Abstract

VIEIRA, M et al. A real-time colour and image processing p-i-n/p-i-n device with optical readout. Rev. mex. fis. [online]. 2006, vol.52, suppl.2, pp.79-82. ISSN 0035-001X.

A two-terminal, optically addressed image processing device based on two stacked sensing/switching p-i-n a-SiC:H diodes is presented. The charge packets are injected optically into the p-i-n sensing photodiode and confined at the illuminated regions, locally changing the electrical field profile across the p-i-n switching diode. A red scanner is used for charge readout. The various design parameters and addressing architecture tradeoffs are discussed. The influence on the transfer functions of an a-SiC:H sensing absorber, optimized for red transmittance and blue collection or of a floating anode in-between, is analysed. Results show that the thin a-SiC:H sensing absorber confines the readout to the switching diode and light filters the structure, allowing full colour detection at two appropriated voltages. When the floating anode is used the spectral response broadens, allowing B & W image recognition with improved light-to-dark sensitivity. A physical model supports the image and colour recognition process.

Keywords : Optical sensors; image and color recognition; optical readout; tandem devices.