Study On The Characteristics Of Micro-lens Lens Super-resolution Imaging

Nowadays, beating Abbe's diffraction limit has become a hot topic in photonics. Recently, microscale dielectric spherical lenses have appeared as a simple, real-time, direct and effective approach to obtain super-resolution imaging in white light, which can also have wide application prospects in biology. In this thesis, the diameter, the position of the focal point, the immersion medium and so on have been studied on the microcale spherical lenses to reveal the mechanisms in the imaging formation of micro spheres.The main contents of this thesis are described as follows:(1) The image properties of silica microscale spherical lenses of different diameters 1.97,3.35,4.87 and 7.27?m are studied. The microscale lenses are immersed in air firstly and then semi-immersed in ethanol. We find that the microscale lens can magnify the colloidal crystal samples and the image contrast is greatly improved when the microscale lenses are semi-immersed in ethanol. Our experimental results indicate that small size lenses can receive more high-frequency Fourier components of the object and the semi-immersed microscale lenses can also efficiently intercept more high frequency components. Moreover, the magnification of the microscale lenses is different for different Fourier components of the object(2) Hexagonal close-packed colloidal crystal samples are prepared by a self-assembly method. The image properties of three kinds of microspheres (silica, polystyrene and barium titanate glass) on the colloidal samples are studied. These microspheres are placed in air, semi-immersed and full-immersed in ethanol respectively. We find that all these microspheres can magnify the colloidal crystal samples and have the super-resolution imaging ability. Our experimental results indicate that the position of the focal point of the microsphere can affect the super-resolution imaging property, and with different ways of immersion, the focal point of the different microspheres can be adjusted. Therefore microspheres with different refractive index need different observing ways to get the best imaging quality. The silica microspheres and the polystyrene microspheres need semi-immersion, while the barium titanate glass microspheres need full-immersion to make the focal point close to the microsphere, so that the best imaging quality can be obtained. The mechanisms are also discussed with numerical simulations.(3) Lastly, three kinds of microspheres (silica, polystyrene and barium titanate glass) are semi-immersed or full-immersed in four different refractive index immersion medium (deionized water, ethanol,50% salt solution, microscale immersion oil). We find that the three kinds of microspheres semi-immersed or full-immersed in the four immersion medium can have super-resolution imaging ability. Moreover, we find that the image magnification and contrast can be decided by the relative refractive index between a microsphere and the immersion medium. A higher relative refractive index can increase image magnification and contrast.