Optical EngineeringModulation transfer function of bar code scanning
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Bar code scanners are ubiquitous in supermarkets. As a bar code is passed over a scanner, a laser beam scans across the bar code. The scattered light is modulated by the reflectivity of the bars and spaces of the bar code. The bar code scanning process can be described as a 1-D convolution of the scanning laser profile and the bar code reflectivity function. The modulation transfer function (MTF) of bar code scanning is the Fourier transform of the marginal profile of the laser beam. The properties of the MTF of bar code scanning is similar to that of an incoherent imaging system. Measurements of the MTF of bar code scanning at one focal position are presented. The experimental results are then discussed.