The production of an optical component often results in a lower-quality surface near its edge. The clear aperture refers to the diameter of the portion of the optical component that must fulfill optical specifications, such as surface accuracy, surface quality, and coating. Due to limitations in the manufacturing process, it’s impossible to achieve a clear aperture that encompasses the entire optical component.

The Clear aperture can be expressed as a measurement like millimeters or as a percentage of the lens’s overall surface area. For instance, if a lens has a diameter of 50mm, the drawing might show the clear aperture as 49mm or 96%. In general, the higher the clear aperture of an optical component, the harder it is to manufacture, as the necessary specifications must extend closer to the outer edge of the optic. The optical component’s quality is determined by various manufacturing tolerances, clear aperture is one of the important specifications.

Clear ApertureQuality
≥ 80%Commercial Quality
≥ 90%Precision Quality
R100%Manufacturing limit


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