Abstract: A self-contained system uses light reflectivity to examine intensity of a dyed spot on a device membrane surrounded by background area to discern information about the specimen that produced the spot. In a preferred embodiment, a master clock alternatively drives one LED focussed upon the spot center, and then drives two LEDS focused on the background area. Light reflected from the spot and background is detected by preferably two photodetectors (“PDs”) spaced-apart a multiple of 90° azimuthal, a configuration discovered to minimize the effects of uneven membrane topography upon light intensity measurements. The PD outputs are average-summed together and are input to a phase lock-in amplifier system that enhances detected signal/noise by measuring signal voltage without producing noise. The lock-in system simultaneously positively and negatively amplifies the average-summed PD outputs, which amplified signal is then switched in synchronism with the LED drive signals.

Abstract: A method and system for automatic analysis of a testing substrate for an analyte in a liquid sample. The sample is applied to a testing substrate having an immobilized thereon, in a limited region of the testing substrate, a receptor capable of binding to the analyte. A labeled reagent, capable of binding to the analyte, is added to the testing substrate. If the analyte is present, a color is generated at the area of the testing substrate where the receptor is immobilized. The testing substrate is then illuminated and, using electronic equipment a digital image of the testing substrate is acquired and automatically scanned to locate an area of the testing substrate having the highest color density and generating a first measurement of color density. Next, an area peripheral to the area of highest color density is located and a second measurement of color density is generated.