A new adaptive method of wavefront sensing is proposed and demonstrated. The method is based on the Talbot self-imaging effect, which is observed in an illuminating light beam with strong second-order aberration. Compensation of defocus and astigmatism is achieved with an appropriate choice of size of the rectangular unit cell of the diffraction grating, which is performed iteratively. A liquid-crystal spatial light modulator is used for this purpose. Self-imaging of rectangular grating in the astigmatic light beam is demonstrated experimentally. High-order aberrations are detected with respect to the compensated second-order aberration. The comparative results of wavefront sensing with a Shack-Hartmann sensor and the proposed sensor are adduced.

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The accuracy of measuring optical aberrations in the random phase field by the Talbot wavefront sensor is theoretically investigated. The possibilities of a grating self-imaging phenomenon in the random phase field are investigated based on the simulation results. Random fields of two different types are considered: amplitude and phase Gaussian fields. Simulation results show that the cosine grating is more stable for phase noise in comparison with gratings that have Gaussian and square binary profiles on each cell unit. It is found that phase noise gives increments of high-order aberrations for wavefront reconstruction.

A holographic wavefront sensor based on the Talbot effect is proposed. Optical wavefronts are measured by sampling the light amplitude distribution with a two-dimensional (2D) precorrected holographic grating. The factors that allow changing an angular measurement range and a spatial resolution of the sensor are discussed. A comparative analysis with the Shack-Hartmann sensor is illustrated with some experimental results.

The results obtained at simulating the functioning of an adaptive sensor based on the Talbot effect are reported. The input grating period was varied depending on the examined wavefront shape and provided the constant observation plane corresponding to the Talbot plane for a plane wave. Using the spherical and astigmatic wavefronts as an example, it is shown that this method can make the sensor measurement range several times wider, by retaining the original angular sensitivity. K e y w o r d s: wavefront, Talbot effect, wavefront sensor.

An analysis of diffraction images in the deep Fresnel region produced by gratings with random pit displacements around a nominal value is performed in this paper. Such pit displacements can be produced while developing a grating with etchers since the process can be slightly unpredictable. A theoretical prediction to describe the intensity distribution is obtained, produced by the grating at the near field, showing that smoothing of self-images is produced in the Talbot plane. In addition, random pit displacements produce different diffraction behaviors for cosine and binary gratings. It is shown that if the standard deviation of pit displacements is less than 30% of the grating period, the pit image, observed in the Talbot plane, shows some additional intensity fluctuation that leads to its displacement by meaning of the mass center for binary gratings and pit displacements for cosine gratings with some additional structural changes. Theoretical conclusions taken from a direct integration method based on the Rayleigh–Sommerfeld equation are in good agreement with the simulation results.

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