Calculate lens diameter using NA

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SUMMARY

The calculation of lens diameter for a projection aligner with an object to lens distance of 500mm and a numerical aperture (NA) of 0.28 results in a lens diameter of 280mm. The formula used is NA = r / D, leading to a radius (r) of 140mm. Considering that only 90% of the lens area is usable, the effective diameter remains 280mm, confirming that the initial calculation is accurate. This discussion clarifies the application of the NA formula in practical scenarios.

PREREQUISITES
  • Understanding of numerical aperture (NA) in optics
  • Familiarity with basic lens formulas
  • Knowledge of radius and diameter relationships
  • Concept of usable area in optical systems
NEXT STEPS
  • Research the impact of numerical aperture on lens performance
  • Learn about lens design principles in optical engineering
  • Explore calculations for lens diameter in different optical setups
  • Investigate the effects of usable area on imaging quality
USEFUL FOR

Optical engineers, physics students, and anyone involved in lens design and optical system optimization will benefit from this discussion.

Lanc1988
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Homework Statement


A projection aligner has an object to lens distance of 500mm. Calculate lens diameter for the aligner if NA = 0.28. Assume the usable area of lens is 90% of its diameter.

Homework Equations


NA = r / D
Note: NA is the numerical aperture.

The Attempt at a Solution


I know that NA = r / D which means 0.28 = r / 500 and then r = 140mm so the diameter of the lens would be 280mm but I'm unsure how to use the idea of 90% of the lens being usable.
 
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It seems that the answer would still be 280mm but I'm not completely sure. Any help would be appreciated. Thanks.
 

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