Patent US 5,528,022

A symbol read device useful as a bar code reader, optical character reader or the like. A symbol bearing surface is illuminated by two different light sources that are distinguishable based on their respective wavelengths or modulated frequencies. A detector detects light reflected from the symbol surface and provides a detection signal indicative thereof. The detection signal is processed to recognize the symbol being read. In a multi-scan embodiment, an automatic gain control (AGC) circuit controls a level of detector signal to aid in recognition of the symbols being read.