Uncertainty analysis on optical testing with a Shack-Hartmann sensor and a point source

Abstract

In this study, we analyze the uncertainty in an optical testing system using a Shack-Hartmann sensor for a wavefront measurement device. The main uncertainty sources of the optical testing system are the Shack-Hartmann sensor, the image relay optics, and the pinhole source. Using a homemade high-precision plane-wave source as a reference, we develop a simple method to calibrate the optics of the system and the Shack-Hartmann sensor itself. It is found that the wavefront error of a pinhole source is negligible, and that the error due to the image relay optics installed between the test lens and the Shack-Hartmann sensor is 0.030 λ (RMS). By warming up the Shack-Hartmann sensor for about 1 hour, the measurement values are stabilized to within 0.001 λ (RMS). After calibrating the optical testing system with the reference source, overall uncertainty in the optical testing system is reduced to 0.009 λ (RMS). Performance of the optical testing system is evaluated by measuring the wavefront errors of various optical components, such as a numerical aperture (NA) 0.25 aspheric lens and a digital video disc (DVD) pick up lens.