Speckle noise in bar-code scanning systems--power spectral density and SNR

Area of Science:

• Optics and Photonics
• Signal Processing
• Laser Scanning Technology

Background:

• Laser-based flying-spot scanners utilize coherent illumination, leading to intrinsic speckle noise from diffusing targets.
• Information extraction in these systems often relies on processing photodetector signals derived from scattered laser light, which is susceptible to speckle noise.

Purpose of the Study:

• To investigate the power spectral density and total noise power of signals affected by speckle in laser scanning systems.
• To analyze the influence of speckle noise on edge detection accuracy.
• To derive signal-to-noise ratio estimates for laser scanning of edge sequences.

Main Methods:

• Analysis of signal characteristics including power spectral density and total noise power.
• Investigation of speckle noise impact on edge detection algorithms.
• Derivation of theoretical signal-to-noise ratio estimates for various edge sequences.
• Application of derived theories to Gaussian scanning beams for closed-form solutions.

Main Results:

• Characterization of speckle noise in terms of its power spectral density and total noise power.
• Quantification of speckle noise's detrimental effect on edge detection performance.
• Development of signal-to-noise ratio estimation methods for laser scanning applications.
• Closed-form expressions for signal-to-noise ratio derived for Gaussian scanning beams.

Conclusions:

• Speckle noise is a critical factor limiting performance in laser-based flying-spot scanners.
• Understanding and quantifying speckle noise is essential for improving signal processing and edge detection accuracy.
• The derived theoretical framework and closed-form expressions provide valuable tools for designing and optimizing laser scanning systems.