Wells Research & Development

Library

Technical Library and FAQs
Tests and Configurations

Tests and Configurations

Common Configurations
Measuring Image Quality
Other Measurements

Other Measurements

Measuring EFL
Measuring BFL/FFL
Measuring Magnification
Measuring Astigmatism
Measuring Axial Color
Measuring Lateral Color
Measuring Distortion
Measuring Field Curvature

Other Measurements

Measuring Astigmatism

"Astigmatism" means that vertical features (tall skinny features) focus to one plane, and horizontal features (wide short features) focus to a different plane.

Measuring astigmatism

  • Focus carefully on X feature
  • Set the digital micrometer to zero
  • Focus carefully on Y feature
  • Read the distance between the two focal planes directly from the digital micrometer

The standard XYZ stage is suitable for Z axis measurements down to 2-5 microns. A crossed roller bearing stage is available if sub-micron precision is required.