Image fusion based on multiscale transform and sparse representation to enhance terahertz images.

High-quality terahertz (THz) images are vital to integrated circuit (IC) manufacturing. Due to the unique sensitivity of THz waves to different materials, the images obtained from the point-spread function (PSF) model have fewer image details and less texture information in some frequency bands. This paper presents an image fusion technique to enhance the resolution of THz IC images. The source images obtained from the PSF model are processed by a fusion method combining a multiscale transform (MST) and sparse representation (SR). The low-pass band is handled by sparse representation, and the high-pass band is fused by the conventional "max-absolute" rule. From both objective and visual perspectives, four popular multiscale transforms-the Laplacian pyramid, the ratio of low-pass pyramids, the dual-tree complex wavelet transform and the curvelet transform-are thoroughly compared at different decomposition levels ranging from one to four. This work demonstrates the feasibility of using image fusion to enhance the resolution of THz IC images.