Patent ID: 8789759

Claim:
A code symbol reading system, comprising: a scanning module for scanning a light beam across a scanning field in a scanning cycle; a scan line detector for detecting a start of each scanning cycle performed by the scanning module and generating a start of scan (SOS) signal in response to the detection of the start of each scanning cycle; a photo-detector for detecting the intensity of light reflected from the scanning field and generating a first signal corresponding to the detected light intensity; a signal processor, comprising: a first processing channel for generating a first data signal and a first derivative data signal, the first processing channel having: a first differentiation stage for processing the first signal and generating a first derivative signal; and a first amplification stage for amplifying the first signal and the first derivative signal using a gain; and a second processing channel for generating a second data signal and a second derivative data signal and having a second amplification stage for amplifying the amplified first signal and the amplified first derivative signal generated by the first amplification stage using a fixed gain; a gain control module for, during each scanning cycle, controlling the gain of the first processing channel's first amplification stage within the signal processor using the SOS signal generated by the scan line detector, the first data signal and the first derivative data signal generated by the first processing channel, and the second data signal and the second derivative data signal generated by the second processing channel; and a decode processor for processing the first data signal, the first derivative data signal, the second data signal, and the second derivative data signal and generating data representative of a code symbol in the scanning field.