Multimodal illumination for quantitative transmitted-light microscopy

Compact Open-Source Multimodal Illumination Cluster ('COSMIC') is a condenser-free illumination module that enables bright field, dark field, diascopic fluorescence and differential phase contrast (DPC) imaging on both commercial and open-source microscope platforms. COSMIC is constructed using low-cost, widely available components and is controlled through µManager, facilitating straightforward integration into existing imaging systems. We demonstrate multimodal transmitted-light imaging of live cell cocultures and living Caenorhabditis elegans specimens, including quantitative phase imaging (QPI) derived from DPC measurements. We further validate and calibrate quantitative DPC (qDPC) using a quantitative phase target on a range of open-source and commercial systems and introduce a practical method for optimising the axial position of the illuminator without access to the objective's back focal plane. COSMIC provides an effortless route to multimodal and quantitative phase imaging on any optical microscopy system, using minimal optical hardware and supporting both research-grade and resource constrained microscopy environments.