Patent ID: 7364081

Claim:
A method for reading a bar code symbol with an optical reader, the optical reader including a two-dimensional imager, the method comprising: scanning the bar code symbol to obtain a plurality of scan lines, each of the plurality of scan lines including a linear array of pixel values, adjacent pixels in the linear array of pixel values being separated by a sample separation distance; designating one of the plurality of scan lines as a reference scan line; inserting a pre-defined number of interpolated data points between each adjacent pixel pair in each of the plurality of scan lines to form a plurality of interpolated scan lines; for each scan line of said plurality of interpolated scan lines, determining a plurality of values of a cross-correlation function relative to said reference scan line, said each scan line being shifted by a shift value, said plurality of values of a cross-correlation function corresponding to a plurality of shift values from a pre-defined range; determining an optimum delay value for each interpolated scan line, the optimum delay value yielding a maximum of said cross-correlation function of the interpolated scan line and the interpolated reference line; choosing one or more selected interpolated scan lines from the plurality of interpolated scan lines; adding a pre-defined number of zero pixel values between each pair of said pixel value for each scan line of said plurality of scan lines; selecting a spatial shift amount for each selected interpolated scan line, the spatial shift amount being the integer multiple of the sample separation distance that corresponds to the optimum delay value for the selected interpolated scan line; shifting each of the selected interpolated scan lines relative to the reference line by its corresponding spatial shift amount to obtain a plurality of shifted scan lines creating a reconstructed scan line by summing said pixels of said shifted scan lines.