Study On Large-Aperture Lens Detection Techniques Based On Wavefront Sensing

Ultra-long focal-length lens with large aperture (UFL) is now being widely used in large optical systems, such as high energy laser system and laser fusion system. It is a great challenge for the precise detection of its focal length and defects in the optical detection area.In this paper, we detect the UFL based on wavefront sensing techniques. A new long focal-length measurement method (LFMM) based on divergent beam and two Ronchi gratings of different periods is proposed, and features remarkably high accuracy and repeatability. Also two methods based on Shack-Hartmann wavefront sensor are proposed for the detection of phase vortex caused by the defect in the UFL.The method of long focal-length measurement is based on Talbot interferometry. In this method, a divergent laser beam is employed as an alternative to the traditional collimated beam, and the scanning system in traditional method is not needed. Meanwhile, two gratings of different periods are employed to match the divergent beam for higher measurement accuracy. From both numerical simulation and experiment, our method exhibits good performance in testing accuracy, validity, repeatability and stability.The methods of optical vortex detection are based on wavefront sensor. The defect, such as scratch and striae, causes uncontinuous phase when a wavefront passes though the lens. The phase vortex, or called optical vortex (OV), exists at the edge of the uncontinuous phase. Based on Shack-Hartmann wavefront sensor, we propose phase-slope-combining correlation matching method (PSC-CMM) for the position detection and slope vector matching method (SVMM) for the topological charge detection of OV. Both two methods work well with high accuracy in experiments. The position detecion accuracy is better than 3μm, and the accuracy rate of the topological charge detection is 100%.