| 摘要 |
Apparatus for conducting secondary tests for security validation are presented. In one embodiment of the invention a light source, either infrared or visible, is cast upon two neighboring areas of a paper purported to be a valid instrument, these areas being of different light reflective characteristics. Photo cells are maintained in close juxtaposition to each of these two areas and the light reflected therefrom or passed therethrough is sensed by the photo cells. Comparator circuits are interconnected with the photo cells and, in part, determine the validity of the instrument on the basis of the comparison of the intensity of light reflected by each of the two areas. In another embodiment of the invention, a reference reflective surface is provided in juxtaposition to one of the photo cells to test those instruments not having neighboring areas of different light reflective characteristics. In yet another embodiment of the invention, a reference photo cell is provided for sensing the light actually emitted from the light source and establishing this light emission level as a reference level. Further, dividers and comparator circuits interconnect this reference photo cell with one of the other two photo cells for further determining the instrument's validity by testing whether the light reflected from one of the areas falls within a predetermined percentage of the light actually emitted from the light source. The entire unit of the light source, photo cells, and reference photo cell are all maintained within a singular molded housing preferably constructed of a highly light reflective material.
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