optimal symbologiebeleuchtungsvorrichtung and procedures

摘要

An imager for illuminating and imaging encoded symbology to facilitate decoding of the symbology and which provides both "bright field" and "dark field" illumination patterns is provided with an illumination directing device to direct the "bright field" illumination pattern into an alternative "dark field" illumination pattern. In one embodiment the illumination directing device takes the configuration of a disc that is selectively positionable in front of the imager and removable therefrom depending upon whether or not the illumination pattern is to be changed. The disc snap fits into a position at the front of the imager housing and includes a fresnel configured outer ring, a light blocking inner ring, and a light transmissive center. The fresnel configuration receives light and redirects the light forward of the imager and towards a center line passing through the device to provide the alternative illumination pattern. Other embodiments of illumination directing devices are to be carried by the imager for disposition in either operative or inoperative positions; while still other embodiments of illumination directing devices selectively position collimating lenses and reflective surfaces to receive and redirect light from the images or permit the light from the imager to provide an unmodified illumination pattern.