Signal processing in barcode reading with a wavelet transformation

Abstract

A method for processing a digital signal obtained in a barcode reading operation comprises a step of applying a wavelet transformation to the digital signal. The noise threshold at each level of the wavelet transformation is determined from a total transfer function in the analogue processing stage, and the coefficients are set to be zero if less than the noise threshold.

1 . A method for processing a digital signal obtained in a barcode reading operation, comprising the steps of applying a wavelet transformation to said digital signal; determining a threshold for coefficients for each level in said wavelet transformation, and setting said coefficients as zero if lower than said threshold. 
   
   
       2 . The method of  claim 1 , further comprising a step of determining a threshold for coefficients for each level in said wavelet transformation, and setting said coefficients as zero if lower than said threshold. 
   
   
       3 . A method of reducing white noise from an analogue signal obtained in a barcode reading operation, comprising the steps of:
 converting said analogue signal to a digital signal;   applying a wavelet transformation to said digital signal;   determining a noise threshold for each level in said wavelet transformation; and   setting all coefficients of said wavelet transformation to be zero if lower than said noise threshold.   
   
   
       4 . The method of  claim 4 , wherein said noise threshold is determined based on information obtained in an analogue processing stage for processing said analogue signal.