The intensely illuminated central circular region of a focused beam limited by diffraction. It contains about 84 percent of the total optical power. In laser machining and microscopy, the size of the Airy disk defines the absolute minimum spot size achievable with a perfect, aberration-free lens.
Heard on the job
The pinhole acts as a spatial filter, sized perfectly to pass the Airy disk while blocking the higher-order spatial noise.
Related terms
Airy pattern
The full diffraction pattern of a circular aperture, featuring a central spot and concentric rings.
Rayleigh's resolution limit
The minimum separation required between two point sources for an optical system to distinguish them as separate.
Aperture
A physical opening that limits the bundle of light rays passing through a system.