Due to its ability to selectively excite fluorophores near a substrate, Total Internal Reflection Fluorescence (TIRF) microscopy has gained a prominent role in biological imaging and is particularly well-suited for cell membrane studies and in vitro single molecule assays. Similarly, a highly inclined laminated optical sheet (HILO) has been used for high S/N imaging away from the glass-water interface. Although rapid azimuthal scanning of the laser beam has been shown to confer certain advantages, namely fringe reduction and better uniformity of illumination, the effects of optical design on field-of-view and TIRF quality has not been systematically studied. Using commercial ray tracing software, we demonstrate how various choices in the optical system design affect each of these parameters. Using these simulations as a guide, we have built a simple circular scanning microscope for TIRF and HILO imaging using a standard inverted microscope, an XY galvanometer scanner and inexpensive lab-built driver electronics and software. Microscope design was optimized to provide a large field of view without compromising TIRF quality and the performance is demonstrated under demanding conditions (high background fluorescence). Finally, we demonstrate that circle-scanned TIRF is successful for a wide range of applications, including live-cell studies, single molecule assays and super-resolution microscopy.