title: Wide-dynamic-range APS-based silicon retina with brightness constancy.
abstract: A silicon retina is an intelligent vision sensor that can execute real-time image preprocessing by using a parallel analog circuit that mimics the structure of the neuronal circuits in the vertebrate retina. For enhancing the sensor's robustness to changes in illumination in a practical environment, we have designed and fabricated a silicon retina on the basis of a computational model of brightness constancy. The chip has a wide-dynamic-range and shows a constant response against changes in the illumination intensity. The photosensor in the present chip approximates logarithmic illumination-to-voltage transfer characteristics as a result of the application of a time-modulated reset voltage technique. Two types of image processing, namely, Laplacian-Gaussian-like spatial filtering and computing the frame difference, are carried out by using resistive networks and sample/hold circuits in the chip. As a result of these processings, the chip exhibits brightness constancy over a wide range of illumination. The chip is fabricated by using the 0.25- μm complementary metal-oxide semiconductor image sensor technology. The number of pixels is 64 × 64, and the power consumption is 32 mW at the frame rate of 30 fps. We show that our chip not only has a wide-dynamic-range but also shows a constant response to the changes in illumination.
authors.affiliation: Department of Robotics, Ritsumeikan University, Kusatsu, Shiga, Japan. skazu@fc.ritsumei.ac.jp
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Shimonomura
authors.forename: Seiji
authors.initials: S
authors.lastname: Kameda
authors.forename: Atsushi
authors.initials: A
authors.lastname: Iwata
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yagi
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D015350:Contrast Sensitivity; D005137:Eye, Artificial; D006801:Humans; D008959:Models, Neurological; D016571:Neural Networks, Computer; D017711:Nonlinear Dynamics; D010775:Photic Stimulation / Q000009:adverse effects*; D012160:Retina / Q000502:physiology*; D012825:Silicon
chemical_list: D012825:Silicon