Fienup is a term that can refer to various subjects, but it is often associated with Fienup-Riordan, a mathematical algorithm used in signal processing and imaging. This algorithm helps reconstruct images from incomplete data, making it valuable in fields like medical imaging and astronomy. In a different context, Fienup may also refer to individuals or organizations with that name. For example, Dr. Fienup is known for contributions to research in optics and imaging science. Overall, the term encompasses both mathematical techniques and notable figures in scientific research.