Patent ID: 7518094
Filing Date: 2009-04-14
Classification: G01J,G01N

Abstract:
1. A system comprising: a plurality of sensing diodes adapted to convert light to a current output, wherein at least one of the sensing diodes is reversed-biased; a light source adapted to emit light to be received by the sensing diodes; a plurality of trans-impedance amplifier circuits, each trans-impedance amplifier circuit comprising an op-amp, and an impedance connecting an output of the op-amp to a first input of the op-amp; a plurality of adjustable voltage sources; and a controller adapted to control the light source to determine at least one diode characteristic and to adjust a corresponding adjustable voltage source so as to compensate for non-uniformities among the plurality of sensing diodes, wherein the current output of each sensing diode is coupled to a corresponding trans-impedance amplifier circuit by an electrical connection to a first input of a corresponding op-amp; a second input of the corresponding op-amp is coupled to a corresponding adjustable voltage source; the output of the corresponding op-amp is a signal responsive to a sensing voltage, and to a voltage signal provided by the corresponding adjustable voltage source, said sensing voltage being responsive to a current output of a corresponding sensing diode; and changes in a voltage signal provided by the corresponding adjustable voltage source affect a characteristic of the corresponding sensing diode.