The recently developed optical radiation detectors need well-designed radiometers to perform improved radiometric, photometric, colorimetric, and radiation-temperature measurements. They can produce higher performance than traditionally used blackbody sources and lamps in wider application areas. This book presents research-based material in this field that has been implemented, realized, tested, verified, and evaluated. It can be used as a reference source for students, practicing scientists, engineers, technicians, instrument manufacturers and measurement/calibration people to learn, design, build, select, and use new generation radiometers. The book describes a number of design issues and applications to implement the correct input geometry for detectors to measure radiometric (power, irradiance and radiance) quantities, and DC, AC, and pulsed electrical output signals.