presents the design and electro-optical test of a 160 × 120-pixels CMOS sensor specifically conceived for Time-Of-Flight 3D imaging. The in-pixel processing allows the implementation of Indirect Time-Of-Flight technique for distance measurement with reset noise removal through Correlated Double Sampling and embedded fixed-pattern noise reduction, whereas a fast readout operation allows the pixels values to be streamed out at a maximum rate of 10 MSample/s. The imager can operate as a fast 2D camera up to 458 fps, as a 3D camera up to 80 fps, or even coupling both operation modes. The chip has been fabricated using a standard 0.18 μm 1P4M 1.8 V CMOS technology with MIM capacitors. The resulting pixel has a pitch of 29.1 μm with a fill-factor of 34% and includes 66 transistors. Distance measurements up to 4.5 m have been performed with pulsed laser light, achieving a best precision of 10 cm at 1 m in real-time at 55 fps and 175 mA current consumption.

m CMOS Imaging Technology

The article reports the interdisciplinary project of the virtualization of the Great Inscription of Gortyna, Crete, for 3D documentation, structural studies, and physical replica purposes. The digitization of the longest epigraphic text of the Greek civilization (6 m long and 1.75 m high, with approximately 2--3 mm-depth engraved letters) and its surrounding heritage area (around 30 × 30 m), required long planning and the construction of a dedicated acquisition system to speed up the surveying time, limited to few hours per day. Primarily, range sensors were employed in a multi-resolution way, digitizing detailed parts in high resolution and less smoothed areas with lower geometric resolution. Some selected areas were also modeled with our multiphoto geometrically constrained image matching approach to demonstrate that the same accuracy and details can be achieved using either scanners or photogrammetry. The derived 3D model of the heritage is now the basis for further archaeological studies on the incision techniques and a deeper structural analysis on the monument. The challenges of the work stay in the acquisition, processing, and integration of the multi-resolution data as well as their interactive visualization.

A CMOS smart pixel for active 3D vision applications

A description of the integrated sensors developed for flying-spot active triangulation is given. All the sensors have been fabricated using standard CMOS technology that allows the monolithic integration of photo-sensors, together with readout circuits, and digital signal processors. Position sensors are classified into two classes that allow a better understanding of the pros and cons of each one. A description of the proposed position sensor that is optimized for accurate and fast 3D acquisition is given alongside some experimental results.