Project’s title: Volumetric image reconstruction with filtering of redundant phase information

Project’s leader: Prof. dr hab. Maciej Daniel Wojtkowski

Partner: State research institute Center for Physical Sciences and Technology, Lithuania

Project implementation period: 2021 – 2025

Granting institution: National Science Centre

Project’s number: 2020/38/L/ST2/00556


The aim of this project is to introduce and experimentally verify the authors’ original description of physical processes related to the influence of light with partial spatial coherence on image reconstruction in the presence of optical heterogeneity. The proposed research works will allow for a better understanding of the physical and technical limitations for the case of imaging with partially spatially coherent light in systems with phase-sensitive (interferometric or holographic) detection.

In this fundamental research program, we would like to solve one of the most basic problems of optics, which is in-vivo microscopic imaging in biological samples.

This project aims to broaden our knowledge about the image formation process in the presence of highly scattering media.

The leading hypothesis in this project is the assumption that it is possible to introduce spatial modulation of the phase of spatially coherent light in a controlled way so as to achieve non-invasive three-dimensional imaging reconstruction with quality of cross-sectional images comparable to that obtained by microscopy with spatially incoherent light.


To speed up OCT imaging a Fourier-domain Full-Field OCT (FF-FD-OCT) has been introduced that significantly improved the imaging speed by parallelizing signal acquisition using a camera instead of the point detector [1, 2]. However, the technique introduces coherent noise in the OCT images due to the wide-field acquisition by a camera and use of a spatially coherent swept laser source. The noise, which is called crosstalk, manifests itself as a speckle pattern in images and challenges its interpretation, especially at deeper layers.

One of the most promising techniques for volumetric imaging that can acquire images coming from different layers of an object (optical axial sectioning) is Optical Coherence Tomography (OCT). OCT has become an indispensable tool in biomedical imaging. However, OCT in its classic form with a scanning beam does not allow to get rid of speckle noise, which in turn makes it impossible to reconstruct the image of a selected layer with the quality obtained in classical microscopy at cellular resolution (Fig. 1). Additionally, imaging speed still remains the limitation of OCT since involuntary motion during in vivo imaging can blur OCT images to the degree that it cannot be utilized for the diagnostic purposes. In addition, speed can be traded-off for better imaging depth, which is another important parameter in biomedical imaging, such as that of the human eye.

In the previous projects we have proposed and developed a new method that we call Spatio-Temporal Optical Coherence (STOC) imaging [4]. The STOC technique allows to obtain imaging effects equivalent to those that could control the spatial coherence of the light beam. We have created a theoretical description of this process. Based on this theory, we have proposed an optimal and simple way of “filtering” scattered photons, and minimizing their effects on imaging [3]. The new knowledge allowed us to develop a new method based on full -filed OCT called STOC-T imaging, which allows for in-vivo imaging with microscopic accuracy [4].

Figure 1. A diagram showing the idea of improving the quality of in-vivo microscopic imaging. OCT is a method that has a great potential to provide unique image information comparable to classical microscopy without invasive sample preparation. State of the art OCT is unable to reconstruct individual cells. Computational reconstructions of objects based on measurements with newly developed modification of OCT method (STOC-FF-FD-OCT) will enable to obtain image quality analogous to histology. Such improvements require to introduce new, comprehensive mathematical model, new computational techniques and efficient spatial phase modulation technology.

However, we still do not understand whether the imaging reconstructions obtained with the STOC-T method can be comparable with the histology (microscopic images of extracted and stained slices of tissue) and what are the physical limits of applicability of this technique. The key here is to understand the impact of the introduced spatial phase modulation on disturbed interferometry signals with the current technical limitations and how much we can improve these reconstructions by advanced signal and image processing techniques. Therefore, we would like to extend our STOC model describing the disruption of images introduced by scattering with a specific image reconstruction configuration of FD-FF-OCT and include additional numerical methods enabling to improve the image quality (Fig. 1).


1.            T. Bonin, G. Franke, M. Hagen-Eggert, P. Koch, and G. Hüttmann, “In vivo Fourier-domain full-field OCT of the human retina with 1.5 million A-lines/s,” Optics Letters 35, 3432-3434 (2010).

2.            D. Hillmann, H. Spahr, C. Hain, H. Sudkamp, G. Franke, C. Pfaeffle, C. Winter, and G. Hüttmann, “Aberration-free volumetric high-speed imaging of in vivo retina,” Scientific Reports 6(2016).

3.            D. Borycki, M. Hamkało, M. Nowakowski, M. Szkulmowski, and M. Wojtkowski, “Spatiotemporal optical coherence (STOC) manipulation suppresses coherent cross-talk in full-field swept-source optical coherence tomography,” Biomedical Optics Express 10, 2032-2054 (2019).

4.            M. Wojtkowski, P. Stremplewski, E. Auksorius, and D. Borycki, “Spatio-Temporal Optical Coherence Imaging – a new tool for in vivo microscopy,” Photonics Letters of Poland 11, 45-50 (2019).