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基于SSD框架的自然场景盲文识别方法

Natural Scene Braille Recognition Based on SSD Framework

  • 摘要: 盲文是视障人士学习知识和技术的工具, 正常人通常对盲文知之甚少, 造成正常人与盲人之间的沟通障碍重重. 为此, 首先构建了自然场景盲文段图像数据集, 该数据集中包含 1 157 幅不同宽高比、不同背景的盲文段图像和对应的标签信息; 随后分析自然场景图像中盲文的特点, 并基于 SSD 框架提出自然场景盲文识别方法. 所提方法根据盲文字符尺寸小且具有固定宽高比的特点选择用于识别的特征层, 设计 CNN 结构、 默认框大小、 盲文字符标签、图像输入策略和损失函数, 以提高盲文字符识别的准确率; 根据盲文字符中盲文点位于边缘区域的特点设计像素层面的注意力机制, 提高盲文字符识别的回归率. 实验结果表明, 在所构建的盲文段图像数据集上, 所提方法的 H 值达到 0.903, 盲文字符检测速度为 66.22 帧/s; 与 SSD, Faster R-CNN, EAST, 以及基于 CNN 的盲文识别方法 EAST-Edge和 UNet-Braille 相比, 该方法的盲文识别性能提升明显.

     

    Abstract: Braille is a tool for visually impaired individuals to learn knowledge and skills. Normal individuals often have little knowledge of braille, resulting in numerous communication barriers between normal and visually impaired individuals. A natural scene braille segment image dataset was first constructed, which includes 1 157 braille segment images with different aspect ratios and backgrounds, as well as corresponding label information; Subsequently, the characteristics of braille in natural scene images were analyzed, and a natural scene braille recognition method was proposed based on the SSD framework. The proposed method selects feature layers for braille recognition, designs CNN structures, default box sizes, braille character labels, image input strategies and loss functions to improve the precision of braille recognition based on the small size and fixed aspect ratio of braille characters. Moreover, a pixel level attention mechanism is designed based on the characteristic that braille points are located in the edge region of braille characters, to improve the recall of braille recognition. Experimental results show the proposed method achieves a value of 0.903 in H and a braille character recognition speed of 66.22 frame/s. Compared with SSD, Faster R-CNN, EAST, and CNN based methods named EAST-Edge and UNet-Braille on the constructed natural scene braille segment image datasets, the braille recognition performance of the proposed method has been significantly improved.

     

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