Department of Electronic Engineering, Hwa Hsia Institute of Technology, 111 Gong Jhuan Rd., Chung Ho district, New Taipei City, 23568, Taiwan.
Sensors (Basel). 2011;11(12):11447-63. doi: 10.3390/s111211447. Epub 2011 Dec 1.
This study develops an approach to improve the quality of infrared (IR) images of vein-patterns, which usually have noise, low contrast, low brightness and small objects of interest, thus requiring preprocessing to improve their quality. The main characteristics of the proposed approach are that no prior knowledge about the IR image is necessary and no parameters must be preset. Two main goals are sought: impulse noise reduction and adaptive contrast enhancement technologies. In our study, a fast median-based filter (FMBF) is developed as a noise reduction method. It is based on an IR imaging mechanism to detect the noisy pixels and on a modified median-based filter to remove the noisy pixels in IR images. FMBF has the advantage of a low computation load. In addition, FMBF can retain reasonably good edges and texture information when the size of the filter window increases. The most important advantage is that the peak signal-to-noise ratio (PSNR) caused by FMBF is higher than the PSNR caused by the median filter. A hybrid cumulative histogram equalization (HCHE) is proposed for adaptive contrast enhancement. HCHE can automatically generate a hybrid cumulative histogram (HCH) based on two different pieces of information about the image histogram. HCHE can improve the enhancement effect on hot objects rather than background. The experimental results are addressed and demonstrate that the proposed approach is feasible for use as an effective and adaptive process for enhancing the quality of IR vein-pattern images.
本研究提出了一种改进静脉图案红外（IR）图像质量的方法，这些图像通常存在噪声、对比度低、亮度低和目标物小等问题，因此需要预处理来提高其质量。该方法的主要特点是不需要先验的 IR 图像知识，也不需要预设参数。主要有两个目标：脉冲噪声减少和自适应对比度增强技术。在我们的研究中，开发了一种快速中值滤波（FMBF）作为降噪方法。它基于 IR 成像机制来检测噪声像素，并基于改进的中值滤波来去除 IR 图像中的噪声像素。FMBF 的优点是计算负载低。此外，当滤波器窗口增大时，FMBF 可以保留相当好的边缘和纹理信息。最重要的优点是，FMBF 引起的峰值信噪比（PSNR）高于中值滤波器引起的 PSNR。提出了一种混合累积直方图均衡化（HCHE）方法用于自适应对比度增强。HCHE 可以根据图像直方图的两条不同信息自动生成混合累积直方图（HCH）。HCHE 可以改善对热点物体的增强效果，而不是背景。实验结果表明，所提出的方法是可行的，可以作为一种有效且自适应的处理方法，用于增强 IR 静脉图案图像的质量。
