Wide-field imaging is widely adopted due to its fast acquisition, cost-effectiveness, and ease of use. Its extension to direct volumetric applications, however, is burdened by the trade-off between resolution and depth of field (DOF), dictated by the numerical aperture of the system. It is demonstrated that such trade-off is not intrinsic to wide-field imaging, but stems from the spatial incoherence of light: images obtained through spatially coherent illumination are shown to have resolution and DOF independent of the numerical aperture. This fundamental discovery enables to demonstrate an optimal combination of coherent resolution-DOF enhancement and incoherent tomographic sectioning for scanning-free, wide-field 3D microscopy on a multicolor histological section.
