Diffraction ringing induced terahertz image edge enhancement

In traditional optics, diffraction ringing induced by a finite system aperture is often treated as an artifact requiring suppression. In this work, we experimentally demonstrate that diffraction ringing can directly enhance the edges of terahertz images. The experiment uses a terahertz time-domain spectroscopy system coupled to a 4f imaging system to image sharp-edged objects, including both square and hexagram, at 0.6, 0.8, and 1.0 THz. Under a limited aperture, clear edge enhancement is observed. This enhancement shows a negative correlation with frequency, meaning that lower frequencies produce stronger oscillations. This result is supported by good agreement among theory, simulation, and experiment. The research demonstrates that edge enhancement can be achieved directly during the imaging process, requiring neither additional optics nor complex digital processing. This approach improves processing efficiency and system integration, thereby holding promise for applications in object identification and classification.