Patent Number: 
Section: claims

1. A beam forming system comprising one or more beam forming elements that are arranged to provide a non-planar doubly ruled radiation surface, the surface being defined by two families of rulings and wherein the length of the rulings within each family are configured to provide a radiation surface with substantially straight boundary edges, and wherein the beam forming system is arranged to form acoustic beams. 2. A beam forming system according to claim 1 wherein the radiation surface is a hyperbolic paraboloid. 3. A beam forming system according to claim 1 wherein the radiation surface is a hyperboloid of one sheet. 4. A beam forming system according to claim 1 wherein the beam forming elements comprise an array of straight elongate beam forming elements that are arranged relative to each other to collectively provide the non-planar doubly ruled radiation surface. 5. A beam forming system according to claim 4 wherein each straight elongate beam forming element comprises a plurality of beam forming elements that act together to from the straight elongate beam forming element. 6. A beam forming system according to claim 4 wherein the straight elongate beam forming elements are fixed relative to each other within a support structure so as to provide a predetermined beam-width of beams propagating from the radiation surface. 7. A beam forming system according to claim 4 wherein the straight elongate beam forming elements are movably supported relative to each other within a frame system, the frame system being operable to rotate the straight elongate beam forming elements relative to each other to alter angular parameters of the non-planar doubly ruled radiation surface so as to vary the beam-width of beams propagating from the radiation surface. 8. A beam forming system according to claim 1 in which a single beam forming element provides the non-planar doubly ruled radiation surface. 9. A beam forming system according to claim 8 wherein the single beam forming element comprises a continuous sheet of beam forming material that conforms to a non-planar doubly ruled surface. 10. A method of producing an acoustic beam comprising driving a beam forming system of claim 1 with a uniform phase. 11. A beam forming system according to claim 1 that is arranged as an acoustic transducer for projecting and/or receiving acoustic beams from or at the radiation surface. 12. A beam forming system according to claim 11 wherein the or each beam forming element is an acoustic transducer element comprising an active acoustic material that is operatively driven by front and back electrodes provided on opposing surfaces of the active acoustic material. 13. A beam forming system according to claim 12 further comprising a control system that is operatively connected to the electrodes and is arranged to drive the electrodes with electrical signals to cause the acoustic transducer to project and/or receive acoustic beams. 14. A beam forming system according to claim 13 wherein the control system is configured in an active mode to drive the acoustic transducer element(s) with electrical signals having uniform phase to produce an acoustic beam from each acoustic transducer element such that the overall acoustic beam projected from the radiation surface is the superposition of all of the acoustic beams from each acoustic transducer element. 15. A beam forming system according to claim 12 wherein the front and back electrodes are aligned with one family of rulings of the doubly ruled radiation surface. 16. A beam forming system according to claim 12 wherein the front electrodes of the acoustic transducer element(s) are aligned with one family of rulings of the doubly ruled radiation surface and the back electrodes are aligned with the other family of rulings of the doubly ruled radiation surface to provide a matrix electrode network. 17. A beam forming system according to claim 16 wherein a control system is operatively connected to all the electrodes in the matrix electrode network, and is operable to selectively drive different combinations of electrodes with electrical signals to thereby drive different combinations of selected acoustic transducer elements to produce any of the following: a wide-angle acoustic beam, acoustic beam-stripe, or an acoustic spot-beam. 18. A beam forming system according to claim 1 wherein each beam forming element comprises passive acoustic material such that the beam forming system can operate as an acoustic reflector or acoustic diffuser of acoustic beams incident on its radiation surface. 19. A beam forming system according to claim 18 wherein the passive acoustic material of the beam forming element(s) is acoustically reflective. 20. A beam forming system according to claim 1 wherein the system is an active beam forming device. 21. A beam forming system according to claim 1 wherein the system is an active acoustic device comprising beam forming element(s) comprising acoustically active material. 22. A beam forming system according to claim 1 wherein the system is an acoustic reflector comprising beam forming element(s) that are straight elongate active or passive acoustic elements of reflective material. 23. A beam forming system according to claim 1 wherein the system is an acoustic diffuser comprising beam forming element(s) that are straight elongate active or passive acoustic elements of reflective material. 24. A beam forming system comprising one or more beam forming elements that are arranged to provide a non-planar doubly ruled radiation surface, wherein the beam forming system is arranged to form acoustic beams.