Basic real-time programmable image-processing operations are accomplished by use of acousto-optic (AO) cells. Instead of frequency-plane filters, the AO cells are placed directly behind the object. The one-dimensional edge-enhancement results with one AO cell can be improved by use of two AO cells that are placed in tandem with contrapropagating sound. The dominant second-derivative operation obtained from the transfer function of the undiffracted order works like a one-dimensional Laplacian operator that enables improved edge enhancement.