OPTICAL SYSTEM FOR A LARGE DEPTH-OF-FIELD BAR CODE SCANNER

摘要

ABSTRACT of the DISCLOSUREAn optical system for a bar code scanner has aworking range that is not determined by the lensaperture, but by the dimension and orientation of thedetector. In the preferred embodiment, the desiredworking range is imaged onto a detector array using amodified Scheimpflug arrangement. The array in thefirst Scheimpflug plane with respect to the lens definesa second Scheimpflug plane that intersects the bar codetag to be read. So long as the bar code tag intersectsthe image of the detector array in the secondScheimpflug plane, a portion of the image of the barcode tag will be in focus on at least one of theelements of the detector array. The lens aperture canbe as large as desired to maximize resolution andminimize illumination needs without adversely affectingthe working range. The scanner's bar code illuminationcan be directed along the second Scheimpflug plane,which is off the optical axis of the lens. Withseparate illumination and detection paths, the opticalsystem of the invention does not require beam splittersor mirror/aperture arrangements needed by theconventional systems.