Laser beams used for bar-code scanning exhibit speckle noise generated by the roughness of the surface on which bar codes are printed. Statistical properties of a photodetector signal that integrates a time-varying speckle pattern falling on its aperture are analyzed in detail. We derive simple closed-form expressions for the autocorrelation function and the power spectral density of the detector current for scanning beams with arbitrary field distributions. Theoretical calculations are illustrated by numerical simulations as well.
© 2001 Optical Society of AmericaPDF Article