Paolo Dario

A Foveated Retina-Like Sensor Using CCD Technology

A CCD imager whose sampling structure is loosely modeled after the biological visual system is described. Its architecture and advantages over conventional cameras for pattern recognition are discussed. The sensor has embedded in its structure a logarithmic transformation that makes it size and rotation invariant. Simulations on real images using the actual sensor geometry have been performed to study the sensor performance for 2D pattern recognition and object tracking.

A retinal CCD Sensor for fast 2D shape recognition and tracking

Abstract A human-retina-like image sensor has been developed for applications in robotics. The CCD imager has a circular pixel organization and the resolution is a decreasing function of the radius. Detailed software modeling resulted in an imager design consisting of four main parts: a circular CCD, a radial CCD, a coupler and an output structure. In order to avoid a blind spot in the center, a central fovea with a rectangular interline transfer imager is included. This paper outlines in detail the design concepts and reports on the electrical performance and functionality of the first prototypes.

Retinalike space variant CCD sensor

The retina is a smart sensor, but in the sense of intelligent design and not on-chip computing power. It uses a unique layout and elementary charge computing elements to implement in hardware a polar-exponential transform on visual data. The final chip includes a large section of photosites arranged in a circular pattern. Further, the pixels grow m size as radial distance increases. The retina also has a fovea (a high resolution area at the chips center) and the computational circuitry. The sensor works and will serve as the key component of a real-time imaging system.

Spinned P(VDF-TrFE) Copolymer Layer for a Silicon-Piezoelectric Integrated US Transducer

Table I The copolymer of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) has been found to be an excellent ultrasonic (US) transducer material because of its impedance matching with biological tissues and its large electromechanical coupling factor. In order to explore the feasibility of an integrated silicon-piezoelectric copolymer transducer array, we prepared some sample devices by depositing a thin P(VDF-TrFE) layer directly on silicon wafers and by poling the resulting 1.5 micron thin copolymer layer by thermal corona discharge. Pyroelectric and piezoelectric properties were evaluated in those copolymer samples and on casted copolymer film, and compared with those of a commercial PVDF film. Preliminary results suggest that it could be possible to design an integrated transducer for US imaging based on spinned copolymer-silicon technology.

Design and fabrication of a silicon-P(VDF-TrFE) piezoelectric sensor

Abstract Using a 70/30 molar ratio vinylidene fluoride/trifluoreethylene copolymer, N-channel enhancement type MOS transistors with extended metal gates were batch fabricated with standard IC technology. Thin (2.5 microm) copolymer film was spin coated on the wafers, electroded, poled, and selectively etched. The small area, thin polymer film on silicon provides good acoustic match to soft tissue, high-frequency response and minimization of losses and noise. Advances in poling procedures and thin polymer film deposition uniformity allowed improvements in the resulting transducers. Fabrication and material property details and measurements of transducer I–V characteristics and low-frequency pyroelectric activities of the processed polymer film on wafer transducers are described. The pyroelectric activity at 25°C of our copolymer film on silicon is 50% higher than that of homopolymer PVDF films.

Design and characterization of a space-variant CCD sensor

Arranging the photosensitive elements of an imaging sensor in a log-polar grid automatically samples an image in a logpolar space. The Retina project is a chip with such a spatially varying layout that can produce the advantages of image processing in the new space at real-time speeds. The actual chip is a small part of a complete imaging system. The system is part of a class of imagers called foveal sensors and these sensors have distinct and significant computational savings over conventional imagers as many as 3-10 orders of magnitude improvement in processing time and memory. The design maintains a large region of high-resolution data although it is still only a fraction of the total photosensitive area.