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Illumination Spot Size Calculator

Determine the illuminated spot size resulting from a collimated light source passing through a singlet based on the input beam diameter, the lens focal length, and the propagation distance. Calculator assumes a thin lens and uses the paraxial approximation. The calculator works for three possible scenarios: f > 0 and the propagation distance > f, f > 0 and the propagation distance < f, and f < 0. The larger the difference between propagation distance and focal length the greater the spot size will be.

Geometrical Spot Size Calculator

Spot Size (mm) : --     

db (mm):

f (mm):

x (mm):

Note: if f<0, be sure type in a negative sign into a calculator.

Equations and corresponding legend

Spot Size Represents the resulting geometrical spot size after the beam has exited the lens
db Represents the diameter of the beam that enters the lens (units are in mm)
f Represents the focal length of the lens
x Represents the propagation distance from the output side of the lens to the illuminated spot

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