Researchers at the University of Tartu Institute of Physics have unveiled a groundbreaking advancement in three-dimensional holographic imaging technology that promises to revolutionize the way biological specimens and complex structures are visualized. By developing an innovative computational imaging technique, the team has succeeded in significantly enhancing the depth of focus in holograms — increasing it fivefold post-recording. This leap is not only a major stride forward in imaging science but also opens up new possibilities for biomedical research and other fields requiring detailed 3D visualization.
Traditional microscopes and 3D imaging setups have long been constrained by the inflexibility of their recorded images. Once a hologram or microscopic image is captured, conventional methods do not allow alterations to key imaging parameters such as focal depth, limiting the ability to optimize or tailor images for detailed analysis later. Addressing this challenge, Shivasubramanian Gopinath, a Junior Research Fellow at the University of Tartu, alongside his colleagues, has pioneered a method that captures multiple holograms at varying focal distances simultaneously at the time of acquisition.
Unlike classical single-shot holography, this technique enables the acquisition of a set of holographic data representing different focal planes. These multiple recordings are then computationally combined using an advanced reconstruction algorithm, creating a synthetic hologram endowed with dramatically improved depth of focus. This computational post-processing approach transforms the rigid nature of holograms, allowing scientists to adjust imaging properties after capture, tailoring images to the needs of precise scientific analysis.
This breakthrough builds on the foundation of Fresnel Incoherent Correlation Holography (FINCH), a well-established method for recording three-dimensional information under incoherent illumination conditions. FINCH’s ability to reconstruct spatial images computationally from holograms revolutionized incoherent light imaging; however, it has always been limited by fixed imaging properties once recorded. The novel method, termed Post-Engineering of Axial Resolution in FINCH, or PEAR-FINCH, marks a paradigm shift by enabling post-recording adjustment of focal depth, widening the operational capacity of the technology.
A significant advantage of PEAR-FINCH is its capacity to maintain both high image quality and signal-to-noise ratio during the two-step computational reconstructions. This ensures that the enhanced depth of focus does not come at the cost of image clarity, a common trade-off in many imaging methods that attempt to increase focal depth artificially. Achieving a fivefold increase in depth of focus compared to standard FINCH techniques places PEAR-FINCH as a superior tool for detailed biological imaging, especially in specimens with intricate spatial structures.
One of the technical highlights of this method is its robustness under diffusive illumination — the kind of scattered light typically found in real biological samples. Conventional holography often struggles in such conditions due to loss of contrast and resolution; PEAR-FINCH’s computational sophistication tackles these challenges, making it exceptionally well-suited for real-world biological and biomedical microscopy applications where light scattering and diffusive effects are unavoidable.
The flexibility offered by PEAR-FINCH is unmatched. Researchers now have the unprecedented capability to fine-tune the axial resolution and depth of focus after the hologram recording stage, granting a new realm of adaptability. This flexibility means scientist can tailor imaging parameters according to the requirements of individual samples or experiments without needing to repeat data acquisition—saving time and resources while enhancing scientific precision.
Beyond fundamental research, the implications of this technology extend to medical diagnostics, drug discovery, and other fields that demand intricate 3D imaging under varied and often challenging light conditions. By enabling adaptive and intelligent microscopy, PEAR-FINCH brings researchers closer to the next generation of microscopes that actively respond to and optimize for the imaging challenges presented by complex biological samples.
The research team’s findings were meticulously documented in the Journal of Physics: Photonics, illustrating the profound capabilities and applications of the PEAR-FINCH method. The study not only details the algorithmic framework and optical configuration but also presents rigorous experimental evidence validating the system’s performance across a variety of imaging conditions.
“This technology represents a new standard in holographic imaging,” Gopinath explains. “By facilitating extensive control over imaging properties post-capture, PEAR-FINCH surpasses conventional imaging systems and opens up new investigative possibilities that were previously unattainable.” Such advancements signify a move toward smarter, more precise, and user-driven microscopy platforms.
As microscopy continues to evolve, the intersection of optics with computational methods is proving extremely fruitful. PEAR-FINCH stands as a testament to how these interdisciplinary approaches can overcome physical limitations and enhance image capture for scientific advancement. Future explorations may expand the method’s capabilities further, integrating machine learning and real-time processing to create fully autonomous, self-optimizing imaging systems.
This pioneering work elevates the potential of 3D microscopy, particularly in biological contexts, where observing living organisms or complex tissues in their native state with high fidelity is essential. The ability to manipulate image acquisition and reconstruction post hoc provides researchers with a powerful tool to uncover subtle structural and functional details otherwise masked by traditional techniques.
The University of Tartu’s innovation heralds a transformative step towards more adaptive and intelligent microscopy systems. These developments are set to propel numerous scientific domains forward, providing new insights into biological complexity, improving experimental efficiency, and refining the understanding of intricate three-dimensional structures.
Subject of Research: Not applicable
Article Title: Axial resolution post-processing engineering in Fresnel incoherent correlation holography
News Publication Date: 26-Jan-2026
Web References: https://iopscience.iop.org/article/10.1088/2515-7647/ae38ae
References: University of Tartu Institute of Physics, Journal of Physics: Photonics
Image Credits: Author: Shivasubramanian Gopinath
Keywords
3D holography, computational imaging, PEAR-FINCH, FINCH, depth of focus, holographic microscopy, biological imaging, axial resolution, incoherent light imaging, post-processing imaging, optical imaging advancements, University of Tartu
