Over one year ago, the concept of this special issue was first formulated. It was conceived, initially, as one special issue on digital image processing and a second special issue on optical data processing. These topics have been retained. However, rather than two separate issues, we have chosen to intersperse digital and optical papers throughout two issues. This has been done both for content and to emphasize the similarities in techniques and application areas between these two powerful computing disciplines. We trust that these truly joint-dual special issues will typify the rapidly increasing marriage of the disciplines of optical data processing and digital image processing.