Wavefront measurement of a multilens optical system based on phase measuring deflectometry

Usually,a multilens optical system is composed of multiple undetectable sublenses.Wavefront of a multilens optical system cannot be measured when classical transmitted phase measuring deflectometry[PMD] is used.In this study,a wavefront measuring method for an optical system with multiple optics is presented based on PMD.A paraxial plane is used to represent the test multilens optical system.We introduce the calibration strategy and mathematical deduction of gradient equations.Systematic errors are suppressed with an N-rotation test.Simulations have been performed to demonstrate our method.The results showing the use of our method in multilens optical systems,such as the collimator and single-lens reflex camera lenses show that the measurement accuracy is comparable with those of interferometric tests.

Hyperspectral compressive wavefront sensing

Presented is a novel way to combine snapshot compressive imaging and lateral shearing interferometry in order to capture the spatio-spectral phase of an ultrashort laser pulse in a single shot.A deep unrolling algorithm is utilized for snapshot compressive imaging reconstruction due to its parameter efficiency and superior speed relative to other methods,potentially allowing for online reconstruction.The algorithm’s regularization term is represented using a neural network with 3D convolutional layers to exploit the spatio-spectral correlations that exist in laser wavefronts.Compressed sensing is not typically applied to modulated signals,but we demonstrate its success here.Furthermore,we train a neural network to predict the wavefronts from a lateral shearing interferogram in terms of Zernike polynomials,which again increases the speed of our technique without sacrificing fidelity.This method is supported with simulation-based results.While applied to the example of lateral shearing interferometry,the methods presented here are generally applicable to a wide range of signals,including Shack-Hartmann-type sensors.The results may be of interest beyond the context of laser wavefront characterization,including within quantitative phase imaging.

Accuracy characterization of Shack-Hartmann sensor with residual error removal in spherical wavefront calibration

The widely used Shack-Hartmann wavefront sensor(SHWFS)is a wavefront measurement system.Its measurement accuracy is limited by the reference wavefront used for calibration and also by various residual errors of the sensor itself.In this study,based on the principle of spherical wavefront calibration,a pinhole with a diameter of 1μm was used to generate spherical wavefronts with extremely small wavefront errors,with residual aberrations of 1.0×10^(−4)λRMS,providing a high-accuracy reference wavefront.In the first step of SHWFS calibration,we demonstrated a modified method to solve for three important parameters(f,the focal length of the microlens array(MLA),p,the sub-aperture size of the MLA,and s,the pixel size of the photodetector)to scale the measured SHWFS results.With only three iterations in the calculation,these parameters can be determined as exact values,with convergence to an acceptable accuracy.For a simple SHWFS with an MLA of 128×128 sub-apertures in a square configuration and a focal length of 2.8 mm,a measurement accuracy of 5.0×10^(−3)λRMS was achieved across the full pupil diameter of 13.8 mm with the proposed spherical wavefront calibration.The accuracy was dependent on the residual errors induced in manufacturing and assembly of the SHWFS.After removing these residual errors in the measured wavefront results,the accuracy of the SHWFS increased to 1.0×10^(−3)λRMS,with measured wavefronts in the range ofλ/4.Mid-term stability of wavefront measurements was confirmed,with residual deviations of 8.04×10^(−5)λPV and 7.94×10^(−5)λRMS.This study demonstrates that the modified calibration method for a high-accuracy spherical wavefront generated from a micrometer-scale pinhole can effectively improve the accuracy of an SHWFS.Further accuracy improvement was verified with correction of residual errors,making the method suitable for challenging wavefront measurements such as in lithography lenses,astronomical telescope systems,and adaptive optics.