Large dynamic range wavefront sensor based on a cylindrical microlens array

Abstract

The trade-off between resolution and dynamic range must be managed in the design of a Shack-Hartmann wavefront sensor (SHWS). A relatively large f -number of the microlenses should be chosen to get good lateral and vertical resolutions, but the corresponding dynamic range of measurement is degraded. To extend the dynamic range while keeping a good resolution, we propose a novel SHWS based on a cylindrical microlens array. Instead of the conventional spot pattern, two orthogonal line patterns with the microcylinders oriented in the horizontal and vertical directions are detected on a conventional CCD array. Because the sampled data are now connected along continuous lines, a self-developed line-tracking algorithm unequivocally localizes them even if they are highly distorted. With the sensor constructed, a wavefront transmitted by a commercial progressive addition lens with more than 80l peak-to-valley height has been succesfully measured. The vertical resolution of the sensor was also calculated, resulting of l/25 at the wavelength used (l=635 nm).