Abstract
A two- and four-step phase shifting (PS) technique in terahertz (THz) digital holography is proposed. Relying on the Mach–Zehnder interferometer-based setup, it was demonstrated that the two-step and four-step PS in Fresnel holograms can assist in a five times greater background subtraction. It allows us to improve the quality of the obtained holographic images, in particular when objects introduce phase changes. It was shown that the recording of holograms of an object consisting of two separated planes can enable qualitative reconstruction of 3D images. Here, the planes were separated by 30 mm, thus defining the longitudinal (depth) resolution in this experiment. It is shown that the PS can serve in distinguishing transparent objects and, by a proper selection of phase variation within the 0–2π range, enable us to increase the quality of the reconstructed hologram. Finally, the advantages of the suggested holographic technique are illustrated by comparing the results with the data of weak absorbing objects obtained via point-to-point, plane-to-plane (4f setup), and dark-field THz imaging approaches. Experiments were performed at frequencies of 0.3 and 0.6 THz recording THz images using resonance antenna-coupled titanium microbolometers.
Highlights
Terahertz (THz) holography is a rapidly developing investigation technique stimulated by a large variety of possible applications, in particular in discriminating weakly absorbing or transparent materials due to its high sensitivity to phase shifts
Relying on the Mach–Zehnder interferometer-based setup, it was demonstrated that the two-step and four-step phase shifting (PS) in Fresnel holograms can assist in a five times greater background subtraction
It is shown that the PS can serve in distinguishing transparent objects and, by a proper selection of phase variation within the 0–2π range, enable us to increase the quality of the reconstructed hologram
Summary
Terahertz (THz) holography is a rapidly developing investigation technique stimulated by a large variety of possible applications, in particular in discriminating weakly absorbing or transparent materials due to its high sensitivity to phase shifts. In the case of four-step PS reconstruction, the contrast was not increased in relation to single hologram reconstruction and two-step PS; it should be noticed that all reconstructed parts of the image have a very similar contrast value In other methods, they differ, while the object had uniform brightness. The revealed improvement introduced by the usage of different phase-shifting techniques opens new possibilities to reconstruct the multi-plane images of recorded multi-plane weakly absorbing objects. It can be found well-suited for a large variety of applications, in particular in biology and biomedicine. We demonstrated the dual-wavelength recording of a two-plane object and its successful reconstruction in both planes
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
