Schematic of (a) Ray-tracing for virtual image formation in microsphere-assisted microscopy (MAM); MAM setup using a (b) low-index sphere working in air, (c) high-index sphere submerged in a liquid droplet, and (d) high-index sphere embedded in a solidified film; S: sample; MS: microsphere; VI: virtual image; MO: microscope objective. (e) Schematic representation of a microsphere-assisted interference microscope based on the Linnik configuration comprising two MO lenses and a beam splitter (BS). The illumination beam path, which corresponds to Kӧhler illumination is shown in blue, the imaging beam path in red. The illumination beam path appearing as a plane wave below the objective lens is omitted for better visibility. The figure is not drawn to scale to enhance comprehensibility. (f) Schematic setup for microsphere-assisted Mirau-DHM, in which a slight tilt (few degrees) is applied to the sample stage to achieve an off-axis digital holography configuration. (g) Schematic setup of the microsphere-assisted self-referencing DHM in transmission mode; S: sample; RI: real image; MO: microscope objective; GP: glass plate; TL: tube lens.