Study on High Detection Resolution for Two-Dimensional Bar-Code Detection System

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In these research periods, we investigated high detection resolution for a two-dimensional bar-code detection system (2-D BCDS) with time-sharing laser light emission method, which is essential to make it fit for practical use. Abstracts of the results are as follows.(1) Development of a masked collimatorA masked collimator system has been newly developed for the 2-D BCDS to improve barcode detection resolution in a 10-cm detection range from 0.4mm to 0.25mm. This system provides high detection resolution while remaining small system size and inexpensive. Detection range for a 3-line 0.25-mm barcode was expanded from 4cm in conventional systems to 10cm in the new system, using masks with a 3-mm hole diameter. The effectiveness of the masked collimator was confirmed from the result.(2) Study on long detection range due to optimization of an optical systemWe found out that an unbalanced masked collimator system using mask collimators with different hole diameters for three laser diodes i … More s effective for achieving the deepest depth of focus. The detection range using this mask system was expanded to 12.5cm from the maximum of 10.3cm for conventional collimator systems.(3) Development of a wide-aperture condensing lensA wide-angle condensing lens with a 40-mm aperture and a 28.5-mm focal length has been developed to improve the reliability of detection system. The result showed that its detection range was extended to 14.2cm. We also designed a new geometric optical scheme for images of the incident window of light and made the reason for the detection range extension clear.(4) Study on significant difference between a wide-angle condensing lens and a normal wide-aperture lens with long focal lengthWe fabricated a detection lens system using a wide aperture lens with a 50-mm long focal length and compared its optical characteristics with that in the wide-angle condensing lens with the short focal length. The result showed that the latter was superior to the normal wide-aperture lens because its detection sensitivity does not decrease, different from the former. Less