#apertură

• Apertometer — A precision optical instrument or device used in physics and microscopy to measure the numerical aperture of an optical lens, particularly microscope objectives, thereby determining their light-gathering capacity and resolving power.
• Aperture — An opening, orifice, or useful diameter of an optical system (lens, telescope, microscope) through which light rays pass, determining image brightness; in linguistics, it represents the degree of opening of the vocal tract during the pronunciation of a sound (especially vowels), whereas in anatomy it denotes a natural opening of a bony or organic cavity.