Loupe
loupe | ˈlüp
noun
A small magnifying glass, often held in the eye socket, used for analyzing gemstones
A loupe is a specialized magnifying glass used to evaluate small objects at a much closer distance. It is not designed to be held at a distance, but directly up to the eye to ensure the best and most accurate possible magnification of the object being evaluated. The lens is contained in a cylinder or cone that can be held to the eye socket or close to the eye. Loupes are most commonly associated with analyzing gemstones but are also used in watchmaking, photography, medicine, tattooing, and other sciences where it makes sense to physically be as close as possible to the object being analyzed. There are three common types of loupes - simple lenses for low-magnification levels, compound lenses for higher degrees of magnification, and prismatic lenses.