Deterministic Phase Retrieval Based On Spatial Light Modulation

The properties of light field can be completely described from three aspects:the amplitude(brightness),wavelength(color)and phase(phase within a wavelength equal to the depth).Statistics show that more than 80%of information is saved in phase.Thus,phase information is particularly important,compared with other information such as intensity.However,the frequency of the electromagnetic field(about 1015Hz)is far higher than the maximum frame rate of optical detector(108Hz).Thus it is necessary to use the measureable intensity distribution to calculate the phase information.This is the problem of phase retrieval.At present,phase retrieval has been applied to many fields,such as optical measurement,astronomical imaging,electron microscopy,adaptive optics,optical phase microscopy.The phase retrieval based on transport of intensity equation is a typical noninterferometric deterministic method.The equation establishes the quantitative relationship between the axial variation of light intensity and phase and only to measure the intensity distribution of the object plane so the phase information can be calculated directly by solving the equation.Compared to the interferometric phase recovery method,the phase recovery based on the transport of intensity equation does not require a complex optical system and is insensitive to the vibration of the experimental environment.In addition,the solution does not require iteration,and the solved phase does not need to be unwrapped.However,the result of the solution based on the transport of intensity equation has the disadvantages of low resolution and need to mechanically move the imaging device CCD when acquiring the image,which is susceptible to nonlinear error on the higher order approximation of intensity difference and measurement noise,thus this limits the accuracy of the recovery result.The spatial light modulator is a kind of adaptive optical device,which can be used to modulate the spatial and temporal variation of a light wave front,then change the amplitude,phase and polarization of the wavefront.In this paper,we use the characteristics of spatial light modulator for light field modulation,and apply it to the correlation calculation of phase recovery.New phase recovery algorithms are proposed,corresponding experimental platform is built and highly quality phase recovery results are obtained.The main research work and innovation are as follows:(1)Phase retrieval based on phase modulation in space domain,and this paper studies phase retrieval based on tilted illumination synthetic.The spatial light modulator is placed in space domain,and the tilted gratings with different angles are loaded to modulate the phase of the incident light field,and the phase is calculated by the synthetic aperture technique,the recovery result with high quality is obtained and the resolution of the restored image is improved.(2)Phase retrieval based on amplitude modulation in space domain,and this paper proposes the phase retrieval algorithm based on cosine grating modulation and transport of intensity equation.The spatial light modulator is placed in the space domain,and the cosine grating is loaded to modulate the amplitude of light field.The intensities are obtained in the imaging plane.The phase derivatives are calculated by the TIE correlation processing,and the phase distribution is recovered.The experimental results show that the algorithm can effectively suppress the influence of noise on the recovery result.(3)Phase retrieval based on amplitude modulation in frequency domain,and this paper proposes the phase retrieval algorithm based on sinusoidal grating modulation.The spatial light modulator is placed in frequency domain of the system,and the sinusoidal grating is loaded to modulate the amplitude of light field.Then,using the relationship between intensity and the phase,the phase derivative is recovered by the intensity image,the phase distribution is obtained.The optical experiment platform is designed,which can collect the intensity image quickly,and suppression the error caused by moving the imaging device mechanically in the traditional method and the phase distribution is calculated by the collected real image.Simulation and real experimental results verify the correctness and effectiveness of the algorithm.