title: An optimized optical system for backlit imaging.
abstract: An optimized optical system for back-illuminated imaging was developed and was applied to automotive-type fuel injectors; the system provides significantly higher light collection efficiency than standard flood illumination. An engineered diffuser is used to distribute an extended light source through a controlled range of angles, and a field lens is used to redirect the light to the camera. A ray tracing analysis provides the required source size and diffuser angle to ensure that the necessary range of ray angles is included to allow fully diffuse imaging. Direct comparison with a flood illumination system showed that the collection efficiency increased by more than two orders of magnitude without any degradation of image quality.
authors.affiliation: Department of Mechanical Engineering, University of Wisconsin-Madison, 1500 W. Engineering Dr., Madison, Wisconsin 53706, USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Ghandhi
authors.forename: D M
authors.initials: DM
authors.lastname: Heim