A Performance Characteristic for Net Light Collection in Hyperspectral and Conventional Cameras: A*

Abstract

The signal-to-noise ratio of modern cameras under normal operating conditions tends to be limited by “photon noise” originating from the random arrival of photons. For best signal-to-noise ratio, it is desirable to collect as much light as possible, and to avoid losses internally in the camera. There is currently no widely accepted metric for the resulting net light collection, which depends on many aspects of camera design. The IEEE Standards Association P4001 group is developing a standard for hyperspectral imaging, including ways to fully specify camera performance in an efficient way. Motivated by P4001 requirements, this work proposes to specify the net light collection in a single quantity, denoted A∗ , essentially defined as the product of nominal geometrical étendue, optics transmission, and detector quantum efficiency. It is shown how A∗ can be physically interpreted as the detector pixel area of an equivalent lossless camera whose exit pupil subtends 1sr. This article discusses how this quantity can be used as a figure of merit applying to hyperspectral cameras as well as to conventional multispectral and broadband cameras and other sensing systems employing imaging optics.