The multi-scales nonlinear enhancement method of THz image

The THz image has lower contrast and bigger noise because the THz radiant power is small, so a multi-scales nonlinear enhancement method of THz image is proposed for the purpose of improving the image definition. The THz image is decomposed into multi-scales detail coefficients and approximation coefficients by utilizing the wavelet transform. The detail coefficients are taken to denoise and histogram equalization in order to enhance the definition of image edge and image detail. The approximation coefficients are taken to nonlinear transform in order to suppress the background noise and enhance target information. The experiment takes the 0.2 THz image for example to validate the algorithm. The results of experiments and theory analyzing demonstrate that proposed method could boost up the target information of THz image and remove the noise of THz image at the same time. Accordingly the new method could improve the THz image definition, and avoids the phenomenon that the histogram equalization not only enhances the target information but also enhances noise. Theory analysis and experiment show that the new method is reasonable and efficient, and the THz image enhancement effect is more matching the character of human eye.