title: Far-field distance for surface light source with different luminous area.
abstract: Most of the lighting designs are based on the far-field characteristics of light sources. It is important to know whether the measurement distance is far enough to simulate the light source as a point source. In this paper, we deduce the far-field conditions for surface light sources with continuous luminous area. The relative far-field distance for several typical flat and curved surface light sources, such as the round, rectangular, annular, hemispherical, and semi-cylindrical sources are calculated. Results show that the classical five times rule is not applicable to surface light sources with hemispherical, arc-shaped semi-cylindrical, and narrow annular luminous areas.
authors.affiliation: Key Lab for Optoelectronic Technology & Systems of Ministry of Education, Chongqing University, Chongqing, China. xianming65@163.com
authors.forename: Xianming
authors.initials: X
authors.lastname: Liu
authors.forename: Wentao
authors.initials: W
authors.lastname: Cai
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Lei
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Du
authors.forename: Weimin
authors.initials: W
authors.lastname: Chen