US Patent 7791795 Microscope with a focusing assist apparatus

A microscope for focusing by inserting a split prism at a focusing support time. The image of an iris stop is branched into such two images by the angle deflecting action of the split prism as are individually shifted and focused at symmetric positions across the optical axis of the microscope. These two branched images of the iris stop are further focused on an objective lens through a beam splitter by the focusing action of a lens. The operation unit of a vertical motion device is operated to move an optical system up and down so that the images of a focused pattern are viewed to move in opposite directions from each other in the field of view.