| 摘要 |
An optical element causes emission of a visible spotter beam [emitted by]from a hand-held scanning bar code reader. The visible beam provides visible indications of the area of a surface which is being scanned by an invisible scanning beam. The optical element transforms the visible spotter beam, at its extreme of travel, into two pairs of cursor beams which are directed along predetermined trajectories relative to the trajectory followed by the scanning beam. The predetermined trajectories can be above and below, or to the left and right of the center of travel of the invisible scanning beam. In one embodiment, a method of identifying the proper focusing distance of the scanning reader is presented. The method identifies the focusing distance by directing the pairs of cursor beams formed from the visible beam at its two angular extremes to form a predetermined pattern indicating the proper focusing distance. The optical element can be made from segmented or gradient surfaces, such as Fresnel surfaces, or from a holographic optical element.
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