Autofocusing Research on Terahertz Off-Axis Digital Holography

Terahertz (THz) digital holography is a combination of THz technology and digital holography which has drawn wide attention. Exact measurements of real recording distances in terahertz (THz) digital holography are important. Autofocusing experimental researches have been conducted based on the holograms in THz off-axis digital holography. Five criterion functions are utilized in this paper. Autofocusing performance of these criterion functions has been analyzed and compared by changing the numbers of the superposition frames of holograms. Experiment results show that five criterion functions all have preferable autofocusing performance with the 5-frame averaged holograms; standard deviation-based correlation criterion function has the worst autofocusing performance.