Lenslet array systems are different from conventional, single aperture systems in that many, possibly somewhat dissimilar, apertures, each containing its own lens, are used. This may add some (mostly conceptual) complexity, but it allows for a great deal of added flexibility. The availability of many independent optical channels offers many opportunities for optical information processing. One important possible class of applications for these systems are smart sensors - combining image acquisition with preliminary processing for machine vision and efficient image transmission. Another potential application of the device is the DiLAP, for Digital Lenslet Array Processor. This is a combination of an analog lenslet array device with a point non-linear electro-optical device. It provides highly parallel digital processing capability. This work describes the principles of operation of these LAP or Lenslet Array Processor systems, review some specific experimental examples, and discuss their potential limitations and capabilities.