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

在这些研究期间，我们研究了分时激光发射法的二维条形码检测系统（2-D BCDS）的高检测分辨率，这是使其适合实际应用的必要条件。研究结果摘要如下：(1)掩模准直系统的研制为提高二维BCDS在0.4 ~ 0.25mm 10 cm检测范围内的条码检测分辨率，研制了一种新的掩模准直系统。该系统提供了高检测分辨率，同时保持了小的系统尺寸和廉价。使用孔径为3毫米的掩模，将3行0.25毫米条形码的检测范围从传统系统的4厘米扩展到新系统的10厘米。仿真结果验证了掩模准直器的有效性。(2)光学系统优化后的长探测距离研究我们发现，采用不同孔径掩模准直器的三种激光二极管的不平衡掩模准直器系统能够更有效地实现最深的聚焦深度。使用该掩模系统的检测距离从传统准直系统的最大10.3cm扩展到12.5cm。为了提高检测系统的可靠性，研制了口径为40 mm、焦距为28.5 mm的广角聚光镜头。结果表明，其检测范围扩大到14.2cm。对入射光窗图像设计了一种新的几何光学方案，明确了延长探测距离的原因。(4)广角聚光透镜与普通长焦距大光圈透镜的显著性差异研究我们采用长焦距50mm的大光圈透镜制作了一种检测透镜系统，并将其光学特性与短焦距广角聚光透镜进行了比较。结果表明，后者与普通大光圈镜头不同，其检测灵敏度不降低，优于普通大光圈镜头。少

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