Microscopic structured light 3D imaging via a scattering lens

Transforming a scattering medium into a lens for imaging very simple binary objects is possible; however, it remains challenging to image complex grayscale objects, let alone measure 3D continuous distribution objects. Here, we propose and demonstrate the use of a ground glass diffuser as a scattering lens for imaging complex grayscale fringes, and we employ it to achieve microscopic structured light 3D imaging (MSL3DI). The ubiquitous property of the speckle patterns permits the exploitation of the scattering medium as an ultra-thin scattering lens with a variable focal length and a flexible working distance for microscale object measurement. The method provides a light, flexible, and cost-effective imaging device as an alternative to microscope objectives or telecentric lenses in conventional MSL3DI systems. We experimentally demonstrate that employing a scattering lens allows us to achieve relatively good phase information and robust 3D imaging from depth measurements, yielding measurement accuracy only marginally lower than that of a telecentric lens, typically within approximately 10 μm. Furthermore, the scattering lens demonstrates robust performance even when the imaging distance exceeds the typical working distance of a telecentric lens. The proposed method facilitates the application of scattering imaging techniques, providing a more flexible solution for MSL3DI.