ABSTRACT
Optical devices designed using the flow-line method, are quite large in the case of small acceptance angles, and they also need to touch the edges of the receiver. A possible way around this limitation is to consider a step curve along the flow-lines, with some portions of the curve along the flow-lines and others perpendicular to those lines. The vector flux lines inside the optic are straight, vertical parallel lines. Several of the optics can be combined using a stepped flow-line approach. In the case of a frontlight, light is reflected toward a reflective screen, which is reflected back through the optic and then observed. More elaborate designs may illuminate a large target with a single small source, or have a thickness that is nearly constant for the whole optic.
