Studying biological processes in living organisms over extended periods sets stringent conditions and limitations on their visualization. The physiological properties of living organisms change over varying time scales and rates; on one hand, there is a requirement for imaging events taking place at ultrashort time scales, and on the other hand, prolonged imaging methods are needed for biological processes that take longer periods to complete.

To visualize the physiological processes with high accuracy and to study the structure and function of living organisms, such as cells on a Petri dish, one needs an accurate referencing method to image and quantify a particular region of interest. In this article, Sandoz and Jacquot used a reference plate with pseudoperiodic patterns, in what they term as “position-referenced microscopy,” to obtain absolute positioning of specimens with submicrometer accuracy.

The authors developed a position-referencing principle based on pseudoperiodic patterns. Such a reference can be used for lateral coordinate determination of recorded images with respect to the sample holder in a microscope imaging setup and has been demonstrated in cell preparations fixed onto such a “smart” Petri dish. According to the authors, since position of the imaging objects is referenced to the sample holder, it is not necessary that the specimens remain on the microscope stage, and regions of interest can be easily localized from the position data for further and subsequent studies.

In their current work, the authors have further developed a noncontact position-sensing system based on digital holography in which holograms of a pseudorandom pattern encoded glass plate are recorded to determine the absolute position of features of interest on a sample that is placed on such a reference glass plate.

Pseudoperiodic encoding of lateral position of samples in an imaging microscope has been used after the “linear feed-back shift register principle” that is used for pseudorandom number generation. A pseudorandom pattern that is marked on a glass plate for imaging based on digital holography is used to determine the fine details of a sample’s position on such a plate. This method has great potential in the accurate localization of sample holders/stages in imaging systems for the retrieval of small regions of interest on samples that need to be transferred from one instrument to another while studying the physiological processes of longer durations.

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