Effective focal length through a microscope

Abstract

The optical power of a thick spherical lens and its Coddington shape factor are essential magnitudes that characterize its image quality. We propose an experimental procedure and apparatus that allow accurate determination of those magnitudes for any spherical lens from geometrical measurements. It overcomes the drawbacks of other devices that need of the refractive index or may damage the lens surfaces, like spherometers, and provides similar results to commercial lensmeters.