Researchers from the University of Tartu Institute of Physics have developed a novel method for enhancing the quality of three-dimensional images by increasing the depth of focus in holograms fivefold after recording, using computational imaging techniques. The technology enables improved performance of 3D holographic microscopy under challenging imaging conditions and facilitates the study of complex biological structures.
One of the main limitations of conventional microscopes and 3D imaging systems is that, once an image or hologram has been recorded, its imaging properties cannot be altered. To overcome this limitation, Shivasubramanian Gopinath, a Junior Research Fellow at the University of Tartu Institute of Physics, and his colleagues have developed a new method that enables to capture a set of holograms with different focal distances at the time of acquisition, instead of a single image. These can then be computationally combined to produce a synthetic hologram that offers a much greater depth of focus than conventional approaches, and allows for post-processing of the recorded image.
The new method represents a major advance on the existing digital holography technique, which enables 3D information of an object to be recorded under ordinary illumination and later reconstructed into a spatial image by a computer (known as Fresnel incoherent correlation holography, or FINCH). The new method is called post-engineering of axial resolution in FINCH, or PEAR-FINCH.
What makes the novel method unique?
- The depth of focus can be adjusted after the hologram has been recorded.
- The new two-step computational reconstruction method maintains high image quality and signal-to-noise ratio.
- A fivefold increase in depth of focus has been achieved compared to the conventional FINCH technique.
- Works well under diffusive illumination, which is characteristic in the case of real biological samples.
"This level of post-recording flexibility has not been reported before. It can therefore be said that our achievement represents a new paradigm in holographic imaging, consistently outperforming both conventional direct imaging systems and standard FINCH," Gopinath said.
Smarter and more precise microscopy
The PEAR-FINCH method makes 3D holographic microscopy more flexible, powerful, and easier to use in biological and biomedical research. The technique opens up new possibilities for studying complex biological structures under challenging imaging conditions, and brings us closer to creating more adaptive and intelligent microscopes.
The research results were published in the Journal of Physics: Photonics in the article "Axial resolution post-processing engineering in Fresnel incoherent correlation holography" . The open-access publication of the article was supported by the University of Tartu.
