A new method to obtain elliptic ray bundles in three-dimensional geometry i
s presented. This type of bundle is of special interest in nonimaging optic
s because the only known three-dimensional ideal concentrators with homogen
eous media transmit elliptic bundles. First, we reformulate the condition f
or a bundle to be elliptic; that is, the rays passing through any point of
the space form a cone with an elliptic base. The solution found includes al
l the elliptic bundles obtained by other methods as a particular case. Seco
nd, we look for the concentrators defined by the new elliptic bundles with
the flow-line design method of nonimaging optics. Most of these bundles do
not generate new devices but are transmitted ideally through the already kn
own three-dimensional ideal concentrators. (C) 1999 Optical Society of Amer
ica [S0740-3232(99)01808-6] OCIS codes: 220.1770, 080.2740, 080.2720.