Research On Multiwave Lateral Shearing Interferometry Based On Diffractive Optical Elements

Wavefront detection had been an important research topic in the field of optics.Multiwave lateral shearing interferometry was a new approach to the wavefront detection methods.The multiwave lateral shearing interferometer had the advantages of a simple structure,a high measuring accuracy and a high dynamic range,which is a kind of wavefront method of detection that have great research value and practical significance.Such as evaluation on laser beam quality,imaging quality inspection of optical system,human eye aberration measurement and laser communication.It has a wide application prospect in adaptive optics.Multiwave lateral shearing interferometry using a phase grating based on the checkerboard structure.The under detected wavefront was divided into four sub wavefronts.The four sub wavefronts generated self-phase interference.The generated interferogram contains wavefront gradient information of two orthogonal directions.Only by further phase extraction and wavefront reconstruction can we obtain the wavefront phase image.The detecting optical path of system based on multiwave lateral shearing interferometry was simple and was easy to construct.What's more,the adaptive detection target is rich in variety,which is a highly cost-effective wavefront detection technology.The wavefront detection device based on multiwave lateral shearing interferometry is simple and very easy to adjust.It also had a high spatial resolution,which is worthy of a further study by researchers.On the basis of analyzing research progress both of the domestic and foreign experts,a large number of simulation and experimental work had been carried out.The multiwave lateral shearing interferometry principle,performance improvement and application technology were discussed and analyzed.And on the analysis of a large number of verification on temperature distribution measurement of static and dynamic temperature field of concrete had been carried out.The work carried out as follows:1.Throughout the mathematical modeling and theoretical analysis of multi front shear interference principle of technology and means,starting from the shack Hartmann wavefront sensor optical diffraction model,introduces several multi front shearing interferometry model and interference image intensity distribution theory.According to the characteristics of the checkerboard type phase grating,the diffraction efficiency of two bit phase gratings and various factors that may cause errors are analyzed by using scalar diffraction theory.2.The phase extraction algorithm of multi wave front transverse shearing interferogram and the application of Fourier transform in phase extraction are introduced.Comparing the characteristics of different kinds of phase extraction filter,theoretical analysis shows that the circular pupil using the Gauss window function as the filter error,and the phase caused by using rectangular window function filter mosaic cylindrical pupil under the extraction of minimum error.Then,the interferogram fringe extension technique is introduced,in which the Gerchberg extrapolation iterative method has better extension effect for interference fringes with high carrier frequency.3.The use of wavefront fitting interference wavefront gradient extraction in images of the Fourier integral method and Zernike method was analyzed.The theoretical model of two kinds of methods and the scope of application was introduced.The wavefront gradient mirror the anti-symmetric extension of the method to eliminate the low frequency error due to the Fourier transform cycle characteristics and discontinuous basis functions the boundary of conflict in the process of reconstruction,and the advantages and disadvantages of simulation experiments to compare the two kinds of wavefront phase integral method.4.In the engineering application of the quadriwave lateral shearing interferometer,The errors due to a checkerboard type phase grating and the target surface is not parallel to the detector was analyzed.The calibration of the spectrum diagram is the design of a quadriwave lateral shearing interferometry based on iterative phase shifting calibration method for precise positioning of the interferogram the spectrum of a center,as far as possible to reduce the error,the residual slope caused by calibration of wavefront RMS error is less than 1.5 × 10-4.The ideal result was obtained in the experiment.We use calibrated shear interferometer and Phasics' SID-4 wavefront sensor to measure the random wavefront generated by deformable mirror at the same time.The wavefront RMS is 0.74 lambda and 0.76 lambda respectively.This method guarantees the accuracy and reliability of the calculation results,which can meet the requirements of high-precision wavefront detection.5.An interferogram denoising algorithm based on non-local mean filtering had been carried out.In the process of quadriwave lateral shearing interferometry,the signal-to-noise ratio becomes lower because of the noise of the imaging equipment and the lack of the wavefront intensity.Combined with the noise model,the characteristics of different denoising algorithms are compared and analyzed.The simulation experiment of interferogram denoising had been carried out.The simulation results showed that the interferogram denoising algorithm based on the non-local mean filter can effectively remove the Gauss white noise in the interferogram and improve the signal to noise ratio of the reconstructed wavefront.To deal with the noise in the interferogram to join ?=0.01 Gauss white noise,PSNR increased from 12.6 to 35.4,while MSE reduced from 3.5 to 0.8.The experimental results verified the effectiveness of denoising method based on non-local mean filter.6.A series of experiments had been carried out on the application of the quadriwave lateral shearing interferometry.It is proved that the quadriwave lateral shearing interferometry has the characteristics of high frame rate,high spatial resolution and high accuracy.In the field of temperature measurement,a static temperature field measurement experiment based on quadriwave lateral shearing interferometry and a high dynamic temperature field measurement experiment are designed.A temperature field distribution video with a maximum frame rate of 200 frames per second and a spatial resolution of 512×512 was obtained.Experimental results showed that the measurement of temperature field by quadriwave lateral shearing interferometry can reach the measurement accuracy of ±0.5?,and has important significance in the field of flame parameter analysis and so on.