(JP10501073-W)      The lens includes an array of planar reflecting slots (22) reach of which is of non-uniform extent or surface area (t), and/or is non-uniformly spaced from adjacent slots. The slots may be parallel or non-parallel. Each slot is positioned such that the ratio of spacing (dn) to extent (tn) is determined by the angle of incidence on the nth slot, given by a mathematical relationship (a) where (dn) is the spacing between the nth and (n+1)th adjacent slats of the lens, (tn) is the length of the nth slot, and M is the magnification of the lens.    The slats are designed and positioned to minimise shadowing on other slats. The generatrix of the lens is of simple or compound, hyperbolic, parabolic, elliptical or circular shape. The reflectors may be crystals or multi-layer mirrors, and reflection to due to Bragg reflection. A multi-lens formed of two lenses may be used as a beam profile homogeniser to arrange a first type of beam into a second type of beam.    USE/ADVANTAGE -   For sky-light enhancer, solar concentrator. Has increased gain.    (US5982562-A)      The lens includes an array of planar reflecting slots (22) reach of which is of non-uniform extent or surface area (t), and/or is non-uniformly spaced from adjacent slots. The slots may be parallel or non-parallel. Each slot is positioned such that the ratio of spacing (dn) to extent (tn) is determined by the angle of incidence on the nth slot, given by a mathematical relationship (a) where (dn) is the spacing between the nth and (n+1)th adjacent slats of the lens, (tn) is the length of the nth slot, and M is the magnification of the lens.    The slats are designed and positioned to minimise shadowing on other slats. The generatrix of the lens is of simple or compound, hyperbolic, parabolic, elliptical or circular shape. The reflectors may be crystals or multi-layer mirrors, and reflection to due to Bragg reflection. A multi-lens formed of two lenses may be used as a beam profile homogeniser to arrange a first type of beam into a second type of beam.    USE/ADVANTAGE -   For sky-light enhancer, solar concentrator. Has increased gain.