Patent ID: 8087589

Claim:
A method of reading a barcode, comprising: providing a local oscillator frequency source that generates a local oscillator signal at a local oscillator frequency, wherein the local oscillator frequency is an intermediate frequency selected to be above a frequency threshold of expected ambient light noise; providing a laser source that generates a laser output signal having a set of laser frequencies; combining the local oscillator signal with the laser output signal to produce at least one combined signal; directing the combined signal to be scanned over and reflected off the barcode; receiving a reflected signal from the barcode, wherein the reflected signal includes at least a first component at a first set of frequencies that is a sum of the local oscillator frequency and a barcode signal frequency, and a second component at a second set of frequencies that is a difference between the local oscillator frequency and the barcode signal frequency; filtering the reflected signal with a bandpass filter to attenuate unwanted frequencies; amplifying the filtered signal; digitizing the filtered signal to produce a digitized signal; processing the digitized signal to produce a processed signal, wherein the processed signal is a reading of the barcode; and storing the processed signal in a tangible computer readable medium.