title: Bifocal optical system for distant object tracking.
abstract: A new bifocal optical system used for distant object tracking is proposed. This system combines a birefringent element with a conventional glass lens so that the spot image size and its variation with the axial distance can be controlled according to the requirement of a distant object tracker. The lens design for the tracking application is discussed and an example is given. The new lens system provides a more uniform spot image size and an extended focal depth compared to a conventional lens with one focus.
authors.forename: Xinping
authors.initials: X
authors.lastname: Liu
authors.forename: Xianyang
authors.initials: X
authors.lastname: Cai
authors.forename: Shoude
authors.initials: S
authors.lastname: Chang
authors.forename: Chander
authors.initials: C
authors.lastname: Grover