A low-light-level sensor for medical diagnostic applications

A low-level light sensor and preprocessor for a disposable medical probe is described. A 10-Hz 4-/spl mu/A/cm/sup 2/ input optical signal in the visible spectrum is assumed in chemoluminant diagnostic applications. A single-bit first-order sigma-delta modulator has been employed for analog-to-digital conversion, thanks to its robustness, simplicity, inherent linearity, and high signal-to-noise ratio. A current buffer has been used to replicate the weak signal with sufficient bandwidth. Tests have shown the feasibility of this approach, and have also enabled improvements of the design.