angular aperture

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Related to angular aperture: aperture angle

an·gu·lar ap·er·ture

the angle, in air, of light that passes from the object to the ends of the diameter of the front lens of the microscope objective.
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r], the angular aperture of the incident beam Soller slits [[DELTA].
D] are the angular apertures of the slits (see Fig.
However, most commercial diffractometers are supplied with Soller slits having angular apertures [DELTA] between 2[degrees] and 5[degrees], and in such cases the breadth of the aberration profile is reduced quite dramatically.