A modulator design for smart pixel multispectral imaging arrays

In multispectral imagers direct conversion of pixel current to digital data using oversampling and a noise shaping modulator circuit enables advanced digital signal processing to reduce noise and enhance image quality. This may be an important technology for noisy imaging detectors such as infrared or experimental UV detectors. However, when more than one detector is used with the modulator circuitry, as in multispectral imaging systems, frames rates drop dramatically. Using one modulator circuit per detector maximizes the frame rate possible and further reduces noise by eliminating analog signal distribution lines. We describe the design and simulation of a 0.25 micron CMOS modulator small enough to allow multiple modulators to reside beneath each pixel of an experimental multi-detector multi-spectral imager