In this work we describe simulation, optical design and assembly of a tunable light sheet microscope capable of high-resolution 3D imaging of biological specimen. The system utilizes aspheric lenses that are combined with one axial-conical lens (e.g. Powell lens). Due to the conic aspheric shape of such lenses a special phase shift transformation is induced along one direction if an incident laser beam interacts with the tip of the lens. Unlike conventional laser line generators, such as cylindrical lenses, Powell lenses redirect the beam towards their edges forming a bone-shaped beam. This effectively minimizes the central hot spot and enables the formation of a semi-uniform intensity distribution at the center of the output beam. Our simulated and experimental results demonstrate that a thin light sheet can be achieved with a combination of a single Powell lens and further aspherical optical elements. We obtained best results using Powell lenses providing fan angles between 5° and 10° and tip-radii between 0.1 mm and 0.4 mm. To validate this optical design, we imaged various biological specimen in sizes ranging from several hundred µm up to multiple centimeters. The captured images reveal marked improvements in resolution along all spatial axes.