Browsing by Subject "FDTD"

Imaging done with conventional microscopes is diffraction-limited, which sets a lower limit to the resolution. Features smaller than the resolution cannot be distinguished in images. This limit of the diffraction-limit can be overcome with different setups, such as with imaging through a dielectric microcylinder. With this setup it is possible to reach smaller resolution than with a diffraction-limited system, which is called super-resolution. Propagation of light can be modelled with various simulation methods, such as finite-difference time-domain and ray tracing methods. Finitedifference time-domain method simulates the light as waves which is useful for modelling the propagation of light accurately and take into account the interactions between different waves. Ray tracing method simulates the light as rays which requires approximations to the light’s behaviour. This means that some phenomena cannot be taken into account, which can affect the accuracy of the results. In this thesis the model for simulating super-resolution imaging with microcylinder is studied. The model utilizes the finite-difference timedomain method for modelling the near-field effects of the light propagating through the microcylinder and reflecting back from a sample. The reflected light is recorded on the simulation domain boundaries and a near-field-to-far-field transformation is performed to obtain the far-field corresponding to the recorded fields. The far-field is backward propagated to focus a virtual image of the sample, and the virtual image is then used in ray tracing simulation as a light source to focus it to a real image on a detector.