Wavefront Sensor for spatial scan using the Hartmann-Shack method

Abstract

This paper presents a simplified instrument to measure the profile of a refractive object contactlessly based on the Hartmann-Shack (H-S) method. The sensing device has been designed with a simple CMOS Position-Sensitive Detector (PSD) of the quad-cell (QC) type, comprising four Active-Pixel Sensor (APS) pixels. A collimated laser beam traverses the object and the resulting wavefront is shaped by its profile. We demonstrate the reconstruction of this wavefront, and therefore the profile of the object, by sequentially sampling the wavefront through a moving single aperture coupled to a converging lens. Notwithstanding, we propose a sequence of steps for instrument calibration, among them the focalization step, using a feature of the QC not yet explored. A target lens was used as a test structure and its sagitta was measured, presenting an average error of 4% with respect to the datasheet value.