Microsphere-assisted self-referencing digital holographic microscopy in transmission mode

In this paper, we introduce a self-referencing microsphere-assisted transmission digital holographic microscopy (DHM) system in real-image operating mode. Self-referencing DHM arrangements provide a compact geometry that are temporally stable against environmental vibrations and suitable for the measurement of dynamic specimens such as cells. These advantages may be more pronounced for microsphere-assisted DHM systems. In the real-image mode, unlike the virtual-image mode, the working distance is increased. This, in turn, provides flexibility for insertion of additional elements for enhancement of the image quality, or for other required tasks. The lateral resolution enhancement is similar to the virtual image arrangement and the axial resolution is decoupled from the lateral one. The methodology is discussed theoretically and validated experimentally by conducting DHM experiments on standard micro-objects and aggregation of micro-particles. Our results show that, by the assistance of a rather big size 550 μm silica microsphere, a 10× microscope objective can resolve the 3D structure of a compact disk. The arrangement may be useful toward having a compact and inexpensive bench-top high-resolution three-dimensional imaging apparatus. (paper)