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Abstract

An improved sensor array and illumination scheme for a bar code scanner use a modified Scheimpflug arrangement optical system that simplifies signal processing. The preferred embodiment includes a detector array comprising a multi-element array of photosensors positioned in one Scheimpflug plane and an illumination beam in the form of a sheet of light along the other Scheimpflug plane. The detector array has a plurality of elements having a long axis and a short axis, with the long axis of the elements arranged substantially perpendicular to the image of the illuminated strip of the bar code tag. The projection of the long axis of the elements of the array onto the other Scheimpflug plane defines the working range of the optical system. So long as the bar code tag intersects the illumination beam within the working range, the image of the illuminated strip of the bar code tag will be substantially in focus across the elements of the detector array. Filtering allows substantially only the light from the illuminated strip to reach the detector array. Thus, substantially all of the light that reaches the detector array is useful signal, and all the output data from the array during a bar code scan is relevant. The output signal from the array can be processed with conventional digitizing and decoding circuitry with audio signal processing techniques.

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