Smart-Optical Detector Array in CMOS for Absorbance Measurement of Physiological Fluids

This paper describes a smart-optical detector array for application in microchip size analytical laboratories for physiological fluids measurement by absorbance. For this purpose, an array of optical detectors with analog-to-digital conversion is designed and fabricated in a standard CMOS process. Its application is in the low-cost measurement of physiological fluids by optical absorption, e.g., a microplate cuvette array containing the physiological fluids in analysis is placed on top of the optical detector array that quantify the light absorbed by those fluids. The on-chip analog-to-digital conversion is performed using a one-bit first-order sigma-delta converter for each optical detector. The output signal of the device is a bit stream containing information about the absorbed light, which allows simple computer interfacing. This scheme of having simultaneous measurement of the light absorbed by the fluids avoids the errors that can be introduced due to the light fluctuations and performs on-chip calibration during each measurement allowing a non-calibrated light source.