System and method for noise reduction in a bar code signal

A method for reading a bar code, comprising:

• transmitting light pulsed at a selected frequency to illuminate said bar code;
• converting light received at the bar code reader from the bar code into an electrical signal;
• transmitting the electrical signal through a signal conditioning circuit to filter and amplify the electrical signal, to thereby provide a conditioned electrical signal;
• sampling the conditioned electrical signal at the selected frequency to produce a sampled electrical signal;
• removing energy due to light scattering within a housing of the bar code reader from the sampled electrical signal, wherein removing the energy comprises:
• (i) transmitting the sampled electrical signal through a high-pass filter to produce a filtered, sampled electrical signal, and
• (ii) transmitting the filtered, sampled electrical signal to an automatic gain control that Is operable to amplify the filtered, sampled electrical signal at an output of the high-pass filter to produce an amplified, filtered, sampled electrical signal;
• directly outputting, by the automatic gain control, the amplified, filtered, sampled electrical signal to an input of a comparator and a low-pass filter;
• comparing, by the comparator, a voltage of the amplified, filtered, sampled electrical signal to a threshold voltage provided by the first low-pass filter in order to generate, based on the comparison, one of:
• (a) a voltage value corresponding to a logical “1” value, and
• (b) a voltage value corresponding to a logical “0” value;
• and
• resolving output from the step of generating into data indicative of information on the bar code.

A bar code reader comprising:

• a laser light output circuit operable to provide a pulsed laser light output toward a bar code, the pulsed laser light output having a specified frequency;
• a photodiode to convert light received at the bar code reader into an electrical signal;
• a first signal conditioning circuit to amplify the electrical signal, to thereby provide a conditioned electrical signal;
• a detection circuit operable to sample the conditioned electrical signal at the specified frequency to produce a sampled electrical signal;
• a second signal conditioning circuit comprising a first high-pass filter and a first automatic gain control circuit, wherein the first high-pass filter is operable to filter out light energy from the sampled electrical signal due to scattering to produce a filtered, sampled electrical signal, and wherein the first automatic gain control Is operable to amplify the filtered, sampled electrical signal at an output of the first high-pass filter to produce an amplified, filtered, sampled electrical signal;
• a digitizer comprising a comparator, wherein an output of the first automatic gain control is directly electrically connected to an input of the comparator for generating digital output based on a value of the amplified, filtered, sampled electrical signal of said second signal conditioning circuit;
• and
• a decoder for resolving output from the digitizer into data indicative of information on the bar code.

A method for reading a bar code, comprising:

• transmitting light pulsed at a selected frequency to illuminate said bar code;
• converting light received at the bar code reader from the bar code into an electrical signal;
• transmitting the electrical signal through a signal conditioning circuit to amplify the electrical signal, to thereby provide a conditioned electrical signal;
• sampling the conditioned electrical signal at the selected frequency to produce a sampled electrical signal;
• removing light energy from the sampled electrical signal that arises from laser scattering within a housing of the bar code reader, wherein the step of removing comprises:
• (i) transmitting the sampled electrical signal through a high-pass filter to produce a filtered, sampled electrical signal, and
• (ii) transmitting the filtered, sampled electrical signal to an automatic gain control that Is operable to amplify the filtered, sampled electrical signal at an output of the high-pass filter to produce an amplified, filtered, sampled electrical signal;
• generating a digital output based on a value of the signal generated by the step of removing, wherein the step of generating is performed by a digitizer that comprises a comparator and a low-pass filter having an input that is directly electrically connected to an output of the automatic gain control for receiving the amplified, filtered, sampled electrical signal;
• and
• resolving output from the step of generating into data indicative of information on the bar code.