Method and scanning arrangement for identifying a code consisting of successive light and dark fields

摘要

The invention relates to an optical scanning arrangement for identifying a code 11 composed of successive light and dark zones forming in each case a module 16, 17, 18, 19, 20, 21, 22 consisting of an upwardly limited integral multiple of basic running lengths Bl to a module width M, in which code a predetermined number of successive modules 16, 17, 18, 19, 20, 21 and basic running lengths Bl form one character 25. The scanning device guides, by means of a light transmitter 14, a light spot 13, whose extension is smaller than the basic running length Bl, but is at a maximum only slightly larger than the basic running length Bl of the code 11, periodically successively over the modules 16, 17, 18, 19, 20, 21, 22. By means of its light receiver 15, the light scattered back from the region, of the code 11, encountered by the light spot 13 is received, and a corresponding electric signal is output at the output 24. By means of differentiation and rectification, a series of individual pulses 41 is formed. Connected to the light receiver 15 is a differential stage 26 with rectification and a counting stage 27 for the clock pulses generated by a clock generator 28 between in each case two predetermined levels of the edges of successive individual pulses 41. The individual counting results are applied to a memory 29 and stored there. Subsequently, a two-module selection stage 30 records in each case the measured width M' of two successive modules in units of the basic running length Bl. A correction stage 31 corrects each module width in the direction of the actual module width M in accordance with correction values stored there previously for each module width pair. For each measured module width M', a corrected module width signal is output.