Key Technology Research On Phase Diversity Wavefront Measurement Based On Adaptive Optical Technology

With the development of modern optical technology and the increase of complex observation missions,large optical observation systems such as astronomical telescopes and space telescopes have put forward strict requirements on the main mirror in terms of aperture,surface shape accuracy and so on,bringing great challenges to the design and processing of the telescope inspection.Existing inspection methods for main mirror are usually segmented inspection methods that replace different inspection instruments as the surface machining accuracy increases.This usually includs profilometer inspection,infrared interferometer inspection and visible light interferometer inspection,etc.It does not only require the replacement of inspection equipment,but also the complexity of tooling commissioning,which is a bottleneck limiting the development of the main mirror.The phase diversity method(PD)is a relatively new wavefront measurement technology,which recovers the wavefront to be measured through an algorithm based on the light intensity distribution on the measured image surface.It has the characteristics of simple structure,no special requirements for the device,and is applicable to both point target and extended target.It can be used for detection of common phase error of segmented telescope,and has potential application value for mirror surface shape detection.The traditional phase diversity method collects the intensities of the focal plane and the defocus plane for phase recovery.Only a single measurement can be performed each time,and the constraints are insufficient.It is easy to fall into the local optimal solution under the influence of noise.The phase difference method based on adaptive optics can realize multi-channel constraints and improve the optimization efficiency of single measurement.It treats the wavefront to be measured as an aberration to be corrected.During the correction-measurement iteration,wavefront to be measured will gradually approach plane wave,improve the signal-to-noise ratio of the far-field image,and further improve the measurement accuracy.High-precision wavefront measurement results can be obtained when the iteration results are stable.Phase difference method as a fluctuating optical measurement technique,the measurement result is usually folded into a wavelength range of the wrapped phase and contains a certain amount of high-frequency noise,after the introduction of adaptive optics technology,the measurement process needs to be filtered to avoid the accumulation of noise,which requires the first accurate deconvolution of the measurement result,so that it is restored to a continuous phase,and then mode filtering to eliminate the noise.In this paper,under the background of the above topics,the phase difference method wavefront measurement technology is studied.The main research contents are as follows:1.The physics of the phase difference method is analyzed,and the calculation process of the phase difference method is introduced in detail using the focal plane and defocus plane images as examples,and the numerical simulation experiments of the method are conducted.2.Researched the phase unwrapping technique,an important technique in phase coherent measurement,and performed parallel accelerated research on the fast phase unwrapping algorithm,theoretically ensuring that the improved algorithm is consistent with the original algorithm's running results,and the actual experimental speedup is up to 50%.3.Numerical simulation of plane-wave through lens is carried out,and the matching relationship between the parameters in the simulation and the actual physical parameters is studied.4.Error generation and elimination methods on the experimental platform of the liquid crystal adaptive optical system are analyzed,and the problem of non-convergence in the wavefront measurement experiment is solved,and good measurement results are achieved.