Fig. 4.

Performance of different solvers in TensorFlow: (a)Adam, (b) RMSprop, (c) SGD, and (d) SGDM. We use 5 by 5 plane waves for sample illumination and the step size for $k_{xn}$ and $k_{yn}$ is 0.15 in this simulation. The recovered amplitude ((a1)-(d1)) and phase ((a2)-(d2)) with 500 epochs (the best learning rates are chosen in this simulation). Different color curves in (a3)-(d3) represent different learning rates and the loss is in log scale. Adam gives the best performance overall. Batch size is 1 in this simulation.