Fig. 1. ( a ) Schematic diagram of the remote mode optical microsphere setup. ( b ) Mechanism to illustrate the enlarged virtual image by the microsphere. ( c ) Optical image captured by this system (Sample: semiconductor testing sample; scale bar: 10 μm; imaged by a 20 μm silica microsphere compiled to an oil-immersion optical microscope with a 100× objective lens, NA=1.4). Inset: SEM image (scale bar: 1 μm).

Fig. 2. ( a ) Schematic of the design of the universal lens adaptor for the microsphere (silica microsphere with 400 μm diameter attached on a 20× objective lens. Characterization was done in ambient air and distance between the onion cell and the microsphere is ~65 μm, with white light illumination). ( b ) Integrated image of onion cells (scale bar: 20 μm). ( c ) Optical image of the universal sample adaptor after integration. ( d ) Comparison of the optical images by three optical lenses: the 20× objective lens (left, scale bar: 20 μm); 20× objective lens with the microsphere (middle, which is our nanoscope design, scale bar: 8 μm); and 50× objective lens (right, scale bar: 8 μm).

Fig. 3. ( a ~ c ) Imaging of nano-dot pairs with nano-gap on a Si wafer. ( a ) SEM image of the samples, showing sizes of nano-gaps in between each pair of nano-dots. ( b ) Imaging of the samples by an oil-immersion microscope (neighboring nano-dots cannot be resolved clearly). ( c ) Neighboring separated nano-dots are resolved clearly by a microsphere with 20 μm diameter. The back dash line in ( c ) indicates the line cut (the intensity analysis is presented in supplementary materials). ( d ~ f ) Imaging of samples with complex features (the "nano-rose"). ( d ) Zoomed-in SEM image with size notations, it shows that the typical line width of the structure is ~140 nm, and separated by nano-grooves with a typical size ranging from 50~60 nm. ( e ) Imaging result by the oil-immersion optical microscope. ( f ) Image under the 27μm microsphere in scanning mode. The diameter of the microsphere is larger in order to contain the entire nano-rose in the central region. (Compared to the microsphere used for the imaging of nano-dots, the microsphere with a larger diameter is chosen to ensure the entire nano-rose pattern is in the central region of the microsphere. Inset: zoomed-in image under the microsphere). ( g ~ i ) Imaging of a magnetic head in a hard disc drive from the production line. ( g ) SEM image of the magnetic head, with a nano-gap of 77 nm. ( h ) Imaging by a conventional oil-immersion microscope. ( i ) Imaging by the microsphere nanoscope in non-contact mode. The three columns represent images obtained by SEM, oil-immersion optical microscope (100×, NA 1.4), and microsphere nanoscope, respectively.