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Numerical aperture
Numerical aperture is a measure of the quality of a lens or optical element that determines the quality of light passing through it. It is calculate...
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Numerical aperture is a measure of the quality of a lens or optical element that determines the quality of light passing through it. It is calculate...
Numerical aperture is a measure of the quality of a lens or optical element that determines the quality of light passing through it. It is calculated using the ratio of the full width at half maximum (FWHM) of the image to the diameter of the entrance pupil.
FWHM is the width at the full width of the image where the light intensity is half its maximum value. It can be calculated using the formula:
FWHM = 2 * (full width at FWHM) / (diameter of entrance pupil)
The diameter of the entrance pupil is the diameter of the clear opening at the center of the lens or element.
Numerical aperture (NA) is a dimensionless quantity that ranges from 0 to 1. A NA of 1 indicates that the light passing through the lens is concentrated in a circle at the image plane. A NA greater than 1 indicates that the light is spread out over a larger area on the image plane.
Examples:
A lens with a NA of 0.5 is considered to be good as it allows a wide range of light to pass through the lens and produce a clear image.
A lens with a NA of 1 is considered to be average as it allows light to pass through the lens and produce a slightly blurred image.
A lens with a NA of 1.4 is considered to be poor as it allows only a narrow range of light to pass through the lens and produces a very blurred image.
In conclusion, the numerical aperture is a crucial parameter that determines the quality of light passing through an optical element. It provides valuable insights into how light is focused and spread out on the image plane, allowing engineers to select appropriate lenses and optical elements for specific applications