The Election-pass Filtering and Image Fusion Algorithm Based on the Wavelet Transform for CW THz Image Processing

摘要

The method of election-pass filtering and image fusion based on the wavelet transform is presented for eliminating the fringes in the continuous wave (CW) Terahertz (THz) Images. The CW THz images have the appearance of sinusoidal waves covering the image with standing wave patterns. The patterns result from reflected inside of the imaging system interfering with the images coming from the sample. The pattern interferes with contrast enhancement techniques, and can make the analysis of small areas difficult. An analysis is taken on the traditional method dealing with this problem by Frequency Domain Filtering and notch filtering, and the disadvantages of the traditional methods are shown. The Wavelet Transform is chosen to deal with the THz images and eliminate interference fringes. In the method, when the size of object is larger than one interference fringe, the character of the object can also be reserved. And the image fusion based on the Wavelet Transform is used to combine the background and the target with pixel-level fusion, which is proposed to improve the speed of identification and the quality of the fused image. Comparing the image restored via wavelet transform with other images, it can be found that the scope of continuous wave THz imaging's application can be extended and clearer images can be acquired.