Research On The Characteristics Of Super-resolution Thin Film Imaging Based On Microsphere Lens

As we all known, microscopes play important roles in scientific researches.However, an optical microscope can not resolve features smaller than ?/2 due to Abbe's diffraction limit. Recently, imaging by dielectric microspheres embedded in thin film becomes a simple technique to achieve optical super-resolution. In this thesis,we propose a high-efficiency way to fabricate barium titanate glass (BTG)microsphere-embedded polydimethylsiloxane (PDMS) ultrathin film and study the imaging properties of microspheres.The main contents of this thesis are described as follows:(1) We propose a new approach to fabricate BTG microspheres embedded ultrathin PDMS film with the aid of a transparent tape, and PDMS films with thickness down to few micrometers can be fabricated successfully.(2) We study the imaging properties of BTG microsphere-embedded PDMS films with different PDMS thicknesses. Our experimental results reveal that: for an individual microsphere, its field of view (FOV) obviously increases as the film thickness decreases, while the corresponding magnification barely changes. When the PDMS film thickness is 5-10?m, the FOV of a microsphere is the largest, and a method to broaden FOV by microsphere array is inspired. To analyze the change of the FOV, the electric field distributions of a microsphere embedded in PDMS with various thicknesses are simulated by Computer Simulation Technology (CST).Moreover, we fabricate BTG microspheres embedded PDMS film with a thickness of 7.4?m and observe images of 2, 3,4, and 6 connected microspheres respectively.(3) We deposit a dielectric layer (SU-8) between the microsphere lens and the object surface, and study the imaging properties with different SU-8 thicknesses. Our experimental results reveal that the FOV increases from 10.8 to 13.2?m when the film thickness increases from 0 to 270 nm. It is found that the SU-8 layer with a thickness around 160 nm can obviously increase the imaging FOV and contrast.Moreover, for different dielectric layers with the same film thickness 160 nm, the SU-8 layer can improve FOV while the TiO2 layer cannot. We also find that the amount of light coupling into the dielectric layer decides the image quality. This phenomenon is explained by the destructive interference effect.