Phase retrieval based on wavefront modulation - art. no. 661614

A practical method is proposed for the wavefront measurement of arbitrary complex-valued fields. A mask having random phase is placed in the path between the object and the image sensor. Three or more diffraction patterns are collected, as the mask translated in the direction parallel to the sensor. Phase retrieval is performed by propagating the wave field back and forth between the sensor and the mask plane and making the following change on the calculated wavefront: at the sensor plane, the modulus of calculated wavefront is replaced with the square root of recorded intensity; while at the mask plane, the modulation phase is updated to the one corresponding to the next mask position for next iteration. This process starts from a random estimate of the object field falling on the mask and ends when the change of the amplitude of two successively retrieved object fields before the mask is below a given threshold. Further propagation of the retrieved field from mask to object plane yields the original object field. Results from both simulated data and experimental data show that this method works quite well in terms of its absence of stagnation, suitability for complex-valued field, and high immunity to the noise in recordings. The technique is believed to find wide applications, such as aspherical lens testing, and diffraction imaging of micro-objects.