Information flux captured by a bio-optical imaging device with a high space-bandwidth-product (SBP)
The information need in bio-optical imaging has been ever increasing. This demand is due to the landscape shift of contemporary biology from morphological explorations and phenotypic probing of organisms to seeking quantitative insights into underlying mechanisms at cellular and molecular levels. For example, the size of neurons—the building blocks of the brain and nerve systems—is typically at micron scales. However, the functional connectivity of neurons ranges across the entire brain. Therefore, to study such biosystems with tremendous information content, we must use an imaging tool with both a high resolution and a wide field of view (FOV).
The amount of information acquired by an optical system is described by the space-bandwidth product (SBP), a dimensionless quantity that equals the number of optically resolvable spots within a FOV. The higher the SBP, the more information we acquire, and the richer the measurement. Even in a simple biosystem such as a zebrafish brain, a complete characterization usually requires an SBP over hundreds of billions, far exceeding the capability of conventional optical systems.
The standard approach to increase the SBP in an optical system is to stack multiple lenses with complicated optical designs. However, even with a long history of continuing effort, the achievable SBP is typically limited to a hundred million—we are approaching the end of the Moore's law-like limit that the SBP of an imaging system can be hardly improved solely by manipulating the lens parameters.
Although the importance of SPB has been widely recognized in the optics field, there was no unified survey on this topic in bioimaging despite an increasing amount of research. In this review, a group of leading researchers surveyed various high-SBP imaging techniques, divulging their underlying principles and niche applications in biology. Their work is timely and important because, for the first time, it unifies a large number of high-SBP imaging approaches in a common framework. The in-depth insights and perspectives provided will help shape this fast-growing field.
Landscape of current high-SBP imaging systems. (a) Performance of high-SBP imaging systems (b) Comparative advantages of high-SBP imaging systems