This paper provides an overview of both CCD (charged coupled device) and CMOS (complimentary metal oxide semiconductor) imaging array technologies. CCDs have been in existence for nearly 30 years and the technology has matured to the point where very large, consistent (low numbers of defects) devices can now be produced. However, CCDs suffer from a number of drawbacks, including cost, complex power supplies and support electronics. CMOS imaging arrays, on the other hand, are still in their infancy, but are set to develop rapidly and offer a number of potential benefits over CCDs. This review provides an overview of both CCD and CMOS imaging technology, and includes explanations of how images are captured and read out from the imaging arrays. Also covered are issues such as performance characteristics, cost considerations and the future of imaging arrays. This review does not provide details of colour sensors, colour filter arrays and colour interpolation, etc., as these will be the subject of a separate report.