Evaluation of image quality in terahertz pulsed imaging using test objects

Area of Science:

• Optics and Photonics
• Medical Imaging Technology
• Applied Physics

Background:

• Terahertz (THz) imaging systems, like other modalities, face limitations in spatial resolution, contrast, and noise.
• Quantitative and objective evaluation methods are crucial for advancing THz imaging technology.

Purpose of the Study:

• To introduce novel test objects and image analysis techniques for objective THz image quality assessment.
• To enable quantitative comparison of different THz imaging system configurations and acquisition methods.
• To assess the impact of various image parameters on THz image performance.

Main Methods:

• Design and fabrication of two specialized test objects: one for Modulation Transfer Function (MTF) determination and another for Signal-to-Noise Ratio (SNR) derivation across varying contrasts.
• Evaluation of spatial resolution using the 20% threshold of the MTF.
• Comparison of image SNR between time-domain and frequency-domain parameters.

Main Results:

• Higher terahertz frequencies correlated with larger MTFs, indicating improved spatial resolution.
• Time-delay based THz images consistently exhibited higher SNR compared to intensity-based parameters (e.g., relative transmittance).
• Intensity-based parameters were more susceptible to noise sources like laser fluctuations and detector shot noise.

Conclusions:

• The developed test objects and methods provide a quantitative framework for evaluating THz imaging systems.
• Time-delay imaging is a superior approach for achieving higher SNR in THz imaging compared to intensity-based methods.
• Objective image quality assessment is vital for the optimization and advancement of terahertz imaging applications.