Foveal model of artificial retina with phototransistors in Darlington configuration in the high-resolution region

Abstract

In this article is proposing a structure of foveal artificial retina to use bipolar phototransistors in configuration Darlington within the central zone and bipolar phototransistors in the periphery. These last ones are forming groups of four elements with a size that is growing towards the periphery, this causes an increase of the area of incidence without modifying to a great extent the size of the phototransistors and thus to take advantage of better the area silicon, in addition it occurs to know a new structure in where the analysis of the foveal model with rectangular phototransistors is possible. This a structure new is not necessary that the photodetectors have a specific and complex design, as can be the circular form that has been used in diverse models. An analysis is made on the voltage of operation the two configurations of phototransistors with the objective to present the idea raised in relation cones and canes a biological retina. With the previous, is a simulation in which an image with the proposed model can be observed. The results in Matlab appear with which the degree of resolution in the center of the foveal model is observed.

Sistemas de imagem CMOS com alta responsividade e elevada faixa dinamica

“…Particularmente para intensidades luminosas mais baixas, a fotocorrente gerada na junção não é suficiente para polarizar o BJT na região em que o ganho de corrente é significativo. Apesar das dificuldades citadas acima alguns estudos sobre o fototransistor BJT podem ser encontrados na literatura direcionados para aplicações específicas nas quais o processamento analógico no modo corrente é mais adequado[11][12][13][14][15]. A Figura 2.10 ilustra a estrutura dos dois tipos de BJTs disponíveis em processo padrão CMOS: (i) BJT vertical e (ii) BJT lateral.…”